Central and Peripheral Nervous System Medications
Objectives
1. Explain the physiologic processes of the central and peripheral nervous systems.
2. Identify the major classes of drugs that affect the central nervous system (CNS).
3. List different actions of antimigraine products.
4. Explain the major actions of drugs used to treat disorders of the CNS.
5. Identify the role of psychotropic drugs in psychotherapeutic intervention.
6. Compare and contrast different categories of medications used to treat mood disorders.
Key Terms
acetylcholine (ăs-ě-tĭl-KŌ-lēn, p. 252)
adrenergic blocking agents (ăd-rěn-ĚRJ-ĭk, p. 253)
adrenergic fibers (ăd-rěn-ĚRJ-ĭk, p. 252)
anticholinergics (ăn-tĭ-kō-lĭn-ĚRJ-ĭks, p. 253)
autonomic (ŏ-tō-NŎM-ĭk, p. 252)
barbiturates (bär-BĬ-chŭ-rets, p. 259)
catecholamines (kăt-ě-KŌ-lă-mēnz, p. 253)
central nervous system (CNS) (SĔN-trŭl NŬR-vŭs SĬS-tĕm, p. 251)
cholinergic drugs (kō-lĭn-ĚRJ-ĭk, p. 253)
cholinergic fibers (kō-lĭn-ĚRJ-ĭk, p. 252)
hypnotic agent (hĭp-NŎT-ĭk, p. 293)
idiopathic (ĭd-ē-ō-PĂTH-ĭk, p. 257)
initial insomnia (ĭn-ĬSH-ăl ĭn-SŎM-nē-ă, p. 293)
intermittent insomnia (ĭn-těr-MĬT-ěntĭn-SŎM-nē-ă, p. 293)
neurotransmitters (nŭr-ō-TRĂNS-mĭt-ěrz, p. 252)
norepinephrine (NŎR-ěp-ĭn-ĚF-rěn, p. 252)
Parkinson disease (PĂR-kĭn-sĕnz dĭ-ZĒZ, p. 267)
parasympathetic (p. 252)
peripheral nervous system (PNS) (pě-RĬF-ěr-ă l, p. 252)
receptor (rē-SĚP-tŏr, p. 253)
sedative agent (SĚD-ă -tĭv, p. 293)
seizures (SĒ-zhŭ rz, p. 257)
somatic (sō-MĂT-ĭc, p. 252)
status epilepticus (STĂT-ŭsě p-ĭ-LĚP-tĭ-kŭ s, p. 260)
sympathetic (p. 252)
terminal insomnia (TŬR-mĭn-ăl ĭn-SŎM-nē-ă, p. 293)
Overview
http://evolve.elsevier.com/Edmunds/LPN/
This chapter has six sections discussing drugs that act on various parts of the central nervous system (CNS) and the peripheral nervous system (PNS). Although many drugs are used in treating CNS diseases, the principles of drug usage, actions of the medications, and adverse reactions are very similar. The nurse will benefit from learning how these drugs are the same and how they are different for the various categories of drugs. Although narcotic and nonnarcotic analgesics are also CNS drugs, they will be discussed in Chapter 17.
The first section of this chapter explores antimigraine agents. The second section covers the medications used to treat various types of seizures. The third section discusses drugs for vertigo (feeling of dizziness or spinning), and the fourth section presents drugs used to treat Parkinson disease. The fifth section introduces all the psychotropic drugs and includes subsections dealing specifically with medications used to treat anxiety, depression, and psychosis. Lithium, a unique antimanic medication, is covered in this section. The sixth section discusses sedative-hypnotics and their use in anxiety and sleep disorders.
Nervous System
The major structures of the nervous system include the brain, spinal cord, nerves, and sensory receptors (Figure 16-1). The nervous system regulates and coordinates the body’s activities (including the senses), controls movement, and coordinates physiologic and intellectual functions.
The nervous system has two divisions, the central and the peripheral. The central nervous system (CNS), made up of the brain and the spinal cord, is located within the cranial cavity of the skull and the vertebral canal of the spinal column. The peripheral nervous system (PNS) includes all nervous structures (ganglia and nerves) that lie outside the cranial cavity and the vertebral canal. These include the cranial and spinal nerves and the sympathetic division of the autonomic nervous system.
Pathologic conditions in the brain may produce either local or general symptoms; abnormalities in the peripheral system usually cause only local symptoms. Because the nerve and muscle systems are mixed together so closely, it is often difficult to tell if disease lies within the nerves or the structures activated by the nerves.
Although the drugs covered in this chapter focus on the actions of the CNS, or those actions controlled by the brain and spinal cord, many of these agents act through the PNS. The PNS produces changes or activity in the body through the nerves and chemicals of the motor nervous system and the autonomic nervous system as they carry out directions from the CNS.
Drugs act on the CNS and peripheral nerves by sending or transmitting information from the brain through chemical messengers or neurotransmitters. The neurotransmitter chemical is released at the end of one neuron and passes across a small gap (the synapse) to activate the next neuron in the chain. At the end of the nerve chain, it stimulates an organ, smooth muscle, or gland to produce a physiologic response.
In the PNS, nerves of the somatic nervous system have voluntary control over skeletal muscle. Nerves of the autonomic nervous system provide involuntary control over organs and tissues of the heart muscles, and over smooth muscles and glands affecting the salivary glands and digestive tract, eyes, respiratory tract, and reproductive tracts. The action of the autonomic nervous system is very important to understanding the action of key drugs that act on this system.
The autonomic system works through two subdivisions—the sympathetic nervous system and the parasympathetic nervous system. These two systems work together in directing how most organs and glands work. The sympathetic system helps the body prepare for stressful situations by producing chemicals that will induce the “fight or flight” response. The parasympathetic nervous system provides the basic, routine maintenance of the body actions and has been called the “rest-and-digest response”.
The nervous system is made up of small cells called neurons. The cells might be thought of as people standing in line passing a message to each other to do something. Instead of one person telling the next person the message, in the nervous system, a neurotransmitter chemical is released by the neuron which crosses the space or synapse between the two messengers (neurons) and is received by the receptor neuron on the other side. Then that neuron messenger turns to the next neuron cell to send the message forward until the final message is received, perhaps to affect skeletal muscle that will move the hand.
