Influence of hypoglycemic sulfonylurea compounds on the incidence of ventricular ectopic beats in non-insulin-dependent diabetic patients treated with digitalis

Oral antidiabetic treatment in patients with coronary disease: time-related increased mortality on combined glyburide/metformin therapy over a 7.7-year follow-up

BACKGROUND

A sulfonylurea--usually glyburide--plus metformin constitute the most widely used oral antihyperglycemic combination in clinical practice. Both medications present undesirable cardiovascular effects. The issue whether the adverse effects of each of these pharmacologic agents may be additive and detrimental to the prognosis for coronary patients has not yet been specifically addressed.

HYPOTHESIS

This study was designed to examine the survival in type 2 diabetics with proven coronary artery disease (CAD) receiving a combined glyburide/metformin antihyperglycemic treatment over a long-term follow-up period.

METHODS

The study sample comprised 2,275 diabetic patients, aged 45-74 years, with proven CAD, who were screened but not included in the bezafibrate infarction prevention study. In addition, 9,047 nondiabetic patients with CAD represented a reference group. Diabetics were divided into four groups on the basis of their therapeutic regimen: diet alone (n = 990), glyburide (n = 953), metformin (n = 79), and a combination of the latter two (n = 253).

RESULTS

The diabetic groups presented similar clinical characteristics upon recruitment. Crude mortality rate after a 7.7-year follow-up was lower in nondiabetics (14 vs. 31.6%, p<0.001). Among diabetics, 720 patients died: 260 on diet (mortality 26.3%), 324 on glyburide (34%), 25 on metformin alone (31.6%), and 111 patients (43.9%) on combined treatment (p<0.000001). Time-related mortality was almost equal for patients on metformin and on combined therapy over an intermediate follow-up period of 4 years (survival rates 0.80 and 0.79, respectively). The group on combined treatment presented the worst prognosis over the long-term follow-up, with a time-related survival rate of 0.59 after 7 years, versus 0.68 and 0.70 for glyburide and metformin, respectively. After adjustment to variables for prognosis, the use of the combined treatment was associated with an increased hazard ratio (HR) for all-cause mortality of 1.53 (95% confidence interval [CI] 1.20-1.96), whereas glyburide and metformin alone yielded HR 1.22 (95% CI 1.02-1.45) and HR 1.26 (95% CI 0.81-1.96), respectively.

CONCLUSIONS

We conclude that after a 7.7-year follow-up, monotherapy with either glyburide or metformin in diabetic patients with CAD yielded a similar outcome and was associated with a modest increase in mortality. However, time-related mortality was markedly increased when a combined glyburide/metformin treatment was used.

What kind of cardiovascular alterations could be influenced positively by oral antidiabetic agents?

Since the first publication of the University Group Diabetes Programme in 1970 the possible deleterious cardiovascular effects of certain hypoglycaemic sulphonylurea products has been well known. In contrast, international knowledge of the advantageous cardiovascular effects of certain sulphonylurea compounds became available recently. Glibenclamide decreases the incidence of fatal myocardial infarction and the development of ventricular fibrillation in patients suffering from acute myocardial infarction. It also lowers the incidence of ventricular ectopic beats in digitalized patients compared with patients treated with other investigated sulphonylurea compounds. The survival of patients treated with glibenclamide, insulin or diet alone is longer after the first attack of angina pectoris or after first acute myocardial infarction compared with those on other investigated sulphonylurea therapy. Glibenclamide decreases arrhythmogenesis during acute myocardial infarction in rats and strophanthin cardiotoxicity in rabbits. Arterial blood pressure and myocardial contractile force are not influenced by glibenclamide whereas these parameters are increased by other investigated sulphonylurea compounds. Consequently, deleterious cardiovascular effects of certain hypoglycaemic sulphonylurea drugs may contribute to the high cardiovascular mortality rate in diabetes mellitus, partly due to the effect on membrane channels and partly due to independent cardiac and extracardiac actions. Finally, recent observations suggest that glimepiride has a more advantageous cardiovascular effect than glibenclamide.