# Interpreting Physicians’ Orders for Dosages

• Calculate total dosage of medication when quantity is unknown

• Calculate number of doses of medication from total dosage presented on a prescription

• Calculate the number of doses in a prescription if medication is taken according to a physician’s order, including duration in days

• Read and interpret prescriptions to calculate doses and dosages

Pretest

**Using the information provided, calculate the doses or dosages for the prescriptions as appropriate. Note that all doses will be administered on the first day as ordered unless otherwise stated. Note that a month means 30 days unless otherwise stated. Round answers to measurable doses depending on the utensil to be used or the available form of medication. Show your work.**

1 A physician prescribes amoxicillin suspension 250 mg/5 mL 150 mL to be taken 1 teaspoonful three times a day until the entire amount has been taken. A dosespoon is to be included with the prescription.

How many days would the medication last? __________

What total volume of amoxicillin would be administered daily? __________

How many milligrams of antibiotic would the child receive daily? __________

Indicate label directions using a dosespoon. __________

What dose of medication would the person receive with each administration? __________

2 A physician prescribes furosemide 20 mg po daily × 1 mo refills × 2. The available medication is furosemide 40 mg/tablet.

How many tablets would the patient take daily from the available stock medication? __________

How many tablets would be provided for a month’s supply to the patient from the stock bottle? __________

3 Using the provided prescription, how many tablets are necessary to fill the prescription? __________

4 A physician prescribes NPH insulin 80 units qam. The vial contains 10 ml of NPH insulin U-100. Indicate the amount of medication on the syringe so that you can supply patient instruction for self-administration.

How many days would this vial of medication last? __________

If the patient needs the insulin for 1 month, how many vials of medication would be necessary? __________

5 An order is written for the preparation of CEFTIZOXIME 500 mg in 50 mL of D-5-W to be infused at the rate of 50 mg/kg per day. CEFTIZOXIME is available for dilution at 1 g/10 mL of sterile water.

How many milliliters of infusion would a patient weighing 88 lb receive per day? __________

If this is to be administered in divided doses q6h, how many milliliters would the patient receive with each dose? __________

How many milligrams would the patient receive per day? __________

How many milligrams would the patient receive with each dose? __________

6 A physician prescribes Vibramycin 100 mg po tab ii stat and repeat in 12 hours. The prescription then reads to provide the patient with 100 mg/d for one week.

How many Vibramycin 100 mg tabs would be supplied to fill the prescription? __________

How many milligrams would the patient receive with the first dose? __________

7 A physician orders AMPICILLIN 0.2 g/kg/d IV in divided doses q6h. The physician wants AMPICILLIN 500 mg to be added to each 100 mL of D-5-W. AMPICILLIN is available in 500 mg vials for reconstitution with 1.2 mL of diluent. The patient weighs 110 lb.

How many milliliters of D-5-W would be necessary for the addition for each dose of the AMPICILLIN according to physician orders for dilution? __________

How many milligrams would the patient receive with each dose? __________

How many grams of AMPICILLIN would the patient receive daily? __________

How many total milliliters of fluids would the patient receive daily? __________

8 Use the prescription provided to make the necessary calculations. The tablet is available as Toprol-XL 25 mg.

How many tablets would be necessary to fill the prescription for a month’s supply? __________

What metric weight of drug would the patient receive with each dose? __________

Interpret the prescription as written. __________

Indicate prescription label directions. __________

9 A patient weighing 198 lb is to receive chloramphenicol 50 mg/kg/d in divided doses q4h to be administered in D-5-NS 500 mL for a *Salmonella typhi* infection. The available medication is in 1-g vials at 100 mg/mL.

*Hint: Only full vials are available for use.*

How many milliliters of chloramphenicol are in a full vial? __________

How many milliliters of chloramphenicol would be added to each container of fluids for the ordered dose? __________

How many vials of chloramphenicol would be necessary to supply the daily chloramphenicol for the physician’s order? __________

Explain your answer. _____________________________________________________________

10 A child has a streptococcal infection of the throat. The child weighs 66 lb. The physician tells the pharmacist to supply the accurate amount of medication so that the child receives erythromycin 40 mg/kg/day in divided doses to be administered q6h for 10 days. The medication is available as erythromycin 200 mg chewable tablets.

What would the prescription label read for the prescription with the medication shown as available? __________

If the parent states that the child will not chew the tablet but will take oral liquids, after obtaining the physician’s permission, what volume of medication would be supplied to the child with each dose if the erythromycin is available as 400 mg/5 mL? __________

How would the label read in household measurements? __________

How many tablets would be necessary to complete the order if chewable tablets are used? __________

How many milliliters of medication would be used to prepare the prescription? __________

Using a choice of utensils for dispensing with the medication, what utensil should be chosen for more exact administration of the medication at home? __________

*Hint: Go back to* *Chapter 7* *to see available utensils.*

11 The patient presents the provided prescription for preparation. The patient has no drug insurance coverage and wants 2 months’ supply. The prescription has prn refills for one year. The medication is available in 40-mg capsules.

How many capsules would be prepared for the amount of medication requested? __________

Interpret the prescription as written. __________

Indicate prescription label directions. __________

12 A physician prescribes amoxicillin 62.5 mg po tid for 10 days for a child weighing 44 lb. Available is amoxicillin 125 mg/5 mL in 100-mL and 150-mL containers.

Which container of amoxicillin would be provided for the prescription? __________

What quantity of the medication would the parents give to provide the correct dose? __________

How much medication would be discarded if the orders are followed correctly? __________

Indicate prescription label directions for the prescription using household measurements. ___________________________________________________________________

13 A physician writes a prescription for Humulin N 65 units subcutaneously qam and qpm. The prescription also contains an order for Humulin R 25 units subcutaneously with the afternoon dose.