There are a variety of neuron transmitters that carry these messages. The two major neurotransmitters in the body are norepinephrine, which acts on the sympathetic nerves, and acetylcholine, which acts on the parasympathetic nerves. There are several other important neurotransmitters, especially in the brain. Nerve fibers that release norepinephrine are called adrenergic fibers. Nerve fibers that release acetylcholine are called cholinergic fibers. Most organs in the body are influenced by both types of fibers, which have opposite effects. For example, adrenergic activity speeds up the heart rate, and cholinergic activity slows it down. It is possible to compare this system to a car that is influenced by an accelerator and a brake. It is very important to understand these concepts because many drugs look or act like neurotransmitters and they act to help or block the action of neurotransmitters.
There are several names for the types of drugs that act on the nervous system. Because autonomic drugs either block or stimulate either the sympathetic or parasympathetic nervous systems, these autonomic drugs are classified based on their actions. These drugs have been called by several different names as, over time, research reveals more information about them.
These basic terms are used throughout this chapter. Remembering these terms and definitions will help in understanding drug actions.
When neurotransmitters release their chemicals, the chemicals are targeted to act at certain parts of the body. Each neurotransmitter has a certain chemical shape (like a key), which produces an action only when it “fits into” a specific receptor (lock) for that chemical.
Acetylcholine (cholinergic) receptors are classified as either muscarinic (which stimulate smooth muscle and gland secretions and decrease the heart rate and force of heart contraction) or nicotinic (which stimulate smooth muscle and gland secretions). Norepinephrine (adrenergic) receptors are identified as alpha 1 (provides for constriction of blood vessels and dilation of pupils); alpha 2 (blocks norepinephrine release); beta 1 (increases heart rate and force of contraction and release of renin); and beta 2 (blocks smooth muscle action). Note that when stimulated, alpha receptors often have the opposite effect of beta receptors on the heart, blood vessels, GI tract, or eye muscles. The text often refers to a medication as having alpha or beta properties. For example, some medications are called beta blockers because of their selective action in blocking only the beta-adrenergic effects in the body.
Many of the drugs discussed in the following sections act on more than one type of receptor. Each agent acts differently, making it possible for certain drugs to be given for specific actions without many adverse reactions. It should be clear that if dosages are exceeded, many receptors may be overly stimulated, causing widespread and serious effects. Thus accuracy in giving the right amount of drug and at the proper time is very important in giving these drugs safely.
Sympathomimetic Drugs
Adrenergic agonists or sympathomimetic drugs produce chemicals involved in the fight-or-flight syndrome and have many of the same effects as the anticholinergics. Some of the drugs have been developed so that they act specifically on either the alpha or beta subreceptors. This makes their actions more focused and predictable.
The effects of these drugs depend on which adrenergic subreceptors are stimulated. Some act very selectively, for example, on drying secretions in the nose. Other drugs act primarily on the heart or to help bronchodilation in the lungs. Thus these drugs may have specific uses prior to surgery, with specific heart problems, or asthma. Other drugs may stimulate more than one type of adrenergic receptor and so are considered nonselective. Thus product information may say that drugs act on both beta 1 and beta 2 receptors or both alpha 1 and beta 2 receptors. This should help the nurse anticipate what these drug actions might be.
Because of the variability in drug actions, many of these drugs are discussed in other relevant chapters in the book. Only a few of the most common sympathomimetics are listed in Table 16-1, along with their receptors.
Table 16-1
Selected Sympathomimetics and Adrenergic Drugs
| DRUG | TRADE NAME | RECEPTOR SUBTYPES | USE |
| Sympathomimetics | |||
| Albuterol | Proventil, Ventolin | Beta 2 | Asthma treatment |
| dobutamine | Dobutrex | Beta 1 | Heart stimulant |
| dopamine | Intropin | Alpha 1 and beta 1 | Treatment of shock |
epinephrine  |
Adrenalin, Primatene | Alpha and beta | Comes in variety of forms to treat asthma, shock, cardiac arrest |
| isoproterenol | Isuprel | Beta 1 and beta 2 | Comes in variety of forms to treat heart failure, asthma, dysrhythmias |
| metaproterenol | Alupent | Beta 2 | Used to treat asthma attacks and maintenance |
| metaraminol | Aramine | Alpha 1 and beta 1 | Used to treat shock |
| norepinephrine | Levarterenol, Levophed | Alpha 1 and beta 1 | Used to treat shock |
| oxymetazoline | Afrin | Alpha | Topical OTC product to treat nasal congestion |
| phenylephrine | Neo-Synephrine | Alpha | Topical OTC product to treat nasal congestion |
| pseudoephedrine | Sudafed | Alpha and beta | Topical OTC product to treat nasal congestion |
| ritodrine | Yutopar | Beta 2 | Slow uterine contractions and reduce risk of abortion |
| salmeterol | Serevent | Beta 2 | Used to treat nasal congestion and asthma |
| terbutaline | Brethine | Beta 2 | Used to treat asthma |
| Adrenergic Blockers | |||
| acebutolol | Sectral | Beta 1 | Used for treating dysrhythmias, angina, hypertension |
| atenolol | Tenormin | Beta 1 | Used for treating hypertension and angina |
| carteolol | Cartrol | Beta 1 and beta 2 | Used in treatment of glaucoma and hypertension |
| carvedilol | Coreg | Alpha 1, beta 1, and beta 2 | Used in treating hypertension |
| doxazosin | Cardura | Apha 1 | Used in treating hypertension |
| esmolol | Brevibloc | Beta 1 | Used in treating hypertension |
| metoprolol | Lopressor | Beta 1 | Hypertension, heart failure, MI |
| nadolol | Corgard | Beta 1 and beta 2 | Used in treating hypertension |
| phentolamine | Regitine | Alpha | Used in severe hypertension |
| prazosin | Minipress | Alpha 1 | Used in treating hypertension |
propranolol  |
Inderal | Beta 1 and beta2 | Used in dysrhythmias, angina, hypertension, treatment of migraines |
| sotalol | Betapace | Beta 1 and beta 2 | Used in dysrhythmias |
| terazosin | Hytrin | Alpha 1 | Used in treating hypertension |
| timolol | Blocadren, Timoptic | Beta 1 and beta 2 | Used in treating angina, hypertension, glaucoma |
MI, Myocardial infarction; OTC, over the counter.
Indicates “Must-Know Drugs,” or the 35 drugs most prescribers use.
Adrenergic Agonists or Blockers
The actions of the sympathetic nervous system are blocked by adrenergic blocker medications. These agents are common and are used in the treatment of hypertension. The actions of adrenergic blockers are quite specific and this makes them very useful. They are used primarily in blocking the effect on beta 1 receptors only present in the heart, or blocking receptors in vascular smooth muscle in small arteries, causing vasodilation and reducing blood pressure. Other beta blockers are nonselective so they block both beta 1 and beta 2 receptors. These drugs usually have more side effects. A list of these drugs and their primary receptor subtype is in Table 16-1. A more complete discussion of these drugs and their uses in hypertension is found in Chapter 15.
