Sildenafil citrate - mode of action

Q: The article on Sildenafil on your site says that if one consumes Sildenafil (Viagra), he may have an erection upto 4 hours. Does this mean that given there is continuous sexual excitement the user will reach orgasm after 4 hours? Or is it that the user reaches his regular orgasm in 15 minutes but the erection still remains? Please indicate for a normal guy for the erection to last for 30 about minutes, will 25 mg be enough?

A:Kindly note the following points:

(a) In India, the brand name of Sildenafil is Penegra and not Viagra.
(b) Sildenafil has an anatomic role and helps in erection. It DOES NOT cause sexual excitement. In fact if there is no desire, sildenafil will not act.
(c) Normally the erection will be considerably decreased after ejaculation. Reference to 4 hours is to indicate maximum duration of action of the drug.