What best defines a drug dose rate?

• A. Amount of drug given in one dose
• B. Amount of drug given per unit of body weight
• C. Description of the treatment regimen
• D. The concentration of the drug preparation

Answer: (B)

The main concept here is how a drug dose is scaled for an animal’s size. Dose rate is the amount of drug given per unit of body weight, usually expressed as mg per kg (mg/kg). This normalization lets you compare and apply the same level of exposure across animals of different sizes, so a bigger animal gets more drug in total but the same exposure relative to its body weight as a smaller one. For example, giving 5 mg/kg means a 20 g animal receives 0.1 mg (5 mg/kg × 0.02 kg) and a 1 kg animal would receive 5 mg, keeping the dose proportional to body size.

In contrast, the total amount given in one administration is an absolute dose, which could vary if you’re not adjusting for weight. The description of the treatment regimen refers to how often and for how long the drug is given, not the amount per weight. The concentration of the drug preparation is about how much drug is dissolved per unit volume, which helps determine how much volume you need to deliver to reach a desired dose, but by itself does not define the dose rate.