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History
Sildenafil citrate, known as Revatio, Viagra and many others, is a medicine used for treating impotence or erectile dysfunction of men and PAH, pulmonary arterial hypertension. It was invented by Pfizer, the pharmaceutical company. Its main competitors are tadalafil, and vardenafil.
A group of chemists from Pfizer's Sandwich, Kent synthesized Sildenafil. First it was studied in connection with using in angina pectoris and high blood pressure. After the first phase of clinical trials it became clear that the drug had almost no effect on angina, however it could induce penile erections. So Pfizer made a decision to market it as remedy for erectile dysfunction. The medicine was patented in the late 1990s. It was approved by the Food and Drug Administration in 1998. It was the first pill that was approved for treating erectile dysfunction in the US. Soon it was a big success.
Albert Wood and Peter Dunn are considered to be the drug inventors by the British press, but it is disputed by Pfizer. Their names are written on the patent application drug; however Pfizer says this was done just for convenience.
Many online sites offer for sale Viagra after just an "online consultation". The popularity of "Viagra" has leaded to that lots of fake aphrodisiacs name themselves as "herbal Viagra". Viagra is called informally as "the Blue Pill", "Vitamin V", and many others as well.
Hepatic enzymes metabolize Sildenafil and the kidneys and liver excrete it. Taking it with a high-fat food, may cause a delay in sildenafil absorption and the effect might decrease slightly because the concentration of plasma will be less.
Dosage and price
Like all the prescription medicines, correct dosage should be prescribed by a licensed doctor.
The sildenafil dose for impotence is from 25 mg to 100 mg, it should be taken once a day between thirty minutes and four hours before sexual intercourse.
Viagra is generally recommended to begin with 50 mg and after that raise or lower the dosage according to the result. Viagra is sold in 3 dosages (100, 50, and 25mg); they cost about 10 dollars per pill. Viagra sildenafil isn't scored and it's rather difficult to cut the pills accurately in half because of a hard coating.
Viagra tablets are diamond-shaped and blue, on one side there is "Pfizer" and on the other there's "VGR x" (x means "100", "50" or"25", the dose).
There are side effects, but among sildenafil is rare but grave unfavorable effects are: severe hypotension, priapism, ventricular arrhythmias, myocardial infarction, intraocular pressure.
Ordinary side effects are headache, sneezing, dyspepsia, flushing, photophobia and palpitations.
Patients should take it carefully if they are using Protease inhibitors for the HIV treatment as well.
Some users of sildenafil have complained that they see everything painted blue - cyanopsia. Several complained of peripheral vision loss and blurriness.
Using with an alpha blocker may cause low blood pressure (hypotension), but it doesn't happen if you take them four hours later at least.
Aphrodisiac
Sildenafil is increasingly and commonly taken as an aphrodisiac, for example to enhance sexual desire. But, there isn't any clinical evidence about its aphrodisiac ability, since it doesn't affect directly on the brain, though increased capability to attain an erection is likely to interpret as better sexual arousal by these drugs users.
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