Vasodilators - Allowing the Heart to Work Effortlessly

What Are Vasodilators?

A vasodilator is a drug that widens blood vessels to allow blood to flow easily through the blood vessels. They relax the blood vessels and help to increase blood flow and oxygen delivery through the body. Vasodilators may act directly on the arteries or veins to produce dilation. This allows the heart to get more oxygen and pump efficiently.

What Are the Uses of Vasodilators?

Vasodilators are prescribed to treat the following conditions:

• High Blood Pressure - Certain vasodilators are more arteries-specific and treat blood pressure. Examples may include calcium channel blockers, Hydralazine, Renin-angiotensin-aldosterone system (RAAS) blockers, and Minoxidil. They help to control high blood pressure during pregnancy or childbirth.

• Angina and Heart Attack - Nitroglycerins and long-acting nitrates like Isosorbide Mononitrate improve blood flow to the heart and help to treat chest pain by dilating veins and coronary arteries. It is used to prevent heart attacks and strokes.

• Pulmonary Hypertension - Vasodilators like Phosphodiesterase inhibitors and endothelin receptor antagonists help to lower the elevated blood pressure to treat pulmonary hypertension.

• Arrhythmia - Vasodilators are given to children with hypertension, congenital heart disease, cardiomyopathy, or arrhythmia.

How Do Vasodilators Work and What Are the Different Types of Vasodilators?

Different vasodilators work differently. The direct vasodilators directly affect the muscle cells lining the blood vessels. These work quickly and relax the muscle cells. Some vasodilators control the chemicals responsible for the blood vessels expansion and contraction.

The different types of vasodilators include

• Angiotensin-Converting Enzyme ( ACE Inhibitors) - ACE inhibitors slow the activity of the enzyme ACE and the production of angiotensin. It helps to dilate the blood vessels and reduces blood pressure. Examples of ACE inhibitors include Lisinopril, Benazepril, and Enalapril.

• Angiotensin Receptor Blockers (ARBs) - These are indirect vasodilators that block the angiotensin from attaching to the walls of the blood vessels. This causes vasodilation. Some examples of Angiotensin receptor blockers include Amesartan, Losartan, and Candesartan.

• Calcium Channel Blockers (CCBs) - These are systemic vasodilators. The smooth muscle cells of the arteries use calcium for muscle contraction. The calcium channel blockers block calcium from entering the muscle cells. It relaxes the artery muscles causing dilation of the arteries. Some examples of calcium channel blockers include Verapamil, Diltiazem, and Amlodipine.

• Nitrates - These are direct vasodilators. The nitrates convert into nitric oxide and activate certain chemicals to open the blood vessels. Examples of nitrates include Nitrostat and Isordil.

How to Take Vasodilators?

Vasodilators can be administered in a variety of ways, including sublingual, IV, and oral. The route of administration depends on the clinical setting.

Oral Administration:

• Myocardial Infarction - Patients with myocardial infarction benefit more from sublingual Nitroglycerin, as it is absorbed faster.

• Blood Pressure - Oral route of administration is best for reducing blood pressure in non-emergency cases with Amlodipine and Nifedipine, While Nitroprusside and Nitroglycerin are used in hypertensive emergencies.

Intravenous Route:

Sodium Nitroprusside is administered intravenously to lower blood pressure.

Nitroglycerin can be used to lower blood pressure. Intravenous Hydralazine or oral Nifedipine prevents intracranial hemorrhage or eclampsia in severe hypertension during labor. Calcium channel blockers such as Clevidipine and Nicardipine are used in hypertensive emergencies.

Are Vasodilators Safe for Children?

Vasodilators may be given to children with hypertension, congenital heart disease, or arrhythmias. ACE inhibitors are the first line of medication to treat hypertension in children and those with kidney disease, proteinuria, and diabetes. These drugs are safe for children aged six years and up and are dosed according to their weight. Angiotensin receptor blockers like Candesartan and Losartan are approved to be given to children. Calcium channel blockers like Norvasc and Amlodipine are good choices in children with diabetes. Pediatric doses of these medications are based on the age and weight of the child.

