There are currently four different regimens available for injection: papaverine, papaverine plus phentolamine, prostaglandin (alprostadil), and a combination of papaverine, phentolamine, and alprostadil (the synthetic prostaglandin Ej). Injection of intracavernous drugs in the office setting can be both diagnostic and subsequently therapeutic. Since the early 1980s, intracavernous injection therapy has played a major role in treating patients with both psychological and physical impotence. On the other hand, individuals who require larger doses of a mixture of papaverine plus Regitine generally have a more significant underlying physical problem and are less likely to be able to leave off the papaverine and Regitine mixture completely. In general, those patients whose penile blood flow is closer to normal will get a good response to a small dose of papaverine and are more likely to be able to gradually discontinue injections and return to satisfactory, spontaneous erections. It's always gratifying to hear a patient tell me that he keeps "the papaverine in the medicine cabinet at home as a backup, but most of the time I don't need it." Some patients in the group with the partial recovery continue to inject about one-half to one-third of the time, but in between they can have spontaneous erections. Those patients with physical causes may see a complete recovery of normal spontaneous erections from 10 to 15 percent of the time and a partial recovery up to 65 percent of the time. From reports in the literature,' patients with a psychological cause to their erectile dysfunction have as high as a 90 percent chance of return to natural spontaneous erections.