Last Updated January 2006
What is sildenafil?
Sildenafil is an oral medication used in the treatment of pulmonary arterial hypertension (PAH). It was approved by the Food and Drug Administration
(FDA) in June, 2005 for treatment of PAH patients with New York Heart Association (NYHA) Class II-IV symptoms. Sildenafil belongs to a class of drugs called phosphodiesterase 5 inhibitors. Sildenafil is also marketed as ViagraŽ
which is FDA approved for the treatment of erectile dysfunction but not for the treatment of PAH. Only RevatioŽ is FDA approved for the treatment of PAH.
How does sildenafil work?
Phosphodiesterase 5 (PDE-5) is a substance produced in the lungs and other parts of the body that breaks down (metabolizes) another substance called cyclic GMP. Cyclic GMP causes the blood vessels to relax, that is, to widen. Sildenafil inhibits PDE-5, so that more cyclic GMP is available for the blood vessels inside the lungs, leading to widening of the blood vessels. Relaxing and widening of the blood vessels in the lungs makes it easier for the heart to pump blood through the lungs. This reduces blood pressure in the lungs which should lead to improvement in physical activity level and well being. Sildenafil may also prevent platelets from clumping together and decrease the overgrowth of muscle in the walls of the blood vessels in the lung. Improvement in exercise ability and less shortness of breath has been shown in a recent multi-center study of adult PAH patients. Long-term follow-up data involving the patients enrolled in the multi-center study showed sustained improvement in exercise ability over one year for those patients who remained on sildenafil either alone or with the addition of other PAH specific medications.
How is sildenafil given?
Sildenafil is a pill taken orally three times a day. RevatioŽ is available as a round, white 20 mg pill only, to distinguish it from ViagraŽ, which is a blue diamond-shaped pill. The FDA approved the dose of 20 mg three times a day; although patients have received up to 80 mg three times a day in clinical trials.
What are the side effects of sildenafil?
Sildenafil is generally well tolerated. Common reported side effects of sildenafil are headache, heartburn, flushing, stomach upset, dizziness, temporary muscle aches, dizziness, nose bleeds, difficulty sleeping, and rash. Prolonged erection (greater than 4 hours) in a male patient is a rare but very serious side effect; if this should happen to you, you should contact your doctor immediately.
Taking certain drugs such as nitrates, nitric oxide donors or alpha blockers along with sildenafil can cause a significant drop in blood pressure, which could result in loss of consciousness or even death. Therefore, use of these classes of medications is not recommended while taking sildenafil. You should make certain that you are not taking these medications before starting sildenafil.
Is there any risk of blindness when using sildenafil?
There have been rare reports of blindness with use of sildenafil in the form of ViagraŽ. This type of blindness is called Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION). It is not yet clear whether this is related to the use of sildenafil, or to the underlying cardiovascular diseases that place the persons at risk for this particular type of blindness, even in the absence of sildenafil use. NAION has not been reported thus far with RevatioŽ.
How can a patient obtain sildenafil?
Sildenafil must be prescribed by a physician and insurance approval generally must be obtained prior to starting therapy. Sildenafil can be obtained at commercial pharmacies.
Will insurance pay for sildenafil?
The cost of sildenafil is about $10,000 a year.
At this time, most insurance companies, including most state Medicaid programs will pay for sildenafil. As of January 2006, Medicare - Part D will pay for this medication. There is also a patient assistance program from the drug manufacturer, Pfizer, Inc., that is available for some patients who do not have insurance coverage for sildenafil and can not afford to pay for it.
Can sildenafil be taken with other medications?
As stated earlier, you should not be taking nitrates or nitric oxide donors in any form while taking sildenafil.
Caution should also be used when taking sildenafil in combination with drugs known as alpha-blockers. These drugs can lower blood pressure to dangerous levels when used together with sildenafil.
Studies are currently underway investigating the use of sildenafil in combination with the other PAH therapies.
Although a drug interaction has been demonstrated with sildenafil and bosentan, dose adjustments are presently not recommended for either drug.
Could a patient be allergic to sildenafil?
This is possible, although unlikely. Any medication can cause side effects or sensitivities and you should check with your doctor if you experience a problem. To date, two cases of acute bronchospasm have been reported with RevatioŽ use.
Can men and women take sildenafil?
Yes, studies have evaluated sildenafil in both men and women with PAH and no differences in side effects have been reported between genders. Peer-reviewed studies have not shown any effect on sexual function in women who have taken sildenafil.
Use of sildenafil in pregnant and nursing women
Sildenafil has not been studied in pregnant or nursing women, and therefore is not recommended for use in pregnant or nursing women. Appropriate contraceptives should be used for prevention of pregnancy while taking sildenafil.
Use of sildenafil in children
The safety and effectiveness of sildenafil in pediatric PAH patients has not been established. Studies are currently ongoing.
