Viagra is an oral therapy approved by the Food and Drug Administration for the treatment of erectile dysfunction. It is supplied as a blue film coated rounded diamond shaped tablet in strengths of 25mg., 50mg. and 100mg. for oral administration.

The physiologic mechanism of erection of the penis involves the release of nitric oxide in the erectile mechanism during sexual administration. Viagra differs in this respect from the other medications that are directly injected into or absorbed by the erectile mechanism, in that it more closely resembles the normal erectile state. Viagra (sildenafil) at its recommended doses has no effect in the absence of sexual stimulation and, indeed, requires sexual stimulation to be effective.

Viagra is rapidly absorbed after oral administration. Its absorbtion is hindered somewhat by the ingestion of a fatty meal. Both Viagra, and its breakdown metabolites, have a terminal half life of about 4 hours. It reaches its maximum effectiveness approximately 1 hour after administration. As previously mentioned, when Viagra is taken with a high fat meal, the rate of absorbtion is reduced by as much as an hour. In 8 double blinded placebo controlled cross over studies, Viagra was found to be effective in patients with either organic or psychogenic erectile dysfunction.

Viagra is generally administered in single dose of 50mg. If that is not effective then the 100mg dose is utilized. In patients with liver or kidney disease, it is recommended that a smaller dose of 25mg be utilized. Viagra has been demonstrated to be both safe and effective with a very wide margin of safety concerning dose levels. Side effects observed in the test group of nearly 3000 patients included headache, flushing, indigestion, nasal congestion, some abnormal visual effects, rare episodes of dizziness and rash. The visual effects need special mention in that it usually is an interference from the blue green color discrimination.

The safety and efficacy of combination of Viagra with other treatments for erectile dysfunction have not been studied. The use of such combinations is not recommended.

There are some specific drug interactions with Viagra, most notably above these is the administration of the organic nitrates such as nitroglycerine and nitrobid used in the treatment of cardiac chest pain. There can be a very significant and dangerous drop in blood pressure and for that reason the use of Viagra in patients who are receiving these agents is absolutely contraindicated.

For most patients the recommended dose is 50mg. taking, as needed, approximately 1 hour before sexual activity. Viagra may be taken anywhere from 4 hours to 1/2 an hour before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100mg. or decreased to 25mg. The maximum recommended dosing frequency is once per day.