Calculating Antibiotics Measured in Units

Penicillins G and V are products measured in the unit system, as are other antimicrobials such as nystatin suspension. In many cases, these medications are available in a powdered form that requires reconstitution before administration. The information on the drug label will inform you about the type and amount of needed diluent. If the label does not specify the needed diluent, in most cases the diluent will be provided with the powdered medication. In some cases the label also provides different strengths for the medication that can be prepared by the amount of diluent added (Figure 11-1). If you need to review the necessary steps for reconstitution of medications, see Chapter 9.

Practice Problems A

Calculate the following problems and if reconstitution is necessary, decide on the amount of diluent that would best provide the dose ordered with the least volume of medication per dose, whether for injection or oral administration. Use ratio and proportion or formula method for calculations. Show your calculations. Round your final answers to the hundredth unless the question asks for a measurable dose.

1. A physician orders penicillin G potassium 750,000 units to be added to IV fluids for a postoperative patient. The following label is the medication available for use for administration.

What volume of diluent should be added to the medication for the strength to be 500,000 units/mL? ____________________

What volume of medication should be added to the IV fluids? _______________________

What volume of medication would be left in the vial after medication is prepared? _______________________

Should the residual medication be diluted to another dosage strength? _______________________ Explain your answer ____________________

Which syringe for injection should be used to prepare the medication for addition to IV fluids? _______________________

2. A physician orders Pfizerpen 800,000 units to be added to IV fluids. Use the label in Problem No. 1 for calculation.

What amount of diluent is added to the vial for medication strength of 250,000 units/mL? _______________________

What volume of medication should be prepared for a patient dose? _______________________

What volume of medication would remain in the vial following preparation of the ordered medication? _______________________

Show the documentation that would be needed on the vial, using today’s date and time as guide if necessary. _______________________

How long would the medication be stable in the vial following reconstitution? _______________________

Which syringe should be used to add the medication to the IV fluids? _______________________

3. A patient with severe bronchitis has an order for penicillin V 250,000 units qid. The medication on hand is oral penicillin V 400,000 units/5 mL.

What volume of medication should be given to the patient with each dose? _______________________

Which measuring device should be included with the prescription for the patient to take the medication at home? _______________________

What is the measurable dose? _______________________

If the patient should misplace the measuring device provided, how could this be estimated using household utensils? _______________________

4. A physician orders V-Cillin K tablets 800,000 units to be given bid. The available medication is V-Cillin K 400,000-unit tablets.

What number of tablets should be administered per dose? _______________________

5. A physician orders penicillin G 450,000 units IM daily for 4 days. The available medication is penicillin G 300,000 units/mL.

What volume of medication should be administered to the patient daily? _______________________

What type of syringe would be needed to administer this strength of medication? _______________________

6. A physician orders penicillin G 750,000 units IM q12h for a patient with a severe bacterial infection. The available medication is penicillin G 300,000 units/mL.

Interpret the order. __________________________________________________________________

What volume of medication should be administered with each dose? _______________________

Show the correct amount of medication on the correct syringe in the following illustrations.

7. A physician orders penicillin G 500,000 units IM q6h. The label reads 1,000,000 units/vial.

If 4 mL of diluent is added to the vial, what is the resultant strength of the penicillin? _______________________

What volume of medication should be prepared for administration? _______________________

How long would this medication be stable after reconstitution? _______________________

Where should the medication be stored after reconstitution? _______________________

What is the total strength of medication in the vial? _______________________

Mark the label with the correct documentation following reconstitution, using today’s date, time, and initials if applicable.

What size syringe should be used for administration of the drug? _______________________

8. A physician orders Mycostatin Oral Suspension 300,000 units to be administered bid in divided doses for each side of mouth. The available medication is shown on the following label.

What volume of medication should be administered with each dose? _______________________

If the dose is to be divided between each side of the mouth, what volume of medication should be placed in each side? _______________________

Which measuring device would provide the dosage amount most accurately? _______________________

Indicate the amount of medication on the measuring device to be used.

9. A physician orders penicillin V oral suspension 200,000 units po qid. The medication available is penicillin V oral suspension 400,000 units/5 mL.

