ASSAY
An assay measures the quantity or concentration of a drug’s active ingredient, typically expressed as a percentage or mg/mL. It answers the question: “How much of the drug is present?”
This is determined through chemical analysis to verify that a product contains the labeled amount, such as confirming a paracetamol tablet contains 500 mg of the active ingredient.
POTENCY
Potency measures a drug’s biological effectiveness or functional strength, often expressed in relative units compared to a reference standard. It answers: “How well does the drug work?”
This is particularly crucial for biologics like vaccines and antibodies, where the relationship between quantity and effect isn’t always linear.
EXAMPLE INSULIN
For insulin products, the assay might show 100 units/mL in both products A and B (same concentration). However, their potency could differ significantly based on how effectively they lower blood glucose in standardized tests.
Product A might require less volume than Product B to achieve the same glucose-lowering effect, despite identical assay values.
Related Topics: