Metabolic effects of controlled-release metoprolol in hypertensive men with impaired or diabetic glucose tolerance: a comparison with atenolol

Safety and tolerability of β-blockers: importance of cardioselectivity

Cardioselective β-blockade is generally well tolerated in practice and contraindications to this therapy are uncommon. β-blockers are a diverse therapeutic class, and their individual tolerability profiles are influenced strongly by their pharmacodynamic effects across different adrenergic receptors. Bisoprolol, probably the β-blocker with the highest selectivity for blockade of β1- vs. β2-adrenoceptors, does not block β2-adrenoceptors to an appreciable extent at doses in therapeutic use. Side-effects often attributed to β-blockers, such as erectile dysfunction and adverse metabolic effects are uncommon with bisoprolol and other β-blockers used at doses which only block β1-adrenoceptors. Cautious use of a cardioselective β-blocker is not contraindicated in people with chronic obstructive pulmonary disease or asthma and the outcomes benefits of β-blockers in patients with coronary heart disease or heart failure are also apparent in patients with concurrent COPD. Starting with a low dose and titrating upwards carefully is important for optimising the tolerability of a β-blocker. Most people with hypertension will receive combination antihypertensive therapy in practice, and the low-dose combination therapy approach provides a useful strategy for optimising the efficacy and tolerability of a regimen that includes a β-blocker, compared with up-titrating an existing monotherapy.

Dyslipidemia induced by drugs used for the prevention and treatment of vascular diseases

Dyslipidemia is a major vascular risk factor. Interestingly, several agents used for the prevention and treatment of vascular diseases have an adverse effect on the lipid profile. In addition, agents belonging to the same class (e.g. beta blockers) can have significantly different actions on lipid levels. We summarize the effects of drugs used for the prevention and treatment of vascular diseases on the lipid profile. These effects should be considered when selecting a specific agent, particularly in high-risk patients.

Comparison of effects of quinapril and metoprolol on glycaemic control, serum lipids, blood pressure, albuminuria and quality of life in non-insulin-dependent diabetes mellitus patients with hypertension. Swedish Quinapril Group

OBJECTIVE

To compare the long-term effects of the angiotensin-converting enzyme (ACE)-inhibitor quinapril and the cardioselective beta-adrenergic blocking agent metoprolol on glycaemic control, with glycosylated haemoglobin (HbA1c) as the principal variable, in non-insulin-dependent diabetes mellitus (NIDDM) patients with hypertension.

DESIGN

A randomized, double-blind, double-dummy, multicentre study during 6 months preceded by a 4 week wash-out and a 3 week run-in placebo period. Quinapril (20 mg) and metoprolol (100 mg, conventional tablets) were given once daily. No change was made in the treatment of diabetes (diet and hypoglycaemic agents).

SUBJECTS

Seventy-two patients fulfilling the criteria were randomized and entered the double-blind period. Twelve patients did not complete the study. Sixty patients, 26 on quinapril and 34 on metoprolol, were available for the final analysis.

MAIN OUTCOME MEASURES

The effect was assessed by changes in HbA1c, the fasting serum glucose and the post-load serum glucose, C-peptide and insulin levels during the oral glucose tolerance test.

RESULTS

In the quinapril group, the fasting serum glucose, oral glucose tolerance and the C-peptide and insulin responses, determined as the incremental area under the curves (AUC), showed no change, but the mean HbA1c level increased from 6.2 +/- 1.1% to 6.5 +/- 1.3% (P < 0.05). In the metoprolol group, the rise in the mean level of HbA1c, from 6.3 +/- 1.0% to 6.8 +/- 1.3% (P < 0.01), tended to be more marked than after quinapril, although there was no significant difference between the increments. The mean fasting serum glucose showed an increase from 9.1 +/- 1.9 mM to 10.1 +/- 2.8 mM (P < 0.01) which correlated significantly with the duration of diabetes (P < 0.01) and the increase in fasting serum triglycerides (P < 0.001). Moreover, in the metoprolol group we found significant decreases in the oral glucose tolerance as well as C-peptide and insulin responses to the glucose load.

CONCLUSIONS

Treatment with quinapril for 6 months appears to have advantages over metoprolol in NIDDM patients with hypertension. Although treatment with quinapril or metoprolol over 6 months was concomitant with a rise in the HbA1c, increased fasting blood glucose, decreased oral glucose tolerance and decreased C-peptide and insulin responses to a glucose challenge were observed only in patients treated with metoprolol.

