1. Chapter 13
Oral Dosages

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Objectives
Converting all measures within the problem to equivalent measures in one system of measurement
Using a proportion to solve problems of oral dosage involving tablets, capsules, or liquid medications
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Objectives (cont’d)
Using a proportion to solve problems of oral dosages of medications measured in milliequivalents
Using the stated formula as an alternative method of solving oral drug dosage problems
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Oral Dosages
Tablets
Capsules
Liquids
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Tablets, capsules, and liquids are the three types of oral medications. They are taken po, or by mouth.
Where are oral medications absorbed in the body?
Oral medications are absorbed primarily in the small intestine.

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Converting Measures
Example:
A physician ordered amoxicillin 0.5 g po four times a day. The drug is supplied in 500-mg capsules.
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Why is it necessary to convert oral drug measurements from one system to another?
Physicians can order a drug in one system of measurement when it is supplied in another. It is then necessary to convert between measures so that both measurements are in the same system.
Convert the measurements in the example.
Because the drug is supplied in milligrams, convert the measurement in the order to milligrams.
1000 mg : 1 g :: x mg : 0.5 g
1x = 1000 × 0.5
x = 500 mg

6. Using Proportions to Solve Tablet and Capsule Medication Problems
FIGURE 13-1 Forms of solid oral medication. (Top row: Uniquely shaped tablet, capsule, scored tablet. Bottom row: Gelatin-coated liquid, extended-release capsule, and enteric-coated tablet. (From Potter PA, Perry AG: Fundamentals of nursing, ed 6, St Louis, 2005, Mosby.)
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What is a capsule?
A capsule is a hard or soft gelatin that houses a powder, liquid, or granular form of a specific drug.
What is the most common form of oral medication?
The most common form of oral medication is a tablet. Tablets are produced from a drug powder.

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Using Proportions to Solve Tablet and Capsule Medication Problems (cont’d)
Example:
The physician orders minocycline 200 mg po daily. Minocycline 50 mg is available. How many capsules will the nurse administer?
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How many tablets will the nurse administer?
Because the order and the available drug are already listed in the same metric measurement, a proportion can be written to calculate the amount of the drug to be administered.
50 mg : 1 capsule :: 200 mg : x capsules
50 : 1 :: 200 : x
50x = 200
x = 200 ÷ 50
x = 4
The nurse will administer 4 capsules.

8. Using Proportions to Solve Liquid Medication Problems
FIGURE Plastic oral syringe. (From Clayton BD, Stock YN: Basic pharmacology for nurses, ed 13, St Louis, 2004, Mosby. Courtesy Chuck Dresner.)
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Liquid medications come in what two forms?
The liquid forms of medications are elixirs and oral suspensions.
How is liquid oral medication administered?
Liquid oral medication is administered with a medicine cup, plastic oral syringe, or medicine dropper.

9. Using Proportions to Solve Liquid Medication Problems (cont’d)
Example:
The physician ordered atovaquone 750 mg twice daily pc. Atovaquone is available 150 mg/mL. How many milliliters will the nurse administer?
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How many milliliters will the nurse administer?
Because the order and available drug are in the same metric measurement, the proportion can be written.
150 mg : 1 mL :: 750 mg : x mL
150 : 1 :: 750 : x
150x = 750
x = 750 ÷ 150
x = 5
The nurse will administer 5 mL of atovaquone.

10. Using Proportions to Solve Problems Involving Milliequivalents
Example:
The physician ordered Slow-K 20 mEq four times a day with meals. The drug is available 10 mEq/5 mL. How many milliliters will the nurse administer?
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A milliequivalent is the number of grams of a solute contained in 1 mL of a normal solution.
How many milliliters will the nurse administer?
10 mEq : 5 mL :: 20 mEq : x mL
10 : 5 :: 20 : x
10x = 100
x = 100 ÷ 10
x = 10
The nurse will administer 10 mL of Slow-K.

11. Alternative Formula Method
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The formula method has been used for many years in calculating drug dosages.
D represents the desired amount of the medication ordered by the physician.
A represents the strength of the medication that is available.
When using the formula method, do the desired and available amounts need to be in the same system of measurement?
Yes, they must be in the same system.

12. Alternative Formula Method (cont’d)
Formula (cont’d): Q x
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Q represents the quantity of the medication that contains the available strength.
x represents the dosage that is unknown.
How is the formula read?
Desired over available multiplied by the quantity available equals x, or the amount to be given to the patient.

13. Alternative Formula Method: Capsules and Tablets
Oral dosages involving capsules and tablets
Example:
The physician orders aspirin gr v po four times a day. Aspirin tablets gr ii are available. How many tablets will the nurse administer?
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How many tablets will the nurse administer?
The desired amount is 5 gr. The available strength is 2 gr. There is no need to convert.
[(5 gr)/(2 gr)] × (1 tablet) = x tablets
x = 5/2
x = 2 ½
The nurse will administer 2 1/2 tablets.

14. Alternative Formula Method: Liquids
Oral dosages involving liquids
Example:
The physician orders phenobarbital gr ii po twice a day. Phenobarbital elixir 10 mg/5 mL is available. How many milliliters will the nurse administer?
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Convert the order to milligrams per milliliter.
60 mg : 1 gr :: x mg : 2 gr
x = 120 mg
Place the numbers into the formula (D/A) × Q = x.
[(120 mg)/(10 mg)] × (5 mL) = x
x = 120/2 = 60
The nurse will administer 60 mL.