Cialis contains the active ingredient tadalafil, which lasts longer in the body than sildenafil, the active ingredient in Viagra. This means that Cialis can provide a longer-lasting effect, up to 36 hours, compared to Viagra’s 4-6 hours. However, it’s important to note that you should not mix cialis and viagra without first consulting your doctor. Mixing these medications can increase the risk of serious side effects, including a sudden drop in blood pressure and dizziness