Which test is used to assess the potency or effectiveness of a drug in biological systems?

• A. Assay
• B. Purity
• C. United States Pharmacopeia
• D. Bioassay

Answer: (D)

Measuring how potent or effective a drug is requires observing its actual biological effect in a living system. That is exactly what a bioassay does: it exposes a biological model—cells, tissues, or whole organisms—to different drug concentrations and records the resulting response. From this dose–response data you can determine potency (how much drug is needed to achieve a given effect) and sometimes efficacy. This direct link between dose and biologic response is what sets a bioassay apart from other terms. An assay is a general measurement method and may not involve a living system; purity tests look at contaminant levels rather than biological activity; and the United States Pharmacopeia is a standards compendium, not a specific test. Therefore, the test used to assess potency in biological systems is a bioassay.