The two drugs are both type 5 phosphodiesterase inhibitors, but there are differences in the use of the two drugs, it can be said that each has its own characteristics, can not be generalized to say which drug is better. The first generation of 5 phosphodiesterase inhibitors, Viagra is rapidly absorbed after oral intake, 10-40 minutes to take effect, food will have an impact on absorption, so you need to take it on an empty stomach, the effect can last about four hours, good erection hardness. The effect can last for about 36 hours. You can take the drug orally when you feel convenient, and you can freely choose any time period for sex within 36 hours after taking it, without time pressure, and taking cialis is not affected by eating. However, the erection hardness of cialis is inferior to that of Viagra, so you can choose the right drug according to the actual situation.