Sildenafil (비아그라) is the most effective oral therapy currently available for erectile dysfunction. Patients should be given clear instructions regarding the use of sildenafil. The most common side effects include flushing, headaches, dyspepsia, and transient visual changes. In combination with nitrates, it can and has caused fatal hypotension. It should not be prescribed to patients on nitrates. Additionally, nitrates should not be administered to anyone who has recently ingested sildenafil. Synergetic blood pressure lowering has not been observed when sildenafil was used with other classes of antihypertensives. Sildenafil is not offered to patients with low cardiac output states, those on intensive regimens to prevent heart failure or those with acute coronary ischemia.
Impotence – the preferred term is now erectile dysfunction is a common problem affecting between 10 to 30 million men in the United States.1 Worldwide, more than 100 million men are estimated to have some degree of erectile dysfunction. The introduction of sildenafil (비아그라) has been a valuable contribution to many patients suffering from erectile dysfunction, and the drug, has now been approved by the Ministry of Health in Saudi Arabia. There have been >20 million prescriptions written for sildenafil. A total of 69 death has been reported to the FDA as of August 26, 1998, in patients who have used sildenafil. Recently, the American College of Cardiology/American Heart Association (ACC/AHA) published their “Expert Consensus Document” on the use of sildenafil in patients with cardiovascular disease. This article is based primarily on the recommendations made in that “document”.
Sildenafil acts as a selective inhibitor of cycle GMP-specific phosphodiesterase type, resulting in smooth muscle relaxation, vasodilation, and enhanced penile erection. The vasodilating action of sildenafil affects both the arteries and the veins.
Reported side effects in the normal healthy population are usually associated with vasodilation. These include headaches (16%), flushing (10%), rhinitis (4%), dizziness (2%), hypotension (<2%), and postural hypotension (<2%). Other side effects include dyspepsia (7%), blue-green color-tinged vision and blurred vision (3%), and an unexplained myalgia.
Although their incidence is small, serious cardiovascular events including significant hypotension can occur in certain population at risk. Most at risk are individuals who are concurrently taking organic nitrates.
Sexual dysfunction in men after the diagnosis of coronary artery disease or a myocardial infarction is common.7 Most is due to the fear that the exertion of sexual activity will precipitate another myocardial infarction, but 10 to 15% of erectile dysfunction is due to organic causes.8 In USA, approximately 5.5 million men take nitrates on a regular basis for angina pectoris,9 and another half million will experience a heart attack annually and are potential candidates for nitrate therapy. Sildenafil is potentially contraindicated in these 6 million patients. All patients taking either sildenafil or nitrates must be warned of the contraindications and potential consequences of taking sildenafil within 24-hour intervals after taking a nitrate preparation, including sublingual nitroglycerin.
비아그라 is predominantly metabolized by both the P 450 2C9 and the P450 3A4 pathways. Thus, potent inhibitors of the P450 3A4 pathway may increase the plasma concentrations of sildenafil and its pharmacological effects. Cimetidine and erythromycin are commonly prescribed drugs that inhibit the P450 3A4 pathway. The simultaneous administration of either of these agents significantly increases the plasma concentration of sildenafil; a lower initial dose (25 mg) rather than the recommended 50 mg should be considered in the coadministration of sildenafil to patients receiving either of these agents.
