Metyrosine (Oral)

Metyrosine is an antihypertensive drug used to treat high blood pressure in people who suffer from pheochromocytoma, which is a noncancerous tumor in the adrenal glands.


It is not used as a general drug for high blood pressure and is not to be given to people who do not suffer from pheochromocytoma. It works by reducing the levels of certain chemicals called "catecholamines"in the body. These chemical tend to increase blood pressure. Metyrosine is also commonly used in research, to learn how low levels of catecholamines affect behavior and mood.

This medication should be used with caution by people with mental health disorders, particularly depression, and Parkinson's disease, as it can make the symptoms of these conditions worse.

Metyrosine may be harmful when taken at the same time as a central nervous system depressant, such as sedatives, tranquilizers, some cold medications, some antidepressants, and alcohol. People who are taking grass pollen allergen extract are usually advised not to take this medication.

Metyrosine is commonly known under the brand name "Demser".

Conditions Treated

Type Of Medicine

  • Antihypertensive

Side Effects

As well as its desired effect of treating your high blood pressure, metyrosine can also trigger undesired side effects in some people.

Contact your doctor right away if you experience any of the side effects below:

More common side effects

  • Diarrhea or loose stools, especially if this continues for a long time
  • Drooling
  • Drowsiness
  • Problems speaking
  • Shaking, tremors or trembling in the hands or the fingers

Less common side effects

  • Agitation or restlessness
  • Anxiety or nervousness
  • Black or tarry stools
  • Bleeding or bruising easily
  • Blood in the stools
  • Blood in the urine
  • Changes to how you walk, such as shuffling
  • Confusion or disorientation
  • Difficulty urinating
  • Hallucinations, such as seeing or hearing something that is not actually there
  • Mood problems, such as sadness or depression
  • Muscle spasms, jerky movements, or convulsions, particularly around the neck, face, and back
  • Shortness of breath
  • Small red dots, spots rashes or itching on the skin
  • Swelling in the feet or legs
  • Tiredness, fatigue, or weakness

Less serious side-effects

Metyrosine can cause some side-effects that are less serious and usually do not require medical attention. Sometimes these side-effects will pass with time, once your body gets used to the medication. If you experience any of the side-effects listed below, and you are concerned about them, consult your doctor for advice.

  • Drowsiness
  • Dry mouth or increased thirst
  • Nausea or vomiting
  • Reduced sex drive or sexual ability in men
  • Swelling or unusual milk production in the breasts
  • Upset stomach

This is not a complete list of the side-effects you might experience. Medications affect people in unpredictable ways, so you might experience something that is not mentioned here. If you notice anything unusual or bothersome while you are taking metyrosine, contact your doctor for advice.

After you finish taking the drug

Some people will experience some side-effects after they finish their course of treatment with metyrosine. These include:

  • Diarrhea: consult your doctor if you experience diarrhea after you stop taking this medication.
    Increased energy or difficulty sleeping: this side-effect is most common in people who experienced drowsiness while taking the drug, and usually passes after a few days. Consult your doctor if it lasts any longer than this.


Always take the medication exactly as prescribed by your doctor, because there are potentially serious health consequences if you take an overdose of this medication. If you believe you may have overdosed, seek emergency medical assistance immediately. Common symptoms of an overdose may include:

  • Extreme drowsiness
  • Severe anxiousness or agitation
  • tremors
  • Tightness in your jaw

Allergic reaction

Serious allergic reactions to this medication are rare, but they can occur. You may also be allergic to the other ingredients in the medication, such as the materials that the capsule is made of. Signs of an allergic reaction include:

  • Extreme drowsiness, tiredness, fatigue, dizziness, or fainting
  • Finding it hard to breathe, shallow breaths, or wheezing
  • Itching, rashes, hives, or redness on the skin
  • Swelling in the through, tongue, or face


Your doctor will determine how much metyrosine you should take and how frequently you should take it based on the symptoms you are experiencing. Always take this medication as prescribed by your doctor. Do not take larger doses and do not take the medication for longer than you have been advised to.

As guidelines below are the common dosages that are typically prescribed:

  • For adults and children 12+ years of age: 1 to 3 grams per day, split into four evenly-spaced doses

If you miss one of your doses of metyrosine, take it as soon as possible. The only exception to this is when you are approaching the time of your next dose -- in that case, skip the missed dose and carry on with your normal schedule. Do not double your next dose if you have missed a previous one, as it may put you at greater risk of experiencing side-effects.


