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...

I- Phosphodiesterase (PDE) Inhibitors:


This is the group of medications that includes Viagra, Cialis, Levitra..etc, the on-demand pills. One must take the pill, wait for some time for it to be absorbed, then be exposed to sexual stimulation. The pill increases the penile vascular response to that stimulation.

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 an enzyme named "phosphodiesterase" or (PDE).  There exist various types of PDE, PDE1, 2, 3..15. PDE5 and PDE11 are the most relevant to erection. PDE inhibitors preserve NO and enhance erection by working against PDE.

a. Viagra (Sildenfail Citrate):


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.

b. Levitra (vardenafil HCl):


LEVITRA (vardenafil HCl) is an FDA-approved oral prescription medication for the treatment of erectile dysfunction (ED) in men. It belongs to a class of drugs called “PDE5 inhibitors”, as does Viagra

It works by increasing blood flow to the penis to help improve erectile function. The active ingredient in LEVITRA works specifically on the chain of events that occurs in the penis during arousal, when two large chambers in a man’s penis fill with blood.

Among the most important benefits of Levitra is that it does not need to be taken on an empty stomach. No relationship to food intake,

The most common side effects with LEVITRA are headache, flushing, stuffy or runny nose, indigestion, upset stomach, dizziness, and back pain.

Taking Levitra: 

  • It is available in 2.5-mg, 5-mg, 10-mg, and 20-mg tablets
    LEVITRA may be taken with or without food
    Take LEVITRA no more than once a day, at least 24 hours apart
    LEVITRA is taken orally, approximately 60 minutes before sexual activity

c. Cialis (Tadalafil)


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, levitra 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.

II-Hormones: Testosterone


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 (Pan Androgen Deficiency of the Aging Male / Andropause).Deficiency can also occur in young individuals due to various disorders.

Testosterone deficiency can result in low sexual desire, weak erection, depression, exhaustion, among other manifestations.

Once diagnosed by testosterone serum level assay, testosterone replacement therapy can be resorted to. 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, otherwise, side effects are possible on the prostate, testicular sperm production, among others.

The latest in testosterone replacement therapy is NEBIDO (Testosterone Undecanuate): Long-acting Injection Therapy

Way used: Injected IM every 3 months following an initial loading dose to stabilise testosterone levels
Testosterone absorbed directly into blood stream
Infrequent dosing
Provides a steady level of testosterone
Avoids peaks and troughs over the day
Fewer adverse events such as mood swings or blood changes
Local pain on injection
Abscess formation (rare)


Other Testosterone replacement therapy options:

  1. Depot Injection TherapyWay used: Injected deep intramuscularly (IM) every 1 to 4 weeks (usually in the buttocks)
    Testosterone absorbed directly into bloodstream
    Requires regular IM injections
    Fluctuating levels of testosterone with high initial levels
    Mood swings as testosterone levels rise and fall ("roller coaster" effect)
    Local pain on injection
    Abscess formation (rare)
  2. Implant TherapyWay used: Injected IM every 3 months following an initial loading dose to stabilise testosterone levels
    Infrequent dosing - usually required twice a year
    Testosterone levels remain stable for up to 6 months as the pellets are slowly absorbed
    May be pain and/or local infection at the site where pellets are inserted
    Special equipment and minor surgical procedure required
    Occasionally a pellet is expelled by the body
    Scars after pellet removal
  3. GelsWay used: A clear testosterone gel rubbed onto the shoulders, chest or back once a day – dries within a few minutes. Testosterone is released steadily from the skin into the bloodstream over a 24-hour period
    Convenient sites of application
    Quickly normalizes testosterone levels
    Stable blood levels of testosterone throughout the day
    Less skin irritation than patches
    No operation needed
    Skin irritation may be a rare side effect
    Potential for transfer to partner or child
  4. PatchesWay used: Applied to various areas of the skin (generally on a non-hairy part of the upper body)
    Efficient – steady absorption of testosterone over 24 hour period
    May not achieve levels of testosterone as effective as other preparations, such as gels
    High chance of skin irritation
    May be inconvenient to apply and can be dislodged
  5. Oral TherapyWay used: Forms of testosterone taken orally as pills or capsules – not recommended for long-term replacement of testosterone
    Considerable variation in absorption of dose
    Should be taken with a fat-containing meal
    Testosterone has to be in an altered form so that it is not broken down by the liver
    One such form (testosterone undecenoate) has to be taken 2 or 3 times a day to maintain adequate levels
    Another form (methyl testosterone) produces harmful side effects including liver damage and elevated cholesterol levels

III. Intra Corporal Injection (ICI)


Rigid erection can be induced and maintained for hours by injecting the penis with medications that act by relaxing the cavernosal muscles and dilating the arteries, therefore increasing blood pumping into the penis and thereby inducing erection.

These medications act directly on the penis without need for sexual stimulation, and have the virtue of  reaching the penis straight forwards without dilution in the blood.

They are therefore among the most powerful and effective erection-inducing medications. Unfortunately, this has the drawback of causing prolonged erection that may require medical intervention (priapism) if injected without medical supervision.

The dose and type of medication can be calibrated to avoid priapism. Another drawback is that repeated injection may result in fibrosis of the penis.

The most popular medication among the injectable drugs is Prostaglandin E1 (PGE1).

The use of these injections vary from diagnostic to therapeutic applications. One of the first step to diagnose the cause of impotence whether organic or psychogenic is to inject PGE1 into the penis and measure the response.

Moreover, the patient can be taught to inject himself at home, and the dose can be determined by the physician, enabling "Home Therapy". If prolonged home therapy is intended, followup is necessary by penile duplex every 4-6 months to stop treatment if fibrosis starts.

Injection therapy is ideal in cases of impotence caused by cutting the nerves connected to the penis, such as in paraplegia. This is because a small dose is capable of achieving a strong response, and because oral pills need nerve impulses to activate their action while injections do not.

In very severe cases, injections alone may not work, viagra and similar drugs alone may not work, but a combination of both may work. If this is not enough to correct impotence, then surgery is mandatory.

Injection How-to:

Medication is injected in the corpus cavernosum and not into the urethra, into arteries, veins or under the skin.

The expiry date and storage condition of the medication is checked. The bottle is wiped with alcohol. The syringe is prepared. Injection is performed by an insulin needle. An accurate amount of the medication is aspirated into the syringe as dictated by the physician. The needle should be kept from touching anything but the sterile bottle.

The site of injection is determined: the near third of the penis, towards the base of the penis, on the right or left side

Injection should NOT be through the upper surface of the penis, or else the nerves and vessels that course on the upper surface will be injured.

Injection should NOT be through the lower surface of the penis, or else the urethra that courses on the lower surface will be injured.


An anesthetic spray can be applied prior to injection to avoid pain, though this is usually unnecessary.

The area is sterilized by an alcohol swab. The penis is stretched outwards and forwards by holding it from the glans with the left hand (or the right hand in left-handed men).

The needle is inserted at the point chosen for injection, 1 cm deep. The plunger is pulled. As the plunger is pulled, blood should not be aspirated into the syringe. If blood appears in the syringe, this means that the tip of the needle is in a blood vessel. Injection SHOULD NOT proceed. The needle is pulled back for a short distance and the process repeated. If no blood appears, the plunger is pushed all the way to release the medication into the penis.

IV. 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 specialintroducer.

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.

V-Other Medications

Medical Treatment for ED

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.