Parasympathetic Drugs
Parasympathomimetic drugs that produce the rest-and-digest responses act like the parasympathetic chemicals in the body. The action of these drugs is difficult to limit to a small part of the body and they have many adverse effects. Thus there are only a small number of these drugs and they are used carefully for specific neurologic problems. For example, bethanechol (Urecholine) is a direct-acting agonist and neostigmine (Prostigmin) is a reversible cholinesterase inhibitor. Both are used to help contract the muscles in the ureters or bladder when treating for urinary retention. Physostigmine (Antilirium) and pilocarpine (Isopto Carpine) are commonly used to treat glaucoma by reducing intraocular pressure. Pyridostigmine (Mestinon) is a drug used only for the treatment of myasthenia gravis, a relatively uncommon neurologic problem.
Anticholinergic Drugs
Anticholinergic drugs mimic the fight-or-flight response. These drugs are commonly used for their autonomic function in the treatment of many respiratory and GI disorders. The drugs increase heart rate, dilate pupils, dry secretions, and dilate the bronchi of the respiratory tract. The usefulness of these drugs is limited because of their adverse effects—primarily producing a rapid heart rate and causing urine release to be blocked in older men who have enlarged prostate glands. Some of the newer medications have fewer side effects than older drugs in this category.
Examples of common anticholinergics are atropine and glycopyrrolate (Robinul) that are used prior to anesthesia to dry up secretions, to increase heart rate in some arrhythmias, and dilate the pupils in assessment of some eye problems. Glycopyrrolate also has been used in the treatment of peptic ulcers and irritable bowel syndrome, along with Propantheline (Pro-Banthine) and dicyclomine (Bentyl). Cyclopentolate (Cyclogyl) is also used to dilate pupils. Ipratropium (Atrovent) is used in treating asthma, oxybutynin (Ditropan) is used in treating urinary bladder urgency and incontinence, and scopolamine (Hyoscine, Transderm-Scop) is used not only for treating irritable bowel syndrome, but also has a central effect in controlling motion sickness and alcohol withdrawal symptoms. Many of these drugs have significant interactions when given with other medications. The more important of these medications will be discussed as relevant drugs in other chapters.
Antimigraine Agents
Overview
Headaches are a common problem seen in primary care patients. Tension headaches that occurs when stress causes the muscles of the head and neck to tighten are successfully treated with over-the-counter (OTC) drugs such as acetaminophen (Tylenol), ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn), or aspirin.
Migraine headaches are more serious and complex headaches in which the patient feels throbbing or pulsating pain, often made worse by noise or bright light. These headaches are often triggered by specific products (like monosodium glutamate in some foods), food additives, chocolate, red wine, and caffeine. A warning sign or aura that a migraine headache is developing might occur when the patient has changes in vision, hearing, taste, or smell. These headaches might also produce nausea, vomiting, and severe fatigue. These migraine headaches are treated with a variety of different drugs and may also be prevented by some types of medicines (prophylactic medicine).
Antimigraine agents block nerve impulses in the receptors of the sympathetic nervous system and so may be used for either prevention or treatment. The ergot alkaloids used in the treatment of vascular headaches are adrenergic-blocking agents. Treatment medications should be given as soon as the pain begins. Other medications can be taken to prevent migraines from occurring (prophylactically).
Action
There are two commonly used classes of drugs used in migraine treatment: (1) ergot alkaloids; and (2) triptans. Both of these drug classes stimulate serotonin (5-hydroxytryptamine [5-HT]) and affect the many serotonin receptor subtypes found throughout the CNS. There are a variety of other anticonvulsant, antidepressant, beta-adrenergic blockers, or calcium channel blockers that may be used to treat severe migraines. Riboflavin (Vitamin B2) and feverfew are alternative therapies some have found to be effective.
The process that produces migraine headaches is thought to be local dilation of the blood vessels in the cranium or the release of sensory neuropeptides through nerve endings in the trigeminal system. The vascular 5-HT receptor is present on the human basilar artery and in the vessels of human dura mater. Use of the 5-HT, or serotonin, receptor antagonists results in cranial vessel constriction (narrowing) and blocking of neuropeptides that cause inflammation, which happens at the same time the patient feels the relief from migraine headache. Some of these products also cross the blood-brain barrier, produce central activity on the trigeminovascular system, and stop nerve depolarization at peripheral sites in the cranium.
Additionally, adrenergic-blocking agents dilate the veins in smooth muscle tissue in the peripheral vascular system, reducing cerebral blood flow and arterial pulsing, which reduces headache pain. Other actions include dilation of veins in the uterus, an increase in uterine contractions (oxytocic effect), and a decrease in blood pressure.
Uses
Antimigraine agents are used in both the prevention and treatment of vascular headaches. They relieve the pain of vascular headaches by narrowing dilated cerebral arteries. OTC drugs such as ibuprofen or aspirin are usually started first. If these drugs are not helpful, triptans such as sumatriptan (Imitrex) are used. The triptans come in a variety of forms, including injection and inhalation, so that if the patient has nausea or vomiting, he or she may still take the drug. The action of 5-HT agonists is not affected by whether or not the person with the migraine has an aura or by the length of the attack, sex or age of the patient, relationship to menstrual periods, or the use of other common migraine prevention drugs. Ergot alkaloids like ergotamine (Ergonal) are used if triptans are not effective, although less commonly. Ergot alkaloids are also used for pregnant women for oxytocic (labor-inducing) and other smooth-muscle spasmogenic effects. They are not used in early pregnancy as they are pregnancy category X drugs.
Adverse Reactions
Adverse reactions to antimigraine agents in general include heart murmurs, brief tachycardia (rapid heartbeat), confusion, depression, dizziness, drowsiness, fixed miosis (constriction) of the pupil of the eye, paresthesias (numbness and tingling) in the toes, weakness (especially in legs), nausea and vomiting, leg cramps, localized pruritus (itching) and edema (fluid buildup in the body tissues), and neutropenia of the blood. Symptoms of overdosage include numb, cold, pale extremities; constant muscle pain, even at rest; decreased or absent arterial pulses; drowsiness; confusion; depression; convulsions; hemiplegia; and fixed miosis. Because of the potential for 5-HT agonists to cause coronary vasospasm, patients with ischemic heart disease or other major cardiovascular disease, or uncontrolled hypertension (high blood pressure) should not use these products.