How many 10-mL vials of Humulin N (100 units/mL) are necessary for a month’s supply? __________

How many 10-mL vials of Humulin R (100 units/mL) are necessary for a month’s supply? __________

What size insulin syringes should be supplied to administer both injections? __________

Indicate the volume of medication to be administered in am and in pm on the appropriate syringe. Label the time for the appropriate syringe.

14 A physician prescribes atenolol 75 mg po qam and 25 mg po at bedtime. The available stock medication is atenolol 50 mg.

How many tablets would be necessary for a 30-day supply? __________

Indicate prescription label directions. _____________________________________________

15 A physician prescribes ibuprofen liquid 10 mg/kg to be administered po qid prn for pain for a child who weighs 66 lb. The available medication is 100 mg/5 mL. The volume of medication to be dispensed is 8 ounces.

How many milliliters of medication would be needed for one day? __________

How many milliliters of medication would be administered to the child with each dose? __________

How many doses of medication are available in this prescription? __________

Indicate the prescription label directions. __________________________________________

## Preparing Medications When The Quantity For Dispensing Is Unknown

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Example 14-1

A physician prescribes digoxin 0.125 mg tab ii stat then tab i daily. How many tablets would be necessary for a 30-day supply if the available medication is that seen on the following label?

Prescription label directions: Take two tablets now then one tablet daily

Practice Problems A

*Calculate the following problems, showing all calculations. Note that a month means 30 days unless otherwise stated.*

1. A physician prescribes phenobarbital gr po q6h for epilepsy. The order is to provide a month’s supply with each prescription refill.

Using the provided label, how many tablets would be provided for the patient? __________

What is the dose q6h in tablets? __________

What is the dose in milligrams? __________

Indicate prescription label directions. _____________________________________________

2. A physician prescribes Voltaren 50 mg po tid with meals or snack. How many tablets are necessary to fill this prescription for a month? __________

3. A physician prescribes cephalexin oral suspension 62.5 mg po q6h × 10 days. Indicate the dose on the available utensil below.

What volume of medication would be administered with each dose? __________

Would the label shown provide adequate medication to fulfill the prescription? __________

If this is adequate, what volume of medication would be discarded? __________

If the amount is inadequate, how many more milliliters of medication would be necessary for the prescription? __________

What would be the dose in household measurements? __________

Indicate prescription label directions using an oral dose syringe. __________

__________________________________________________________________________________

4. A physician prescribes Macrodantin 0.1 g to be given po qid for a month for a severe urinary tract infection.

Using the provided label, how many capsules would be necessary to complete the order? __________

Indicate the prescription label directions. __________________________________________

5. Using the provided prescription, how many tablets would be necessary to fill the prescription? __________

Interpret the prescription. _________________________________________________________

Indicate prescription label directions. _____________________________________________

6. Using the provided prescription, what volume of medication must be supplied to fill the order? __________

Interpret the prescription. _________________________________________________________

The medication is available in 80 mL, 100 mL, and 150 mL containers. Which container should be chosen to prepare the medication? __________

What volume of medication should be discarded by the patient if the medication is taken correctly? __________

Indicate prescription label directions using household measurements. ______________

7. During a severe influenza epidemic, the physician writes the provided prescription as a prophylactic in an older adult with COPD. The only amoxicillin in stock is amoxicillin 250 mg/capsule.

How many capsules should be given to the patient to complete this order? _________

Interpret the prescription. _________________________________________________________

Indicate the prescription directions that would be on the label. _____________________

8. Using the provided prescription, what volume of medication must be provided to fulfill this order? __________

9. A patient presents the provided prescription for preparation. __________________

How many patches does the patient need for a month’s supply? __________

Interpret the prescription. _________________________________________________________

Indicate the prescription label directions. __________________________________________

10. On Friday a nurse orders medication to be sent to the floor for the weekend using the provided medication label. The patient is to receive cimetidine 300 mg IM q6h.

How many vials of medication would be sent to the floor for Friday noon through the weekend with sufficient amount to provide the medication on Monday 6 am? __________

11. A physician orders Solu-Cortef 150 mg IM q8h for a patient with severe allergic dermatitis.

How many vials of medication would be sent to the floor for administration in 1 day using the provided label? __________

12. A physician prescribes cyanocobalamin 1.5 mg subcutaneously for administration twice a week for a month. Use 4 weeks for a month with this calculation.

Using the provided label, how many vials of cyanocobalamin would be provided to the patient for this order? __________

What syringe should be provided with the prescription to meet this prescription? __________

Indicate the amount of medication that should be shown as patient education on the appropriate syringe.

13. A physician prescribes Keflex 500 mg to be given po qid.

Using the provided label for available medication, how many capsules would be supplied for 2 weeks? __________

Interpret the prescription. _________________________________________________________

Indicate the prescription label directions. __________________________________________

14. How many tablets would be necessary to supply this medication for 2 weeks? __________

Interpret the prescription. _________________________________________________________

Indicate the prescription label directions. __________________________________________

15. How many tablets are necessary for a month’s supply of the provided prescription? __________

If each refill is for a month’s supply, how many total tablets would the patient receive over the period of the prescription for 3 months? __________

Interpret the order. _______________________________________________________________

Indicate the prescription label directions. __________________________________________

16. The physician orders phenobarbital gr 1/4 po q8h for seizures.

How many tablets would be provided for one week’s supply? __________

Indicate prescription label directions. _____________________________________________

17. Four prescriptions are written as shown in the provided illustration. Determine how many tablets of each medication would be necessary for the prescription as written.

Depakote 500-mg tablet is available.

Depakote to be supplied: __________

Interpret the order for this medication. ____________________________________________

Indicate label directions. __________________________________________________________

Desyrel 50-mg tablet is available.