If you are taking tadalafil on a regular schedule, take it at around the same time every day. Cialis can be taken with or without food. Follow your doctor’s directions carefully, and ask your doctor or pharmacist to explain any part you do not understand. In , Pfizer scientists discovered that sildenafil, which also inhibits the PDE5 enzyme, caused penile erection in males participating in a clinical study of a heart medicine. Who should not take Cialis?Cialis and generic Cialis, known as tadalafil, are available from online services, along with other ED treatment options for people looking to buy ED medication online. Here’s what you need to know about generic tadalafil and how to save. Cialis vs. generic tadalafil. Cialis and generic tadalafil are fundamentally the same medication, and the FDA has a rigorous process for ensuring that generics perform just like their brand counterparts. Both Cialis and tadalafil treat ED at the following doses: . Generic versions of Cialis that are FDA-approved are equally as effective and safe as brand-name Cialis. Generic versions are often less than half the cost. Last medically reviewed on November