Viagra and health: Beyond ED
When the history of men's health is written, 1998 will go down as a banner year. That's when sildenafil (Viagra) was approved by the FDA to treat erectile dysfunction (ED). But when the history of sildenafil is written, 2005 will also be special. That's when the FDA approved the medication that revolutionized male sexuality for a nonsexual condition. The illness is pulmonary hypertension, and sildenafil is prescribed for it under the brand name Revatio.
Other targets: Therapeutic roles
Scientists who noticed that the ED pills can produce side effects in many parts of the body are asking if they can also serve therapeutic roles beyond male (or female) sexuality. Because of its seniority, most of the research has used sildenafil, so it's not clear if the newer medications will fill similar roles. But for sildenafil, at least, some new uses appear promising.
Pulmonary hypertension. It's the only nonsexual condition that has earned FDA approval for sildenafil. When we think of blood pressure, we usually think of the systemic circulation, of the blood pumped from the heart's left ventricle to the aorta and then to the smaller arteries that carry oxygen-rich blood throughout the body. But to pick up vital oxygen, blood must first pass from the less powerful right ventricle through the pulmonary artery to the lungs, then back to the left side of the heart.
Exercise is the most common cause of rising pulmonary artery pressure, but the elevation is mild and subsides promptly with rest. High altitudes are another cause, which can lead to mountain sickness .Far more serious are the large number of lung diseases, vascular diseases, heart disorders, and miscellaneous conditions that can cause pulmonary hypertension.
Pulmonary hypertension causes shortness of breath, first during exertion but eventually at rest if the condition progresses. A variety of treatments are available, depending on the underlying problem. And the FDA has approved sildenafil (Revatio) in a dose of 20 mg three times a day for men and women with pulmonary hypertension.
Mountain sickness. Pulmonary hypertension is a feature of acute mountain sickness. High altitudes produce low blood-oxygen levels. In turn, low oxygen produces a narrowing of the pulmonary arteries. The heart must therefore work harder, reducing the capacity to exercise.
Sildenafil widens the pulmonary arteries. To find out if it might improve exercise capacity in low oxygen conditions, scientists tested 14 healthy mountain climbers in a lab in Germany and again at a Mount Everest base camp. Under both conditions, a 50-mg sildenafil tablet decreased pressures in the lungs' blood vessels and increased the maximum exercise capacity.
It's a small study, though, and it's too soon to say if sildenafil will help prevent or treat acute mountain sickness.
Raynaud's phenomenon. In affected individuals, exposure to the cold triggers spasm of the small arteries that supply blood to the fingers, toes, or both. Temporarily deprived of adequate blood flow, the involved digits become pale, cold, and very painful.
In the vast majority, there are no underlying diseases (primary Raynaud's), and patients do well simply by minimizing their exposure to cold. But secondary Raynaud's can complicate collagen-vascular diseases or certain other conditions. It's not common, but secondary Raynaud's can be very painful and difficult to treat. But a 2005 study of 16 patients with severe Raynaud's phenomenon that had not responded to other medications reported benefit from sildenafil in a dose of 50 mg twice a day.
Heart disease. Several studies of patients with congestive heart failure reported that the medication improves oxygen consumption, pulmonary artery pressure, and exercise capacity in these patients. Research shows that sildenafil helps the heart muscle relax properly, which could help patients with heart failure due to diastolic dysfunction.
Sildenafil has already been licensed to treat men and women with pulmonary hypertension. Time will tell if any of these drugs will fill other potentials beyond promoting potency.
September 2007 update