A COMT inhibitor for Parkinson's
Entacapone
A COMT inhibitor always taken with levodopa to extend each dose and reduce 'wearing off' in Parkinson's disease.
What is Entacapone?
Entacapone is a COMT inhibitor used in Parkinson's disease. It is always taken together with levodopa to make each levodopa dose last longer and reduce 'wearing off'. It works by blocking an enzyme that breaks levodopa down, so more of it reaches the brain.
Education and reference only. This is a plain-language guide to Entacapone — 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
Entacapone is a COMT inhibitor used as an add-on to levodopa in Parkinson's disease. It is never used on its own; it only works alongside levodopa, where it helps each dose last longer. It is taken with every levodopa dose and is sometimes available combined with levodopa in a single tablet for convenience. It is used long-term to help people who experience 'wearing off' between doses.
How it works
Entacapone blocks an enzyme called catechol-O-methyltransferase (COMT), which normally breaks down levodopa in the body before it reaches the brain. By slowing this breakdown, more levodopa is available for longer, so each dose works for a longer time. This helps reduce the 'wearing off' that happens when levodopa effects fade before the next dose.
Company & origin
Originated / developed by: Developed by Orion Pharma..
Developed by the Finnish company Orion Pharma and approved in the late 1990s as an add-on to levodopa in Parkinson's disease.
What it treats
Conditions Entacapone is used for
Practical use
How to take Entacapone
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it with each dose of levodopa, following your usual levodopa schedule.
- It is never used on its own; it only works alongside levodopa.
- Expect your urine to turn a harmless reddish-brown colour.
- Your levodopa dose may be reduced when entacapone is started, to limit nausea and involuntary movements.
- Tell your prescriber if you develop persistent diarrhoea.
Weighing it up
Advantages & disadvantages of Entacapone
Advantages
- Extends each levodopa dose and reduces 'wearing off'.
- Can be taken as a combined levodopa-entacapone tablet for convenience.
- Simple to use because it follows the existing levodopa schedule.
Disadvantages
- Only works with levodopa, never on its own.
- Can increase involuntary movements and nausea, often needing a levodopa dose reduction.
- May cause diarrhoea and harmless but noticeable urine discolouration.
Practical use
Good to know
Entacapone is taken with each levodopa dose, so its timing follows your levodopa schedule. It commonly turns urine a harmless reddish-brown colour, which is nothing to worry about. Because it boosts levodopa's effect, it can increase levodopa-related involuntary movements (dyskinesia) and nausea, and the levodopa dose is often reduced when it is started. Diarrhoea can occur and should be reported if persistent.
Who should not take it / use with caution
- People with significant liver impairment, or a history of a serious reaction to a related COMT inhibitor.
- People taking certain non-selective MAO inhibitors, which should not be combined.
- Anyone whose specialist advises against it after reviewing their full medicine list.
Monitoring
- Review of 'wearing off', involuntary movements and nausea after starting.
- Watch for persistent diarrhoea and unexplained weight loss.
- Blood pressure, including checks for dizziness on standing.
Side effects
- Harmless reddish-brown discolouration of the urine.
- Increased involuntary movements (dyskinesia) and nausea.
- Diarrhoea, which can occasionally be troublesome.
- Dizziness or light-headedness on standing.
Key interactions
- Levodopa — entacapone is designed to be used with it, but boosts its effect, so the levodopa dose may need adjusting.
- Non-selective MAO inhibitors — should not be combined.
- Iron supplements — can reduce absorption, so are best separated in time.
- Some antidepressants and adrenaline-like medicines — use with caution.
Available as: Tablets, including a combined levodopa-entacapone tablet.
Answers
Entacapone: frequently asked questions
Why is entacapone always taken with levodopa?
It has no Parkinson's effect on its own. It works by slowing the breakdown of levodopa, so it is only useful when taken alongside each levodopa dose.
Why has my urine turned reddish-brown?
This is a well-known and harmless effect of entacapone. It does not mean anything is wrong and does not need treatment.
Will entacapone make my involuntary movements worse?
It can, because it boosts levodopa's effect. For this reason the levodopa dose is often reduced when entacapone is started.
What should I do about diarrhoea?
Mild diarrhoea is common early on, but if it is persistent or troublesome you should tell your prescriber, as the medicine may occasionally need to be reviewed.
Can I take entacapone on its own?
No. It only works with levodopa and is never used as a stand-alone Parkinson's treatment.
The wider class
About COMT inhibitors
Entacapone belongs to the comt inhibitors class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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