5 Pharmacy Calculations Free Online FlashCards

What general formula converts a prescribed dose into an amount to give?

Amount to dispense or administer = $\left(\frac{\text{desired dose}}{\text{dose on hand}}\right)\times\text{quantity containing the dose on hand}$. Keep units visible so they cancel correctly.

How many milligrams are in $1$ gram?

$1\ \mathrm{g}=1{,}000\ \mathrm{mg}$.

What is the standard medication-measure equivalent of one U.S. teaspoon?

One U.S. teaspoon equals $5\ \mathrm{mL}$, the standard medication-measure equivalent. Household spoons are unreliable; use a marked dosing device for oral liquids.

What is the difference between a fluid ounce and an ounce?

A fluid ounce measures volume, while an ounce measures mass; they are not interchangeable.

How many $250$-mg tablets make a $500$-mg dose?

$500\ \mathrm{mg}\div250\ \mathrm{mg/tablet}=2$ tablets per dose.

What volume provides $375\ \mathrm{mg}$ from a liquid containing $250\ \mathrm{mg}$ per $5\ \mathrm{mL}$?

$\left(\frac{375\ \mathrm{mg}}{250\ \mathrm{mg}}\right)\times5\ \mathrm{mL}=7.5\ \mathrm{mL}$.

What dose corresponds to $10\ \mathrm{mg/kg}$ for a patient weighing $20\ \mathrm{kg}$?

$10\ \mathrm{mg/kg}\times20\ \mathrm{kg}=200\ \mathrm{mg}$ per dose. This calculation does not determine whether the dose is clinically appropriate.

How is quantity calculated for a fixed medication schedule?

Quantity = amount per dose $\times$ doses per day $\times$ days of therapy.

How is days’ supply calculated?

Days’ supply = quantity dispensed $\div$ amount used per day. The units must match, such as tablets divided by tablets per day.

What decimal notation helps reduce medication errors?

Use a leading zero for values below one, such as $0.5\ \mathrm{mL}$, and avoid a trailing zero: write $5\ \mathrm{mg}$, not $5.0\ \mathrm{mg}$.

How many micrograms are in $1$ milligram?

$1\ \mathrm{mg}=1{,}000\ \mathrm{mcg}$.

How many tablets are needed for $1$ tablet three times daily for $30$ days?

$1\times3\times30=90$ tablets.