Forzest 20 mg is a medicine used to treat erectile dysfunction (ED) in men. It generally contains tadalafil 20 mg, which helps increase blood flow to the penis during sexual stimulation. Do not take Forzest with nitrate medicines, such as nitroglycerin, or recreational nitrites called poppers, because this combination can cause a dangerous drop in blood pressure. Consult your doctor if you have heart disease, low blood pressure, or significant liver or kidney problems.