ENALAPRIL VERSUS METOPROLOL IN PRIMARY HYPERTENSION - EFFECTS ON THE GLOMERULAR-FILTRATION RATE

Background. Hypertension is a significant cause of end-stage renal fai lure and effective treatment of hypertensive will reduce the progressi on rate of chronic renal failure in various kidney disorders. Differen t classes of drugs may be more effective than others in this respect. In this study we compared the effects on the glomerular filtration rat e (GFR) of the ACE-inhibitor enalapril and the betablocker metoprolol in patients with mild and moderate primary hypertension during 6 years . Methods. Patients with GFR in the normal range (greater than or equa l to 80 ml/min/l.73 m(2) BSA) were included after a placebo treatment period of 4-8 weeks if diastolic blood pressure was 100-120 mm Hg. Tar get blood pressure was set to <90 mm Hg diastolic. One hundred and thi rty patients were randomized in an open parallel study to receive eith er enalapril or metoprolol. No placebo group was included. GFR was mea sured using the (CR)-C-51-EDTA clearance method and 81 patients comple ted the study. Results. At inclusion, there were no significant differ ences regarding GFR or blood pressure between the groups. The blood pr essure treatment goal was reached in all patients and was maintained d uring the whole observation period. A small but significant fall in GF R by 4 ml/min/1.73 m(2) BSA was noted in both groups after the first y ear of treatment but thereafter GFR decreased by only 1 ml/min/year/1. 73 m(2) BSA, in both groups. Body weight, serum uric acid and triglyce rides increased slightly with metoprolol treatment but no other differ ences between the two treatments were noted. Conclusions. With the blo od pressure maintained at the same level using either enalapril or met oprolol during a 6-year study period, GFR decreased to the same extent in the two groups both during the first year and thereafter. The over all magnitude of the GFR decline approached that of the normal age-rel ated decrease of kidney function, i.e. GFR decreased only about 1 ml/m in/year. Thus, treatment with an ACE-inhibitor, enalapril, and a beta- blocker, metoprolol, protected the kidney function to the same extent in this 6 year long study in mild and moderate primary hypertension.