Steady-state plasma desmethyldiazepam during long-term clorazepate use: effects of antacids

The effect of antacid on steady-state plasma desmethyldiazepam (DMDZ) concentrations during long-term treatment with clorazepate dipotassium (CZP) was evaluated in 10 subjects. Each took 7.5 mg CZP nightly for 30 consecutive nights divided into three 10-day treatments given in random sequence as follows: (1) 7.5 mg CZP nightly with no antacid, (2) CZP nightly for 30 ml Maalox, and (3) CZP nightly with Maalox with an additional 30 ml Maalox three times daily. The overall mean steady-state DMDZ plasma level, measured during the last 3 days of each treatment condition, was 175 ng/ml. Within-day means ranged from 159 to 202 ng/ml and were not influenced by treatment condition, time, or trial sequence. DMDZ washout after termination of the 30-day trial was slow, proceeding with a half-life of 75 hr (range, 63 to 109 hr). Thus, Maalox does not alter steady-state DMDZ levels during long-term CZP therapy.