Methyldopa: Pharmacology, Action Mechanism, Side Effects, Interaction, Warnings and Administration

It is a drug that is used to treat high blood pressure, reducing it will help reduce the risk of having a stroke or a heart attack.

Methyldopa is a prescription medicine. It comes in the form of an oral tablet and is available only in generic form. Generic drugs generally cost less than branded versions.

You can take Methyldopa alone or in combination with other drugs.

Pharmacology and Mechanism of action

Methyldopa is a derivative of phenylalanine and an inhibitor of aromatic amino acid decarboxylase with antihypertensive activity.

Methyldopa is a prodrug and is metabolized in the central nervous system. The antihypertensive action of Methyldopa seems to be attributable to its conversion into alpha-methylnorepinephrine, which is a potent alpha-2 adrenergic agonist that binds and stimulates potent central inhibitory alpha-2 adrenergic receptors.

This results in a decrease in sympathetic output and a decrease in blood pressure.

How does it work?

Methyldopa belongs to a class of medications called centrally acting antiadrenergic drugs.

Your brain normally sends signals to the blood vessels that make the vessels narrow. This increases your blood pressure. Methyldopa prevents your brain from sending these signals. And this helps prevent the increase in blood pressure.

Side effects

The oral tablet of Methyldopa may cause temporary drowsiness. This usually happens when you start taking the medication for the first time. It can also happen if your doctor increases your dose.

Methyldopa can also cause other side effects such as:

Most common side effects

  • Drowsiness.
  • Headache.
  • Lack of energy.
  • Weakness.
  • Dizziness.
  • Daze.
  • Fainting.
  • Nausea or vomiting
  • Swelling of your hands or feet.
  • Weight gain.

If these effects are mild, they may disappear in a few days or a couple of weeks. If they are more severe or do not go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor immediately if you have serious side effects. Serious side effects and their symptoms may include the following:

Heart problems

Symptoms may include:

  • Worsening of angina pectoris (pain in the chest).
  • Swelling of your hands, feet, legs or ankles.
  • Weight gain.
  • Difficulty breathing.
  • Irregular or strong heartbeat.
Low red blood cells

Symptoms may include:

  • Exhausted
  • Daze.
  • Difficulty breathing.
  • Pale skin.
Low levels of white blood cells

Symptoms may include:

  • Fever.
  • Cold symptoms such as runny nose or sore throat that do not go away.
  • Symptoms of the flu, such as body aches and fatigue.
Low levels of platelets

Symptoms may include:

  • Cuts or wounds that do not stop the bleeding.
Liver problems

Symptoms may include:

  • Yellowing of your skin or the whites of your eyes.
  • Nausea.
  • Not wanting to eat.
  • Dark colored urine.
  • Fatigue.
Allergic reactions

Symptoms may include:

  • Fever.
  • Acute pain in the chest.
  • Eruption.
  • Joint pains
  • Fatigue.
  • Difficulty breathing or swallowing
Skin problems

Symptoms may include:

  • Redskin.
  • Scaly skin.
  • Blistered skin.

Interaction with other medications

The oral methyldopa tablet may interact with other medications, vitamins or herbs that you may be taking. An interaction is when a substance changes the way a medication works. This can be harmful or prevent the drug from working well.

Examples of medications that can cause interactions with Methyldopa are listed below.


If you have surgery, your doctor may need to use anesthetics to avoid pain. If you take Methyldopa, your doctor may need to use lower doses of anesthetics.

These also lower your blood pressure. If you take Methyldopa and receive regular doses of anesthetics, your blood pressure may go too low.

Medication for bipolar disorder:

The use of lithium with Methyldopa can cause lithium in your body to rise to dangerous levels.

Other drugs for blood pressure:

Taking Methyldopa with other drugs that also lower your blood pressure can increase your risk of dangerously low blood pressure. Examples of these medications include:

Inhibitors of angiotensin converting enzyme (ACE), such as:

  • Benazepril.
  • Captopril.
  • Cilazapril.
  • Enalapril.
  • Enalaprilat.

Angiotensin receptor blockers (BRA), such as:

  • Irbesartan.
  • Losartan.
  • Olmesartan.
  • Telmisartan.
  • Valsartan.

Beta-blockers, such as:

  • Acebutolol.
  • Arotinolol.
  • Atenolol.
  • Betaxolol.
  • Bisoprolol.
  • Esmolol.
  • Metoprolol.

Blockers of calcium channels, such as:

  • Amlodipine.
  • Felodipino.
  • Nicardipina.
  • Nifedipine .

Direct renin inhibitors, such as:

  • Aliskiren.

Loop diuretics, such as:

Some potassium-sparing diuretics, such as:

Some thiazide diuretics, such as:

Depression drugs :

Certain medications for depression called monoamine oxidase inhibitors (MAOIs) should not be used with Methyldopa. Taking these medications with Methyldopa can cause your blood pressure to rise to dangerous levels.

This is called a hypertensive crisis and it is a medical emergency.

Examples of MAOIs include:

  • Isocarboxazid.
  • Phenelzina.
  • Tranylcypromina.

Iron supplements:

Do not use iron supplements if you take Methyldopa. Taking iron supplements can decrease the amount of Methyldopa in your body. This can make it less effective in lowering high blood pressure .

Other interactions and interaction guide

When Methyldopa is used with other antihypertensive drugs , an antihypertensive effect potentiation may occur.

Patients should be followed carefully to detect secondary reactions or unusual manifestations of drug idiosyncrasy.

