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Viagra

Sildenafil citrate is better known as Viagra and under various other trade names. It is a drug used to treat erectile dysfunction and pulmonary arterial hypertension (PAH).

Sildenafil was initially studied for use in hypertension (high blood pressure) and angina pectoris. Phase I clinical trials suggested that the drug had little effect on angina, but that it could induce marked penile erections. Pfizer therefore decided to market it for erectile dysfunction, rather than for angina. It soon became a great success: annual sales of Viagra peaked in 2008 at US$1,934 million.

In 2000, Viagra sales accounted for 92 percent of the global market for prescribed erectile dysfunction pills. By 2007, Viagra's global share had plunged to about 50 percent due to the entry of tadalafil (Cialis) and vardenafil (Levitra) onto the market, along with the introduction of both counterfeits and clones, and reports of vision loss in people taking PDE5 inhibitors.

• Erectile dysfunction – Viagra  in theory should not work without sexual stimulation. If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third.
• Pulmonary arterial hypertension - Sildenafil is named Revatio in this context ' to avoid confusion with Viagra', but it is the same drug. 
• Other uses – the same drug has also been used for prevention and treatment of high-altitude pulmonary edema associated with altitude sickness such as that suffered by mountain climbers[!]

On Jun, 14, 2015: 33,744 people reported to have side effects when taking Viagra. Among them, 55 people (0.16%) have Hallucination.

On Jun, 13, 2015: 33,744 people reported to have side effects when taking Viagra. Among them, 17 people (0.05%) have Hallucination, Auditory.

On Jun, 1, 2015: 33,744 people reported to have side effects when taking Viagra. Among them, 36 people (0.11%) have Hallucinations.

On Jun, 4, 2015: 33,744 people reported to have side effects when taking Viagra. Among them, 1,037 people (3.07%) have Death.