Controlled release metoprolol formulations. A review of their pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension and ischaemic heart disease

Conventional formulations of metoprolol have become well established in cardiovascular medicine and are particularly useful in the management of hypertension and ischaemic heart disease. Recently developed controlled release metoprolol delivery systems (metoprolol CR/ZOK and metoprolol OROS) were designed to overcome the drug delivery problems of matrix-based sustained release forms by releasing the drug at a relatively constant rate over a 24-hour period, and thus producing sustained and consistent metoprolol plasma concentrations and beta 1-blockade while retaining the convenience of once daily administration. Clinically and statistically significant reductions in blood pressure have been observed with metoprolol CR/ZOK and metoprolol OROS 24 hours after administration in mildly or moderately hypertensive patients. Studies in patients with mild to moderate hypertension have demonstrated that a similar or higher percentage of patients achieved a goal response with metoprolol CR/ZOK compared with matrix-based sustained release formulations of metoprolol, or conventional atenolol or bisoprolol, while metoprolol OROS achieved an equal or greater response rate compared with conventional or matrix-based sustained release metoprolol preparations. In patients with stable effort angina pectoris, once daily administration of metoprolol CR/ZOK provided at least equal antianginal efficacy as conventional metoprolol in divided doses, while metoprolol OROS reduced the mean number of anginal attacks by the same margin as atenolol. Controlled release metoprolol formulations have been well tolerated in clinical trials. Metoprolol CR/ZOK was associated with a similar or lesser degree of adverse effects related to the central nervous system compared with atenolol or long acting propranolol. Metoprolol CR/ZOK also demonstrated less pronounced beta 2-mediated bronchoconstrictor effects than atenolol in asthmatics, and less general fatigue and leg fatigue in healthy subjects. Metoprolol OROS produced less pronounced bronchoconstrictor effects than atenolol, matrix-based sustained release metoprolol or long acting propranolol in patients with asthma or obstructive airways disease, and healthy volunteers. These results are presumably due to the beta 1-selectivity of metoprolol in addition to the relatively low plasma concentrations maintained by metoprolol CR/ZOK and metoprolol OROS, and the avoidance of high peak plasma concentrations with these agents. Despite the relative safety of the controlled release forms of metoprolol, the use of all beta-adrenoceptor antagonists should be avoided in patients with a history of bronchospasm. Thus, controlled release metoprolol formulations offer the potential to maximise the confirmed benefits of this agent in the management of hypertension and angina, by maintaining clinically effective plasma concentrations within a narrow therapeutic range over a 24-hour dose interval.

Reducing the risk for coronary heart disease and stroke in hypertensives--comments on mechanisms for coronary protection and quality of life

The four most popular classes of antihypertensive drugs may all be considered suitable choices when initiating treatment for hypertension. The practitioner must decide which agent is appropriate for each individual patient. The main goal of treatment should be to prevent coronary events and stroke, while preserving quality of life. A 40% reduction in stroke can probably be achieved with any antihypertensive treatment, a reduction in coronary events is much harder to achieve. Available evidence from studies in men, summarized in this review, indicates that beta-blockade is superior to thiazide diuretics for the prevention of coronary events. Clinical trials have not yet produced long-term prognostic data on the effects of ACE-inhibitors or calcium antagonists on coronary events in hypertensive patients. A recent review on calcium antagonists in post-MI patients concluded that the results were disappointing, as pooled data actually showed a trend towards increased mortality with calcium antagonists as compared with placebo. Because of the large number of hypertensive patients at increased risk for coronary events in the community, the difference observed in coronary events between beta-blockade and other first-line drugs in hypertension (24%) may have important implications for clinical practice. This overall conclusion, however, has to be accepted with some reservations in view of the following observations. Firstly, no reduction in sudden death has been observed with the hydrophilic beta-blockers. Secondly, no reduction in coronary mortality in the smoking subgroup has been observed with the non-selective beta-blockers. Thus, it seems that the prevention of coronary events is more likely to be observed in patients given beta-blockers with certain pharmacological characteristics: relative lipophilicity, which enables passage of the beta-blocker through the blood-brain barrier to exert effects on pertinent central nervous beta 1-receptors. This is potentially useful in reducing the risk of sudden death. The addition of beta 1-selectivity is important for the risk reduction in smokers. Cardioselectivity is also an advantage in relation to side-effects and quality of life. The reduced risk for coronary events with certain beta-blockers is probably independent of the reduction in blood pressure: possible mechanisms studied are cardiac anti-ischaemic effects, antifibrillatory effects, antiatherosclerotic and anti-thrombotic effects.