Math: Basic Tutorials : Oral Dosages

Oral Dosages

Oral medication administration is one of the most common and convenient methods for delivering drugs, but accurate dosage calculations are essential to ensure client safety and effectiveness. Medications taken by mouth can come in various forms, including tablets, capsules, liquids, and suspensions, each requiring proper measurement and administration.

This section covers how to calculate oral dosages based on prescribed amounts, available drug concentrations, and unit conversions. Step-by-step examples will help reinforce these concepts for accurate medication administration.

Calculating Dosages

Single Dosage Amount

$X = D \times \frac{Q}{H}$

$X$ : Single Dose	$D$ : Dosage Ordered	$H$ : Strength on Hand	$Q$ : Quantity
The single individual dose amount of medication given (usually in tablets or mL).	The amount of drug prescribed or ordered by the physician to be administered to the patient.	The available strength of one dose of the drug to be administered to the patient.	The available form of one dose of the drug.

Examples

Click on the titles below to view each example.

Example 1

Example 1:
Physician orders 500 mg of ibuprofen p.o. q.8.h. x 14 days for a client. Quantity of Ibuprofen is 250 mg.
a. What single dose should you administer?
$D = 500$ mg of ibuprofen $H = 250$ mg $Q = 1$ tablet of ibuprofen	$X = 500 mg \times \frac{1 tablet}{250 mg} = 2 tablets$
Solution:	You would administer 2 tablets of ibuprofen in a single dose orally.
b. What is the daily dose?
The order is q.8.h. represents every 8 hours. Since there are 24 hours each day. Every 8 hours represents three times a day.	$3 \times 2 = 6$
Solution:	The client will receive 6 tablets each day.
c. What is the total dose for 14 days?
$14 \times 6 = 84$
Solution:	In 14 days, the client will recieve 84 tablets.

Example 2

Example 2:
The prescriber orders Zoloft (sertraline hydrochloride) oral solution 25 mg b.i.d. for 7 days. The drug label can be seen below.
a. What single dose should you administer?
$D = 25$ mg of sertraline oral solution $H = 20$ mg $Q = 1$ mL	$X = 25 mg \times \frac{1 mL}{20 mg} = 1.25 mL$
Solution:	You would administer 1.25 mL of Zoloft oral solution in a single dose orally.
b. What is the daily dose?
The order is b.i.d. or twice a day.	$2 \times 1.5 = 2.5 mL$
Solution:	The client will recieve 2.5 mL each day.
c. What is the total dose for 7 days?
$7 \times 2.5 = 17.5$
Solution:	In 7 days, the client will recieve 17.5 mL.

Example 3

Example 3:
How many 300-mg Ziagen (abacavir sulfate) tablets contain 0.9g of Ziagen? Notice that there are mg and g listed as the unit of the tablets. Thus, you need to convert into the same unit of measurement before finding the number of tablets.
We can start by converting 0.9g into mg, knowing that $1 g = 1000 mg$	$0.9 g \times \frac{1000 mg}{1 g} = 900 mg$
Now we convert 900mg into tablets	$900 mg \times \frac{1 tablet}{300 mg} = 3 tablets$
Solution:	Three 300 mg tablets contain 0.9 g of Ziagen.

Example 4

Example 4:
An order of Aldactazide (spinolactone and hydrochlorothiazide) 100 mg/100 mg p.o. b.i.d. Read the label below and determine how many tablets of this diuretic you will administer each day?
The order is for 100 mg/100 mg and the label reads 25 mg/25 mg per tablet.	$100 mg / 100 mg \times \frac{1 tablet}{25 mg / 25 mg} = 4 tablets$
Solution:	Each dose will contain 4 tablets of Aldactazide. B.i.d. represents twice a day, so in one day, the client will receive 8 tablets of Aldactazide.

Example 4:

An order of Aldactazide (spinolactone and hydrochlorothiazide) 100 mg/100 mg p.o. b.i.d. Read the label below and determine how many tablets of this diuretic you will administer each day?

The order is for 100 mg/100 mg and the label reads 25 mg/25 mg per tablet.

$100 mg / 100 mg \times \frac{1 tablet}{25 mg / 25 mg} = 4 tablets$

Solution:

Each dose will contain 4 tablets of Aldactazide. B.i.d. represents twice a day, so in one day, the client will receive 8 tablets of Aldactazide.

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Last Updated: Jun 5, 2025 4:16 PM
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