How Quickly Does Cialis Work? ED occurs more frequently in older men. It may take some time and trial and error to determine the best dosage as well as the best time to take Cialis. This process helps increase blood flow to the penis and achieve an erection. Medical consultations were also taken into consideration, as PDE5 inhibitors require a valid prescription from a licensed medical provider. Large-scale clinical trials would be needed to establish such a cause-and-effect relationship. · Below, we’ll detail nine of the most common tadalafil interactions to keep in mind. 1. Nitrates. Nitrates are used to treat and prevent angina (chest pain) caused by heart disease. Examples include nitroglycerin (Nitrostat), isosorbide mononitrate (Monoket), and isosorbide dinitrate (Isordil). AdSave Time & Money with Online Prescription for Viagra, Cialis, Sildenafil and Tadafil. Free & Private Online Consultant with Real Doctors. Reliable E.D. Meds Shipped es: Privacy Policy, Telehealth, Telemedicine and more. As needed for ED: 5 to 20 mg by mouth as a one-time dose, with a maximum of one dose in 24 hours. Effects may last up to 36 hours. Daily dosing for ED: or 5 mg by mouth daily. For daily dosing, the maximum dose is 5 mg per day. The medication should be taken once daily at about the same time every day to maintain a consistent level of.