Drugs for erectile dysfunction
Erectile dysfunction is a condition associated with an inability to achieve and maintain an erection resulting in an inability to participate in penetrative sexual intercourse. It is commonly seen in diabetic patients, patients with severe atherosclerosis (narrowing of arteries due to fat deposits), and spinal cord accident patients (paraplegics and quadriplegics)
Pfizer researched a chemical entity called as Sildenafil Citrate and found that the drug being researched for pulmonary hypertension was consistently giving rise to penile erections. Thus Pfizer obtained a patent from the USFDA and began marketing Viagra in 1998. It soon became a massive hit for Pfizer and grossed over a billion USD in sales year after year. Sildenafil works by inhibiting an enzyme called as Phosphodiesterase 5. Ercetion occurs normally when Nitric Oxide binds to Guanylate Cyclase in the penile muscles which releases cyclic Guanosine Monophosphate which in turn causes smooth muscle relaxation and blood being pooled in the penis. Phosphodiesterase 5 degrades the cyclic Guanosine Monophosphate normally and sildenafil blocks this action.
Viagra has now got stiff competition from two other brands called as Levitra (Vardenafil, from Bayer) and Cialis (Tadalafil, from Eli-Lilly.)
Viagra has been called as Vitamin V, the Blue Pill (because of its color.) and is available in strengths of 25, 50 and 100 mg. The drug should be taken 30 minutes to 4 hours before a planned intercourse. The difference between the three available drugs is the time interval they allow to plan an intercourse with Cialis offering a window of almost 36 hours.
Side effects from these drugs can be painful and prolonged erections, dangerous drop in blood pressure, tendency to precipitate heart attacks and strokes. There are many other minor side effects. These drugs should be taken only after consulting a physician. They are not aphrodisiacs. They should not be taken concomitantly with Nitrates (medicines used to relieve chest pains.)
Viagra has been extensively studied as a medical management for pulmonary hypertension, Raynaud’s phenomenon and high altitude sickness and has shown promising results. Non-Medical uses include as an aphrodisiac, in combination with amphetamines (mainly with MDMA or ecstasy and called as sextasy) and has been studied in jet-lag research.