Also called metyrosine
Metirosine
A specialist medicine that lowers the body's production of adrenaline-like chemicals in people with a phaeochromocytoma.
What is Metirosine?
Metirosine is a specialist medicine used in people with a phaeochromocytoma, a tumour that produces too much of the adrenaline-like chemicals (catecholamines) that can cause high blood pressure, palpitations and sweating. It works by blocking an early step the body uses to make these chemicals, so less is produced. It is used mainly to prepare people for surgery or when surgery is not possible, usually alongside other blood-pressure medicines. Drowsiness is very common, and drinking plenty of fluid is important to avoid crystals forming in the urine.
Education and reference only. This is a plain-language guide to Metirosine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Metirosine is a specialist medicine used in people who have a phaeochromocytoma, a rare tumour, usually of the adrenal gland, that pours out too many adrenaline-like chemicals called catecholamines. These chemicals cause symptoms such as high blood pressure, a racing heart, headaches and heavy sweating. Metirosine reduces how much of them the body makes. It is taken by mouth and is generally used to control the tumour's effects before an operation to remove it, or as a longer-term measure when surgery is not suitable. It is prescribed and supervised by a specialist team.
How it works
The body makes adrenaline-like chemicals through a chain of steps, the first of which depends on an enzyme called tyrosine hydroxylase. Metirosine blocks this enzyme, slowing down that first step, so the tumour produces fewer of these chemicals overall. With less of them circulating, the surges in blood pressure and the palpitations, sweating and headaches they cause become easier to control. Because it dampens production rather than blocking the chemicals' effects directly, it is often used together with other medicines, such as alpha-blockers, that block those effects.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist medicine used in the UK to help control the effects of a tumour called phaeochromocytoma, usually in the run-up to surgery or when surgery is not possible.
Practical use
How to take Metirosine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth as your specialist team directs, spaced across the day as advised.
- Drink plenty of fluid throughout treatment to help prevent crystals forming in your urine.
- Be aware it commonly causes drowsiness, especially at first, so take care with driving and tasks needing concentration.
- Keep taking any other medicines, such as an alpha-blocker, that your team has prescribed alongside it.
- Tell your team about drowsiness that does not settle, tremor, jaw stiffness, anxiety or low mood.
Weighing it up
Advantages & disadvantages of Metirosine
Advantages
- Reduces the body's production of the adrenaline-like chemicals that cause symptoms in phaeochromocytoma.
- Helps control blood pressure and symptoms in the run-up to surgery, or when surgery is not possible.
- Taken by mouth and used as part of a planned specialist approach.
Disadvantages
- Very commonly causes drowsiness and sedation, which can affect driving and daily activities.
- Can cause crystals to form in the urine, so plenty of fluid is needed.
- May cause tremor, jaw stiffness, anxiety or low mood in some people.
Practical use
Good to know
The most noticeable effect of metirosine is drowsiness and a feeling of being sedated, which is very common, particularly when treatment is first started; this usually eases but can affect driving and concentration. A key practical point is to drink plenty of fluid throughout treatment, because the medicine can form crystals in the urine, and staying well hydrated helps prevent this. Some people develop tremor, jaw stiffness, anxiety or, occasionally, low mood, and these should be reported. Metirosine is usually one part of the picture: it is often used alongside an alpha-blocker to bring the tumour's effects under control, especially before surgery. The specialist team monitors blood pressure, symptoms and how you are tolerating the medicine, and adjusts treatment accordingly.
Who should not take it / use with caution
- People who have had a serious allergic reaction to metirosine should not take it.
- It is used with caution in people who already have kidney problems, with attention to fluid intake.
- It should only be used under specialist supervision, with regular monitoring of blood pressure and symptoms.
Monitoring
- Regular checks of blood pressure and symptoms to judge how well it is working.
- Watching for drowsiness, tremor, jaw stiffness and changes in mood.
- Encouraging good fluid intake and checking for any urinary problems.
Side effects
- Drowsiness and sedation, which are very common, especially early in treatment.
- Crystals in the urine if fluid intake is too low, which staying well hydrated helps prevent.
- Tremor, jaw stiffness, anxiety, restlessness or low mood in some people.
- Diarrhoea or other stomach upset, which can sometimes be troublesome.
Key interactions
- Other medicines that cause drowsiness, including alcohol, can add to the sedating effect.
- It is commonly used alongside an alpha-blocker, which the specialist team coordinates.
- Tell your team about all your medicines, as some affecting the nervous system may interact.
Available as: Capsules taken by mouth.
Answers
Metirosine: frequently asked questions
What is metirosine used for?
It is used in people with a phaeochromocytoma to reduce the body's production of adrenaline-like chemicals, helping control high blood pressure and symptoms, often before surgery.
Why does it make me so drowsy?
Drowsiness and sedation are very common, especially when treatment first starts; it usually eases but can affect driving and concentration, so take care.
Why must I drink plenty of fluid?
Metirosine can form crystals in the urine, and staying well hydrated throughout treatment helps prevent this problem.
Is it used on its own?
Often not; it is commonly used alongside other medicines such as an alpha-blocker to bring the tumour's effects under control, particularly before an operation.
What changes should I report?
Tell your team about drowsiness that does not settle, tremor, jaw stiffness, anxiety or low mood, as these can be linked to the medicine.
Authoritative sources
- BNF
- NICE CKS
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