Racial differences in response to acute dosing with hydrochlorothiazide

Blacks demonstrate a higher response rate to diuretic therapy for hypertens ion than do whites. This study examined the pharmacokinetic (PK), pharmacod ynamic, and neurohumoral effects of hydrochlorothiazide (HCTZ) administrati on in a matched group of 9 black and 9 white hypertensive patients (mean +/ - SD for black and white). After a 4-week washout period and 7-day control diet, subjects received a single dose of HCTZ (25 mg at 8 AM) With Serial b lood and urine collections for 36 hours. After HCTZ sodium excretion increa sed comparably in both groups (blacks: 122 +/- 42 pre to 265 +/- 49 mEq/24 hours post; whites: 117 +/- 29 pre to 255 +/- 39 mEq/24 hrs post). Potassiu m excretion tended to be higher at baseline and was significantly higher fo llowing HCTZ in whites (blacks: 45 +/- 20 pre to 66 +/- 13 mEq at 24 hours post; blacks: 57 +/- 9 pre to 86 +/- 14 mEq at 24 hours post) with most of the post-dosing difference being observed in the hours 0 to 12 after HCTZ. There were no between group PK differences for urinary HCTZ. Aldosterone ex cretion followed a normal circadian pattern in the whites but did not show this pattern in the blacks. Aldosterone excretion (0 to 12 hours) was gener ally lower post-dosing in blacks. In conclusion, whereas the PK and single- dose natriuretic response for HCTZ were not racially distinct, potassium ex cretion was notably less in blacks. Aldosterone excretion was also lower in blacks and without its normal circadian pattern which may, in part, explai n their altered potassium excretion pattern. (C) 2000 American Journal of H ypertension, Ltd.