These patients may require reduced doses of anesthetics when taking Methyldopa. If hypotension occurs during anesthesia, it can usually be controlled with vasopressors. Adrenergic receptors remain sensitive during treatment with Methyldopa.

When this drug and lithium are administered concomitantly, the patient should be carefully monitored for symptoms of lithium toxicity.

Several studies show a decrease in the bioavailability of Methyldopa when ingested with ferrous sulfate or ferrous gluconate.

This can adversely affect the control of blood pressure in patients treated with Methyldopa. Concomitant administration of the drug with ferrous sulfate or ferrous gluconate is not recommended.


This medicine comes with several warnings.

Allergy warning:

You should know that Methyldopa can cause a severe allergic reaction, and it may have the following symptoms:

  1. Difficulty breathing or swallowing
  2. Swelling of your throat or tongue.
  3. Urticaria.

If you develop these symptoms, call the emergency number in your region or go to the nearest emergency room.

Do not take this medication again if you have ever had an allergic reaction. Taking it again could be fatal (cause death).

Edema warning (swelling):

While taking this medication, you may have swelling in your hands and feet, or you may gain weight. You may need to take a diuretic to help control swelling and weight gain.

If the edema gets worse or if you develop heart failure, you may need to stop taking Methyldopa.

Warning of interaction with alcohol and other alcoholic beverages:

Drinking alcohol while taking Methyldopa may increase the effect of this medication. It can slow down your reflexes, make you feel drowsy or reduce your ability to make good decisions.

Also avoid the intake of other alcoholic substances as a precaution.

Warnings for people with certain health conditions:

For people with liver disease:

You should not take this medicine if you have or have had liver disease.

Methyldopa can cause severe liver damage. Know that your doctor will do some tests to check how well your liver is working during the first 6 to 12 weeks after you start taking this medicine.

For people with kidney disease:

The kidneys remove Methyldopa from your body. If your kidneys do not work well, it is possible that more of the medication stays in your body longer and exposes you to risks of side effects.

Talk to your doctor about any kidney problems you have or have had.

Warnings for other groups:

For pregnant women:

Methyldopa is a category B pregnancy medication. This means two things:

  • Animal research has not shown a risk to the fetus when the mother takes the drug.
  • There have not been enough studies in humans to show whether the drug poses a risk to the fetus.

Talk to your doctor if you are pregnant or plan to be pregnant. Animal studies do not always predict how humans would respond. Therefore, this medication should only be used during pregnancy if clearly necessary.

For women who are breastfeeding:

Methyldopa passes into breast milk. You and your doctor should talk about whether you should take this drug if you want to breastfeed.

How to take Methyldopa?

All possible doses and medication forms may not be included here. Your dosage, form of the drug and how often you take the medication will depend on:

  • Your age.
  • The condition that is being treated.
  • How serious is your condition.
  • Other medical conditions you have.
  • How it reacts to the first dose

Dosage for hypertension (high blood pressure):

Dosage for adults (between 18 and 64 years old):

  • Typical starting dose: 250 mg, 2 or 3 times per day in evenly divided doses, during the first 48 hours.
  • Increase the dose: if your blood pressure is still high after 2 or 3 days, your doctor can increase your dose.
  • Maximum dose: 3,000 mg per day.

Dose for children (ages 0-17 years):

  • Typical starting dose: 10 mg per kilogram of body weight per day, administered in 2 to 4 doses divided equally.
  • Maximum dose: 65 mg per kilogram or 3 grams per day, whichever is less.

Dosage for elderly people (over 65 years old):

Older adults can process drugs more slowly. A typical dose of an adult can cause the levels of the drug to be higher than normal in the elderly.

Older adults are more likely to pass out or lose consciousness while taking this medication. You may need a lower dose or you may need a different treatment schedule.

Dosing warnings

May be tolerant to Methyldopa between the second and third month of treatment. This means that you may need more of the medication to get the same results.

Your doctor may choose to increase your dose or add a diuretic to help your blood pressure come back under control.


Methyldopa is a prescription medicine. It comes in the form of an oral tablet and is available only in generic form. Generic drugs generally cost less than branded versions. And its use may involve some considerations to take into account.

Take as prescribed

The oral tablet of Methyldopa is used for long-term treatment. It comes with risks if you do not take it as prescribed.

If you stop taking the medication suddenly or do not take it at all: your blood pressure will not be controlled. You will have a higher risk of having a stroke or heart attack.

Did you forget a dose?

If you miss a dose or do not take the medication as scheduled, your medication may not work as well or may stop working completely. For Methyldopa to work well, there needs to be a certain amount in your body at all times.

If you forget to take your dose, take it as soon as you remember it. If you remember it a few hours before the time of your next dose, just take one. Never try to catch up by taking two doses at a time. Since this could cause dangerous side effects.

What happens if I take too much?

It could have dangerous levels of the drug in your body. Symptoms of an overdose of this medication may include:

  • Severe fall in blood pressure.
  • Weakness.
  • Lower heart rate
  • Dizziness.
  • Daze.
  • Vomiting
  • Diarrhea or constipation

If you think you have taken too much of this medication, call your doctor or the local poison control center. If your symptoms are severe, call the emergency number for your region or go to the nearest emergency room right away.

How to know if the medicine is working?

You may not feel a change while taking Methyldopa, but your blood pressure should decrease. This can be seen when measuring your blood pressure with a blood pressure monitor.

Note: Your doctor will monitor your blood pressure to make sure that Methyldopa works for you.

Is there an alternative to this medication?

There are other medications available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about other medication options that may work for you.