Nitroglycerin ointment, mainly used to reduce or relieve the pain caused by anal fissure. The main ingredient of nitroglycerin ointment is nitroglycerin, and the excipient is petroleum jelly, in which nitroglycerin can directly loosen the smooth muscle of blood vessels, especially the smooth muscle of small blood vessels, so as to make the systemic vasodilatation, reduce peripheral resistance, reduce venous return, and can relieve myocardial hypoxia. Anal fissure is also due to the spasm of the anal sphincter muscle caused by pain, so nitroglycerin ointment can be very good relief of anal sphincter muscle spasm, thus reducing the pain caused by anal fissure. However, nitroglycerin may have some adverse reactions when used, such as dizziness, nausea, rapid heartbeat, blurred vision, fatigue and a series of adverse reactions, at the same time, nitroglycerin ointment can not be used for lower blood pressure, cerebral blood supply insufficiency, insufficient function of the liver and kidney are not allowed to use, so be sure to carefully read the instructions before use, and its adverse reactions and contraindications are more.