Impotence Medications
Viagra (Sildenafil)
Sildenafil (Viagra) was the first oral phosphodiesterase type 5 (PDE5) inhibitor approved by the FDA in the United States for the treatment of erectile dysfunction (it is not approved for women). Sildenafil inhibits PDE5, which is an enzyme that destroys cGMP. By inhibiting the destruction of cGMP by PDE5, Sildenafil allows cGMP to accumulate within the penis. The cGMP, in turn, prolongs the relaxation of the smooth muscle of the Corpora cavernosa. The relaxing of the Corpora cavernosa smooth muscle allows blood to flow into the penis resulting in the overall increased size of the penis. In short, Sildenafil increases blood flow into and within the penis and decreases blood flow out of the penis.
Vardenafil (Levitra)
Vardenafil (Levitra) was the second oral medicine approved by the United FDA in the US for the treatment of impotence. Like Sildenafil (Viagra), Vardenafil (Levitra) inhibits PDE5 which destroys cGMP (as discussed earlier).
Tadalafil (Cialis)
Tadalafil (Cialis) is the third oral medicine approved by the United FDA in the US for the treatment of impotence. Like Sildenafil (Viagra) and Vardenafil (Levitra), Tadalafil inhibits PDE5 (as described earlier).
Intra-cavernosa injections
Injections can be made directly into the Corpora cavernosa to achieve and maintain erections. Medications such as Papaverine Hydrochloride, Phentolamine, and Prostaglandin E1 can be used alone or in some sort of combination to attain erections. Combining small amounts of each drug is preferred over using a single drug because of increased efficacy as well as fewer side effects. Even though such injections can be effective, they are not widely used because the injections are painful, scarring may occur, and there is a risk of developing priapism (prolonged period of erection that will not go down. In this case it is necessary to see a doctor immediately).
Intra-urethral suppositories
Prostaglandin E1 can be inserted in a pellet (suppository) form into the urethra to attain erections. This technique is also not popular because of the occasional side effects. Common side effects can include: pain in the penis, occasional pain in the testicles, mild urethral bleeding, dizziness, and vaginal itching in the sex partner. Men also need to remain standing after inserting the pellet in order to increase blood flow to the penis, and it may take 15-30 minutes to attain an erection, thus making this form of treatment very convenient. Prostaglandin can cause uterine contractions and should not be used by men having intercourse with pregnant women unless condoms or other barrier devices are used to help protect the sexual partner.
