Myron I. Murdock, M.D., F.A.C.S.

Oral Medications used for Erectile Dysfunction

    Oral medications available at this time include the PDE5 inhibitors :Viagra (Sildenafil) and Levitra (vardenafil), yohimbine (Yocon), trazodone (Desyrel), and methylated testosterone. 

PDE5 Inhibitors

    The PDE5 inhibitors are a family of drugs that increase blood flow to the penis causing improved erection and sexual performance in the male. They also work in females contributing to clitoral engorgement, increased lubrication and sexual arousal.  They work by inhibiting the inhibitor of cyclic GMP, causing an increased production of cyclic GMP by the lining of the blood vessels of the penis. The cyclic GMP acts as a potent  relaxor to the muscles of the blood vessels, dilating them and improving erections. There are currently two PDE5 inhibitors on the market, Viagra (Sildenafil) and Levitra (vardenafil), and a third soon to be released, Cialis (vardenafil).

   Viagra (Sildenafil) was the first PDE5 inhibitor used for treating male erectile dysfunction. It was introduced  in 1998 and improves erections in  75-80% of all men with erectile dysfunction, 40% of men who are impotent due to radical prostatectomies for prostate cancer, and most men with psychogenic impotence. Viagra can be tried by  men who have erectile dysfunction no matter what degree of impotence they have.  However, Viagra should be strictly avoided by  patients taking organic nitrates such as nitroglycerin, as the combination has led to shock and death. Patients allergic to Sildenafil, or with severe cardiac disease in which sexual function is prohibited,  or who have the rare eye disease retinitis pigmentosa should strictly avoid Viagra.

    Viagra is taken one to four hours prior to sexual activity and needs sexual stimulation to be effective. It is more effective if taken at least two hours after a meal, especially a fatty meal. The effects last about 4 hours but many patients experience positive effects 8-12 hours later. The side effects include: mild headaches, facial flushing, stomach upset, nasal congestion and unusual  visual disturbances including a bright vision and a blue-green halo around  objects. When these symptoms occur they are usually of short duration, lasting less than 15 to 30 minutes and of mild degree and always self limiting.

   Levitra (vardenafil) was released in September 2003, it is somewhat more potent than Viagra, and may induce erections in some patients who have failed Viagra.  It should not be used by patients who are on alpha-blockers (Flomax, Hytrin, Cardura, terazocyin, doxazocyn), as it may increase the incidence of low blood pressure. Similarly it should be avoided in patients on nitrates such as nitroglycerin. Patients allergic to Sildenafil, Vardenafil or with severe cardiac disease in which sexual function is prohibited,  or who have the rare eye disease retinitis pigmentosa should strictly avoid Levitra.

    Levitra is taken 20 minutes to 1 hour before sex, and can be taken with a meal, however very fatty meals may decrease and delay its effect.  The duration of action is  slightly greater than Viagra.   Side effects are similar to Viagra.

    Cialis (tadalafil) will probably be released in December 2003 and has a much longer duration of action, perhaps up to 48-72 hours.

Other Agents

    Yohimbine products, such as Yocon 5.4 mg is a natural product derived from the bark of the yohimbine tree of South America.  It has been used in the past and is effective in approximately 25-35% of patients with erectile dysfunction. There is question  as to how it works. Its major side effects are: hypertension, cardiac arrhythmia, and anxiety production. With the introduction of Viagra, the question arises  as to the role of yohimbine in treatment regimens, though patients who have had good results with it should probably continue to use it. Side effects include increased blood pressure, agitation, diarrhea, cardiac irregularities, and sleep disturbances.

    Trazodone or Desyrel is an antidepressant whose side effects include prolonged erections, including a rare occurrence of priapism, an erection that will not go away without medical or surgical treatment. In depressed, impotent men this drug may have a place although with the advent of Viagra its use is limited.

    Testosterones oral testosterone in the form of methylated testosterone should probably never be used because of its major and serious side effect:  chemical cholestatic jaundice and  liver toxicity. If patients are found to be testosterone deficient then utilization of injectable Depo-testosterones 200 mg every two to three weeks or daily morning testosterone gel, (Androgel or Testrine) or testosterone patches, 5 mg nightly should be utilized. Testosterone replacement will  improve sexual desire in men who are testosterone deficient, but will improve their sexual function only 50% of the time since there are other factors involved in many of these men including vascular disease, diabetes, etc.

Rev: 09/03

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Werner - Francis Urology Associates llc - Mid Atlantic Urology Associates llc

Greenbelt - Bowie - Laurel     Maryland

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Rev:03/08