What special precautions should I follow? Tadalafil is also sometimes taken once a day every day without regard to timing of sexual activity. Alternatively, Cialis may be prescribed as an as-needed treatment for ED, to be taken before sexual activity. Ask your pharmacist for a list of the ingredients. Tadalafil is its active ingredient and is available as a generic drug.At Walmart Pharmacy, we work hard to offer our customers affordable prices for generic medications. Find yours for just $4 or $10 for a 30 or day supply. Cialis comes in several strengths: milligrams (mg), 5mg, 10 mg, and 20 mg. The Cialis cost per pill and daily cost depend on several factors, such as: the strength prescribed by your doctor. Tadalafil (Cialis) is a phosphodiesterase-5 enzyme (PDE-5) inhibitor. It works by blocking PDE This is a protein in your body that breaks down the molecules that .