Enhancement of the gastrointestinal absorption of hydrochlorothiazide by propantheline.

Hydrochlorothiazide 75 mg was given twice p.o. to fasting subjects. In the second study they had been pretreated with propantheline 60 mg. Plasma and urine concentrations of hydrochlorothiazide were determined by GLC. Pretreatment with propantheline on average delayed the maximal plasma level of hct from 2.4 to 4.8 h (p less than 0.05); and the total urinary recovery of hydrochlorothiazide by 48 h was increased from 49.3 mg to 66.9 mg (p less than 0.005). It was concluded that propantheline increased substantially the absorption of the diuretic.