Oral medications are commonly administered as tablets (which may be scored), capsules, caplets or liquids.
When calculating dosage, all measures must be in the same units, the same system of measurement. Conversion between system of measurements may be necessary.
Dimensional analysis may be used to calculate dosage, as previously addressed under "Conversions." Dimensional analysis offers the advantage of saving time in calculating medication dosages. It is necessary to first identify the unit of measure being calculated. Next, locate the factor that contains that unit of measure. This becomes the starting factor with the unit being calculated in the numerator. All factors must be entered with both their quantity and unit of measure. The strength of the dose on hand and other equivalencies are entered into the calculation, being sure that the units of measure in each successive numerator is the same as the previous denominator. The units of measure are cancelled out; the remaining units become the label for the answer.
Dimensional analysis example 1:
Order: Ampicillin 0.5 g p.o. q6h
Available: Ampicillin Capsules labeled 250 mg per capsule
How many capsules should be given?
Caps = 1 cap X 1000 mg X 0.5 g =? cap(s) 250 mg 1 g
or
| Caps = | 1 cap X | 1000 X | 0.5 | = 500 | = 2 caps |
| 250 X | 1 | 250 |
Dimensional analysis example 2:
Order: Amoxicillin 500 mg p.o. q6h x
7 days
Available: Amoxicillin for Oral Suspension 250 mg per 5 mL
| mL = | 5 mL X | 500 mg | = ? mL |
| 250 mg |
or
| mL = | 5 mL X | 500 | = 2500 | = 10 mL |
| 250 | 250 |
Click here to go to practice problems in oral dosages: Quiz 3
To email Connie: housercl@cctech.edu