What is a vasodilator?
A vasodilator acts on smooth muscle cells in the blood vessel walls and causes them to relax and widen (vasodilation), which reduces resistance to blood flow, thereby increasing blood flow and allowing blood to flow more freely.
Uses for vasodilators
Vasodilators are used to treat several conditions in which vasodilation helps improve the condition. These include:
Blood pressure is the force needed to pump blood around the body. Blood pressure measurements are divided into systolic pressure, which is when the heart contracts forcing blood out into the arteries, and diastolic when the heart rests and fills with blood. Blood pressure measurement is expressed as systolic pressure over diastolic pressure. Hypertension is high blood pressure at rest and causes reduced blood flow, increases the force needed to pump blood around the body, increases workload on the heart and increases oxygen demand. This can cause damage to blood vessels as well as end organ tissue damage to the kidneys, eyes and nerves. Hypertension also increases risk of cardiovascular disease, including stroke and heart attack.
Angina is a symptom of coronary artery disease when the heart does not get enough oxygen and compensates by pumping harder and faster. Symptoms include discomfort or pain in the chest and breathlessness on exertion. Angina is not the same as heart attack as it is not caused by a blockage only a narrowing of the arteries and there is no permanent damage to the heart muscle.
Peripheral arterial disease
Peripheral arterial disease is narrowing of the arteries due to a blockage and may be caused by atherosclerosis, thrombosis or an embolism. Peripheral arterial disease occurs mainly in arteries supplying blood to the legs, causing pain, weakness, numbness and muscle cramps.
Classes of vasodilators
Several classes of vasodilator are available that work by different mechanism of action.
- Oxpentifylline is used to treat conditions caused by poor circulation including peripheral artery disease. It works by several mechanisms, including acting directly on blood vessel wall to cause vasodilation, preventing the formation of chemicals that cause vasocontriction, decreasing the viscosity of blood, reducing the formation of blood clots.
- Minoxidil is used to treat severe hypertension in addition to other medications and acts directly on smooth muscle cells in blood vessel walls causing them to relax.
- Glyceryl trinitrate is used to treat angina and is absorbed through the skin under the tongue to be converted to nitric oxide in the blood vessel walls causing rapid vasodilation and relief from symptoms.