Before you start taking metyrosine, it is important that you tell your doctor about all other medications, herbal supplements, and vitamin supplements that you are taking. Some medications can interact with metyrosine and the combination of the two drugs may produce unpleasant or harmful side-effects.

The following drugs are known to interact with metyrosine:

  • Central nervous system (CNS) depressants: these medications slow down the nervous system and can cause drowsiness. Since metyrosine can also cause drowsiness, it may be dangerous to take the two drugs together. Examples of CNS depressants include alcohol, antihistamines, some cold medicines, sedatives, tranquilizers, any medication given to help you sleep, some seizure medication, some antidepressants, anesthetics including dental anesthetics and muscle relaxers.
  • Grass pollen allergen extract: if you take grass pollen allergen extract, you are at risk of a certain type of allergic reaction that must be treated with a chemical called epinephrine. However, metyrosine can interfere with the effects of epinephrine. You will probably be advised not to take these two medications at the same time.

Other drugs not listed here may also interact with metyrosine, so make sure your doctor is aware of anything else that you are taking.


Metyrosine generally well-tolerated and it is considered to be safe when taken as prescribed by a doctor. However, there are some people for whom it might not be a suitable choice of medication. Metyrosine should be used with caution by people with certain medical conditions. These include the following:

Kidney disease or liver disease: In patients with either of these conditions, metyrosine may be removed from the body more slowly. This means that the amount of the drug in the body may be higher than expected. Your doctor may want to adjust your dose of metyrosine to compensate for this.
Mental health disorders: metyrosine may make the symptoms of certain mental health disorders more intense, particularly mood disorders such as depression.
Parkinson's disease: Metyrosine may make the symptoms of Parkinson's disease worse.

Tell your doctor about any other medical conditions that you currently have. The presence of these conditions does not necessarily mean that you cannot take this medication, but your doctor might give you a lower dose than normal, and they may want you to undergo more frequent examinations to check that your symptoms are not getting worse.

When you are taking this medication, make sure to drink plenty of water. This will help to keep your kidney functioning normally. Ask your doctor how much water you should drink each day.

If you are due to have any surgery or dental procedures during the time that you will be taking metyrosine, tell the doctor or dentist in charge of your care that you are taking metyrosine.

Metyrosine can cause drowsiness in some people. Do not drive or operate heavy machinery unless you are sure that you can do so safely.

Pregnancy and Breastfeeding

It is not known whether metyrosine is safe for women to take if they are pregnant or breastfeeding. If you are pregnant or plan to become pregnant while you are taking metyrosine, inform your doctor, who will be able to advise you further. If you become pregnant while you are taking metyrosine, inform your doctor right away.


As yet, there is no research available testing the safety and efficacy of this medication when taken by children. Ask your doctor for more information about this.


No studies have yet tested this drug in older individuals. If you are older than 65 years of age, your doctor may want to see you more often for checkups, to make sure that the medication is working properly and that no side-effects are occurring.


Observe the following guidelines when storing this medication:

  • Store the medication at room temperature, and keep it away from sources of heat, including heaters, the stove, and radiators
  • Do not store the medication in a place where it can be exposed to sunlight
  • Do not refrigerate or freeze your capsules
  • Store the medication in a dry location. Do not keep your capsules in the bathroom as this location is too warm and humid to store medications.
  • Keep the medication out of the sight and reach of children. Ensure that the cap is tightly sealed on the bottle when you are not using it.
  • Check the capsules for signs of damage before you take them, such as softness, or capsules sticking together. Do not take capsules that have been damaged.
  • Do not take the medication if it has passed its expiry date.
  • After your course of treatment with metyrosine, take any remaining capsules to your pharmacist or a local take-back scheme for safe disposal. Do not throw them away in the trash.


Metyrosine is used to treat hypertension (high blood pressure) that often arises in people who suffer from pheochromocytoma. It works by reducing the levels of certain chemicals in the body that tend to increase blood pressure.

People who suffer from mental health problems or Parkinson's disease may find that metyrosine makes their symptoms worse.

Metyrosine should not be taken at the same time as grass pollen allergen extract. Central nervous system depressants should also be avoided wherever possible, as they can cause severe drowsiness when taken alongside metyrosine.