Short Communications

Drugs 25 (Suppl. 2): 250-261 (1983)

0012-6667/83/0300-0250/$06.00/0 OJ ADIS Press Australasia Pty Ltd (Inc. NSW). All rights reserved.

Differences between Selective and Non-Selective ~-Blockade

P. W. de Leeuw, G.A. W. van Soest, R. Punt and W.H. Birkenhager Department of Medicine, Zuiderziekenhuis, Rotterdam, The Netherlands

The aim of this study was to compare the haemodynamic and endocrine effects of selective vs non-selective Ii-blockade. 65 patients with un­complicated essential hypertension were admitted to a metabolic ward after previous treatment had been withdrawn for at least 3 weeks. Sodium in­take was fixed at S5 mmol/day and checked by 24-hour urine collections. After obtaining baseline characteristics, treatment was initiated either with propranolol (n = 25) or atenolol (n = 40). Average daily doses were 240mg for propranolol and 100mg for atenolol. After 2 weeks of treatment haemo­dynamics and hormonal assays were repeated. The following measurements were made at the start of treatment and after 2 weeks: blood pressure (intra­arterial recording and automatic readings); cardiac

Haemodynamics of Cardioselective ~-Blockers without Partial Agonist Activity

H.-A. Wester Department of Internal Medicine, University of Lubeck, West Germany

Ten healthy volunteers were given intravenous infusions, in random order, of either the hydro­philic ,B-blocker atenolol (Smg), or the lipophilic agent metoprolol (5mg); the infusions lasted 5 min­utes. The haemodynamics of these 2 drugs were

output (dye-dilution); renal plasma flow (125I-hip­puran clearance at constant infusion); active renin concentration (radioimmunoassay for AI) and nor­adrenaline (radioenzymatic assay, Pnmt). In ad­dition, total peripheral vascular resistance and renal vascular resistance were calculated.

Mean arterial pressure dropped from 124 ± Smm Hg (mean ± SEM) to 112 ± Smm Hg on propranolol and from 125 ± Smm Hg to lOS ± 7mm Hg on atenolol (p < 0.01). Cardiac index fell slightly more on atenolol than on propranolol while total peripheral resistance did not change signifi­cantly with either drug. Renal blood flow, calcu­lated from renal plasma flow and haematocrit, fell to a significantly lower level during atenolol than during propranolol treatment, and changes in renal vascular resistance ran a parallel course. Renin lev­els were more effectively suppressed by atenolol, and while noradrenaline levels were not different before and during treatment with either drug, nor­adrenaline tended to decline in the atenolol group.

The present study indicates that the physiolog­ical responses to propranolol and atenolol differ. Atenolol has a more profound effect on blood pres­sure, perhaps because it more effectively inhibits . pressor mechanisms.

measured by computer-assisted echocardiography. Heart rate decreased significantly with both

drugs (atenolol, IS%; metoprolol, 10%) and con­tractility by 10 or 11% as judged by fibre short­ening or 6 and S% by systolic time intervals. Non­invasive cardiac index and left ventricular end-dia­stolic volume both decreased. Afterload blood pressure remained unchanged. Peripheral resist­ance increased (22-31 %) while the mean arterial pressure and systolic arterial pressure both de­creased.

The computer-assisted analysis of echocardio­grams confirms that both ,B-blockers studied pro­duced a pronounced negative chronotropic, and a small negative inotropic, effect.