OwenDrugs and BehaviorMay 2, 2000Viagra: What, Who, Why, and HowSildenafil Citrate, more commonly known by the brand name Viagra, has become one of the most commonly prescribed drugs in America. Viagra is used to treat erectile dysfunction, also known as impotence. Erectile Dysfunction is best defined as the inability to maintain an erection necessary for sexual satisfaction. Sildenafil has been shown to be effective for a “broad range ED patients, including those with a history of mellitus, depression, … hypertension, diabetes, …and spinal chord injury” (Sildenafil Citrate, par. 29).PharmacokineticsViagra is taken orally. It is quickly absorbed into the system and usually reaches its peak concentration in about 30 to 120 minutes. However, as with most orally administered drugs, taking the pill on a full stomach will slow down its absorption (Sildenafil Citrate, par. 5). Viagra is metabolized in the liver by the cytochrome p450 system. It is converted into a metabolite that has properties similar to that of the pre-metabolized drug. Viagra and its metabolite have a “terminal half-life of about 4 hours” (Sildenafil Citrate, par. 4). Finally, Viagra is excreted primarily through feces in the form of metabolites (Sildenafil Citrate, par. 7). Mechanism of ActionSildenafil is a pharmaceutical breakthrough not only because it is the most effective treatment for erectile dysfunction available, but also because it is “the first in a new class of medications” (FDA, par. 3). But to understand how this drug works, it is necessary to explain the physiology of erection in the normally functioning male. Under normal circumstances, sexual excitement results in the release of nitric oxide. Next, the nitric oxide will activate guanylate cyclase, an enzyme. The effect of this enzyme is an increase in the amount of cylic guanosine monophosphate. This increase produces the relaxation of the smooth muscle i...
