The drug works well in most cases and has changed people's lives for the better.
In this article, we will look briefly at the history of Viagra, its pros and cons and anything to be wary of if you are considering its use.
- What is Viagra?
- Brief history of Viagra
- Viagra dosage
- Adverse events for Viagra
- Other potential effects of Viagra
Here are some key points about Viagra. More detail and supporting information is in the main article.
- Viagra was initially designed for hypertension and angina pectoris.
- Viagra's main competitors are Cialis (tadalafil) and Levitra (vardenafil).
- Side effects include headaches, hearing loss, impaired vision, increased intraocular pressure and dyspepsia.
- Viagra pills are blue and diamond-shaped.
- Individuals with kidney disease should not take Viagra.
- Some athletes take Revatio in the belief that it enhances their performance.
- Viagra works by inhibiting the enzyme cGMP-specific phosphodiesterase type 5.
- Viagra was designed by Pfizer in Kent, England.
- Some people use Viagra recreationally, although it is not thought to have any benefit in people without penile dysfunction.
What is Viagra?
Viagra was initially designed to help lower blood pressure but is now typically used to treat erectile dysfunction.
Sildenafil citrate's chemical formula is C22H30N6O4S.
Viagra works by inhibiting an enzyme called cGMP-specific phosphodiesterase type 5, that delays degradation of cGMP, which controls blood flow in the penis.
Brief history of ViagraViagra has become the prime treatment for impotence (erectile dysfunction), competing with Cialis (tadalafil) and Levitra (vardenafil) for market share.
Initially, the drug was designed by Pfizer scientists working in Kent, England. They were in fact working on a drug for hypertension (high blood pressure) and angina pectoris (a symptom of ischemic heart disease).
During the phase I trials, it was noted that the drug did very little to prevent angina but did induce marked penile erections. Hitting the market in 1998, Viagra was the first oral treatment approved to treat erectile dysfunction in the US.
Viagra's meteoric rise to fame has seen it enter usage as an illicit drug. But, Viagra use in individuals without erectile dysfunction does not seem to have any effect. Although, researchers have noted that there is a significant placebo effect. On a similar note, there is no proven benefit for women taking the drug.
With endorsements from former US Senator Bob Dole and football star Pelé, the drug goes from strength to strength. In 2008, Viagra generated some $1.93 billion of revenue for Pfizer.
DosageViagra, for erectile dysfunction, comes in blue, diamond-shaped pills, in doses of 25, 50, or 100 milligrams. The patient takes a maximum of one pill in a 24-hour period, between 30 minutes to 1 hour before sexual intercourse.
Revatio, for pulmonary arterial hypertension, comes in white, round, film-coated tablets. Patients take one 20 mg Revatio tablet three times a day.
Adverse events for ViagraAccording to clinical trial results, the most common side effects include headaches, nasal congestion, impaired vision, photophobia, and dyspepsia. Less commonly, some users have experienced cyanopsia (everything has a tinted blue tinge).
In very rare cases, Viagra use can lead to vision impairment and nonarteritic anterior ischemic optic neuropathy. Postmarketing surveillance side effects have included (very rare) priapism, heart attack, sudden hearing loss, increased intraocular pressure, and ventricular arryhythmias. Since 2007, its labeling in the US has included a warning of the potential risk of sudden hearing loss.
Viagra can decrease blood supply to the optic nerve, causing sudden vision loss. This very rare adverse event occurred mainly to patients who had heart disease, hypertension, diabetes, high cholesterol, or pre-existing eye problems. Nobody really knows whether the vision loss was caused by the Viagra.
Interactions - HIV patients on protease inhibitors should discuss using Viagra with their doctors - protease inhibitors increase the likelihood and severity of side effects. Experts say such patients should have no more than 25mg, and not more often than every 48 hours.
If the patient is taking alpha blockers, they should make sure they take that medication and Viagra at least four hours apart, to prevent low blood pressure.
Contraindications - the following individuals should not take Viagra (or check with their doctors first):
- Those on nitric oxide donors, nitrates and organic nitrites
- Men who are advised to refrain from sexual intercourse because of cardiovascular risk factors
- Patients with severe hepatic impairment
- Patients with kidney disease
- Individuals with low blood pressure (hypotension)
- Those who have had a recent heart attack
- Those who have had a recent stroke
- Individuals with hereditary degenerative retinal disorders.
Other potential effects of ViagraJet lag - Patricia V. Agostino, Santiago A. Plano, and Diego A. Golombek, from the Universidad Nacional de Quilmes, Argentina, were awarded the ig Nobel Prize in Aviation for discovering that Viagra helped hamsters recover from jet lag. (PNAS, 2007)
Exercise capacity - some athletes take Revatio to increase their exercise capacity, although evidence of its efficacy in this regard is scant.
Written by Christian Nordqvist