Pharmacokinetics of bendroflumenthiazide in hypertensive patients

After four weeks on placebo treatment, 8 hypertensive patients (WHO stage I) were treated for 2 weeks with bendroflumethiazide (bft) 2.5 mg and KCl 1.5 g daily. Subsequently they received bft 5 mg and KCl 1.5 g daily for a further fortnight. At the end of each period of treatment blood pressure was recorded and blood samples and urine were collected for analysis of bft by GLC. Before taking the daily dose of bft, no trace of the drug was found in plasma. Peak levels of bft were seen after 2.3 h and averaged 23 and 50 ng . ml-1 after 2.5 and 5 mg, respectively. After bft 2.5 mg the plasma level was too low for kinetic analysis. The plasma half-life after 5 mg averaged 4.1 h. The mean apparent volume of distribution was 1.18 1 . kg-1. Non-renal clearance averaged 200 ml . min-1. The renal clearance of bft was significantly lower (p less than 0.05) after 5 mg (48 ml . min-1) than after 2.5 mg bft (93 ml . min-1), although the creatinine clearance remained unchanged. No correlation was found between the plasma level of bft and its effect on blood pressure.