A nitrovasodilator is a pharmaceutical agent that causes vasodilation (widening of blood vessels) by donation of nitric oxide (NO), and is mostly used for the treatment and prevention of angina pectoris. This group of drugs includes nitrates (esters of nitric acid), which are reduced to NO in the body, as well as some other substances. Examples
Here is a list of examples of the nitrate type (in alphabetical order):

Nitrovasodilators which arent nitrates include molsidomine and its active metabolite linsidomine, as well as sodium nitroprusside. These substances do not need to be reduced to donate NO. Medical uses
The nitrates are used for the treatment and prevention of angina and acute myocardial infarction, while molsidomine acts too slowly to be useful for the treatment of acute angina. For quick action in the treatment of angina, glyceryl trinitrate is used in form of a sublingual spray (nitro spray) or as soft capsules to be crunched.Nitroprusside is used intravenously for the treatment of hypertensive crises, heart failure, and lowering of blood pressure during surgery. Contraindications
Nitrovasodilators are contraindicated under circumstances where lowering of blood pressure can be dangerous. This includes, with some variation between the individual substances, severe hypotension (low blood pressure), shock including cardiogenic shock, and anaemia. Whether a specific drug is useful or harmful under heart failure and myocardial infarction depends on its speed of action: Fast acting substances such as glyceryl trinitrate and nitroprusside can be helpful for controlling blood pressure and consequently the amount of blood the heart has to pump, if the application is monitored continuously.
Slow acting substances would hold the danger of ischaemia due to an uncontrollably low blood pressure and are therefore contraindicated. Depending on the circumstances, even fast acting substances can be contraindicated – for example, glyceryl trinitrate in patients with obstructive heart failure.These drugs are also contraindicated in patients that have recently taken PDE5 inhibitors such as sildenafil (Viagra). Adverse effects
Most side effects are direct consequences of the vasodilation and the following low blood pressure. They include headache ("nitrate headache") resulting from the widening of blood vessels in the brain, reflex tachycardia (fast heart rate), flush, dizziness, nausea and vomiting. These effects usually subside after a few days if the treatment is continued.Occasionally, severe hypotension occurs shortly after beginning of treatment, possibly resulting in intensified angina symptoms or syncope, sometimes with bradycardia (slow heart rate). Interactions
A number of drugs add to the low blood pressure caused by nitrovasodilators: for example, other vasodilators, antihypertensive drugs, tricyclic antidepressantss, antipsychotics, general anaesthetics, as well as ethanol. Combination with PDE5 inhibitors, including sildenafil (Viagra), is contraindicated because potentially life-threatening hypotension may occur.Nitrates increase the bioavailability of dihydroergotamine (DHE). High DHE levels may result in coronary spasms in patients with coronary disease. This interaction is not described for non-nitrate nitrovasodilators. Mechanism of action
Nitrovasodilators are prodrugs that donate NO by various mechanisms. Nitrates undergo chemical reduction, likely mediated by enzymes.