Drug Interactions
When antimigraine agents are used with other vasoconstrictors, vasoconstriction may be increased. The 5-HT agonists may not be used within 24 hours of taking an ergotamine-containing preparation and may not be used at the same time with monoamine oxidase (MAO) inhibitor therapy, selective serotonin reuptake inhibitors (SSRIs) serotonin/norepinephrine reuptake inhibitors (SNRIs), lithium (given for depression), and many other drugs. Some of the different triptans cannot be used within 24 hours of each other because of drug interactions.
Nursing Implications and Patient Teaching
n Assessment
Learn as much as possible about the overall health history of the patient, as well as the history of headaches (whether tension, migraine, or cluster). Find out whether there are factors that might affect the patient’s use of antimigraine drugs (e.g., coronary artery disease or conditions in which a sudden change in blood pressure may be dangerous).
The patient may have a history of migraine headaches, vascular headaches, or headache pain of a periodic, throbbing, severe nature. The pain may be one-sided (unilateral) and commonly felt over one eye. Photophobia (sensitivity to light) and sensitivity to sound may be present, as well as nausea and vomiting. A family history of vascular headaches or history of motion sickness as a child, series of headaches in clusters, history of hypertension, a food allergy, or use of birth control pills may be present. The headache may have been relieved or eased by sleeping, vomiting, or drinking a caffeinated drink.
Ask whether the patient uses any herbal products or vitamins to control headache or migraines, because some of these products may interact adversely with other drugs, including nonsteroidal antiinflammatory drugs (NSAIDs). The Complementary and Alternative Therapies box summarizes herbal preparations the patient may be using and their drug interactions. The nurse may observe signs of sweaty hands and feet, scalp tenderness, autonomic dysfunction (such as miotic pupil), red eye, and unilateral nasal congestion.
Potential Drug-Drug Interactions with Complementary and Alternative Therapies
Headache
| PRODUCT | COMMENTS |
| Feverfew | Potential interaction with anticoagulants, aspirin, NSAIDs, antiplatelet agents |
| Ginkgo | Potential interaction with anticoagulants, aspirin, NSAIDs, antiplatelet agents; may interact with MAO inhibitors, acetylcholinesterase inhibitors |
| White willow | Potential interaction with aspirin, anticoagulants, methotrexate, metoclopramide, phenytoin, probenecid, spironolactone, valproic acid, NSAIDs, antiplatelet agents |
Data from Krinsky DL, LaValle JB, Hawkins EB, et al: Natural therapeutics pocket guide, ed 2, Hudson, Ohio, 2003, Lexi-Comp, Inc.
n Diagnosis
In addition to the medical diagnosis, what other symptoms does this patient have that require nursing action? Are there needs for patient education, nutrition information, and quiet time away from people? Sometimes identifying the migraine triggers leads to the diagnosis of other emotional or physical problems.
n Planning
Ergot alkaloids increase uterine contraction and may be harmful to the pregnant patient. These migraine medications are slowly and incompletely absorbed from the GI tract. Traces of ergotamine remain in various tissues; this accounts for its long-lasting and toxic actions.
n Implementation
Patients who have had migraines often have a regimen they follow that helps bring relief. These behaviors often include isolating themselves in a dark, quiet room, use of icepacks on head, and avoiding food. If migraine agents are used at the onset of an attack, the ability of the drugs to relieve migraine pain and symptoms is increased. If the patient’s pain is relieved after an intramuscular (IM) injection of 1 mL (0.5 mg) of ergotamine, the diagnosis of vascular headaches is confirmed.
Antimigraine products are available in oral, sublingual, parenteral, and rectal forms, and as a solution for inhalation. Many factors, including whether the purpose of the agent is to prevent or to treat migraine, influence which form will be best tolerated and most effective.
Oral and rectal preparations are absorbed slowly and incompletely from the GI tract. To speed up this absorption, caffeine is included with oral and rectal preparations of ergot alkaloids. Persons who are vomiting and cannot tolerate oral preparations are given rectal forms of the agent. Inhalant methods are preferred by some patients. Sublingual tablets are more quickly absorbed than either rectal or oral preparations. IM and subcutaneous preparations are commonly used, but absorption is often incomplete and slow.
A list of important dosage information about antimigraine products is presented in Table 16-2.
Table 16-2
| GENERIC NAME | TRADE NAME | COMMENTS |
| Serotonin (5-HT) Receptor Agonists | ||
| almotriptan | Axert | For acute treatment of migraine and prevention. |
| eletriptan | Relpax | Used for acute treatment, as well as prophylaxis. Older adults may be particularly sensitive and have hypotension. May cause angina or MI. |
| frovatriptan | Frova | Used for acute treatment, as well as prophylaxis. Produces tachycardia. |
| naratriptan | Amerge | Single doses taken with fluid are typically effective in relieving acute pain. If headache returns or patient has only partial response, dose may be repeated in 4 hr. Higher doses do not produce better results. |
| rizatriptan benzoate | Maxalt | Comes as a tablet or an orally disintegrating tablet that does not require liquid but must not be opened until just before dosing. |
sumatriptan succinate  |
Imitrex | Comes PO, SC injection, or intranasal spray. |
| zolmitriptan | Zomig | Break tablet in half for initial dose. Repeat in 2 hr if headache returns. Use care in patients with liver dysfunction. Also comes as nasal spray. |
| Ergotamine Derivatives | ||
dihydroergotamine  |
DHE 45 | An alpha-adrenergic blocking agent with pharmacologic and toxic properties similar to ergotamine used to treat migraine headaches. The drug causes cerebral vasculature to constrict, but it does not have an oxytocic effect and can be used during pregnancy. |
| Migranal | ||
| ergotamine | Ergomar | An alpha-adrenergic blocking agent that exerts direct vasoconstriction on cranial blood vessels, relieving pulsations thought to be responsible for vasoconstriction. Dependence on ergotamine may develop, necessitating gradual withdrawal from this product. |
| Combination products | Cafergot | Cafergot is a combination of ergotamine, caffeine, and other products used to treat migraine and vascular headaches. Caffeine is included in these products to increase absorption of ergot alkaloids. Small amounts of belladonna alkaloids and barbiturates may also be included to control nausea and produce sedation. Comes PO or suppository. |
| Other Migraine Prophylaxis Products | ||
| Beta-Adrenergic Blockers | ||
| atenolol | Tenormin | Also used in treatment angina and hypertension. |
| metoprolol | Lopressor | Also used in treatment angina and hypertension. Comes in sustained-release and IV forms. |
| propranolol HCl | Inderal | Also used in treating cardiac dysrhythmias. |
| timolol | Blocadren | Also used for treatment glaucoma, angina, and hypertension. |
| Calcium Channel Blockers | ||
| nifedipine | Procardia | Also used for treatment of angina and hypertension. Available in sustained-action product. |
| nimodipine | Nimotop | Used following strokes to improve neurologic statue; unlabeled use in preventing migraines. |
| verapamil HCl | Calan | Unlabeled use in preventing migraines. |
| Tricyclic Antidepressants | ||
| amitriptyline | Elavil | Unlabeled use in preventing migraines. |
| imipramine | Tofranil | Also used to control bedwetting in children and alcohol or cocaine dependence. Many side effects. |
| Miscellaneous Agents | ||
| valproic acid | Depakote | Also used for absence or mixed generalized seizures and mania. |
| methysergide | Sansert | Similar to ergotamine. |
5-HT, 5-Hydroxytriptamine; IV, intravenous; MI, myocardial infarction; PO, by mouth; SC, subcutaneous.
