Pharmacy and Pharmacology
The pharmacy and pharmacology domain tests whether you can turn a written order into a safe, correctly measured dose, and whether you understand how drugs behave in the body. Questions mix math, drug-class recognition, storage and controlled-substance rules, and practical dispensing judgment.
Core rules
- Dose calculations start with body weight in kilograms: kg = lb ÷ 2.2. Dose (mg) = mg/kg × kg. Volume (mL) = dose (mg) ÷ concentration (mg/mL).
- Convert percentages before you calculate: 1% = 10 mg/mL, 0.5% = 5 mg/mL, 2% = 20 mg/mL.
- For a constant-rate infusion: mL/hr = (mg/kg/hr × kg) ÷ mg/mL.
- Controlled substances require double-locked storage, a perpetual inventory log, and documentation of every dose, waste, and return. Only a licensed veterinarian prescribes.
- Extra-label use requires a valid veterinarian-client-patient relationship, a scientific rationale, and, in food animals, an appropriate withdrawal time.
- Respect storage rules: insulin refrigerated but not frozen, isoflurane upright at room temperature, light-sensitive drugs protected.
Worked example
A 15 kg dog is ordered metoclopramide 0.3 mg/kg IV q8h. Stock is 5 mg/mL. Dose = 0.3 × 15 = 4.5 mg. Volume = 4.5 ÷ 5 = 0.9 mL per dose. Check backward: 0.9 mL × 5 mg/mL = 4.5 mg, and 4.5 mg ÷ 15 kg = 0.3 mg/kg, so the order matches.
Traps that cost marks
Mixing mg and mg/kg; using 1.1 instead of 2.2 for pounds; treating a 1:10,000 solution as 1 mg/mL when it is 0.1 mg/mL; using a U-100 syringe for U-40 insulin; splitting enteric-coated or extended-release tablets; and recording a controlled drug without the witness or waste amount.