Does norethisterone change your cycle the main component of Fildena is Sildenafil. The recommended dose of Cialis is 20 mg it should be taken at least 16 minutes before the sexual activity. The effect persists for 36 hours. Take Cialis once daily and do not exceed the recommended dose. It is preferable not to use Cialis with grapefruit juice, alcoholic beverages, tobacco. If you smoke tobacco and take Cialis concomitantly this may lead to a condition called NAION (sudden optic nerve-related vision loss). Inform your doctor before to take. Cialis if you have abnormal penis, including curved penis and birth defects of the penis, had coronary artery disease, arrhythmia, angina, heart attack or heart failure, hypo- or hypertension, bleeding, stomach ulcers, diabetes, hyperlipidemia (excess of lipids in the blood), sickle-cell anaemia, liver or kidney failure in history.