Indicates “Must-Know Drugs,” or the 35 drugs most prescribers use.
n Evaluation
When evaluating the patient with recurrent migraines, determine if the drug is helping. There should be a decrease in number and severity of migraine headaches. To determine if overdosage, toxicity, or adverse reactions are developing, monitor the patient’s blood pressure in standing, sitting, and lying positions and check for peripheral pulses.
Long-term use of migraine agents can lead to acute overdosage or chronic toxicity because of the wide variability in their absorption, metabolism, and excretion. Because patients often treat themselves, they may not realize that they are overdosing.
Abruptly stopping any of the agents used to treat migraines after long-term use can result in rebound (or new-onset) migraine headaches; therefore, they should be stopped very slowly.
n Patient and Family Teaching
Anticonvulsants or Antiepileptic Drugs
Overview
Seizures are sudden muscle contractions that happen without conscious control. They are a symptom of abnormal and excessive electrical discharge in the brain. A variety of diseases and disorders can produce seizures. High temperatures in infants and children may provoke seizures. One of the most common causes of chronic and recurring seizures is epilepsy, which is frequently of an unknown cause (idiopathic). Head injury, brain tumor, stroke, meningitis, temperature elevation, and poisoning, especially from excessive alcohol intake or drugs, are also common causes of seizure activity. The most frequent cause of a seizure is the failure to take medication to control previously diagnosed seizure activity. It is estimated that as many as 10% of all people will have a seizure during their lifetime, although this percentage may rise as more people abuse drugs. The diagnosis of epilepsy often has legal consequences, which vary among states, including restriction of driver’s licenses and restriction from operation of heavy machinery or doing other activities that require alertness. It is obvious how it might be a problem if someone were driving a car or big truck and suddenly had a seizure.
The terms epilepsy, convulsions, and seizures are commonly used to mean the same thing, although they each have a slightly different medical meaning. A variety of terms have been used over the years to describe types of seizures, including grand mal (tonic-clonic), petit mal (absence), psychomotor, myoclonic, atonic, and jacksonian. More recently, there has been agreement to group seizures into two broad categories, generalized or focal, based on their clinical presentation and electroencephalographic (EEG) patterns. This chapter uses both terms.
Sometimes surgery or dietary treatment may be used to control symptoms in a patient with a seizure disorder. More commonly, epileptic seizures are treated with medication. The goal of this type of therapy is to suppress or reduce the number of patient seizures.
Action
A number of drugs control seizures through depression or slowing of abnormal electrical discharges in the CNS. These products work in a variety of ways. There is usually one drug that is more effective than another for a patient, depending on the type of seizure activity. Patients with newly diagnosed and acute seizure disorders are often started on parenteral injection therapy; when seizure activity has come under control, oral therapy is started.
There are five major anticonvulsant or antiepileptic drug (AED) groups: barbiturates, benzodiazepines, hydantoins, succinimides, and γ-aminobutyric acid (GABA) analogues (Figure 16-2). A list of anticonvulsants and their uses is presented in Table 16-3. In addition to prescription medications, patients and families sometimes try a variety of supplements and herbal products to treat seizure disorders. The Complementary and Alternative Therapies box provides a list of common herbal products and drug interactions important for patients to know.
Complementary and Alternative Therapies
Epilepsy
| PRODUCT | COMMENTS |
| Bitter melon | Potential interactions with insulin, oral hypoglycemics |
| Ginkgo | Potential interaction with anticoagulants, aspirin, NSAIDs, antiplatelet drugs; may interact with MAO inhibitors, acetylcholinesterase inhibitors |
| Gymnema | Potential interactions with insulin, oral hypoglycemics |
Data from Krinsky DL, LaValle JB, Hawkins EB, et al: Natural therapeutics pocket guide, ed 2, Hudson, Ohio, 2003, Lexi-Comp, Inc.
Table 16-3
Antiepileptics and their Primary Uses
| GENERIC NAME | TRADE NAME | COMMENTS |
| Barbiturates | ||
| amobarbital | Amytal | Status epilepticus, acute convulsive episodes; also used for preoperative sedation and insomnia, preoperative anxiety and sedation |
| pentobarbital | Nembutal | General seizure, reduce ICP in head trauma; preoperative sedation, insomnia |
phenobarbital  |
Phenobarbital | All forms of epilepsy, status epilepticus, severe recurrent seizures, eclampsia |
| secobarbital | Seconal | Preoperative sedation; insomnia |
| Benzodiazepines | ||
| clonazepam | Klonopin | Petit mal, myoclonic seizures |
| clorazepate | Tranxene | Focal seizures |
diazepam  |
Valium | All forms of epilepsy, status epilepticus, severe recurrent seizures, tetanus |
| lorazepam | Ativan | Used for all seizures except febrile seizures |
| Hydantoins | ||
| fosphenytoin | Cerebyx | Status epilepticus |
| phenytoin | Dilantin | Used for partial seizures, status epilepticus |
| Phenytek | ||
| Succinimides | ||
| ethosuximide | Zarontin | Absence atonic seizures and myoclonic seizures |
| methsuximide | Celontin | Absence seizures; adjunct therapy in mixed seizures |
| phensuximide | Milontin | Absence seizures |
| GABA Analogs | ||
| tiagabine | Gabatril | Inhibits uptake of GABA into presynaptic neurons, prolonging GABA action; used for adjunctive therapy in adult partial seizures |
| Other Drugs | ||
| acetazolamide | Diamox | Absence seizures, metabolic alkalosis in mechanically ventilated patients, altitude sickness |
| carbamazepine | Tegretol | Status epilepticus, partial seizures |
| gabapentin | Neurontin | Partial seizures in adults, children |
| lamotrigine | Lamictal | Partial seizures in adults, children |
| levetiracetam | Keppra | Partial seizures in adults, children |
| oxcarbazepine | Trileptal | Partial seizures in adults, children |
| primidone | Mysoline | Grand mal, psychomotor, focal seizures in adults and children |
| topiramate | Topamax | Adjunctive therapy for partial-onset seizures in adults, children |
| valproic acid | Depakene | Used for all types of seizures |
| Depakote | ||
GABA, γ-Aminobutyric acid.
