Known as male erectile dysfunction, impotence affects younger and older men alike, over 150 million men worldwide. In fact, one out of 10 men over the age of 21 is victims of erectile dysfunction due to different reasons. Impotence is one form of erectile dysfunction and can be the result of low testosterone levels, diabetes, arteriosclerosis, prostate cancer surgery, multiple sclerosis or Parkinson’s disease. There are also drugs associated with causing impotence such as marijuana, heroin, cocaine and prescription ulcer medications such as Cimetidine (Tagamet), hypertension medicines such as beta-blockers and diuretics. Smoking and alcoholism also inhibit sexual performance. The nicotine in cigarettes can aggravate impotence by blocking key arteries, which decreases blood flow to the male genitalia. Often, more than one factor is involved in impotence. In general, anything that can affect the flow of blood to the penis can cause impotence. Stress, anxiety, and loss of self-esteem occur if impotence remains untreated. A number of very effective treatments are available now to address the problem of impotence. Oral medications such as Viagra, Levitra and Cialis have revolutionized the treatment of male impotence.
Let’s compare Viagra, Levitra and Cialis

Viagra, Levitra and Cialis

Currently, there are three oral medications approved by the Food and Drug Administration (FDA) for the treatment of erectile dysfunction: sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis). All these agents block the enzyme phosphodiesterase type 5 (PDE-5) and belong to a class of drugs called phosphodiesterase (PDE) inhibitors.
Viagra was the first and is probably the most famous of the three PDE-5 inhibitors used to treat erectile dysfunction. Viagra was approved as an effective agent for treating erectile dysfunction in March 27, 1998. Viagra is manufactured by Pfizer, Inc.

Female Pink Viagra is a product made in accordance with all the structural features of the female body.

Levitra was the second PDE-5 inhibitor to come to market in the United States, and it was approved by the FDA in August 19, 2003. Levitra is manufactured by Bayer Pharmaceuticals Corporation.
Cialis was the third PDE-5 inhibitor to come to market and was approved by the FDA at the end of November 21, 2003. Cialis is manufactured by Lilly ICOS LLC.
The major advantage of PDE-5 inhibitors is that they do not cause an erection at inappropriate times, because they act only in response to sexual stimulation. If there is no sexual stimulation drug remains in the background. All three are taken orally prior to planned sexual activity, acting to increase blood flow in the penis in response to sexual stimulation. However, there are important differences between the three, differences that could influence safety, specificity, duration of action, adverse effects, and ultimately, public acceptance within this class of drug.

Mechanism of Action

PDE-5 inhibitors do not directly cause an erection of the penis, but they alter the body’s response to sexual stimulation by enhancing the effect of the nitric oxide, a chemical that is normally released during stimulation. Nitric oxide causes relaxation of the muscles in the penis, which allows for better blood flow to the penile area.
ffectiveness of PDE-5 Inhibitors

All 3 PDE-5 inhibitors have demonstrated excellent efficacy. Viagra, at 84%, is slightly more effective than Cialis at 81% and Levitra at 80%.

Pharmaceutical Forms, Onset of Action and Duration of Effect

Viagra and Levitra differ only minimally in terms of their structure, while Cialis differs markedly from Viagra and Levitra in terms of its molecular structure, which is also reflected in pharmacokinetic differences.

Viagra: 25 mg, 50 mg 100 mg tablets

  • Onset of action: 30 minutes (effect delayed if taken with food)
  • Duration of action: 4 to 5 hours

Levitra: 2.5 mg, 5 mg, 10 mg, 20 mg tablets

  • Onset of action: 25 minutes (effect delayed by fatty meal)
  • Duration of action: 4 to 5 hours

Cialis: 5 mg, 10 mg, 20 mg tablets

  • Onset of action: 16-45 minutes (effect NOT delayed by food)
  • Duration of action: 36 hours


  1. Levitra will help maintain an erection a little longer than Viagra. They both begin to take effect in about 30-60 minutes. With Levitra, the effects last for about 5 hours as opposed to Viagra lasting for approximately 4 hours.
  2. Levitra was found to be effective in men who had experienced serious and long-term impotence, and who had no obvious reaction to Viagra.
  3. You must wait 2 hours after a meal to use Viagra and you have to wait at least 3 hours after consuming a meal before taking Levitra, because a reach or fatty meal can slow down the effectiveness of Levitra.

All three drugs require sexual stimulation to be effective. Viagra should be taken on an empty stomach it works better if you do not eat a high-fat meal around the time you take it. Levitra may be slightly less effective if you eat a high-fat meal, but a moderate-fat meal does not reduce its effectiveness. Cialis works without regard to what you eat. Viagra and Levitra have similar half-lives, and onset and duration of action. Cialis has a slower onset of action and longer duration of action, which is attributed to its longer half-life.

Patients who wish for spontaneity may opt for Cialis, which may allow for successful intercourse up to 36 hours postdose, even though it takes longer to reach peak effect. The considerably longer duration of effect for Cialis will likely allow less frequent dosing and greater impulsiveness between partners, but also could potentially prolong adverse effects.

Thus the differences between the 3 drugs are not great. All appear to be effective and safe. Levitra has less side effects compared to Viagra and lasts about the same time as Viagra in the body. Cialis has few side effects and lasts longer in the body. This allows increased spontaneity and less frequent dosing than either Levitra or Viagra. However, the longer half-life of Cialis imposes increased risk for drug interactions.

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