Hi, although Cialis, Levitra and Viagra have all the same inhibitory action of the enzyme PDE-5, they do not have the same active agent.
Cialis is nicknamed the "weekend pill" because it may act in the body up to 36 hours. Clinical studies have shown that Cialis is effective more quickly than Viagra. Indeed, it will 30-40 minutes and will be effective about 4 hours. Cialis has a faster action, it will take about 30 minutes to do and can take up to 36 hours.
It should be noted that Cialis once a day continuous action, so you can get an erection at any time if there is sexual stimulation.
Levitra, which is the active ingredient vardenafil, is recommended for the elderly, who have diabetes or hypertension. It is 20 to 30 minutes and its effect can last up to 5 hours. Levitra or dispersible version exists, which is in 20 minutes, with the tablet that dissolves under the tongue.
To summarize, if you want to focus on one-time sex, Viagra is for you: indeed, its duration of action being only 4 hours, it is not possible to have sex with repeated treatment. Note that these drugs are currently salable online. Here is a good site you can use to buy levitra and cialis: mybestonlinepharmacy.com