This leaflet is to help you understand your medicine. It is not intended to be a comprehensive guide about your medicine and it is not an official manufacturer’s patient information leaflet.
Always consult the manufacturer’s patient information leaflet for the most up to date information regarding COMT (catechol-O-methyltransferase) inhibitors.
Why have I been prescribed a COMT inhibitor?
In Parkinson’s dopamine is lacking in certain areas of the brain and the medicine levodopa is converted to dopamine in the brain. COMT inhibitors prolong the action of levodopa.
Levodopa is used to help improve some of the motor symptoms of Parkinson’s (slowness and poverty of movement, rigidity and tremor). COMT inhibitors reduce the ‘wearing off’ of levodopa doses, but have no effect on Parkinson’s if taken on their own.
Are COMT inhibitors safe to take?
COMT inhibitors are generally safe to take as directed but may not suit everyone. There are some conditions where COMT inhibitors are not always used.
Tell your Parkinson’s team if any of the following apply to you:
- If you are allergic to any of the ingredients.
- If you have a tumour on your adrenal gland
- If you have liver disease
- If you have ever had the muscle disorder rhabdomyolysis
If you have ever suffered from neuroleptic malignant syndrome
If you have taken Monoamine Oxidase Inhibitors, used for depression, in the last 14 days (for example, tranylcypromine or phenelzine)
How should I take COMT inhibitors?
Entacapone, opicapone and tolcapone are taken by mouth as tablets; they are given at personalised timings throughout the day. Entacapone should always be taken at the same timing as your levodopa preparation and is sometimes given as combined preparation
(Stalevo®, Sastravi®). Opicapone is taken once a day at bedtime. Tolcapone is usually taken three times daily.
If you forget a dose, take it as soon as you remember. If it is at or near your usual dose, just take the next dose (do not double your dose).
Do I need any blood tests?
If you are prescribed tolcapone you will need to have regular blood tests to monitor your liver function. This is more frequent initially and with any dose adjustment. Your Parkinson’s team will continue monitor your blood pressure.
What unwanted effects of COMT inhibitors might I experience?
Unfortunately, you may experience some side effects. Most of these are quite mild and should go away after a week or two as you get used to your COMT inhibitor. The table is a guide to what to do if you get any side effects.
Not everyone will get the side effects shown, and most people do not. The more serious side effects are often dose related and may be avoided or minimised by using the smallest effective dose.
|Side effects||How common?||What should I do?|
|Drowsiness||Common||If affected do not drive or operate machinery|
|Dizziness||Common||Do not drive or operate machinery. |
If problem persists, contact your Parkinson’s team
|Dyskinesia (involuntary movements).||Very common||Contact your Parkinson’s team to |
review your dosage and, or timings
|Nausea and vomiting||Common||This should be short lived, contact |
your Parkinson’s team if it persists
|Hallucinations||Common||Contact your Parkinson’s team|
|Allergic reaction or fever||Rare||Seek urgent medical attention if there is swelling of the face or throat|
|Red urine, saliva or tears||Very common||This is harmless|
|Diarrhoea, abdominal pain or loss of appetite||More common at higher doses||Contact your Parkinson’s team|
|Inflammation of liver, jaundice, dark urine||Unknown||Contact your Parkinson’s team if there is yellowing of skin or whites of eyes|
|Sudden onset of sleep||Unknown||Do not drive or operate machinery, contact your Parkinson’s team|
|Mental health problems – impulse control problem||Unknown||Contact your Parkinson’s team|
|Urge to take more Parkinson’s medication||Unknown||Contact your Parkinson’s team|
Seek urgent medical attention if your skin or eyes become yellow, this may be accompanied by abdominal pain and feeling weak and exhausted.
Dyskinesia (involuntary wriggly movements)
Dyskinesia is often a sign that the dosage of levodopa may need review, please contact your Parkinson’s team to review the dose and/or medication timings.
Sudden onset of sleep
Levodopa can sometimes cause extreme daytime drowsiness and sudden onset of sleep (with no warning signs), (entacapone, opicapone and tolcapone increase the effectiveness of levopdopa). If you are affected, you must not drive or operate machinery.
What about alcohol?
Generally, you should not drink alcohol while taking a COMT inhibitor because both can make you drowsy, so taking them together may increase this further. However, once you are used to taking your medication you might wish to try a glass of your normal drink. If you do not suffer any adverse effects, you may be able to drink in moderation.
Do not stop medication so you can have an alcoholic drink.
If my Parkinson’s is well controlled, can I stop taking it?
NO. This can be dangerous and result in a serious deterioration in your Parkinson’s. You and your Parkinson’s team will need to decide when you can stop taking it. Never change your dose or stop taking your dopamine agonist yourself.
Something not right?
Please contact the Parkinson’s Advice Line at your earliest opportunity.
Out of hours please contact NHS 111 or visit A&E in an emergency.
South Tees Hospitals NHS Foundation Trust would like your feedback. If you wish to share your experience about your care and treatment or on behalf of a patient, please contact The Patient Experience Department who will advise you on how best to do this.
This service is based at The James Cook University Hospital but also covers the Friarage Hospital in Northallerton, our community hospitals and community health services.