carbidopa + levodopa: clinical use

Prescribing considerations

• Avoid abrupt withdrawal; monitor closely if interruption is unavoidable.
• Review cardiovascular, pulmonary, renal, hepatic, endocrine, ulcer, seizure and psychiatric history.
• Warn about somnolence, sudden sleep, impulse-control disorders and dopamine dysregulation syndrome.
• Treat Parkinson’s medicines as time-critical during admission, procedures and swallowing difficulties.

Contraindications and cautions

• Hypersensitivity to the active ingredients or excipients
• Non-selective monoamine oxidase inhibitor treatment
• Narrow-angle glaucoma
• Suspicious undiagnosed skin lesions or history of melanoma
• Severe psychosis
• For selected prolonged-release products, situations where sympathomimetic amines are contraindicated

Monitoring

• Motor response, wearing-off and dyskinesia
• Standing blood pressure and falls risk
• Hallucinations, depression, suicidality and other mental changes
• Somnolence, sudden sleep and driving risk
• Impulse-control disorders and compulsive overuse
• Cardiac function where recent myocardial infarction and residual arrhythmia are present
• Intraocular pressure in chronic wide-angle glaucoma
• Changing or suspicious pigmented skin lesions

Clinical pharmacology

Levodopa is converted to dopamine in the brain. Carbidopa inhibits peripheral aromatic amino-acid decarboxylase and does not substantially cross the blood–brain barrier, increasing levodopa delivery to the brain.

Formulation and product differences

• Immediate-release and prolonged-release tablets have different release profiles and licensed roles; do not substitute them without specialist review.
• Prolonged-release tablets must remain whole to preserve controlled release.
• Breakability differs between immediate-release products; consult the exact product information rather than assuming a score line provides equal portions.
• Prolonged-release onset may be slower, particularly for the first morning effect, and dyskinesia may be more frequent than with conventional tablets in people with motor fluctuations.

Tablet

Route: Oral

Strengths: 10 mg + 100 mg, 12.5 mg + 50 mg, 25 mg + 100 mg, 25 mg + 250 mg