Talk to your doctor about which dosing schedule is right for you. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. Ask your doctor if you are not sure whether any of your medications contain nitrates. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow. Do not stop taking tadalafil without talking to your doctor. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Tadalafil is also sometimes taken once a day every day without regard to timing of sexual activity. · But on average, its effects start to lessen 2 to 3 hours after you take a dose. The typical dose for once-daily Cialis for ED is milligrams (mg) to 5 mg. When used as needed for ED, the usual. These prices can vary based on your state, subscription package discounts, and whether you have the prescription mailed to you or filled through a pharmacy. Generic Cialis (tadalafil) Roman. Cialis comes in several different strengths, including: milligrams (mg) 5 mg. 10 mg. 20 mg. The cost for these different strengths depends on whether you have insurance, your individual plan.