Viagra generally only stays in your system for four to six hours. However, it stays in your body for up to 36 hours and can be taken every 24 hours, so it can work for you constantly. Tadalafil, the active ingredient in Cialis, is a PDE5 inhibitor. Your healthcare provider can help you determine the right dosage for you. Current research suggests Cialis is safe to take for several years. If you have sex on a less regular basis, or your ED comes and goes, Cialis may be a better option.The normal dosage of Cialis for occasional use in treating ED is 10 mg taken before sexual activity. If you have side effects with the mg dose, your doctor may prescribe a 5-mg dose. If the The cost of the medication is from $ per month for Cialis and from $40 per month for tadalafil. Online consultations are free of charge. Insurance does not cover product fees, but Hims writes. Tadalafil is a generic drug that is widely known under the brand name Cialis. The estimated retail price of Tadalafil is $1, for 30, 20MG Tablet. When you use a free SingleCare Tadalafil coupon, you may be able to save significantly and lower your Tadalafil prescription cost to $ for 30, 20mg Tablet. Brand vs. Generic Generic Form Dosage.