Indicates “Must-Know Drugs,” or the 35 drugs most prescribers use.
Uses
Barbiturates, which have a long duration of action, are an important category of prescription anticonvulsants and are used for their sedative effect on the brain. They may be used in combination with medications from the other three groups. Benzodiazepines are useful with some problems but also have a lot of serious adverse effects. Hydantoins have a wide range of uses, and phenytoin (Dilantin) is by far the most commonly used anticonvulsant. Succinimides are used to control petit mal seizures. GABA analogs have wide use for many types of seizures. Each of these five groups, along with a variety of other newer miscellaneous anticonvulsants, are discussed in this section.
Because of the variety of drugs and the many possible side effects, the choice of an anticonvulsant tends to be a trial or experiment for each patient. When seizures are not stopped with one drug, another may be added, or the first drug may be stopped and another product used instead.
Lifespan Considerations
Pediatric
Anticonvulsants
Modified from McKenry LM, Tessier E, Hogan MA: Mosby’s pharmacology in nursing, ed 22, St Louis, 2006, Mosby.
Lifespan Considerations
Older Adults
Anticonvulsants
Modified from McKenry LM, Tessier E, Hogan MA: Mosby’s pharmacology in nursing, ed 22, St Louis, 2006, Mosby.
Barbiturates
Action
Barbiturates are CNS depressants. They act primarily on the brainstem reticular formation, reducing nerve impulses that go to the cerebral cortex. Barbiturates depress the respiratory system and slow the activity of nerves and muscles (smooth, skeletal, and cardiac). Barbiturates also raise the seizure threshold, or the level of electrical activity that must be produced before a seizure will occur. Barbiturates may be short-acting, intermediate-acting, or long-acting.
Uses
Long-acting barbiturates are used as anticonvulsants to control and prevent grand mal seizures. They are sometimes used if other drugs do not help to treat status epilepticus, a condition in which a series of severe grand mal seizures occur one after another without stopping. They may also be used to treat seizures caused by tetanus, fever, or drugs.
Adverse Reactions
Adverse reactions to barbiturates include worsening of symptoms of certain organic brain disorders in older adult patients, dizziness, drowsiness, hangover, headache, lethargy (sleepiness), paradoxical restlessness or excitement, unsteadiness, photosensitivity (abnormal response to exposure to sunlight), rash, diarrhea, nausea, hepatitis with jaundice, vomiting, anemia, decreased platelet counts, unusual bleeding or bruising, urticaria (hives), joint and muscle pains, tolerance (increased resistance to the drug caused by repeated use), and withdrawal symptoms due to physical dependence when discontinued.
In cases of acute overdose, the patient may show exaggerated CNS depression, slow, shallow respirations, miosis, tachycardia, areflexia (absence of reflexes), shock, or coma. Death may occur as a result of cardiorespiratory failure.
Drug Interactions
Because barbiturates act through the P450 enzyme system to speed up the metabolism of some drugs in the liver, they reduce the activity of anticoagulants, corticosteroids, and digitalis preparations. MAO inhibitors may increase the depressant effects of the barbiturates. There may be significant additive effects if barbiturates are used along with alcohol, antihistamines, benzodiazepines, methotrimeprazine, narcotics, and tranquilizers.
Benzodiazepines
Action
Benzodiazepines are CNS depressants. Their exact mechanism of action is not known, but they are thought to act on the hypothalamus and limbic system of the brain, decreasing the vasopressor response and increasing the arousal threshold. Benzodiazepines suppress the electrical spike-and-wave brain discharge in seizures and decrease the frequency, amplitude, duration, and spread of the discharge in minor motor seizures.
Uses
Benzodiazepines are used to treat partial seizures and also to treat Lennox-Gastaut syndrome (petit mal variance) and for patients who have failed to respond to succinimide drugs such as ethosuccinimide (Zarontin). Three benzodiazepines are approved for use as anticonvulsants. Diazepam (Valium) is used intravenously to control seizures and is the drug of choice for treatment of status epilepticus. Clonazepam (Klonopin) is used for oral treatment of petit mal seizures in children, and clorazepate (Tranxene) is used with other antiepileptic agents to control partial seizures.
Adverse Reactions
Adverse reactions to benzodiazepines include hypotension (low blood pressure), shortness of breath, difficulty focusing or blurred vision, confusion, drowsiness, flushing (red color in the face and neck), headaches, light-headedness, paradoxical reactions (excitement, stimulation, hyperactivity), slurred speech, sweating, anorexia (lack of appetite), bitter taste, dry mouth, diarrhea, heartburn, nausea, vomiting, pruritus, rash, joint pains, and burning eyes.
Overdosage may produce marked drowsiness, weakness, impairment of stance and gait, confusion, and coma.
Drug Interactions
Alcohol, other sedatives and hypnotics, antidepressants, anticonvulsants, and narcotics may produce additive sedative effects if used with benzodiazepines. Some combinations of anticonvulsants may result in an antidepressant effect or provoke additional seizures.
Hydantoins
Action
Hydantoins act primarily on the motor cortex, where they stop the spread of seizure activity by blocking neuronal sodium and calcium channels. This stabilizes the nerve cell against hyperexcitability and reduces the maximal activity of brainstem centers responsible for the tonic phase of grand mal seizures. It also has an antiarrhythmic property.
Uses
Hydantoins are used to treat tonic-clonic and psychomotor seizures. Sometimes they are used to treat status epilepticus, migraine, and trigeminal neuralgia. They are also used in some nonepileptic psychotic patients.
Adverse Reactions
Adverse reactions to hydantoins include ataxia (poor coordination), dizziness, drowsiness, hallucinations, inattentiveness, nystagmus (rhythmic movement of the eyes), ocular disturbances, poor memory, slurred speech, constipation, nausea, vomiting, blood cell disturbances, purpura (bruising), acnelike eruptions, gingival hyperplasia (overgrowth of gums), lupus erythematosus, hepatitis with jaundice, and lymph node hyperplasia. Hydantoins are also teratogenic-category D (producing changes in the fetus). Overdosage may produce ataxia, coma, dysarthria, hypotension, nystagmus, and unresponsive pupils.
