Tadalafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. However, safety should always be the top priority. Consult your physician about which is right for you. Take tadalafil at around the same time every day. There are two different ways to take tadalafil, either daily or on an as needed basis.Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash. Oral medications, like Viagra and Cialis, which require a prescription and are commonly used to treat ED, can take 30 minutes to take effect, she adds. Injections take less time to work, but they.  · 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.