This information is reviewed by a licensed practitioner who will assess your eligibility for the medication. Cialis can last in the system for up to 36 hours. The table below summarizes the typical dosages for tadalafil: Indications of Tadalafil:. Vardenafil usually works for 4 to 5 hours. The drug is approved for use in adults.Cialis is approved by the FDA to treat erectile dysfunction (ED). Our medical team can prescribe Cialis 5mg, 10mg, and 20mg. The starting dose we generally recommend is 10mg. Tadalafil is the name for the active chemical ingredient in Cialis. PDE-5 inhibitors is the name of the group of medicines. Generic Cialis (tadalafil): $10 per dose (10mg, 20mg) Daily generic Cialis (tadalafil): $3 per dose (mg, 5mg) Product details. Shipping: free shipping; Comparison of online Cialis prices. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide.