Tadalafil in the Treatment of Erectile Dysfunction

Erectile dysfunction (ED) refers to the inability of a man to achieve or maintain an erection that is sufficient for his sexual needs or the needs of his partner. ED affects 150 million men worldwide, including an estimated 15 to 30 million men in the U.S. The incidence of the disorder increases with age. Chronic ED affects approximately 5% of men in their 40s and 15% to 25% of men by the age of 65. As many as 50% of men between ages 40 and 70 are affected by transient ED and inadequate erections.

The incidence of ED is projected to increase sharply over the next 25 years. It may also be a biobehavioral marker for diabetes mellitus, depression, and/or cardiovascular disorders.

Advances in protein chemistry and molecular biology, along with an increased understanding of the mechanisms involved in a penile erection, have sparked the development of medicinal approaches to the treatment of ED. The three orally active medications available for patients with ED are sildenafil citrate (Viagra canadian, Pfizer), vardenafil generic (Levitra drug, Bayer/GlaxoSmithKline), and tadalafil (Cialis canadian, Eli Lilly). Tadalafil medication is the latest of the three to be approved by the Food and Drug Administration (FDA). This medication is a highly selective, potent, reversible inhibitor of phosphodiesterase type 5 (PDE₅).

In the treatment of any disorder for which more than one drug in the same or a similar class is available, the patient’s preference is an important issue for physicians to consider; this is true in the case of ED because it is a subjective complaint. Tadalafil tablet differs from the other two products in that it stays in the body for a longer time, which is an advantage for men with ED.

ETIOLOGY

For a penile erection to occur, a sequence of events must take place. ED can result if the order of any of these events is disrupted. These events include the transmission of nerve impulses in the brain, spinal column, and the area around the penis as well as responses in the muscles, fibrous tissues, veins, and arteries in and near the corpus cavernosum. Nerve damage and a reduced blood flow to the penis are the most common physical causes of disruption. Underlying conditions associated with ED include the fol-lowing:

• Arteriosclerosis. Thickening of the arterial walls results in a reduced blood flow throughout the body and can lead to impotence. Arteriosclerosis is associated with aging and accounts for 50% to 60% of impotence in men above age 60. Risk factors for arteriosclerosis include hypertension, diabetes mellitus, smoking, and hyperlipidemia. Smoking is the most significant risk factor for impotence related to arteriosclerosis.
• Diabetes. Chronic hyperglycemia associated with diabetes mellitus damages the nerves and small blood vessels throughout the body. Some antihypertensive medications, heart medications, tranquilizers, anti-depressants, and sedatives contribute to or cause ED.
• Drug use. Long-term use of alcohol and illicit drugs may affect the vascular and nervous systems and are associated with ED.
• Hormonal disorders. Testosterone deficiency can result in a loss of libido and loss of erections. Hormone imbalances can result from kidney or liver disease.
• Neurological conditions. Brain or spinal cord injuries such as a stroke or paraplegia can cause ED when the transfer of nerve impulses from the brain to the penis is blocked. Multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease are other nerve disorders that sometimes also result in ED.
• Surgery and radiation therapy. Surgery or irradiation of the prostate, bladder, colon, or rectum may damage the nerves and blood vessels involved in erection.
• Injury or trauma. Trauma to the spinal cord or pelvic region can damage the veins and nerves needed for an erection.
• Peyronie’s disease. This rare inflammatory disorder causes scarring of erectile tissue. The scarring produces curvature of the penis and can cause painful erections that often interfere with sexual function. An erection cannot be maintained if the veins in the penis cannot prevent blood from leaving the penis during an erection.
• Venous leakage. A venous leak can result from injury, disease, or damage to the veins in the penis.
• Psychological state. Depression, guilt, stress, and anxiety all contribute to a loss of libido and to ED.