What is Methyldopa?

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  • Written By: D. Jeffress
  • Edited By: Jenn Walker
  • Last Modified Date: 30 January 2019
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Methyldopa is a prescription drug most often prescribed to combat chronic high blood pressure. It relaxes the muscles surrounding blood vessels in the body, causing them them to dilate and allow blood to pass through more easily. When methyldopa is taken exactly how it is prescribed, it is safe for use for most adult and pediatric patients with hypertension. Mild side effects such as dry mouth and headache are common, but there are a few risks for major adverse reactions. The prescribing doctor can explain in detail the importance of taking the drug as directed and what to do if symptoms persist or worsen.

Doctors classify methyldopa as an alpha-2 receptor agonist. The drug stimulates receptor cites in the brain that control the action of certain hormones, including adrenaline. Methyldopa essentially tricks the brain into responding as if hormone levels are too high. As a result, the central nervous system stops exciting smooth muscle tissue that surrounds arteries and veins. Blood vessels can then relax and expand to promote better blood flow.


A doctor can determine the proper dosage amount based on a patient's age, weight, severity of hypertension, and overall health. Most adults are given 250 milligram doses three times daily for the first few days of treatment. The doctor carefully monitors blood pressure test results and other vital statistics to determine if dosages need to be lowered or raised. Once an optimal dose amount is found, a patient is usually instructed to take two to four pills a day indefinitely. Regular health checkups and home monitoring are important to make sure the drug continues to work at maximum efficiency.

The most common short-term side effects of methyldopa include dizziness, lightheadedness, headache, and dry mouth. Drowsiness, joint pain, and weakness may develop in a small number of patients due to changes in central nervous system functioning. Additional side effects may occur if methyldopa is taken in combination with other hypertension drugs or medications for other health problems.

Rarely, patients experience severe reactions to methyldopa. Allergic responses can result in body-wide hives, throat swelling, and chest pain. Sudden attacks of violent diarrhea and vomiting, fainting, and mental confusion are potential signs of an acute overdose. Any unusual reactions need to be treated as soon as possible at an emergency room to prevent permanent complications. The majority of patients are able to take their medications daily without experiencing such significant problems.



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