Sildenafil is a nitric oxide enhancer that facilitates the inflow of blood to the penis necessary for an erection. The drug takes effect about 1 hour after ingestion, and its effect can last up to 4 hours. Sildenafil is not effective in the absence of sexual stimulation. The most common adverse events associated with its use are headaches, flushing, and dyspepsia. Sildenafil is not effective in all cases of erectile dysfunction. It fails to produce an erection rigid enough for penetration in about 50 percent of men. Sildenafil use in women results in vaginal lubrication, but not in increased desire. Anecdotal reports, however, describe individual women who have experienced intensified excitement with sildenafil. Tadalafil and udalafil are the drugs which act in aOral phentolamine and apomorphine are not US Food and Drug Administration (FDA) approved at present, but have proved effective as potency enhancers in men with minimal erectile dysfunction. Phentolamine reduces sympathetic tone and relaxes corporeal smooth muscle. Adverse events include hypotension, tachycardia, and dizziness. Apomorphine effects are mediated by the autonomic nervous system and result in vasodilatation that facilitates the inflow of blood to the penis. Adverse events include nausea and sweating. Injectable and transurethral alprostadil act locally on the penis and can produce erections in the absence of sexual stimulation. Alprostadil contains a naturally occurring form of prostaglandin E, a vasodilating agent. Alprostadil may be administered by direct injection into the corpora cavernosa or by intraurethral insertion of a pellet through a canula. The firm erection produced within 2 to 3 minutes after administration of the drug may last as long as 1 hour. Infrequent and reversible adverse effects of injections include penile bruising and changes in liver function test results. Possible hazardous sequelae exist, including priapism and sclerosis of the small veins of the penis. Users of transurethral alprostadil sometimes complain of burning sensations in the penis. Intravenous methohexital sodium has been used in desensitization therapy. Antianxiety agents may have some application in tense patients, although these drugs can also interfere with the sexual response. The side effects of antidepressants, in particular the SSRIs and tricyclic drugs, have been used to prolong the sexual response in patients with premature ejaculation. Bromocriptine is used in the treatment of hyperprolactinemia, which is frequently associated with hypogonadism. Dopaminergic agents have been reported to increase libido and improve sex function. Those drugs include L-dopa, a dopamine precursor, and bromocriptine, a dopamine agonist. The antidepressant bupropion has dopaminergic effects and has increased sex drive in some patients. Selegiline, an MAOI, is selective for MAOB and is dopaminergic. It improves sexual functioning in older persons.
Androgens increase the sex drive in women and in men with low testosterone concentrations. Women may experience virilizing effects, some of which are irreversible (e.g., deepening of the voice). In men, prolonged use of androgens produces hypertension and prostatic enlargement. Testosterone is most effective when given parenterally; however, effective oral and transdermal preparations are available. Women who use estrogens for replacement therapy or for contraception may report decreased libido; in such cases, a combined preparation of estrogen and testosterone has been used effectively. Estrogen itself prevents thinning of the vaginal mucous membrane and facilitates lubrication. Two new forms of estrogen, vaginal rings and vaginal tablets, provide alternate administration routes to treat women with arousal problems or genital atrophy. Because tablets and rings do not significantly increase circulating estrogen levels, these devices may be considered for patients with breast cancer with arousal problems.
In male patients with arteriosclerosis (especially of the distal aorta, known as Leriche's syndrome), the erection may be lost during active pelvic thrusting. The need for increased blood in the gluteal muscles and others served by the ilial or hypogastric arteries takes blood away (steals) from the pudendal artery and, thus, interferes with penile blood flow. Relief may be obtained by decreasing pelvic thrusting, which is also aided by the woman's superior coital position.
Vacuum pumps are mechanical devices that patients without vascular disease can use to obtain erections. The blood drawn into the penis following the creation of the vacuum is kept there by a ring placed around the base of the penis. This device has no adverse effects, but it is cumbersome, and partners must be willing to accept its use. Some women complain that the penis is redder and cooler than when erection is produced by natural circumstances, and they find the process and the result objectionable.
Surgical treatment is infrequently advocated, but penile prosthetic devices are available for men with inadequate erectile responses who are resistant to other treatment methods or who have medically caused deficiencies. The two main types of prostheses are (1) a semirigid rod prosthesis that produces a permanent erection that can be positioned close to the body for concealment and (2) an inflatable type that is implanted with its own reservoir and pump for inflation and deflation. The latter type is designed to mimic normal physiological functioning.