Viagra (sildenafil) is approved by the FDA to treat erectile dysfunction in men. The drug is also sold under the name Revatio and is used to treat pulmonary arterial hypertension. Viagra (sildenafil) inhibits an enzyme called phosphodiesterase-5 (PDE5), which destroys an enzyme called cGMP, which is needed for blood flow. Side effects of Viagra occur because of the way the drug works in the body.
Facial Flushing
Side effects of Viagra occur because of the way the drug works in the body. When blood vessels dilate from inhibition of PDE5, blood flow is increased and results in facial flushing. Facial flushing with Viagra is one of the most common side effects experienced by men.
Headache
Dilation of the blood vessels can also result in headache, another common side effect of Viagra. Men who experience fatiguing headache should either discontinue the medication or speak with a physician about reducing the dosage.
Priapism
When blood flow to the penis changes, as it does with Viagra use, priapism can occur. Priapism is an erection that does not go away. The side effect can occur because the blood vessels contract and keep blood from flowing out of the spongy tissue that causes erection. After four hours, tissue damage occurs, making it important to seek medical treatment. The condition is extremely painful.
Dizziness
Dizziness can occur when taking Viagra. The potential side effect of lightheadedness after taking Viagra makes it important not to drive or perform activities that require mental alertness. Taking Viagra with nitroglycerin, a drug used to treat angina, or other nitrates that also dilate the blood vessels can cause severe dizziness and hypotension. Death can occur in the presence of heart disease.
Visual Disturbances
Visual disturbances, including blurriness, and changes in color perception are reported as a side effect after taking Viagra. Photosensitivity and inability to distinguish the color blue from green might occur. There have been reports of blindness from Viagra use, from optic neuropathy. According to a May 2005 statement from Pfizer, the manufacturer of Viagra, "A review of 103 Viagra clinical trials involving 13,000 patients found no reports of non-arteritic anterior ischemic optic neuropathy (NAION). Outside of clinical trials, Viagra has been used by more than 23 million men worldwide over the past seven years and reports of visual field loss due to NAION are extremely rare."
Sudden Decrease in Hearing
Sudden decrease in hearing has also been reported as a side effect of Viagra, but according to the manufacturer, it is not clear if hearing impairment is directly related to use of the medication. If hearing loss does occur when taking Viagra, it is recommended that the drug be discontinued. Report the symptoms to your physician.
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