Contraindication

A contraindication is a specific situation — a disease, condition, allergy, concurrent medication, or patient characteristic such as pregnancy — in which a drug, treatment, or procedure should not be used because the risk of harm outweighs the potential benefit.

Contraindications come in two strengths. An absolute contraindication means the therapy should never be used in that situation: a documented severe allergy to a drug is the classic example. A relative contraindication means caution is warranted — the therapy may still be used if the expected benefit outweighs the risk, often with dose adjustments or closer monitoring, as when a drug cleared by the kidneys is given to a patient with reduced renal function.

Contraindications differ from drug interactions and side effects, though the concepts overlap in practice. A side effect is an unwanted response that can occur in anyone taking the drug; a contraindication is a pre-existing reason a specific patient should avoid it. Pharmacy systems screen prescriptions against patient profiles to flag contraindications before dispensing, which is why accurate allergy and medication histories matter so much.

Contraindications are tested across several health-science exams. The PTCE covers drug contraindications and interaction screening for pharmacy technicians, the USMLE Step 1 tests contraindications in pharmacology and pathology contexts, and the CSCS exam applies the concept to exercise selection during rehabilitation and reconditioning.