Influence of metoprolol, alone and in combination with a thiazide diuretic, on blood pressure, plasma volume, extracellular volume and glomerular filtration rate in essential hypertension

Renal effects of antihypertensive medications: an overview

A variety of antihypertensive agents are available for management of elevated arterial pressure. Although these agents all effectively lower arterial pressure, they have somewhat diverse renal hemodynamic profiles. This report reviews the various similarities and differences in renal hemodynamic profiles among the different antihypertensive agents.

Effect of metoprolol on serial measurements of exchangeable sodium, blood pressure, renin and pulse rate in spontaneously hypertensive rats

The cardioselective beta-blocker metoprolol was mixed with the diet (6 mg metoprolol/g food) and given to 9 spontaneously hypertensive rats (SHR) for four weeks, while 9 other SHR were given the plain diet only and served as controls. All rats were also given 0.5% drinking saline labeled with isotope 22Na (37 kBq/1) to drink. Measurements of total exchangeable sodium, blood pressure, pulse rate and weight were performed before and repeatedly during treatment. Plasma renin activity was measured at the end of the study. Before treatment exchangeable sodium, blood pressure, pulse rate and weight were no different between the groups. Metoprolol reduced the pulse rate and prevented the usual blood pressure increase in SHR. Both groups gained weight similarly. Exchangeable sodium increased similarly in both groups along with the weight increase. Plasma renin activity was not significantly different in the two groups. Thus, chronic metoprolol treatment of SHR reduced blood pressure and pulse rate in SHR but did not lower plasma renin or cause measurable sodium or fluid retention.

A comparison of betaxolol and nadolol on renal function in essential hypertension

Betaxolol, a beta 1-selective adrenergic antagonist, and nadolol, a nonselective beta-adrenergic antagonist are both potent long-acting antihypertensive drugs. The effects of betaxolol on renal function have not been reported. The effects of nadolol on renal function are controversial. The current randomized double-blind study was designed to compare the effects of betaxolol and nadolol on glomerular filtration rate, assessed by creatinine and inulin clearances, and renal hemodynamics, assessed by p-aminohippurate clearance. Following a 4-week placebo run-in period, 15 patients with essential hypertension were randomized to a mean dose of 22 mg betaxolol for 12 weeks, and 12 patients with essential hypertension were randomized to a mean dose of 103 mg nadolol for 12 weeks. Results indicate that neither drug produced a clinically relevant effect on renal function. These findings are consistent with previously reported observations with other beta-adrenergic blocking drugs. We conclude that neither of the beta-adrenergic antagonists, betaxolol or nadolol, convey a specific renal pharmacologic advantage; both are equally efficacious and safe in the treatment of mild-to-moderate essential hypertension.

The acute and chronic effects of betaxolol on blood pressure, renin-aldosterone, and renal function in essential hypertension

The effects of betaxolol, a long-acting, lipid-soluble, cardioselective, beta-adrenergic antagonist on renal function have not been previously reported. The present study was designed to prospectively assess the acute and chronic antihypertensive, humoral, and renal response to betaxolol, administered once daily, to patients with essential hypertension. After a four-week placebo run-in period, 13 patients with essential hypertension were treated with betaxolol monotherapy for a total of eight months. Results indicate that blood pressure is reduced, and renal function remains stable. These findings are consistent with previous observations with other beta-adrenergic antagonists.

Acute changes in renal function induced by bisoprolol, a new cardioselective beta-blocking agent

The acute effects of bisoprolol 10 mg i.v., a new beta1-selective adrenoceptor antagonist, on heart rate, mean blood pressure (mBP), glomerular filtration rate (GFR), para-aminohippuric acid clearance (CPAH), sodium clearance, urine volume and plasma renin activity (PRA), were studied in 6 patients with essential hypertension. Heart rate decreased by 23%, mBP remained unchanged, and GFR decreased by 14% and CPAH by 23%. PRA was depressed on average by 25%. Urine volume and sodium clearance also declined by 9 and 13%, respectively, but the changes were not statistically significant. The fall in heart rate was significantly correlated with that in GFR and CPAH. Changes in GFR were correlated significantly with those in CPAH. The acute changes in renal function induced by bisoprolol are considered to be due to a reduction in cardiac output and increased systemic vascular resistance.

Renal perfusion is preserved during cardioselective beta-blockade with metoprolol in hypertension

Treatment of hypertension with beta-adrenergic blockers may impair renal perfusion, perhaps because of beta 2-blockade in the renal vascular bed. We evaluated the effects of the cardioselective (beta 1 selective) beta-blocker metoprolol upon renal hemodynamics, intravascular volume, and renal electrolyte handling in nine essential hypertensive men. Metoprolol normalized systemic BP without significant acute or chronic changes in glomerular filtration rate, renal plasma flow, or renal blood flow. Overall renal sodium excretion and fractional sodium excretion increased on chronic metoprolol, without changes in intravascular volume or renal excretion of other electrolytes. Thus, cardioselective beta-blockade with metoprolol normalizes BP without renal hemodynamic impairment.

