Tadalafil is also sometimes taken once a day every day without regard to timing of sexual activity. This does not mean that the FDA will allow individuals to import medications from Mexico at will. What important information should you know about Cialis? Continue to take tadalafil even if you feel well. Cialis As Needed will be prescribed in doses of 5 to 20 mg. Required Documentation Mexican pharmacies offer prescription medications at lower prices than pharmacies in the United States. Tell your doctor if tadalafil is not working well or if you are experiencing side effects.headache. indigestion. back pain. muscle pain. flushing. stuffy nose. Patients who get back pain and muscle aches usually get them 12 to 24 hours after taking Cialis and these usually go away by. Dosage range: mg to 5 mg. Frequency: once daily, regardless of the timing of sexual activity. Cialis’s recommended dosage when it’s taken as needed for ED is as follows. Dosage range: 5 mg to 20 mg. Frequency: one dose at least 30 minutes before sexual activity, with a maximum of one dose per day*. The recommended starting dose for Cialis intended for once daily use is mg, take at the same time each day, without regard to timing of sexual activity. This may be increased to 5mg/day based on need and tolerability. May be taken with or without food. Cialis is available as a generic, under the name tadalafil. 3.