(1)Sildenafil Citrate:

Sildenafil Citrate
Sildenafil Citrate is an oral drug for male impotence, also known as erectile dysfunction (ED). It works by dilating blood vessels in the penis, allowing the inflow of blood needed for an erection.
Sildenafil Citrate belongs to a group of medicines that delay the enzymes called phosphodiesterases from working too quickly. The penis is one of the areas where these enzymes work. Sildenafil Citrate is used to treat men who have erectile dysfunction (also called sexual impotence).
Sildenafil Citrate causes erections only during sexual excitement. It does not work in the absence of arousal. Taking Sildenafil Citrate approximately 1 hour before sexual activity works best for most men. Depending on how and when the drug works for you, an interval of one-half hour to as much as 4 hours may prove ideal.
(2)Kamagra:
Kamagra, is one of the most recent additions to the bracket of drugs used to treat erectile dysfunction and is catching up as a popular choice, owing to it’s name that has a zing and more than that, the effect it has on manhood!
If you’ve wondered how it works chemically, Kamagra dilates arteries in the penis, allowing the blood to fill in the Sinusoids. The veins are then compressed, thus sustaining the erection for a period. Kamagra (Generic Viagra) too, like others in the league comes with a host of minor side effects which can be averted with certain precautions and sound considerations. Some of the commonly reported side effects of the drug are: Headache, flushing, upset stomach, running nose etc. Also, it is to be avoided if on Nitrates, or on alcohol. Avoiding a high fat meal before popping in a pill is also a good idea. It reportedly works best when taken an hour before sexual intercourse and not more than one should be taken in a period of 24 hours.
The price range of Kamagra depending on the dosage, varying from 25-100mg.
(3)Generic Levitra:

Generic Levitra
Levitra is an oral therapy for the treatment of erectile dysfunction. It can be also used for other purposes. Levitra should be taken as needed, about an hour before sexual activity. Some form of sexual stimulation is needed for an erection to occur with Levitra. Levitra should not be taken more than once daily. Allow 24 hours to pass between doses.
Levitra can act in 16 minutes compared with 30 to 60 minutes for Viagra;Levitra can be taken with food, while Viagra should be taken on an empty stomach;Levitra has no adverse side effects on the heart or vision. Levitra lasted longer in clinical trials compared to Viagra.It Works for up to 6 hours and Recommended time to take before sex is 25 to 45 minutes.With Levitra, there are no food or alcohol restrictions. Romantic dinners are no longer out of the question. Levitra has less side effects compared to Viagra and lasts about the same time as Viagra in the body.