Comparison of the antihypertensive effect of a double dose of metoprolol versus the addition of hydrochlorothiazide to metoprolol

In 27 hypertensive patients whose blood pressure could not be adequately controlled with 200 mg metoprolol Durules alone, the effect of a double dose of metoprolol Durules (400 mg once daily) was compared with a fixed combination of 200 mg metoprolol and 25 mg hydrochlorothiazide (Selokomb). The study followed a double-blind cross-over schedule in 2 parallel groups. The reduction in diastolic blood pressure (p less than 0.01) was comparable in the two groups. A significant fall (p less than 0.01) in systolic blood pressure occurred with the metoprolol/hydrochlorothiazide combination. The subsequent change from the double dose of metoprolol Durules to the combination therapy also resulted in a fall in systolic blood pressure (p less than 0.05). Mean serum potassium and blood glucose levels did not change after each alteration in therapy. Most of the side-effects mentioned were mild and transient in character.

Blood pressure, body fluid volumes and glomerular filtration rate during treatment with labetalol in essential hypertension

1 In a single blind study seventeen patients with mild or moderate essential hypertension and normal renal function were treated with labetalol alone in increasing doses from 300 via 600 to 1200 mg daily. 2 Average supine BP (systolic/diastolic) was reduced by 24/19 mm Hg. Seven patients attained a diastolic BP less than or equal to Hg. A significant postural fall in systolic BP was recorded, but no symptomatic orthostatic hypotension occurred. 3 In twelve patients measurements of plasma volume (125I-albumin), extracellular volume (82Br-space) and glomerular filtration rate (51Cr-EDTA clearance) on placebo and subsequently labetalol showed no systemic changes. 4 Side effects were few causing two withdrawals because of impotence and arthralgia. 5 It is concluded that monotherapy with labetalol results in clinically relevant, persistent and dose dependent reduction in BP in patients with mild or moderate essential hypertension, apparently without concomitant expansion of body fluid volumes or influence on glomerular filtration rate.

Short-term systemic hemodynamic adaptation to beta-adrenergic inhibition with atenolol in hypertensive patients

Early systemic hemodynamic adjustments to antihypertensive therapy with the cardioselective beta inhibitor, atenolol, were investigated in 12 hospitalized men, mean age 52 years, with uncomplicated mild-to-moderate essential hypertension. Twice daily measurements of cardiac output (CO) by CO2 rebreathing, blood pressure by cuff, and heart rate were performed in all subjects for 3 days before and 5 days after initiation of oral atenolol therapy (50 or 100 mg daily). Cardiac output by CO2 rebreathing was checked with dye dilution just before, and 4 hours and 4 days after the start of therapy. Plasma volume (radioiodinated albumin) was measured before therapy and on Day 5 of therapy. The CO results obtained with the two methods were not significantly different (r = 0.88, p less than 0.01, n = 12). A reduction in heart rate, 18 +/- 2 beats/min (mean +/- SE), occurred in all patients while taking atenolol. By 4 hours after the first dose of atenolol, CO fell from 5.49 +/- 0./30 to 4.24 +/- 0.21 liters/min (p less than 0.01), while the control mean arterial pressure (MAP) of 108 +/- 4 mm Hg was not significantly changed, 110 +/- 4 mm Hg. At 24 hours, CO returned near baseline (5.10 +/- 0.21 liters/min) but MAP was reduced (95 +/- 3 mm Hg, p less than 0.001) and remained so thereafter. CO remained at baseline at 48 hours (5.50 +/- 0.29 liters/min) but fell again (p less than 0.01) to 4.81 +/- 0.11 on Day 4 and to 4.68 +/- 0.25 liters/min on Day 5 of atenolol therapy. Plasma volume, 3110 +/- 100 ml before therapy, was reduced to 2850 +/- 100 by Day 5 of atenolol therapy (p less than 0.01). The findings indicate a delayed onset of the antihypertensive action of atenolol. The transient return to baseline of CO on Day 2 and 3 of atenolol therapy suggests a reverse autoregulatory adjustment to the initial fall in CO.

Angiotensin II blockade during combined thiazide-beta-blocker treatment

Sixteen patients (11 M, 5 F), median age 41 years, with essential hypertension insufficiently controlled on hydrochlorothiazide 75 mg/day (DBP greater than or equal to 100 mmHg) were investigated. Plasma renin concentration (PRC), angiotensin II concentration (PA II), aldosterone concentration (PAC), plasma noradrenaline concentration (PNAC), plasma volume (PV) and exchangeable sodium (NaE) were determined and a saralasin-infusion (5.4 nmol/kg/min) was carried out while the patients were on thiazide alone, and in fourteen cases, repeated 3 months later after addition of a beta-blocker (propranolol 6, metoprolol 6 and atenolol 2 patients). On thiazide alone PRC, PA II and PAC was higher than normal in the group as a whole and the angiotensin II-inhibitor, saralasin, caused a significant decrease in MAP in twelve out of sixteen patients. After addition of a beta-blocker SBP and DBP decreased from 164/109 mmHg to 136/94 mmHg. PRC and PA II decreased by 40% and 58%, respectively. At this point saralasin caused no significant change in MAP. No close correlation was found between changes in BP on beta-blocker treatment and either PRC, PA II or saralasin response on thiazide treatment. PV, NaE, PAC and PNAC did not change sigificantly. It is concluded that in pts with thiazide-induced stimulation of the renin-angiotensin system (RAS) addition of a beta-blocker leads to suppression of RAS and the angiotensin II dependence of the blood pressure is nearly abolished. This mechanism might well contribute to the antihypertensive effect of beta-blockade in this particular situation. However, the pharmacological changes induced by beta-blockade are very complex, and most likely other factors are involved in the antihypertensive effect of beta-blocking drugs.