Interpret the order. _______________________________________________________________

What volume of medication should be administered to the patient? _______________________

How can this be administered using household measuring devices? _______________________

Indicate the amount of medication on the measuring device to be used.

10. A physician orders penicillin G procaine suspension 600,000 units IM bid for a patient with a severe infection. The available medication is shown on the following label.

What are the directions for storing this medication? _______________________

What volume of penicillin should be administered to this patient? _______________________

11. A physician orders Bicillin L-A 425,000 units IM. The available medication is found on the following label.

What volume of medication should be administered to the patient? _______________________

What is the measurable dose of medication? _______________________

Which syringe should be used to provide the medication? _______________________

Indicate the amount of medication on the proper syringe.

12. A physician orders penicillin G potassium 450,000 units IM as a stat dose. The available medication is on the following label.

What is the appropriate concentration of penicillin G potassium on the label for dispensing the medication for this order? _______________________

What volume of diluent should be added to prepare the medication for administration of the desired dose? _______________________

What volume of medication is to be administered following reconstitution? _______________________

What is the proper storage of this medication following reconstitution? _______________________

Show the proper documentation for the reconstitution on the label provided; use today’s date, time, and initials as appropriate.

Which syringe is appropriate for the administration of the medication? _______________________

13. A physician orders penicillin G 300,000 units IM. A medication vial containing penicillin G 5,000,000 units is available. Directions for reconstitution state to add 8 mL of sterile water to provide a 500,000 units/mL medication.

What volume of medication should be administered? _______________________

Show the volume of diluent to be added on the proper syringe.

Show the volume of medication to be administered on the proper syringe.

Label each syringe with either diluent or medication.

14. A physician orders penicillin G potassium 125,000 units q6h. The vial contains penicillin G potassium 1,000,000 units. The reconstituted strength is penicillin G potassium 250,000 units/mL.

What volume of medication should be administered? _______________________

What is the measurable dose? _______________________

Show the volume of medication on the correct syringe for administration.

15. A physician orders penicillin G potassium 50,000 units/kg/d in two divided doses for a patient who weighs 220 lb. The available medication is penicillin G potassium 2,000,000 units/mL.

What is the total dosage of medication to be given in a day? _______________________

What is the measurable dose in a 3 mL syringe? _______________________

What volume of medication is to be given to the patient to provide each ordered dose? _______________________

16. A physician orders penicillin G benzathine 2,400,000 units IM stat for syphilis. The available medication label reads penicillin G benzathine 600,000 units/mL.

What volume of medication should be administered? _______________________

If the medication must be measured from a vial, what syringe should be provided to accurately measure the medication for administration? _______________________

17. A physician orders penicillin G IV for severe strep throat for a 66-lb child to prevent strep pneumonia. The normal dose is 150,000 units/kg/day in four divided doses.

What total dose of medication should be given in a day? _______________________

What dose of medication should be administered with each dose? _______________________

What volume of medication should be administered per dose if the label reads penicillin G 1,000,000 units/50 mL? _______________________

18. A physician orders Mycostatin 200,000 units at bedtime vaginally for a patient with a Candida infection. The available medication is labeled Mycostatin Vaginal Suppositories 100,000 units.

How many suppositories should be used by the patient each night? _______________________

19. A patient is being given prophylactic treatment for rheumatic fever. The physician orders penicillin G benzathine 1,200,000 units qmo for this patient. The medication is available as penicillin G benzathine 300,000 units/mL for IM administration.

What volume of medication should be provided with each dose? _______________________

20. Mrs. Jones, an elderly patient, has chronic sinusitis. The physician orders penicillin V 300,000 units po qid. The available medication is penicillin V 400,000 units/5 mL.