Drug Interactions
Hydantoin drug interactions are frequent and often substantial. Even when given alone, the drug requires careful monitoring of the patient. It is very important to see the patient regularly when it is used with any other medication or vitamins because the dose that prevents seizure is very close to the toxic dose. It may also alter the results of various laboratory tests.
Succinimides
Action
Succinimide-type anticonvulsants raise the seizure threshold in the cortex and basal ganglia, making seizures less likely and reduce response at the nerve synapse to some specific types of nerve stimulation.
Uses
Succinimides are used to control absence seizures.
Adverse Reactions
Adverse reactions to succinimides include dizziness, headaches, hiccups, hyperactivity, lethargy, mood or mental changes, rashes, blurred vision, photophobia (intolerance to light), anorexia, abdominal pain, diarrhea, nausea, vomiting, urinary frequency, vaginal bleeding, blood cell changes, alopecia (hair loss), muscular weakness, systemic lupus erythematosus, disturbances of sleep, inability to concentrate, mental slowness, and night terrors.
Drug Interactions
If these drugs are used with other anticonvulsants, they can result in increased sex drive (libido) or increased frequency of tonic-clonic seizures. Bone marrow–depressing drugs used with succinimides can result in significant and fatal blood dyscrasias or conditions.
γ-Aminobutyric Acid Analogs (GABA)
Action
The mechanism of action for GABA analogs is not clearly understood. All of these drugs are chemically unrelated but they all increase the actions of GABA, which is an inhibitory neurotransmitter. It is thought that they might slow the sodium channel, helping to stabilize the neuronal membranes. Some of the newer GABA analogs also increase the action of GABA, block voltage of sodium channels, antagonize glutamate, and modulate calcium channels.
Uses
Although relatively new drugs, GABA analogs are used in the treatment, along with other antiepileptic drugs, for simple partial, complex partial, secondarily generalized, generalized tonic-clonic, and absence seizures. These medications are also used in treating peripheral neuropathy, post-herpatic neuralgia, and fibromyalgia.
Adverse Reactions
Adverse reactions include GI disturbances; weight gain; irregular menses; alopecia; pruritus; rashes, including erythema multiforme; photosensitivity; hair loss; anxiety; mood problems; tremor; and nervousness. Drowsiness and ataxia that are dose-dependent may also be seen. Inattention, anorexia, paresthesias, and renal stones may also be produced by some drugs.
Drug Interactions
Increased CNS depression may occur when valproic acid is administered with other CNS depressants, including other anticonvulsants and alcohol. These drugs interact with many other CNS drugs and may increase or decrease their blood levels. This is particularly true of phenytoin. It is advisable to monitor serum concentrations of any other anticonvulsants being used with these drugs to prevent overdosage.
Other Drugs
A variety of other products that are chemically unrelated have been in use for years in the treatment of seizures. New products continue to be developed in efforts to obtain better seizure control with reduced side effects. These products and their uses are listed in Table 16-3. All of these products have widespread usage for many different neurologic problems. Some also have other indications. For example, Valproic Acid (Depakote) is widely used in patients with bipolar symptoms and for migraine headaches.
Memory Jogger
Drug Dependence
Dependence can develop with indiscriminate use, and abrupt withdrawal is dangerous. These drugs must be carefully monitored and the patient must return for evaluation regularly.
Nursing Implications and Patient Teaching
n Assessment
Learn as much as possible about other drugs currently being taken that may produce drug interactions. Ask about other anticonvulsants, response to anticonvulsants taken in the past, hypersensitivity (allergy), and the possibility of pregnancy. Cardiac, respiratory, hepatic, or renal diseases are contraindications or precautions to the use of anticonvulsants.
n Diagnosis
For patients who are just starting on an antiseizure medication, find out what particular fears or concerns they have, as well as specific learning deficits. The diagnosis of these problems will help the nurse develop an appropriate nursing care plan to meet those needs. If the patient has alcohol and drug abuse problems, there may be problems with drug withdrawal, legal issues, or difficulties with compliance that will need to be part of the care plan.
n Planning
Older adult or weakened patients may be more sensitive to barbiturates and should be started on lower dosages. These patients are more likely to have hangover, confusion, and delirium.
Several of the anticonvulsant medications may produce blood dyscrasias or systemic lupus erythematosus. Benzodiazepines are changed by the liver into long-acting forms that may remain in the body for 24 hours or more and produce increased sedation; liver function may be affected with long-term use. In addition, there is a risk of congenital malformations and neonatal depression with most anticonvulsants, if used during pregnancy.
n Implementation
Barbiturates are legally controlled substances. They should not be given to patients with a history of abuse or addiction. Barbiturates should not be given to patients in pain, because these drugs may worsen the pain. When barbiturates are given parenterally, use great caution to avoid accidentally allowing the medicine to infiltrate tissues, because serious ischemia or gangrene could result. One of the major problems with this whole class of drugs is that they cause respiratory depression. This side effect has caused clinicians to turn to other drugs as they have become available.
When benzodiazepines are used in patients who have a mixed type of seizure activity, the drugs may increase or cause the onset of generalized tonic-clonic seizures. These drugs should also be used with caution in patients with poor or reduced renal function. Stopping the drugs quickly can produce status epilepticus.
The dosage of benzodiazepines is individualized for each patient, depending on the patient’s response. The onset of action is about for oral medicine is 30 to 60 minutes, and the effects last 7 to 8 hours. The drug should be given 15 to 30 minutes before bedtime. Older adult or weakened patients should receive reduced dosages of all anticonvulsants. It is important to very slowly increase or decrease dosages.
Oral phenytoin (Dilantin) suspension is often difficult to give accurately. The oral suspension should be shaken well before being given, and the liquid should not be frozen. Chewable tablets should not be used for once-a-day treatment.
Clinical Goldmine
Oral DilantinTherapy
There are two types of oral Dilantin therapy: “prompt” and “extended” capsules. Capsules labeled “extended” are given only once a day. Capsules labeled “prompt” are given two or three times a day. Giving the wrong type of therapy could result in either undermedication or overmedication.
Subcutaneous or perivascular (around the veins) injection of hydantoins should be avoided because of the highly alkaline nature of the solution. Hydantoins should be administered very slowly when given intravenously.
Talk to the patient and family about the chance of brief but short-term personality changes with phensuximide therapy. These should be reported to the nurse, physician, or other health care provider if they occur.
