This is a serious condition that requires immediate medical attention. Remember that this wikiHow quiz is informational, and your results should not be considered a medical diagnosis. Subsequently, the FDA approved both vardenafil [27] and tadalafil in Cialis is not recommended for people taking any form of nitroglycerin because the combination may lower blood pressure to an unsafe level. Tadalafil is sometimes taken as needed, usually at least 30 minutes before sexual activity and not more often than once every 24 hours. 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.AdWith RexMD you’re saving time and money with our ED delivery. Get started now. Reliable E.D. meds prescribed by real doctors. Get your free & private online visit todayService Catalog: Men’s Health, Erectile Dysfunction, Sexual Health and more. headache *. upset stomach. runny nose. back pain *. upper respiratory infection. heartburn *. muscle pain. For a list of side effects reported by people taking Cialis in clinical trials, including. CIALIS for once daily use is a lower dose you take every day. • Do not take CIALIS more than one time each day. • Take one CIALIS tablet every day at about the same time of day. You may attempt sexual activity at any time between doses. • If you miss a dose, you may take it when you remember but do not take more than one dose per day.