Drug Guide
Levodopa, Carbidopa, Entacapone
Classification
Therapeutic: Parenteral antiparkinsonian agent
Pharmacological: Dopamine precursor, COMT inhibitor
FDA Approved Indications
- Parkinson's disease
Mechanism of Action
Levodopa is converted to dopamine in the brain, alleviating Parkinsonian symptoms. Carbidopa inhibits peripheral decarboxylation of levodopa, increasing central nervous system availability. Entacapone is a COMT inhibitor that prolongs the effect of levodopa by blocking its breakdown in the periphery.
Dosage and Administration
Adult: Dosage varies per formulation, typically titrated based on response. For Stalevo, dosing ranges from 50 mg to 200 mg of levodopa per tablet taken three or four times daily.
Pediatric: Not generally recommended for pediatric use.
Geriatric: Start at lower end of dosing range due to increased sensitivity to side effects.
Renal Impairment: Use caution; adjust dosing as needed.
Hepatic Impairment: No specific adjustments documented.
Pharmacokinetics
Absorption: Peak plasma levels of levodopa occur within 1 hour of oral administration.
Distribution: Widely distributed; crosses blood-brain barrier.
Metabolism: Levodopa is metabolized peripherally and centrally; entacapone inhibits COMT, reducing catecholamine breakdown.
Excretion: Metabolites are excreted primarily in urine.
Half Life: Levodopa: approximately 1-2 hours; entacapone: about 0.4 hours.
Contraindications
- Hypersensitivity to any components.
- Closed-angle glaucoma.
- Non-selective MAO inhibitors taken within 2 weeks.
Precautions
- Use with caution in cardiac, hepatic, or renal impairments. Monitor for neuropsychiatric effects, dyskinesias, and orthostatic hypotension. Pregnancy category C.
Adverse Reactions - Common
- Nausea (Common)
- Dyskinesias (Common)
- Orthostatic hypotension (Common)
Adverse Reactions - Serious
- Neuroleptic malignant syndrome (Rare)
- Liver failure (Rare)
- Daytime sleepiness or sudden sleep episodes (Uncommon)
Drug-Drug Interactions
- Other dopamine agonists, MAO inhibitors, antipsychotics, certain antidepressants
Drug-Food Interactions
- High-protein meals may reduce absorption.
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor PD symptom control, blood pressure, and mental status.
Diagnoses:
- Risk for falls related to hypotension or dizziness.
- Impaired physical mobility.
Implementation: Administer with food to reduce nausea; avoid high-protein meals close to dosing; monitor for side effects.
Evaluation: Assess for improvement in motor symptoms and adverse reactions.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report new or worsening symptoms.
- Avoid alcohol and certain foods that interfere with absorption.
Special Considerations
Black Box Warnings:
- None specific, but caution advised related to neuropsychiatric events.
Genetic Factors: No specific genetic considerations.
Lab Test Interference: May cause false-positive urinary test results for certain drugs.
Overdose Management
Signs/Symptoms: Dopaminergic overdose may cause dyskinesias, hallucinations, or hypotension.
Treatment: Symptomatic and supportive care; no specific antagonist.
Storage and Handling
Storage: Store at room temperature, away from moisture and heat.
Stability: Stable for shelf life as indicated by manufacturer.