In dosage calculation, what does D/H x Q = A represent?

In dosage calculation, what does D/H x Q = A represent?

• A. D = Dose on hand, H = Dose ordered, Q = Quantity on hand, A = Amount to administer
• B. D = Dose ordered, H = Dose on hand, Q = Quantity on hand, A = Amount to administer
• C. D = Dose on hand, H = Dose ordered, Q = Amount to administer
• D. D = Daily dose, H = Half-life, Q = Quantity on hand

Answer: (B)

This uses a ratio to scale from what you have on hand to what is ordered. D represents the dose on hand (the amount of drug in the container per unit of measurement), H is the dose ordered (how much the patient should receive), Q is the quantity on hand (how much of the drug you have in the container in those same units), and A is the amount to administer (how much you should give, in those units). Think of it as: what you have available per unit of dose divided by what’s ordered, then multiplied by how much container you have, tells you exactly how much to draw or administer. For example, if the stock concentration gives 50 mg per 1 mL (D = 50 mg), the dose ordered is 100 mg (H = 100 mg), and the vial has 4 mL on hand (Q = 4 mL), then A = (D/H) × Q = (50/100) × 4 = 2 mL. So you’d administer 2 mL to deliver the 100 mg ordered. Other interpretations of the letters would not align with how stock concentrations are used to compute the correct volume or number of units to give, which is why this particular arrangement is the correct one.

This uses a ratio to scale from what you have on hand to what is ordered. D represents the dose on hand (the amount of drug in the container per unit of measurement), H is the dose ordered (how much the patient should receive), Q is the quantity on hand (how much of the drug you have in the container in those same units), and A is the amount to administer (how much you should give, in those units).

Think of it as: what you have available per unit of dose divided by what’s ordered, then multiplied by how much container you have, tells you exactly how much to draw or administer. For example, if the stock concentration gives 50 mg per 1 mL (D = 50 mg), the dose ordered is 100 mg (H = 100 mg), and the vial has 4 mL on hand (Q = 4 mL), then A = (D/H) × Q = (50/100) × 4 = 2 mL. So you’d administer 2 mL to deliver the 100 mg ordered.

Other interpretations of the letters would not align with how stock concentrations are used to compute the correct volume or number of units to give, which is why this particular arrangement is the correct one.