Gastrointestinal absorption of hydrochlorothiazide enhanced by concomitant intake of food.

Hydrochlorothiazide (hct) 75 mg was administered orally to eight healthy volunteers without (Study I) or together with a standaridized meal (Study II), and plasma and urine concentrations of hct were analyzed by GLC. The plasma levels of hct were higher initially when the tablets were taken on an empty stomach, but after 5 h they were higher in Study II. There was no difference between the two studies in the area under plasma concentration time curves. The urinary recovery of hct totalled 55.6 +/- 4.9 mg when the drug was given with food and 47.4 +/- 6.0 when it was taken on an empty stomach. The difference is significant (p less than 0.01). As the urinary recovery represents the uptake of hct, it appears that the gastrointestinal absorption of hct is enhanced when the drug is given with food.