How Long Does Cialis Last? How long varies with the drug. Viagra and Levitra take about 30 minutes to work, and the effects last for about 4 hours after you take the pill. You should take Cialis at least 2 hours before you plan to have sex. The effects may last for up to 36 hours after you take it. What does cialis do to a man? Fast facts on Cialis: ... Under the name Cialis, tadalafil is used to treat erectile dysfunction. As Adcirca, the same drug treats pulmonary arterial hypertension and benign prostatic hyperplasia. Cialis increases blood flow to the penis, enabling an erection to occur when a man is sexually stimulated.