What volume of medication should be administered to this patient with each dose? _______________________

What measuring device should be included with the prescription for home administration? _______________________

Mrs. Jones calls and states the measuring device given to her to take the medication was stepped on and broken. How would you tell her to take the medication using a household measuring device? _______________________

Explain why using the household measuring device would not provide an accurate dose of medication. _________________________________________________________________

Calculating Insulin Doses in Units

Insulin, which is used to control type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) in some persons whose elevated blood sugar cannot be adequately controlled with oral hypoglycemics, is prescribed and measured in units. Most insulin preparations are only available in U-100 strength, meaning that each milliliter of insulin contains 100 units of medication. Even insulin preparations that are combinations of regular insulin and intermediate-acting insulins are in U-100 specifications. See Figure 11-2 for labels for different insulin preparations.

To administer insulin preparations, insulin syringes that are calibrated in 100 units/mL must be used; no other syringe is based in units for insulin (in an emergency a tuberculin syringe could be used because it is also calculated in hundredths of milliliters). The design of the syringe makes it easy to ensure that the exact dose of medication ordered is administered. Syringes come in 30-, 50, and 100-unit calibrations (Figure 11-3). Some 100-unit insulin syringes are available in two-unit increments, while others are marked in one-unit increments with two-unit increments of odd/even on each side of the syringe barrel. To further complicate matters when preparing insulin for administration, you will find some syringes are in one-unit increments with the markings on the same side of the syringe. Please note that syringes holding a smaller quantity such as 30-unit and 50-unit syringes are in one-unit increments and are easier to use by patients who have visual problems, a common complication of long-term or uncontrolled diabetes mellitus. Insulin syringes should not be used for measuring any medication other than insulin—not even for heparin or antibiotics.

Insulin preparations are also labeled by the type of insulin in the vial. An abbreviation of “R” indicates that the medication is rapid, short-acting, regular insulin. NPH insulin that is intermediate acting with a longer onset of action is marked with “N” (Table 11-1). Care must be taken to ensure that the correct insulin is chosen and delivered to the patient. For that reason, manufacturers have placed large letters on the vials showing the exact type of insulin contained.

Only regular insulin may be given IV. If different types of insulin need to be administered at the same time, the same source of the insulin such as DNA or recombinant sources must be used together. Different sources of insulin cannot be mixed in the same syringe. If patients are changed from one source of insulin to another or from one manufacturer to another, the dose of insulin may require recalibration because each source of insulin reacts just a little differently.

The order for insulin is always to be administered subcutaneously (except IV use)and in units, such as regular insulin 45 units subcuatneously qam. However, regular insulin and some analogs may be administered intravenously. After the order has been written, the exact medication ordered must be obtained and then drawn into the insulin syringe to the level of units ordered.

Practice Problems B

Using the following labels, choose the correct label and indicate the correct dose on the appropriate syringe. Indicate the syringe to be used by the number of units that can be administered using the chosen syringe. If two types of insulin are necessary to supply the order, indicate the volume of each, as well as the total volume to be administered on separate syringes and label each syringe. Show your calculations. If answers need to be rounded, round to the nearest tenth.

1. A physician orders Humulin N insulin 45 units subcutaneously to be given qam.

Which vial of insulin should be used for this order? _______________________

Which syringe should be used to supply the medication to the patient? _______________________

2. A physician orders Humulin R 30 units subcutaneously 30 min ac for a person with poor eyesight.

Which vial of medication should be used for this order? _______________________

Which syringe should be used to supply the most accurate dose of medication to the patient? _______________________

3. A physician orders Humulin N 55 units subcutaneously qam.

Which vial of insulin should be used for this order? _______________________

Which syringe should be used to supply the medication to the patient? _______________________

4. A physician orders Humulin 70/30 42 units subcutaneously qam.

Which vial of insulin should be used to fill this order? _______________________

Which syringe should be used to supply the medication to the patient? _______________________

5. A physician orders Humalog 66 units subcutaneously ac.

Which vial of insulin should be used to complete this order? _______________________

Which syringe should be supplied to the patient for administration of the ordered dose? _______________________

6. A physician orders Novolin R 23 units subcutaneously qam for an elderly patient.

Which vial of medication should be supplied to the patient? _______________________

Which syringes should be supplied to fill the order to ensure patient safety? _______________________

7. A physician orders Lantus insulin 52 units subcutaneously hs.*

Which vial of medication should be supplied to the patient? _______________________

Which syringe should be supplied to fill the order for home administration? _______________________

8. A physician orders Humulin R 47 units 30 min ac.

Which vial of medication should be used to supply this medication? _______________________

If a syringe is appropriate, which one would be used? _______________________

9. A physician orders Humulin 50/50 51 units qam.

Which vial of medication should be used to supply this medication? _______________________

Which syringe should be supplied for the order? _______________________

10. A physician orders Humulin 70/30 30 units and Humulin R 22 units qam.

Hint: 70/30 means that in each 100 units of insulin, 70% is NPH insulin and 30% is regular insulin.

