Medical consultations were also taken into consideration, as PDE5 inhibitors require a valid prescription from a licensed medical provider. Your health information should remain between your provider and yourself. Tadalafil is the active ingredient in a branded drug called Cialis. Likewise, if you experience side effects, we may recommend that you try a lower dose of Tadalafil. What is in tadalafil? Since the effectiveless of tadalafil lasts for a long time , it can be taken well in advance to allow for more spontaneous sexual activity over the course of a day or night. Frequently asked questions about tadalafil What is tadalafil used for?Generic Cialis, or Tadalafil, is available in several doses in tablet form: milligrams (mg), 5 mg, 10 mg, and 20 mg. Depending on the dose for ED, you can use it as needed . Cialis Most common fast-acting PDE5 drug that lasts in your system for up to 18 hours. Sildenafil PDE5 drug that lasts in your system for 4 – 6 hours. Tadalafil Fast-acting . It comes in a higher dose than daily-use tadalafil (5mg, 10mg or 20mg dosages) so it’s best to avoid using it on several consecutive days. Common tadalfil side effects The most .