Once the patient is seizure-free with a particular drug, changing to phenytoin (Dilantin) products should be avoided. All dosages must be determined for the individual. The dosage for children is usually larger by weight than for adults. The patient is usually given a single dose within the therapeutic range, and then the amount is gradually increased until the seizures are controlled and the serum levels are stable, or until symptoms of overdosage or toxicity indicate that no further increases can be made.
Table 16-4 provides a list of important information about anticonvulsants, including dosages. A variety of miscellaneous anticonvulsants are also available. See Tables 16-2 and 16-3 for brief information about those products. Felbamate (Felbatol) has been used for partial seizures and Lennox-Gastaut syndrome. Enough cases of aplastic anemia and hepatic failure have developed from use of this drug that it carries a warning regarding its use.
Table 16-4
| GENERIC NAME | TRADE NAME | COMMENTS |
| Barbiturates | ||
| Long Acting | ||
phenobarbital  |
Luminal | Give IM in large muscle mass, because injection is very painful. Give slowly IV. |
| Phenobarbital | Some forms come in sustained-release capsules. Onset in 1 hr, effective for 16 hr. | |
| Benzodiazepines | ||
| clonazepam | Klonopin | Give initial doses. After 4-9 days, dosage may be increased by 0.5-1.5 mg/day every 3 days until seizures stop or until side effects prevent any further increase. |
| Whenever possible, give in 3 equally divided doses; if this is not possible, give the largest dose before bedtime. | ||
| clorazepate | Tranxene | |
diazepam  |
Valium | Comes PO, sustained-release capsules, and IV. |
| Parenteral therapy: Inject IV medication slowly only into large veins, 1 min for each 5 mg. May cause respiratory arrest if this is exceeded. | ||
| Hydantoins | ||
| fosphenytoin | Cerebyx | Continuously monitor ECG and vital signs. |
phenytoin  |
Dilantin | Monitor blood levels carefully. Watch for adverse neurologic effects. |
| Succinimides | ||
| phensuximide | Shake suspension well before pouring. Take drug with meals to decrease gastric discomfort. Efficacy of the drug decreases with long-term use. | |
| Miscellaneous Anticonvulsants | ||
| acetazolamide | Diamox | |
| carbamazepine | Tegretol | |
| gabapentin | Neurontin | Add-on therapy for patients older than 12 yr. Effective. |
| lamotrigine | Lamictal | Consult package insert for complex dosing instructions. |
| topiramate | Topamax | |
| valproic acid | Depakene | |
ECG, Electrocardiogram; IM, intramuscular; IV, intravenous; PO, by mouth.
Indicates “Must-Know Drugs,” or the 35 drugs most prescribers use.
n Evaluation
It takes several weeks before the success of an anticonvulsant dosage plan can be seen. The therapeutic effects should be monitored. Note seizure pattern and change. Note whether or not the sedation is a problem. Blood levels may be needed to see if the drug dosage is in the therapeutic range.
The patient’s compliance should be followed in regard to the amount of and times the drug is taken, any pattern of abuse, and drinking of alcohol. In addition, the patient should be asked about any paradoxical reactions and evaluated for tolerance, dependence, withdrawal, and toxicity. Liver toxicity is indicated by jaundice (yellow color of skin, eyes, and mucous membranes), rash, and sore throat.
The patient should keep a record of any seizures, with information about the time, length, characteristics, and reaction.
Complete blood cell counts and liver function tests should be followed as a baseline and repeated on a set schedule for patients on long-term barbiturate therapy.
Tolerance is usually related to the total amount of drug received. Dependence and withdrawal symptoms may occur if these drugs are used for very long periods. If the patient has been taking the drug for a long time, the drug should not be discontinued quickly.
Hydantoins are metabolized at various rates by patients; therefore, be alert to symptoms of toxicity. The patient should avoid alcohol while taking most anticonvulsants.
Adverse effects are common in long-term therapy. Gum overgrowth around the teeth (hyperplasia) is a typical finding with phenytoin (Dilantin) and may cause distress to the patient and family. The patient and family must be educated about how to prevent and treat this problem.
Memory Jogger
Oral Hygiene
Hydantoins may be associated with overgrowth of gum tissue in the mouth. The importance of good oral hygiene, especially of gums, should be emphasized to patients taking phenytoin (Dilaintin).
n Patient and Family Teaching
Tell the patient and family the following:
• Tablets and capsules should be kept in a dry, tightly closed container.
• Elixirs should be kept in a tightly closed, brown, glass bottle.
• Smoking may decrease the length of time benzodiazepines are effective.
• The liquid form of ethosuximide (Zarontin) should be shaken well before the dose is measured.
• Succinimide agents may make the urine appear pink, red, or reddish brown.
• Chewable tablets must be chewed or crushed before they are swallowed.
Memory Jogger
Alert Regarding Staying with the Same Brand
The patient must not change the brands or dosage forms unless ordered to do so by the nurse, physician, or other health care provider. Not all brands of these medications are the same so they cannot be substituted for each other (they are not interchangeable). This means that prescriptions for a particular brand of medication will be written by the provider. Once a patient’s seizures are controlled with a certain brand, the patient should continue to receive that brand. This is important for the patient to discuss with his or her pharmacist and they should be asked to make sure their medicines are the same each time the prescription is filled.
Antiemetic-Antivertigo Agents
Overview
Antiemetic or antivertigo agents are used to prevent and treat motion sickness and the nausea and vomiting that occur with anesthesia and surgery or cancer treatment. They are also used to treat severe, intractable (cannot be stopped by the usual treatment methods) vomiting and hiccups.
Action
The vomiting center of the brain may be stimulated by many factors: drugs, metabolic disorders, radiation, motion, gastric irritation, and vestibular neuritis. Vomiting is produced by direct action on the vomiting center of the brain, by indirect action through stimulation of the chemoreceptor trigger zone, and through increased activity of chemical neurotransmitters. Nausea and vomiting resulting from motion are probably caused by impulses to the vestibular network of the labyrinth system of the ear, which is located near the vomiting center. The impulses are conducted to the vomiting center by cholinergic nerves. Thus drugs that inhibit cholinergic nerve impulses should be effective in treating motion sickness.
Uses
Antidopaminergic agents such as chlorpromazine (Thorazine) and prochlorpromazine (Compazine) are used almost exclusively to control nausea and vomiting. Selected first generation H1 blocker antihistamine/anticholinergic medications are used to control motion sickness. Meclizine (Antivert) and dimenhydrinate (Dramamine) are the only products used to control acute vertigo. 5-HT3 antagonists such as ondansetron (Zofran) are routinely used prophylactically in patients expected to have nausea (e.g., patients undergoing chemotherapy).
