Read our editorial process. Common side effects include headache, facial flushing, indigestion, and dizziness. Never purchase ED medications from a site or service that doesn’t require a prescription and medical documentation. If you want your voice to be heard by your healthcare provider, this is the telehealth clinic for you! This allows the smooth muscles in the penis to relax and fill with blood. Its effects might last longer if you have mild to moderate ED. Its effects often last for 4 to 5 hours.Tadalafil (Cialis) is taken by mouth either as needed before sexual activity or once daily for erectile dysfunction (ED).It’s also taken once daily to treat symptoms from an enlarged prostate (benign prostatic hyperplasia, or BPH).Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include . Cialis comes in several different strengths, including: milligrams (mg) 5 mg. 10 mg. 20 mg. The cost for these different strengths depends on whether you have insurance, your individual plan. 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.