What Are the Side Effects of Vasodilators?

Vasodilators can cause the following side effects:

Angiotensin-Converting Enzyme (ACE) Inhibitors

• Dry cough.

• Teratogenicity.

• Hyperkalemia.

• Hypotension.

• Angioedema.

• Enalapril, Lisinopril, and Captopril may cause an increased risk of acute pancreatitis.

Angiotensin Receptor Blockers

• Hyperkalemia.

• Hypotension.

• Decreased glomerular filtration rate.

• Teratogenicity.

Calcium Channel Blockers

• Gingival hyperplasia.

• Dizziness.

• Flushing.

• Peripheral edema.

• Constipation.

Nitrates

• Reflex tachycardia.

• Headache.

• Flushing.

• Orthostatic hypotension.

Nitroprusside

• Cyanide toxicity occurs when there is underlying renal impairment or when used in a high dose.

Hydralazine

• Tachycardia.

• Headache.

• Fluid retention.

Minoxidil

• Hypertrichosis.

• Water retention.

• Pericarditis.

Beta-Blockers

• Bradycardia.

• Dizziness.

• Headaches.

• Nausea.

• Hypotension.

What Are the Precautions to Be Taken When Using Vasodilators?

• Vasodilators in Pregnancy - Some vasodilators may cause teratogenic toxicity and should be administered with caution. Hydralazine may cause fetal thrombocytopenia. The ACE inhibitors and angiotensin receptor blockers may cross into the breast milk and should be avoided while breastfeeding.

• Allergy to Hydralazine - Do not take this medicine if you are allergic to Hydralazine, Aspirin, Tartrazine, any other medications, or any of the ingredients in Hydralazine tablets.

• Vasodilators with Alcohol - Avoid drinking alcohol while taking vasodilators, as it may interfere with the functioning of vasodilators. Drinking excessive alcohol can affect the musculature of the blood vessels, making them narrower.

• Kidney Failure - The use of vasodilators in patients with kidneys should be done with caution as it may cause salt and water retention.

• Liver Dysfunction - Vasodilators may enhance the activity of the renin-angiotensin system in patients with advanced liver disease and increase the high risk of excessive hypotension or acute renal failure.

• Diabetes - Long-term use of vasodilators in diabetic patients may cause microvascular damage, especially, in type 1 diabetes.

• Vasodilators with Activities That Require Alertness - Vasodilators can cause dizziness, and hence, it is advised not to perform activities that require mental alertness, such as driving and operating machinery.

• Geriatrics - Vasodilators may be used with caution in the elderly as they may cause adverse side effects.

What Medications Interact With Vasodilators?

Medications Interaction with Vasodilators:

• Potassium supplements.

• Lithium.

• Verapamil.

• Diltiazem.

• Sildenafil.

• Tadalafil.

• Vardenafil.

Interaction With Food:

• Grapefruit - Grapefruit may interfere with the absorption of vasodilators which can be dangerous as it may exacerbate the effect of the drug.

• High Sodium Diet - Eating a diet high in salt can reduce the effectiveness of vasodilators in lowering blood pressure.

• Capsaicin - Taking capsaicin with food while taking certain ACE inhibitors can worsen the ACE inhibitor-related cough.

• Food High in Potassium - Foods such as avocados, beetroot, oranges, potatoes, spinach, tomatoes, and tomato sauce should be avoided in large amounts by people taking vasodilators.

Conclusion:

Heart disease is a serious condition and requires dedicated treatment. Vasodilators improve blood flow by relaxing the muscles in the blood vessels. It should be taken as prescribed, and microvascular monitoring should be done to detect its therapeutic levels. However, to keep a healthy heart, it is best to adopt a healthy lifestyle such as exercise, meditation, and a nutritious diet.