Entacapone

Key facts

• Entacapone is a COMT inhibitor. It is always taken together with levodopa, usually with carbidopa too, commonly as the combination tablet Stalevo; it has no effect on its own.
• It extends how long each dose of levodopa keeps working, reducing "off" periods when Parkinson's symptoms return between doses.
• Do not stop entacapone or reduce your levodopa dose suddenly: abrupt changes can rarely trigger a serious reaction with high fever, muscle rigidity, and confusion, resembling neuroleptic malignant syndrome.
• Entacapone commonly turns urine a harmless brownish-orange colour; this is expected and not a sign of a problem.

What entacapone treats

Entacapone is added to levodopa and carbidopa treatment for Parkinson's disease in people whose symptom control fluctuates during the day, easing the "wearing-off" effect that happens as each levodopa dose loses effect before the next one is due. It does not treat Parkinson's disease on its own and is not used without levodopa.

How entacapone works

Levodopa is broken down partly by an enzyme called catechol-O-methyltransferase (COMT). Entacapone blocks this enzyme outside the brain, so more of each levodopa dose remains available to cross into the brain and be converted to dopamine. This extends and smooths out levodopa's effect, without directly affecting dopamine itself.

Before you take it

• Tell your prescriber about liver disease, since entacapone is processed by the liver, and about any history of low blood pressure on standing.
• Levodopa combined with entacapone can worsen dyskinesia, involuntary movements; your prescriber may need to lower your levodopa dose when entacapone is added.
• Certain antidepressants and medicines that affect dopamine can interact with entacapone; tell your prescriber about all other medicines you take.
• Do not stop treatment abruptly; any dose changes should be planned with your prescriber.

Side effects

Common effects include nausea, diarrhoea, harmless dark urine, and dizziness on standing.

Seek urgent medical care for:

• High fever, severe muscle stiffness, and confusion, especially after stopping or reducing your dose.
• Yellowing of the skin or eyes.
• New or worsening involuntary movements.
• Fainting or severe dizziness.

Safety essentials

• Never stop entacapone or cut your levodopa dose abruptly. Sudden withdrawal can cause a rare but serious reaction with very high fever, rigid muscles, and confusion that needs emergency treatment.
• Report new or worsening dyskinesia to your prescriber rather than adjusting your levodopa dose yourself.
• Harmless orange-brown urine discolouration is expected and does not need medical attention on its own.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.