The benefits of lowering raised cholesterol concentrations are established in patients with documented coronary artery disease and those at high risk.1 2 Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) are highly effective agents with few reported adverse effects. However, as their use becomes more common, adverse effects may be increasingly recognised. Impotence, rarely volunteered or asked about, is an important adverse effect of drugs and not currently associated with simvastatin.

Five men with coronary artery disease developed impotence within one week of starting treatment with simvastatin 10 mg or having the dose increased to 20 mg (three men); they also had profound lethargy and inertia. Drug treatment for heart disease (aspirin alone in two patients) was not changed. Within one week of stopping simvastatin sexual function was restored. Two patients were rechallenged with simvastatin and impotence recurred and was resolved within a week. Alternative lipid lowering drugs (fluvastatin in four patients and fenofibrate in one) maintained similar degrees of reduction in cholesterol concentration and no sexual difficulties over 12-36 months of follow up.

Adverse effects on sexual function are not reported in the major trials of simvastatin or in the drug's data sheets. The Australian Adverse Drug Reactions Committee has reported 42 cases of impotence associated with simvastatin, the onset being from 48 hours to 27 months after starting treatment.3 Simvastatin was the only drug implicated in 35 cases, with four developing impotence on rechallenge.

Simvastatin may affect the central nervous system directly by passing through the blood-brain barrier or it may interact with other agents that might cause impotence. However, two of these five patients and 35 in Australia were not receiving any other drugs, which suggests an effect on the central nervous system.

Adverse effects on sexual function due to simvastatin are infrequent and should not detract from the strong evidence of the drug's effectiveness in reducing cardiac events. However, as the use of statins increases such individual problems may arise, and early recognition may lead to their alleviation. Furthermore, the benefits of lowering lipid concentrations can be maintained with alternative agents that may avoid impotence.