In recent years, there has been a seismic change in the recognition and management of diabetic patients with erectile dysfunction (ED). Fundamental to this is the recognition that ED represents a vascular complication of the disease. Cardiovascular disease increases the risk of ED, but ED itself is probably a risk factor for cardiovascular disease. The estimated prevalence of ED in diabetic populations is of the order of 38-55% making it one of the most common complications of diabetes in men. ED in diabetes is most likely to be as a result of a defect in nitric oxide-mediated smooth-muscle relaxation as a consequence of autonomic nerve damage and endothelial dysfunction. Large vessel disease and hypertension may also contribute.
In today's climate, male diabetic patients with ED are much more likely to seek advice and treatment. Every opportunity for them to so do should be made available and routine enquiry into sexual function, especially in older patients, may well be appropriate. Few investigations are needed. Measuring serum testosterone might be helpful if sex drive is reduced. Other endocrine testing should only be undertaken in the rare situation when a clinical suspicion of hypogo-nadism exists. A detailed history should be taken to define the precise problem with sexual function.
If a diabetic male with ED wishes treatment for the condition, he should be offered an oral agent as firstline therapy assuming there is no contraindication. It is fruitless to try and determine whether the ED has a psychogenic component or not. Phosphodiesterase inhibitors, such as sildenafil (Viagra®), are the agents of choice. Inhibition of this enzyme diminishes the breakdown of nitric oxide via the second messenger cGMP. Sildenafil only works in the presence of sexual stimulation and has no effect on libido. It should be taken in a dose of 50-100 mg 1 hour before planned sexual activity and sexual activity may take place for about 4 hours after the 1 hour period. The commonest side-effects are headaches, dyspepsia and flushing. Sildenafil is not associated with an increased risk of cardiovascular events, although the resultant sexual activity may be. Treatment with nitrates is an absolute contraindication to the use of sildenafil as the combination may produce profound hypotension. Temporary visual changes have been reported. The success rate for sildenafil for the treatment of ED in diabetic men is about 60%.
Vardenafil and tadalafil are more recently introduced phosphodiesterase inhibitors. Vardenafil is a useful alternative to sildenafil and may be associated with a lower frequency of visual disturbance as a side-effect. It is worth trying when sildenafil has failed. Tadalafil has a much longer half-life than either silden-afil or vardenafil. The advantage of this is that is can be taken several hours before sexual activity rather than shortly beforehand. Additionally, its efficacy may persist for up to 36 hours after oral dosing.
Apomorphine, a centrally acting inducer of erections, is an alternative to phosphodiesterase inhibitors. Nausea is the main side-effect, however, this is much less frequent with the licensed sublingual preparation.
In those failing to respond to oral agents, erection may be induced by the intracavernosal injection of alprostadil (prostaglandin E). However, long-term discontinuation rates are high, penile pain is a relatively common side-effect of such therapy and patients must be warned of the much more serious complication of priapism which, if it occurs, necessitates urgent medical attention. An alternative mode of delivery of alprostadil is by the transurethral routine using a slender applicator to deposit a pellet containing alprostadil in polyethylene glycol. Such therapy, marketed as MUSE (Medicated Urethral System for Erection) has been successful in about 65% of diabetic men although often associated with penile pain. Long-term usage rates are not high and some men may actually prefer to inject intracavernosally.
Devices which produce a passive penile tumescence by applying a vacuum via a hand or battery operated pump are available. Penile engorgement is maintained using a rubber constriction ring at the base of the penis. Although rigidity sufficient for vaginal penetration may be induced in most patients, the quality of erection may not be as good as that achieved by pharmacologic methods and many couples may not find such a technique acceptable for a variety of reasons. For those who have failed to respond to the above approaches and with careful selection and counseling, the surgical implantation of a penile prosthesis can be a successful treatment for erectile failure.
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