There are many categories of medications available for treating impotence / erectile dysfunction, each having its own mechanism of action. This includes viagra, cialis, levitra and many more...

Viagra (Sildenfail Citrate):

Nitric oxide (NO) is a molecule that is secreted inside the penis in response to stimulation. NO is the molecule responsible for induction of erection. Nitric oxide is broken down and degraded by and enzyme named "phosphodiesterase inhibitor" or (PDE). An antagonist to PDE will protect Nitric oxide (NO) from degradation and thus increase erection. There exist various types of PDE, PDE1, 2, 3..15. PDE5 and PDE11 are the most relevant to erection.

Viagra is an inhibitor to PDE5. It increases the level of NO (nitric oxide) in the penis in response to stimulation.

Viagra is effective in many cases of  impotence whether due to psychogenic or organic causes.

Viagra does not treat the cause of impotence, but rather increases blood flow into the penis to compensate various degrees of arterial occlusion, venous leak..etc.

There are some recent reports that viagra in daily doses over a long period of time can prevent or totally cure some cases of impotence. This is yet to be confirmed.

 It is important to understand that initiation by stimulation is important for viagra to act and preserve the secreted (NO). Without initial stimulation,  viagra  will not work.

Viagra is not an aphrodisiac, meaning that it does not increase desire. It rather augments the response of the penis to stimulation.

Thus, for viagra to work, there should be a minimum of sexual desire and response to stimulation, and the local tissues of the penis should be capable of producing nitric oxide and dilating to accommodate blood (contrary to severe cases of fibrosis of the penis or total arterial occlusion).

 Viagra MUST be taken under medical supervision. It should be taken on an empty stomach (4 hours after meals) and the latest meal should preferably be fat-free. Viagra starts working after 30-45 minutes of intake, and its effect will last 3-4 hours.

Side effects of Viagra:

Viagra should be taken under medical supervision. The most dangerous side effect occurs if it is taken together with special medications used for treating coronary artery occlusion (angina).

Trivial side effects include a bluish tinge of vision, headache and flushing. These side effects persist as long as the pill's therapeutic effect lasts: 3-4 hours.

It should be noted that the effect of viagra is accentuated in certain diseases such as with liver failure. The dose should be calibrated by a physician.

Will one get used / addicted to viagra?

No. Viagra will not cause any form of dependence or addiction.

Can one be too young to use Viagra?

No. After puberty, any man can benefit from viagra regardless his age, as long as it is used under medical supervision. Contrary to what many think, this will not make a young man age faster or become dependent on medications.

Cialis:

Cialis is the commercial name for Tadalfil, a PDE11 inhibitor. Accordingly, it prevents the break down of nitric oxide and therefore augments erection in response to stimulation.

The difference in chemical composition between cialis and viagra allows it to act for around 36 hours of erection on demand. This means that it does not need scheduling of sexual intercourse and may thus allow more personal freedom in some cases.

Its side effects include muscle pain in some cases, and as viagra, it can be contraindicated in certain cases including those taking medication for angina.  It has to be taken under medical supervision.

Which is better: viagra or cialis?

There is no such thing as a an absolutely better medication. The efficacy and safety of a medication varies from one person to another and can only be determined by a specialist.

 

Intra Corporal Injection (ICI)

These are medications that are injected directly into the penis to induce erection regardless desire and stimulation. Read more about ICI

Trans-Urethral Medication:

Prostaglandin E1 (PGE1) is a medication that results in dilatation of the arteries and muscles of the penis leading to increased blood flow and increased capacity of the penis to accommodate the pumped blood, resulting in : rigid erection.

 

PGE1 can be administered through the urethral meatus (opening of the urethra through which urine comes out). Small tablets are inserted (painlessly) just inside the opening by a special introducer.

 This method carries the following virtues: direct action on the penis without general side effects on the body, in comparison to pills, and lack of pain and priapism in comparison to intracorporal injections.

Aphrodisiacs / Stimulants

These are medications that enhance sexual desire (libido), acting on the brain to increase  the stimulatory neurotransmitters. Some of them are extracted from herbs such as Yohimbe, others are synthesized to mimic biological stimulatory neurotransmitters

Anxiolytics / Antidepressants

As previously described, psychological stress and performance anxiety can result in impotence. This can be treated by medications that decrease anxiety and/or depression. However, not all such drugs improve erection, some actually do the opposite, which is why those ,medications have to be taken under medical supervision.

 

Hormones

Testosterone is the male sex hormone responsible for normal development of genitals as well as desire and sexual behavior. Deficiency in testosterone occurs as one grows older. This commonly leads to impotence. Deficiency can also occur in young individuals due to various disorders.

Testosterone is available as pills, injections and gels, and is very effective in treating some cases of impotence. However, it has to be used under medical supervision since its abuse may precipitate cancer prostate or infertility.