Tadalafil works for these conditions by promoting muscle relaxation, which improves blood flow in PAH and urinary flow in BPH. If you are already taking medication to treat BPH, your doctor may tell you to stop taking your other medication at least one day before starting treatment with tadalafil. Tadalafil was found to have similar benefits for lower urinary tract symptoms as the usually prescribed tamsulosin. Avoid eating a large meal or a lot of food, as this can slow down the effects of the drug. Your doctor will probably tell you not to take tadalafil if you are taking street drugs containing nitrates. 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. If you are taking tadalafil on a regular schedule, take it at around the same time every day.No, 40 milligrams (mg) is not a safe dose of Cialis to take. The maximum recommended dosage of Cialis is 20 mg once per day. Taking a dose of Cialis that’s . heart attack symptoms – chest pain or pressure, pain spreading to your jaw or shoulder, nausea, sweating. Common tadalafil side effects may include: headache; flushing (warmth, redness, or tingly feeling); nausea, upset stomach; stuffy nose; or. muscle pain, back pain, pain in your arms, legs, or back. This is not a complete list of side.  · Adults—5 milligrams (mg) once a day, taken at the same time each day, without regard for the timing of sexual activity. Children—Use is not recommended. For .