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COMT Inhibitor — Parkinson's Disease

Entacapone

Brand names: Comtess, Stalevo (combined with levodopa/carbidopa)

Entacapone is a COMT inhibitor given together with levodopa to reduce end-of-dose 'wearing off' in Parkinson's disease. It has no antiparkinsonian effect on its own.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION The recommended dose of entacapone is one 200 mg tablet administered concomitantly with each levodopa and carbidopa dose to a maximum of 8 times daily (200 mg × 8 = 1,600 mg per day). Clinical experience with daily doses above 1,600 mg is limited. Entacapone should always be administered in association with levodopa and carbidopa. Entacapone has no antiparkinsonian effect of its own. In clinical studies, the majority of patients required a decrease in daily levodopa dose if their daily dose of levodopa had been greater than or equal to 800 mg or if patients had moderate or severe dyskinesia before beginning treatment. To optimize an individual patient's response, …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2023-10-07. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It inhibits catechol-O-methyltransferase peripherally, slowing the breakdown of levodopa and prolonging and smoothing its delivery to the brain.

Prescribing in practice

  • It is effective only when given with levodopa and can increase levodopa-related dyskinesia and nausea — the levodopa dose may need reducing when entacapone is started.
  • Diarrhoea is common and can occasionally be severe and prolonged, sometimes requiring discontinuation.
  • It harmlessly discolours the urine red-brown, which should be explained so patients are not alarmed.

Monitoring

Review motor fluctuations and dyskinesia after starting, adjusting levodopa as needed; monitor for diarrhoea, nausea and unintended weight loss.

Counselling the patient

  • Your urine may turn a harmless red-brown colour.
  • Tell your prescriber if you develop persistent or troublesome diarrhoea.
  • Increased involuntary movements or nausea can occur — your levodopa dose may need adjusting.

Evidence & guidelines

Recognised option for end-of-dose motor fluctuations in Parkinson's disease (NICE NG71).

Reference: NICE NG71 (Parkinson's Disease); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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