Chemotherapy dosing is often calculated in which units?

• A. mg/kg
• B. mEq/L
• C. g/m^2
• D. mg/m^2

Answer: (D)

Dosing chemotherapy in mg/m^2 rests on using body surface area to estimate how a drug is distributed and cleared in the body. Body surface area correlates more closely with organ perfusion, blood volume, and metabolic capacity than weight alone, so expressing the dose per square meter helps achieve similar drug exposure across patients with different body sizes. This standard helps balance effectiveness with toxicity, giving larger doses to bigger patients and smaller doses to smaller patients.

Other units don’t fit as well for guiding cytotoxic therapy. mEq/L is a concentration in the blood, not a dose to administer. Using grams per square meter would be less precise and could lead to impractically large or small amounts, whereas milligrams per square meter provides the appropriate granularity for typical chemo regimens. While mg/kg is used in some pediatric contexts or for specific drugs, mg/m^2 is the conventional unit for many regimens because it better standardizes dosing across adults of varying sizes.