Which vial(s) of medication should be used to supply this medication? _______________________

Which syringe should be used to administer this medication? _______________________

How many units of regular insulin should the patient receive per day? _______________________

How many units of NPH insulin should the patient receive per day? _______________________

11. A physician orders Lantus insulin 23 units and Humulin R 35 units qhs.*

Hint: Lantus insulin cannot be mixed with other insulin preparations.

Which vials of medication should be used to supply this medication? _______________________

Which syringe(s) should be used to administer the medications? _______________________

12. A physician orders Humulin N 21 units and Humulin R 36 units qam.

Which vials of medication should be used to fill this order? _______________________

Which syringe(s) should be used to administer this medication? _______________________

13. A physician orders Humulin R 24 units and Humulin N 43 units qam.

Which vials of medication should be used to fill this order? _______________________

Which syringe(s) should be used to administer this medication? _______________________

14. A physician orders Lantus 15 units and Humulin R 15 units at bedtime.

Which vials of medication should be used to fill this order? _______________________

Which syringe(s) should be used to administer this medication? _______________________

15. A physician orders Humulin N 36 units and Humulin R 27 units qam.

Which vials of medication should be used to fill this order? _______________________

Which syringe(s) should be used to administer this medication? _______________________

16. A physician orders Humulin 70/30 37 units qam.

Which vial of medication should be used to fill this order? _______________________

How many units of NPH insulin would be administered? _______________________

How many units of regular insulin would be administered? _______________________

Which syringe(s) should be used to administer this medication? _______________________

17. A physician orders Humulin R 15 units and Humulin N 25 units qam.

Which vials of medication should be used to fill this medication order? _______________________

Which syringe(s) should be used to administer this order? _______________________

18. A physician orders Humalog 17 units ac.

Which vial of medication should be used to fill this medication order? _______________________

Which syringe should be used to administer this medication? _______________________

19. A physician orders Humulin 50/50 21 units qam for an elderly person with diminished eyesight.

Which vial of medication should be used to fill this order? _______________________

How many units of regular insulin would be administered? _______________________

How many units of isophane insulin would be administered? _______________________

Which syringe should be used to administer this medication to an elderly patient to administer a safe dose? _______________________

20. A physician orders Humulin N 21 units and Humulin R 21 units qam.

Which vials of medication should be used to fill this order? _______________________

Which syringe(s) should be used to administer this medication? _______________________

---

^*These abbreviations are found on the TJC Do Not Use List and ISMP’s List of Error-Prone Abbreviations, Symbols, and Dose Designations due to medication safety issues. They should not be used. You are being tested on them here because these abbreviations may still appear in the pharmacy setting.

^*These abbreviations are found on the TJC Do Not Use List and ISMP’s List of Error-Prone Abbreviations, Symbols, and Dose Designations due to medication safety issues. They should not be used. You are being tested on them here because these abbreviations may still appear in the pharmacy setting.

Calculating Anticoagulant Doses in Units

Heparin is an injectable anticoagulant measured in units. Heparin may be used as a flush for an IV injection site, as an IV infusion additive to keep the IV line patent, or as a deep subcutaneous injection into fatty tissue. The doses for heparin are highly individualized based on body weight and blood coagulation laboratory values. Because heparin prolongs bleeding times, or the time that it takes blood to clot, an accurate dose is of utmost importance. A dose that is larger than necessary may cause hemorrhage, while a dose that is insufficient may not produce the necessary results to prevent clot formation and possible thrombi.

