No, NOHARD, the window of efficacy for Viagra is 5 hours. I suspect what he is saying is that from the time he takes the Viagra, he can't predict how long until sexual intercourse. By the time sexual activity occurs, he is either late in the window of effectiveness or beyond the 5 hour window when the drug is designed to assist.
Hi Richard, are you saying that the drugs give you an erection for five hours, if you are getting this then you could be giving yourself trouble, its recommended if a man has an erection longer than 4 hours he should get off to hospital, your getting into the grounds of a priapism, this because the blood is just sitting there, it does not move, so if I was you just keep your erections to 3 1/2 hours.
Do you have an ED problem or are you doing this for recreation purposes?
Ask your doctor and/or the pharmacist, but as long as you give the drugs time to clear your system and you don't have any reasons you shouldn't be taking either of them, I see no problem with it. I think it would be like taking ibuprofen some days and naproxen other days.
Keeping in mind that I am not a doctor: jumping back and forth between meds that do the same thing is not a good idea. This could be bad for your system altogether, and could also have a negative effect on your sex life. If I were you, I would not take the viagra, and simply stick with the cialis, that way, you always have the option of sex or no sex, without worry of if its working or not. Blessings - Blu