Tell your doctor if tadalafil is not working well or if you are experiencing side effects. What should I do if I forget a dose? Visit Store What does cialis do? This increased blood flow can cause an erection. If you have certain health conditions or are taking certain medications, your doctor may tell you to take tadalafil less often or may prescribe a lower dose to be taken once a day. Armed with information tailored to your specific health condition ensures you reap maximum benefits while minimizing potential risks. Be sure to mention any of the following: alpha blockers such as alfuzosin Uroxatral , doxazosin Cardura , dutasteride Avodart, in Jalyn , prazosin Minipress , silodosin Rapaflo , tamsulosin Flomax, in Jalyn , and terazosin; amiodarone Cordarone, Pacerone ; certain antifungals such as fluconazole Diflucan , griseofulvin Grifulvin, Gris-PEG , itraconazole Onmel, Sporanox , ketoconazole Extina, Ketozole, Nizoral, Xolegel , and voriconazole Vfend ; aprepitant Emend ; bosentan Tracleer ; carbamazepine Carbatrol, Epitol, Tegretol, Teril, others ; clarithromycin Biaxin, in Prevpac ; diltiazem Cardizem, Cartia,Tiazac, others ; efavirenz Sustiva, in Atripla ; erythromycin E.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. Strengths: mg, 5 mg, 10 mg, and 20 mg; Brand: Cialis. Form: oral tablet; Strengths: mg, 5 mg, 10 mg, and 20 mg; Adult dosage (ages 18–64 years) Tadalafil can be used either as needed or. Viagra, Cialis, Levitra, and Stendra are oral medications for treating erectile dysfunction. Check out side-by-side comparisons of all four drugs. You can take the mg and mg doses as.