Patients should seek prompt medical attention if their erection lasts longer than four hours. If you are taking tadalafil on a regular schedule, take it at around the same time every day. Follow your doctor’s directions carefully, and ask your doctor or pharmacist to explain any part you do not understand. Tadalafil is available on prescription only. Research shows that ED affects up to one in five men in the UK, which is roughly 4. It continues to be available to patients on the NHS who obtain a prescription from their prescriber. If you do not meet the NHS criteria for tadalafil, you may get a private prescription from a doctor.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. Learn more about Cialis® Together & how they can help with erectile dysfunction. Shop the range at or your local Boots pharmacy. AdBrowse new releases, best-sellers & recommendations from our readers4/5 (1, reviews)Popular Links: OUTLET · Beauty · Grocery.