Male impotence or erectile dysfunction (ED) or is defined as the inability of a man to achieve and maintain an erection sufficient for mutually satisfactory intercourse with his partner.
Sildenafil citrate, sold under the names Viagra, Revatio and generically under various other names, is a drug used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH), developed by the pharmaceutical company Pfizer.
Viagra is a prescription medication for the treatment of erectile dysfunction. It's the first oral medicine (a pill you take by mouth) available that's been proven to improve erections in most men with impotence. Since its introduction in March 1998, no other therapy for ED has achieved such wide public recognition.
Viagra doesn't improve erections in normal men, only in those with difficulty in achieving or maintaining erections sufficient for sexual intercourse due to a true medical problem. It is not an aphrodisiac and will not increase desire. Unlike other treatments for erectile dysfunction, Viagra requires sexual stimulation to function. Without this stimulation, Viagra won't have any effect.
Amongst sildenafil's serious adverse effects are: priapism, severe hypotension, myocardial infarction, ventricular arrhythmias, sudden death, stroke and increased intraocular pressure.
Common side effects include sneezing, headache, flushing, dyspepsia, prolonged erections, palpitations and photophobia. Visual changes including blurring of vision and a curious bluish tinge have also been reported.
Care should be exercised by patients who are also taking Protease inhibitors for the treatment of HIV. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side-effects. It is recommended that patients using protease inhibitors limit their use of sildenafil to no more than one 25-mg dose every 48 hours.
Some Viagra users have complained of blurriness and loss of peripheral vision. In May of 2005, the U.S. Food and Drug Administration found that sildenafil could lead to vision impairment and a number of studies have linked Viagra use with nonarteritic anterior ischemic optic neuropathy.
Recently researchers found that Viagra (sildenafil) taken at bedtime may worsen breathing problems in patients with severe obstructive sleep apnea, results of a study published in the Archives of Internal Medicine suggest.
Obstructive sleep apnea is a common problem that occurs when the soft tissues at the back of the throat collapse and close off the airway during sleep, resulting in brief moments in which breathing stops.
Impotence, also known as erectile dysfunction, is highly prevalent in patients with obstructive sleep apnea, note Dr. Suely Roizenblatt, of Federal University of Sao Paulo, Brazil, and colleagues. However, sildenafil prolongs the action of nitric oxide, which promotes upper airway congestion.
The researchers therefore examined the effects of a single 50-mg dose of sildenafil on the sleep of 14 men (average age, 53.1 years) with severe obstructive sleep apnea.
The subjects were randomly assigned to receive sildenafil or a placebo ("sugar pill") before they participated in an all-night sleep study, which included at least 7 hours of recording time). The subjects switched treatments and process was repeated the next night.
Compared with placebo, sildenafil led to a significantly increased desaturation index, the number of episodes of oxygen reduction per hour of recording time (30.3 events per hour versus 18.5 events per hour). There was also a significant increase in the percentage of total sleep time with an oxygen saturation of less than 90 percent (15.6 percent versus 7.9 percent) and a significant increase in the maximal duration of a desaturation event (72.5 s versus 48.1 seconds).
Sleep structure was also altered by sildenafil use, with in increase in stage 2 non-rapid eye movement sleep compared with placebo and a decrease in deep sleep compared with the start of the study and placebo, Dr. Roizenblatt's team reports.
Because of the small sample size, the results should not be extrapolated to all obstructive sleep apnea patients. "Nevertheless," they say, "sildenafil should be used with caution for treating erectile dysfunction in individuals with a sleep-related breathing disorder."
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