It is estimated that in the United States, more than 30 million adult males are experiencing various degrees of erectile sexual dysfunction; more than 50% of men over 65 years of age experience complete or partial impotence.
During the 50s and 60s, our understanding of pathophysiology of male erectile function was very limited, and it was felt that the etiology of male sexual dysfunction almost always was psychological. In the urology textbook of 1965, less than half a page was allocated to this subject. There was no real treatment for it, and urologists usually tried a shot of testosterone which was rarely successful and the recommendation was to refer these patients for psychological evaluation which rarely improved their condition. Then came the 70s and the invention of various types of penile prostheses and better understanding of pathophysiology of erectile function and dysfunction, and pendulums swung from the psychological side to the organic side. In the mid 80s, it was discovered that more than 90% of male impotence was due to poor blood flow to the erectile bodies, called corpora cavernosa, and the treatment with direct injection of smooth muscle relaxants or vasoactive medications with impressive results became quite popular. Two such vasoactive medications are available: Papaverine (with or without phentolamine) or prostaglandin E1 or a combination or all three medications, called super cocktails, with success rates between 80-90%. The 90s brought MUSE or intraurethral prostaglandin E1 suppository with limited success. However, research was intensified to discover the ideal form of therapy is one that is taken orally or sublingually, preferably a short period of time before intercourse with minimal or no side effects. Three such medications were competing to fill the gap: Sildenafil (or Viagra) by Pfizer, phentolamine PO (or Vasomax) by Zonagen, and sublingual Apomorphine by Tape-Holding. Viagra was approved by the FDA in late March of 1998, and in less than two months more than two million prescriptions were written; the other two medications are in the process of completing phase 3, human trial. Pfizer is also working on faster-acting Viagra with less side effects.
Sildenafil, or Viagra, is a selective phosphodiesterase type 5 inhibitor. When sexual stimulation causes release of nitric oxide (NO) in the corpora cavernosa, inhibition of phosphodiesterase type 5 (PDE 5) by Viagra causes increased level of cyclic guanosine monophosphate (cGMP) resulting in smooth muscle relaxation and increase in arterial blood flow to the corpora cavernosa. Viagra by itself is not a smooth muscle relaxant and also is not an aphrodisiac and does not improve or increase sexual desire, and there is no effect on climax. Viagra is available in three doses: 25 mg, 50 mg, and 100 mg. It should be taken preferably on an empty stomach about an hour or so prior to intercourse. Fatty food delays the absorption of Viagra. Side effects are rather mild including headache in about 16% of patients, flushing of the skin in about 10%, dyspepsia in about 7%, nasal congestion in about 4%, and transient visual disturbance consisting primarily in differentiating blue-green color and increased perception of bright light lasting up to two hours in about 3%. Certain medications could increase the serum level of Sildenafil. The most common medications are: 1) Erythromycin which could increase the serum level by 100% and 2) Cimetadine, or Tagamet, which could increase the serum level by 200%. Sildenafil is predominantly cleared by hepatic metabolism, and the predominant route of excretion is the feces (86%) and urine (14%). Elderly patients have reduced clearance of Sildenafil and its main metabolite.
Viagra should not be used with organic nitrates (nitroglycerin patches, sublingual nitroglycerin, or tablets such as Imdur/Isordil) because the combination of Viagra and nitrates will lower the blood pressure and could produce syncope and/or reflex tachycardia, angina, myocardial infarction, or death. Because of this potentially fatal interaction with nitroglycerin, the FDA advises that patients should have a thorough medical history and physical examination to diagnose impotence and determine if there are underlying causes such as diabetes or hypertension or hormonal problems which could be treated. Cardiac risks associated with sexual activity prior to treating impotence should be discussed. A list of all medications with organic nitrates should be given to the patient. There are at least twenty medications on the market that have organic nitrates. Also, it should be emphasized that the patient should not share the medication with their friends.
Viagra is highly effective in partial sexual dysfunction and is about 45-60% effective in more severe forms of impotence due to poor blood flow.
Good luck to all you Viagraneans. Be careful and use it judiciously and try to make your partner happy.
"If it is worth doing, it is worth doing well."
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