Dose rates are generally expressed as:

• A. mg/mL
• B. g/L
• C. mg/g
• D. mg/kg

Answer: (D)

Dosing is standardized by body weight. Expressing dose rate as milligrams per kilogram of body weight (mg/kg) ties the amount of drug to how large the animal is, so each animal receives a similar level of exposure regardless of size. This makes comparisons across animals and studies meaningful and ensures consistent pharmacologic effect.

mg/kg is preferred because it directly represents the actual amount delivered relative to the animal, whether you’re giving a single dose or dosing per day. Other expressions describe the concentration in the dosing solution (mg/mL or g/L) or are not as directly tied to the animal’s size (mg/g is just a similar idea but not the standard). To use mg/kg, you multiply the dose by the animal’s weight to find the total milligrams to administer, and you can then convert to volume based on the solution’s concentration.