NATRIURETIC AND DIURETIC EFFECTS OF FELODIPINE AND HYDROCHLOROTHIAZIDE ALTER SINGLE AND REPEATED DOSES

The effects of the calcium antagonist, felodipine, and hydrochlorothia zide (HCTZ) on natriuresis/diuresis and blood pressure were evaluated in 12 healthy subjects. The investigation was designed as a double-bli nd, three-way, randomised, crossover study, and all comparisons were p erformed against placebo. Urine volume, urine sodium excretion, heart rate and blood pressure were measured after a single dose of felodipin e 10 mg, HCTZ 12.5 mg or placebo as well as during steady-state condit ions (6 days of treatment with felodipine 10 mg b.i.d., HCTZ 12.5 mg b .i.d. or placebo). A significant increase in natriuresis was seen in t he first 4 h after a single dose of felodipine and HCTZ, and the effec t of felodipine was approximately 40 % that of HCTZ. When the entire 2 4-h period after a single dose was studied, there was a significant in crease in natriuresis after HCTZ, but not after felodipine, compared w ith placebo. A significant increase in diuresis was found in the first 4 h after a single dose of HCTZ, but not after felodipine, compared w ith placebo. Under steady-state conditions, there were no statisticall y significant differences between felodipine and placebo or HCTZ and p lacebo when the 24-h period, as a whole was considered. Potassium excr etion was not affected by any of the drugs. Felodipine caused a signif icant decrease in diastolic blood pressure in this study. This was not the case for HCTZ or placebo.