Cialis belongs to the trade name, generically known as Tadalafil. Tadalafil is a PDE5 inhibitor drug that is effective in treating erectile dysfunction and is a long-acting medication that lasts for about 3 days after taking it. The duration of erection after taking the drug varies from person to person. It is important to note that the use of tadalafil may cause adverse reactions such as headache, back pain, and indigestion. Tadalafil is contraindicated in people who are allergic to any of the ingredients in the product, patients who are taking any form of nitrates, guanylate cyclase stimulators, women, children, etc. Tadalafil is a prescription drug, you must strictly follow the doctor’s instructions to take treatment, do not blindly buy and take on their own, so as not to cause harm to the body.