For further information contact your pharmacist or Eli Lilly and Company directly. Patients should seek prompt medical attention if their erection lasts longer than four hours. Tadalafil is also sometimes taken once a day every day without regard to timing of sexual activity. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. However, because sexual stimulation is required to initiate the local penile release of nitric oxide, tadalafil’s inhibition of PDE5 will have no effect without sexual stimulation. You should only be treated with one of these products at a time.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*. 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. The normal dosage of Cialis for occasional use in treating ED is 10 mg taken before sexual activity. If you have side effects with the mg dose, your doctor may prescribe a 5-mg dose. If the