Some low molecular weight heparins, such as Fragmin (dalteparin sodium), are also measured in units, though some, like Lovenox (enoxaparin) are measured on a milligram basis. These do not have the short half-life of heparin. As with heparin, these medications are primarily administered subcutaneously.

Heparin is available in various strengths from 10 units/mL (pediatric heparin flush strengths) to 20,000 units/mL. Injections of heparin for subcutaneous administration should be measured using tuberculin syringes. The dose may be calculated using ratio and proportion, dimensional analysis, or formula methods as found with other dosage calculations.

Example 11-1

A physician orders heparin sodium 5000 units subcutaneously stat. The medication available is heparin sodium 5000 units/mL. Using the formula method, the equation is as follows:

< ?xml:namespace prefix = "mml" />Dose desired(DD)Dose on hand(DA)×Quantity(Qty)=Dose to be given(DG)

5000units5000units×1mL=DG

DG=1×1mLor1mL

Using ratio and proportion the equation would appear as follows:

5000units(DA):1mL(Qty)::5000units(DD):x(DG)

5000x=5000×1mL

x=1mL(DG)

Using dimensional analysis the equation would be as follows:

DG=5000units(DD)1×1mL(qty)5000units(DA)

DG=1mL

Practice Problems C

Calculate the following medication orders using the labels provided with each practice problem. Round your answers to hundredths for measurement on tuberculin syringes. Indicate the amount of medication on the syringe provided. Show your calculations.

1. A physician orders heparin sodium 5000 units subcutaneously.

What volume of medication should be given to the patient for this dose? _______________________

2. A physician orders heparin sodium 1000 units subcutaneously.

What volume of medication should be administered? _______________________

3. A physician orders Fragmin 4000 International units subcutaneously.

What volume of medication should be given to this patient? _______________________

4. A physician orders heparin sodium 2500 units subcutaneously to be given stat.

What volume of medication should be administered to this patient? _______________________

5. A physician orders heparin sodium 17,500 units subcutaneously stat.

What volume of medication should be administered to the patient? _______________________

6. A physician orders heparin sodium 15,000 units subcutaneously.

What volume of medication should be administered? _______________________

7. A physician orders Fragmin 2500 International units subcutaneously stat.

What volume of medication should be administered? _______________________

8. A physician orders heparin sodium 12,000 units subcutaneously.

Which vial of medication is more appropriate to be used to prepare this medication? _______________________

What volume of medication should be administered? _______________________

9. A physician orders heparin sodium 7500 units IV stat.

Which vial of medication is more appropriate to be used to prepare this medication? _______________________

What volume of medication should be given to the patient? _______________________

10. A physician orders heparin sodium flush 25 International units IV.

What volume of medication should be prepared for the flush? _______________________

11. A physician orders heparin sodium 1500 units subcutaneously daily.

What volume of medication should be administered? _______________________

12. A physician orders heparin sodium 600 units subcutaneously stat.

What volume of medication should be administered? _______________________

How many minims would be given to the patient? _______________________

13. A physician orders Fragmin 6000 International units stat.

What volume of medication should be administered? _______________________

14. A physician orders heparin sodium 2250 units IV stat.

Which vial of medication is more appropriate to be chosen for administration? _______________________

What volume of medication should be administered? _______________________

15. A physician orders Fragmin 1200 International units subcutaneously stat.

What volume of medication should be administered? _______________________

What is the total volume of medication in the vial? _______________________

16. A physician orders heparin sodium 10,000 units to be added to IV fluids.

Which vial of medication would be the more appropriate for drawing the medication to add to the fluids? _______________________

What volume of medication should be added to the fluids? _______________________

Show the amount of medication that would be administered from vial A.

Show the amount of medication that would be administered from vial B.

17. A physician orders heparin sodium 6000 units stat.

What volume of medication should be administered? _______________________

Show the amount on the correct syringe.

18. A physician orders heparin sodium 40,000 units added to IV fluids to be given over 12 hours. The available heparin label reads 50,000 units/mL.

