Viagra: on release

Evidence on the effectiveness of sildenafil is good

Editorial p 760 News p 765 Medicine and the media p 824

The popular interest in Viagra (sildenafil) is not solely the result of media hype and the drug's association with sex: the demand for treatment has been enormous. Since its launch in the United States in March it has become the fastest selling drug ever.1 The demand is being met by prescription in the United States and globally through the internet and on the street, which in Europe precedes its licensing for prescription by doctors.

The level of demand was predictable, given a prevalence of erectile dysfunction of over 50% in men aged 50-70, and the unacceptability, poor effectiveness, or unavailability of existing treatments, such as implants, intracavernosal injection, intraurethral pellets, vacuum devices, and sex therapy.2 To most sufferers a tablet treatment must have seemed too good to be true.

A localised effect after oral administration is possible because of sildenafil's specificity of action. The final common pathway for sexual arousal and stimulation leading to erection is the production in cavernosal tissues of cyclic guanosine monophosphate (GMP), which relaxes the smooth muscle and permits swelling of the corpora with blood. Sildenafil is a potent and specific inhibitor of cyclic GMP …