Determinants of satisfactory rigidity after intracavernosal injection with prostaglandin E1 in men with erectile failure.

The study examines the erectile response of intracavernosal injection with increasing doses of prostaglandin E1 (PGE) and papaverine/phentolamine (PP) in 516 men with erectile failure. The response was correlated to age, the duration of erectile failure, the quality of spontaneous erections, tobacco consumption and medicine use. In addition, the erectile response was related to penile brachial index (PBI) the free testosterone index and various hormonal parameters. Over 60% of the subjects obtained satisfactory rigidity of at least 30 min duration with 7-15 micrograms PGE. A further 15% (PGE non-responders at the doses tested) obtained rigidity with PP. The average dose necessary to achieve rigidity was 8.8 micrograms for PGE and 0.94 ml (papaverine: 15 mg/ml; phentolamine 0.5 mg/ml) for PP. The average duration of rigidity was 2.2 h and 2.3 h for PGE and PP, respectively. Tobacco consumption, the duration of erectile failure and the age of the subject did not influence the response to intracavernosal injection. Moreover the PBI, the free testosterone index or libido of the subject, did not appear to be generally important for obtaining satisfactory rigidity. In contrast, chronic medication, especially antihypertensive drugs, was associated with significantly higher numbers of poor responders, a shorter duration of erection in the responders and higher doses of PGE necessary to achieve a satisfactory response. The combination of increasing age and antihypertensive medication was predictive for a poor intracavernosal response. In general, a reduced incidence of morning erections was predictive of a weaker response to PGE. The proportion of men with a PBI lower than 0.75 increased with age. These subjects more often took chronic medication, had a lower frequency of morning erections and exhibited a significantly weaker reaction to PGE than subjects with higher PBI. In summary, a large number of men with erectile failure can obtain satisfactory rigidity with intracavernosal injection. In men taking antihypertensive medication, especially in higher age groups, the dose of the intracavernosal medication had to be increased. A reduced sensitivity to intracavernosal medication could be predicted from a lower PBI and a reduced frequency of spontaneous erections.