What volume of medication should be administered to the patient? _______________________

Which type of syringe should be used to prepare the medication? _______________________

19. A physician orders heparin sodium 1750 units IV stat.

After deciding on the appropriate vial of medication to use, what volume of medication should be administered? _______________________

Which vial of medication would be better to use? _______________________

20. A physician orders heparin sodium 12,500 units subcutaneously stat.

What volume of medication should be given if the label reads heparin sodium 50,000 units/mL? _______________________

Calculating Medications Measured in Milliequivalents

Chemical compounds in solution may dissociate or detach into particles that carry electrical charges called ions. Dissociated substances are also called electrolytes. For example, potassium (K) carries a positive electrical charge (+), and chlorine (Cl) carries a negative charge (–). When positive K (K⁺) ions and negative Cl (Cl^–) ions move in the same direction and combine, potassium chloride (KCl) compound is formed. To begin calculation of the milliequivalent of a compound such as potassium chloride, the atomic weight and the ionic charge of the components of the compound must be known. To obtain this information, a periodic table such as the one found on the inside back cover is used. Looking at the periodic table, you know that potassium has an approximate atomic weight of 39, and chlorine has an approximate atomic weight of 35. Thus the approximate atomic weight of the two elements together is 74 (39 [K] + 35 [Cl] = 74 [KCl]). A milliequivalent represents the amount of active ingredients equal to 1/1000 of the gram equivalent weight of the element or compound. For example, the potassium chloride shown earlier has a molecular weight of 74.5. To find the weight of 1 milliequivalent (mEq), 74 g KCl × 1/1000 = 0.074 g, or 74 mg is one mEq of potassium chloride. A milliequivalent is measured as the grams of a drug dissolved in a volume of solute such as milliliters or liters. Thus when a drug is labeled in milliequivalents (such as potassium chloride 40 mEq/mL), the meaning is that 40 thousandths of a gram (or 40 mg) of potassium chloride are found in 1 mL of solute. Thus if a container of medication shows KCl 40 mEq/mL, the medication has a strength of approximately 2960 mg (40 mEq × 74 [molecular weight]) of KCl per milliliter.

Most electrolytes, such as potassium, sodium, and chlorides, are measured in milliequivalents. Although the metric measurement may be seen on the same label as milliequivalents, a direct conversion between milliequivalents and other measurement systems cannot be made. Either the equivalency of milliequivalents or the metric system measurement must be used for the conversion, but milliequivalents cannot be converted to exact metric equivalences.

Millimole is the term used for calculation of electrolyte concentration in the International System of measurement and is expressed as millimoles per liter (mmol/L). A mole is the molecular weight of a substance in grams, just as found with milliequivalents. Just as with calculation of milliequivalents, the approximate molecular weight of a compound is calculated from the periodic table, and the millimole is the numeric value found when the components of the compound are added. So a millimole and a milliequivalent have the same numeric value because a millimole is 1/1000 of the molecular weight in grams. Therefore the millimole weight of KCl would also be 0.074 g or 74 mg.

As with previous medication calculations, doses for milliequivalents may also be calculated using ratio and proportion, formula method, or dimensional analysis using the information for strength of medication as found on the container. Use the method that is most comfortable for the calculations, and cross out like measurements in formulas.

Example 11-2

A physician orders potassium chloride 20 mEq IV. The medication label reads 2 mEq/mL.

202×1mL=DG

10×1mL=DG

DG=10mL

Practice Problems D

Calculate the following problems using the method for dosage calculation that is most comfortable—ratio and proportion, formula, or dimensional analysis. Indicate the volume of medication on the appropriate syringe. Show all calculations. Round to a measurable dose.

