Dopamine Precursor / Decarboxylase Inhibitor Pregnancy: Avoid if possible — limited data; potential fetal toxicity

Levodopa-Carbidopa (Co-Careldopa)

Brand names: Sinemet, Caramet, Duodopa (enteral)

Adult dose

Dose: Sinemet 25/100 (carbidopa 25 mg/levodopa 100 mg): start 1 tablet TDS, increase every 3–7 days. Target: optimum control with minimum dyskinesia. Standard range: 3–8 tablets/day.

Route: Oral

Frequency: TDS–QDS (standard release); BD–TDS (modified release — Sinemet Plus CR)

Max: 800 mg levodopa/day (standard); higher doses in specialist care

Gold standard dopaminergic therapy for Parkinson's disease. L-DOPA is converted to dopamine in brain. Carbidopa inhibits peripheral decarboxylation (reduces dose needed, reduces nausea). Do NOT take with high-protein meals — amino acid competition reduces absorption.

Paediatric dose

Route: N/A

Frequency: N/A

Max: Not licensed in children (dopamine-responsive dystonia is different — small doses under specialist)

Off-label use in dopamine-responsive dystonia (DRD): starting 0.5 mg/kg/day levodopa with carbidopa — specialist paediatric neurology only

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Clinical pearls

Take 30 min before or 1h after meals — protein competes with L-DOPA absorption at gut and blood-brain barrier
Domperidone (not metoclopramide — crosses BBB and blocks central dopamine): use for nausea with levodopa
Wearing off: timing of doses; prolonged-release formulations or addition of entacapone to extend effect
Impulse control disorders: rare but important — screen at each visit; reduce dopaminergic dose if present

Contraindications

Closed-angle glaucoma
Concurrent MAOIs (within 14 days)
Malignant melanoma (historical contraindication — may theoretically stimulate melanocytes)

Side effects

Motor fluctuations ('wearing off', 'on-off' phenomena) — long-term
Dyskinesias (involuntary movements — peak dose related)
Nausea/vomiting (early; reduce with domperidone)
Orthostatic hypotension
Hallucinations (late Parkinson's)
Impulse control disorders (gambling, hypersexuality, binge eating)
Somnolence and sleep attacks

Interactions

MAOIs — hypertensive crisis, contraindicated (allow 2-week washout)
Antipsychotics (haloperidol, metoclopramide) — antagonise dopaminergic effects, avoid
Iron supplements — chelate levodopa, reduce absorption (separate by 2 hours)
Pyridoxine (vitamin B6) — reduces levodopa efficacy if not combined with carbidopa
Antihypertensives — additive hypotensive effect

Monitoring

Motor function (UPDRS score)
Dyskinesias
Orthostatic BP
Psychiatric symptoms (ICD, hallucinations)
Nutrition and swallowing

Reference: BNFc; BNF; NICE NG71 Parkinson's Disease. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways