Carbidopa/ levodopa

SINEMET

Open Carbidopa/ levodopa in the interactive console ↗

What it isDopamine-precursor levodopa paired with peripheral AADC inhibitor carbidopa; Parkinson motor symptoms.

Why this oneCarbidopa cannot cross the blood-brain barrier, so it blocks peripheral conversion only — quadrupling the levodopa reaching the brain while abolishing the nausea and orthostasis of peripheral dopamine.

What limits itNausea, orthostasis, dyskinesia and wearing-off drive adjustment; protein-rich meals can delay or reduce levodopa absorption.

FDA label

Read the full label on DailyMed ↗

FDA dosing	Population	Start	Target	Max
Parkinson's disease, post-encephalitic parkinsonism, and symptomatic parkinsonism (carbon monoxide or manganese intoxication)	Adults	1 tablet carbidopa/levodopa 25-100 TID (75 mg carbidopa/day)	Individualized; provide >=70–100 mg carbidopa/day	8 tablets/day

Titration Increase by 1 tablet every day or every other day as needed

Renal Use with caution; periodic renal function evaluation recommended during extended therapy

Hepatic Use with caution; periodic hepatic function evaluation recommended during extended therapy

Tablets of 1:4 (25-100) and 1:10 (10-100, 25-250) ratios may be combined to individualize dose; 25-250 no longer marketed by this manufacturer

Instructions

Individualize by careful titration
When transferring from levodopa alone, discontinue levodopa >=12 h before and start Sinemet at ~25% of the prior levodopa dose
Do not abruptly reduce/discontinue (risk of hyperpyrexia, confusion, NMS-like syndrome)
Evaluate vitamin B6 levels before and periodically during treatment; supplement if low

Contraindications

Concurrent use of nonselective MAO inhibitors (discontinue >=2 weeks before); MAO-B-selective inhibitors at recommended doses may be co-administered
Narrow-angle glaucoma

Cautions

Depression with suicidal tendencies
Severe cardiovascular/pulmonary disease, asthma; arrhythmias post-MI
Upper GI hemorrhage (history of peptic ulcer)
Vitamin B6 deficiency and seizures
Falling asleep during activities of daily living/somnolence
Hallucinations/psychotic-like behavior
Impulse control/compulsive behaviors
Melanoma risk

Adverse reactions

Dyskinesias (choreiform, dystonic, involuntary movements)
Nausea
Orthostatic hypotension
Hallucinations/confusion
Somnolence

Pregnancy No adequate human data; visceral and skeletal malformations seen in rabbits and reduced pup survival in rats; use only if benefit justifies risk.

Lactation Undefined

NO BOXED WARNINGS

Principal riskDyskinesia and motor fluctuation with cumulative exposure