1. A physician orders potassium chloride 16 mEq to be added to IV fluids.

What volume of medication should be added to the fluids? _______________________

2. A physician orders potassium chloride 16 mEq to be added to IV fluids. The label reads 8 mEq/5 mL.

What volume of medication should be administered to the patient? _______________________

3. A physician orders Kaon-Cl 20 mEq po daily.

What volume of medication should be administered? _______________________

4. A physician orders Kaon-Cl 80 mEq po daily.

What volume of medication should be administered? _______________________

5. A physician orders Kaon-Cl 1 mEq/kg/day po for an elderly adult who weighs 122 lb.

What volume of medication should be administered daily? _______________________

What is the measureable dose in a medication cup? _______________________

6. A physician orders potassium chloride 36 mEq to be added to IV fluids.

What volume of medication should be added to the fluids? _______________________

7. A physician orders potassium chloride 13.4 mEq po. The available medication is potassium chloride 6.7 mEq/5 mL.

What volume of medication should be administered per dose? _______________________

8. A physician orders sodium bicarbonate 3 mEq/kg/q8h IV for a patient weighing 156 lb. The medication is available as sodium bicarbonate 1 mEq/mL.

What volume of medication should be administered q8h? _______________________

9. A physician orders potassium chloride elixir 20 mEq daily. The available medication is potassium chloride elixir 6.7 mEq/5 mL.

What volume of medication should be administered in the available utensil? _______________________

10. A physician orders potassium chloride 20 mEq po daily. The available medication is labeled potassium chloride extended release tabs 10 mEq.

How many tablets should be included in a daily dose? _______________________

11. A physician orders potassium chloride 26.8 mEq po daily. The available medication is potassium chloride tabs 13.4 mEq.

How many tablets should be administered each day? _______________________

12. A physician orders potassium chloride elixir 10 mEq po daily. The label on the medication available states potassium chloride elixir 6.7 mEq/tsp.

How many milliliters should be administered to the patient? _______________________

What is the measurable dose? _______________________

13. A physician orders potassium gluconate 40 mEq po in divided doses qid. The available medication is potassium gluconate 10 mEq tablets.

How many tablets should be given in the day? _______________________

How many tablets should be given with each dose? _______________________

14. A physician orders potassium bicarbonate powder 20 mEq to be dissolved in water for oral administration. The available potassium bicarbonate powder is 10 mEq packets to be dissolved in 5 mL of water.

How many milliliters of water should be used to dissolve the necessary dose? _______________________

How many powder packets should be used for a single dose? _______________________

15. A physician orders potassium chloride oral solution 4.75 mEq for a child. The available potassium chloride is labeled 2.375 mEq/5 mL.

What volume of medication should be administered to the child? _______________________

16. A physician orders KCl 20 mEq to be added to IV fluid.

What volume of KCl should be added using the following label? _______________________

17. A physician orders magnesium sulfate 150 mEq to be added to IV fluids.

What volume of medication should be added to the fluids? _______________________

18. A physician orders calcium gluconate 2.325 mEq to be added to IV fluids and administered slowly.

What volume of medication should be added to IV fluids? _______________________

19. A physician orders potassium 22 mEq to be added to IV fluids.

What volume of potassium should be added to the fluids? _______________________

20. A physician orders 10 mEq of KCl be added to 500 mL of D-5-W for infusion.

Using the label shown, what volume of KCl should be added to the fluids? _______________________

Show the volume of medication on the correct syringe.

Interpreting Medications in Percentage and Ratio Concentrations

• Percentage and ratio solutions are expressed to indicate the weight of solute found in the solvent.

• The solute is an active ingredient found in either a solid or liquid solvent.

• The percentage would be amount of solute found in 100 mL or 100 g of solvent.

• The ratio would be the amount of medication found in a total prepared volume of solution, usually milliliters.

• Percentage is expressed using % as an indication of the amount of active ingredient in a medication. The ratio is divided by a colon (:) to separate the solute and solvent.

• To calculate the amount of drug in the prepared solution, write the solution strength as a ratio to show the amount of medication found in the total solution. (Refer to Chapter 2 if necessary to review percentage and ratio.)

• To calculate the ratio in a medication preparation, whether solid, semi-solid, or liquid, the total amount of prepared medication minus the amount of solute equals the amount of solvent that should be added for the total volume desired.

• The following formula expresses the actual mathematical formula that would be used to provide a percentage relationship:

Percentage=Weight or volume of solute(grams or milliliters of solute)Volume/100 millimeters of prepared solution

• The formula below shows the mathematical calculation for medications expressed as ratios:

Ratio=Weight or volume of solute:Amount of prepared medication