Viagra, the drug for erectile dysfunction (impotence), has generated an enormous amount of publicity and hype in the papers and other media. In the years since it was introduced much experience has been gained about the effectiveness of the drug, and its potential side effects.
Viagra is not a hormone and has no relationship to testosterone, the male sex hormone, which should not be taken by a man who has had prostate cancer since it might well stimulate the cancer. Because Viagra is not such a hormone, it can be safely tried in men who have had prostate cancer. The question is whether it will help them to regain potency.
To understand how Viagra works, and to perhaps try to answer this question, it is important to understand how men get and maintain an erection. When a man is sexually aroused, nerve impulses flowing to the corpora cavernosa of the penis are stimulated. These nerves release chemicals called nitric oxides, which cause the arteries to relax, thereby increasing the amount of blood flowing in. As the corpora cavernosa begin to fill with blood, the penis starts swelling, and the veins which drain the corpora cavernosa are blocked, preventing the blood from flowing out. This increased blood trapped in the penis produces the erection.
Anything that prevents the production of the nitric oxides, such as cutting the nerves or blocking the chemical pathways that produce them, will interfere with the erection. If the nitric oxides are removed too quickly, this will also prevent a full erection, and it is in this part of the process that Viagra works. Viagra blocks the action of the chemical that inactivates the nitric oxides, allowing them to persist longer in the corpora cavernosa and therefore enhancing the erection. Viagra cannot work if the nitric oxides are not produced. Therefore it will not produce an erection if the man is not sexually aroused, or if the nerves to the corpora cavernosa have been cut.
Radical prostatectomies done for prostate cancer used to result in the cutting of these important nerves, and erectile dysfunction almost always occurred. Advances in surgery have led to the development of nerve-sparing procedures, and erectile dysfunction now occurs in fewer men, but is still common. If you had those nerves cut during your surgery, I would not expect Viagra to help, but surgical techniques do differ, and the nerves may only be cut on one side, or may be temporarily damaged, permitting erections to occur after the nerves have healed. Therefore, it may be worth trying Viagra again after allowing some months to pass for healing to occur.
There are also other treatments that will produce an erection in most men even if those nerves have been cut. Injections of several drugs directly into the corpora cavernosa will produce erections in most men, and a recently marketed drug, alprostadil (Muse) is available which is inserted into the tip of the penis. These treatments are less convenient than taking a pill like Viagra by mouth, but they are effective in most men.
Viagra is known to cause serious side effects in men taking nitrates for heart disease, but appears to be free of interactions with other common drugs such as those used to treat hypertension or diabetes.