Журнал биоэквивалентности и биодоступности

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Assessment of Bioequivalence Using Urinary Excretion Data

Eva Troja , Leonard Deda

A rapid method for assessing the bioavailability of the drug is the use of urinary excretion data. This method is based on the principle that the urinary excretion rate of unchanged drug is directly proportional to the plasma concentration of the drug. So bioavailability can be calculated as the ratio of the total amount of unchanged drug in urine after administration of test (T) and reference (R) formulations. Urine metabolite excretion data are not used to assess bioavailability since the drug undergoes metabolism in different locations and the rate of metabolism may vary for different reasons. This method applies to drugs that are excreted unchanged in the urine, eg, some thiazide diuretics, sulfonamides, and drugs that act on the urine, such as urinary antiseptics (Nitrofurantoin and Hexamine).