Do not stop taking tadalafil without talking to your doctor. Brand-name versions of the drug approved for PAH include Adcirca. One of these is PAH. You should take tadalafil one time a day. Cialis works by enhancing the effects of one of the chemicals the body normally releases into the penis during sexual arousal.AdComplete the Online Consultation with our Doctor. Personalize Your Needs. If Appropriate, Get a Prescription for ED from RexMD®. Free Shipping AvailableSexual health: Premature Ejaculation · Erectile Dysfunction · Breakouts. Cialis (tadalafil) and Viagra are both used for erectile dysfunction, but there are a couple of distinctions between the two. Unlike Viagra, low-dose tadalafil can be taken on a daily basis, allowing for more spontaneity. What’s more, a single dose of tadalafil lasts up to 36 hours, whereas a dose of Viagra only lasts for around four hours. 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.