Steady-state urinary excretion method for determining bioequivalence of conjugated estrogen products.

The steady-state excretion of conjugated estrogens in the urine of postmenopausal women dosed with conjugated estrogens tablets was studied using a modification of a previously published method. The procedure was used to quantitate the estrogens both before and during conjugated estrogens replacement therapy. The method, which is relatively specific, involves enzyme hydrolysis of urine samples a number of classical extraction and purification steps, and analysis of the silylated estrogens on a 2.7-m, 1.7% diethylene glycol succinate column using flame-ionization detection. The results indicate that steady-state urinary estrogen excretion levels were obtained within 17 days of dosing. Furthermore, the urinary estrogen excretion profile was significantly different from the composition of the estrogens in the dosage form.