See our source here What is Tadalafil? It lasts 4 to 5 hours, or longer if you have mild to moderate ED. If you drink a large amount of alcohol more than five glasses of wine or five shots of whiskey while you are taking tadalafil you are more likely to experience certain side effects of tadalafil such as dizziness, headache, fast heartbeat, and low blood pressure. It may be difficult to remain firm despite wanting to have sex. How should this medicine be used?Side Effects. Headache, stomach upset, back pain, muscle pain, stuffy nose, flushing, or dizziness may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. To. Fake Cialis. Avoid buying Cialis without a doctor’s prescription. PDE5 medications are some of the most common counterfeit medications sold online. They can cause serious health risks. Take as. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide.