uniformity of dosage units

Uniformity of dosage units is the pharmacopoeial requirement that each single-dose unit — a tablet, capsule, or filled vial — actually delivers close to its labelled amount of drug. The point is that patients take individual units, not the batch average, so each unit must be right on its own.

The compendium lets you demonstrate this by one of two routes. Content uniformity assays individual units for actual drug content and is the general approach, especially for low-dose or low-content products. Weight variation weighs individual units and infers content, and is permitted only when content reliably tracks weight — such as high-dose tablets, solutions in single-dose containers, or freeze-dried solids. Either way the data are reduced to an acceptance value that must stay below a set limit.

Uniformity of dosage units is the umbrella requirement; content uniformity and weight variation are the two methods used to satisfy it. Whether weight variation is allowed depends on the dose and on how much of the unit the active makes up, so the choice is governed by clear compendial criteria rather than left to preference.