Subsequently, the FDA approved both vardenafil [27] and tadalafil in Cialis will be available by prescription only. FDA encourages anyone aware of a serious side effect, including consumers or patients, to make a MedWatch report. Tadalafil is in a class of medications called phosphodiesterase PDE inhibitors. Talk to your doctor about which dosing schedule is right for you.Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash. The brand version of Cialis can be expensive. Five tablets of Cialis 10 mg is about $ with GoodRx. The generic version is more affordable at about $6 for the same strength and quantity. Tadalafil (Cialis) is used to treat erectile dysfunction (ED, impotence; inability to get or keep an erection), and the symptoms of benign prostatic hyperplasia (BPH; an enlarged prostate) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency in adult men.