Which test determines the therapeutic equivalence of drugs?

• A. Assay
• B. Bioassay
• C. Purity
• D. Bioavailability

Answer: (B)

Therapeutic equivalence hinges on producing the same clinical effect. A bioassay directly measures the drug’s biological activity and the resulting effect in a living (or biologically relevant) system, allowing a direct comparison of potency and response between products. If two formulations elicit the same biological response at the same dose, they’re likely to have the same therapeutic effect.

An assay, by contrast, simply quantifies how much active ingredient is present and doesn’t tell you about the actual therapeutic outcome. Purity checks focus on contaminants or impurities rather than how well the drug works. Bioavailability looks at pharmacokinetics—how much and how fast the drug reaches systemic circulation—information that’s important but doesn’t directly assess the clinical effect.