doesnt effect your natural bloodflow at all.
cialis acts in about half to 3/4 of an hour and lasts for about a day or so.
IF you eat with any of the agents it takes alot longer to start working..like 2-4 hours for cialis and viagra.
alot of people prefer viagra over cialis. have to try both. theres levitra also. ive tried all of them and viagra wins hands down..but it also comes down to dosage as well.
if you eat within 2 hours of viagra, then it takes 2 hours or so to work. take cialis, levitra or viagra on an empty stomach and you feel flush in 15-30 minutes. Viagra lasts about 4 hours, same for levitra.
another thing, your blood pressure has ALOT to do with your ability in this respect.
if you are on BP meds, or have high BP due to muscle size, or genetics, or whatever, you'll have problems. then when you take BP meds, youll have more problems.
some BP meds dont affect ED though. ADs and test levels also are a factor- so are recreational drugs.
HTH.