EFFECTS OF LISINOPRIL AND HYDROCHLOROTHIAZIDE ON PLATELET-FUNCTION AND BLOOD RHEOLOGY IN ESSENTIAL-HYPERTENSION - A RANDOMLY ALLOCATED DOUBLE-BLIND-STUDY

Aim: To compare the effects of an angiotensin converting enzyme (ACE) inhibitor and a thiazide diuretic on platelet function and haemorrheol ogical variables, since these factors may contribute to the atheroscle rotic and thrombotic complications associated with hypertension. Metho ds: Following a 2-week placebo period, 80 male and female patients wit h mild to moderate hypertension, aged 50+/-10 (mean+/-SD) years, were randomly allocated in a double-blind study to 4 weeks of treatment wit h the ACE inhibitor lisinopril at 20 mg once a day or the diuretic hyd rochlorothiazide at 25 mg once a day. Venous blood was sampled before and at the end of the 4-week treatment period to assess platelet funct ion and haemorrheological variables. Results: Both treatments lowered systolic and diastolic blood pressure equally and had no significant e ffect on platelet counts and platelet aggregation in response to ADP a nd to arachidonic acid. Haematocrit plasma viscosity and blood filtera bility were not altered by either drug. Hydrochlorothiazide tended to increase and lisinopril tended to decrease whole blood viscosity at al l shear rates but these changes did not reach statistical significance . Lisinopril increased the erythrocyte aggregation time (from 1.98+/-0 .50 to 2.08+/-0.52 s) and decreased the disaggregation shear rate (fro m 159+/-46 to 153+/-40 s-1) and the disaggregation shear stress (from 705+/-257 to 659+/-204 mPa). Hydrochlorothiazide induced the opposite effects (2.00+/-0.47 to 1.92+/-0.39 s, 181+/-531 to 196+/-82 s-1 and 8 13+/-268 to 868+/-392 mPa, respectively) with a statistically signific ant (P < 0.05) intergroup difference. Conclusions: These findings sugg est that chronic treatment with the ACE inhibitor lisinopril, but not the diuretic hydrochlorothiazide, may produce favourable effects on bl ood rheology, but the clinical relevance requires further investigatio n.