When a man can't get an erection to have sex or can't keep an erection long enough to finish having sex, it's called erectile dysfunction. Erectile dysfunction is the preferred term rather than the more commonly used term of impotence. Sexual dysfunction is often associated with disorders such as diabetes, hypertension, coronary artery disease, neurologic disorders, and depression. In some patients, sexual dysfunction may be the presenting symptom of such disorders. Additionally, ED is often an adverse effect of many medications.
Although there are a number of options available for non-surgical treatment of sexual dysfunction, it is clear that oral therapy has revolutionized the treatment approach to men with erectile dysfunction.
The FDA approved Viagra in 1998, and it became the first oral therapy for erectile dysfunction on the market. Vardenafil hydrochloride (Levitra) was approved in September, 2003, and Tadalafil (Cialis) was approved in November, 2003. Viagra, Levitra and Cialis work in much the same way. These PDE-5 inhibitors share many similarities, but they have differences as well.
Although sildenafil citrate (Viagra), vardenafil HCl (Levitra) and tadalafil (Cialis) sometimes are called sexual enhancers, they do not directly cause an erection of the penis, but 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.
PDE-5 inhibitors can be used to treat sexual dysfunction caused by high blood pressure, problems affecting nerve function, prostate surgery, side effects of medicines, emotional or psychological ED. Although they work in the similar way, they are not the same in all respects. Sildenafil and vardenafil have similar molecular structures, but tadalafil is structurally different.
- The success rate of sildenafil amounts to an average of over 80%.
- Several studies have shown a benefit of Viagra (sildenafil) for women with sexual arousal disorder, including an increased ability to lubricate, achieve orgasm, and experience sexual satisfaction.
- Onset of action: 30-60 minutes.
- Duration of action: up to 4 h.
- Fatty food is known to delay the absorption of Viagra.
- Contraindicated in persons taking organic nitrates; alpha-blockers (in the current labeling the interaction is considered a Precaution.)
- Vision disturbances are more common after taking Viagra, than after other PDE-5 inhibitors. In July 2005, the FDA found that sildenafil could lead to vision impairment in rare cases and a number of studies have linked sildenafil use with nonarteritic anterior ischemic optic neuropathy.
- The patent on Viagra expires in the early 2012.
- Vardenafil is more potent and selective biochemically than other PDE-5 inhibitors.
- Onset of action: 25 minutes (the quickest).
- Duration of action is up to 5-6 hours, little longer than that reported for Viagra.
- Not recommended in patients taking type 1A (such as quinidine, or procainamide) or type 3 antiarrhythmics (such as sotalol, or amiodarone).
- The advantage that vardenafil has over sildenafil is that it does not alter color perception, a rare side effect which occurs with sildenafil (because vardenafil does not inhibit phosphodiesterase-6).
- Vardenafil is contraindicated in patients taking organic nitrates, alpha-blockers (in the current labeling the interaction is considered a Precaution).
- Fatty food delays the absorption of vardenafil. However, it is less sensitive than Viagra to food intake.
- The patent on Levitra expires in 2018.
- The most astounding feature of tadalafil is its length of action. It has long half life, which ensures 36-hour duration of effectiveness, allowing for more flexibility and spontaneity in sexual relations. This feature greatly distinguishes Cialis from its two predecessors Viagra and Levitra.
- Onset of action: 16 to 30 minutes.
- Tadalafil has the lowest prevalence of visual side effects. However, the myalgia seems to be more common with tadalafil, approaching 10%.
- Tadalafil is contraindicated in patients taking organic nitrates, alpha-blockers.
- Cialis is protected by a patent until 2016.
From a safety perspective, all three Viagra, Levitra and Cialis share similar drug interactions involving CY3A4 inhibitors and a contraindication in the use of nitrates. The side effects are similar for all three PDE-5 inhibitors and include headache, flushing, nasal congestion, and dyspepsia.
Which is better Viagra, Cialis or Levitra?
Cialis clearly works for 36 hours or more, making it an ideal choice for men who are very sexually active.
For men who develop angina and therefore might require an organic nitrate (such as nitroglycerine), the longer duration of action is a disadvantage. Also, some people are uncomfortable having the active ingredient in their system for an extended period of time.
Levitra works a little longer than Viagra, and gives a quite sufficient window of effectiveness for spontaneous sexual experience. Vardenafil is the most potent molecule of all PDE-5 inhibitors and works better in hard-to-treat cases of impotence .
Viagra clearly works for women with sexual arousal disorder .
Implicit advantage of Viagra: Many men have been ordering high-dose pills and splitting them, because Pfizer's Viagra blue pills are pretty large (14mm) and easy to split.
Levitra, a small hard orange 8mm pill, is much more difficult to cut. Cialis 12mm pills are also inconvenient to split because of their asymmetrical almond shape.
Keep in mind that you don't have to make a definitive choice and stay on one ED medication all the time. You can choose all three and alternate between them depending on your requirements. For example, Viagra or Levitra on weekdays and Cialis on weekend or holiday.
- 1. Schoen C, Bachmann G. Sildenafil citrate for female sexual arousal disorder: a future possibility? Nat Rev Urol. 2009 Apr;6(4):216-22.
- 2. Wang HY, Huang YF. Vardenafil for refractory erectile dysfunction: the latest advances. Zhonghua Nan Ke Xue. 2009 Nov;15(11):1035-8.
Last Updated: December 14, 2013
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