Symptomatic treatment of adult Parkinson disease, postencephalitic parkinsonism, and symptomatic parkinsonism following carbon monoxide or manganese intoxication. Pediatric efficacy and safety are not established.

Antiparkinson combination of a dopamine precursor and peripheral aromatic L-amino-acid decarboxylase inhibitor. Levodopa crosses the blood–brain barrier and is converted to dopamine in the striatum. Carbidopa does not appreciably cross the blood–brain barrier; it inhibits peripheral levodopa decarboxylation, increasing levodopa delivery to the CNS and reducing peripheral dopaminergic adverse effects.

For the equivalent Rytary extended-release formulation, relative bioavailability versus immediate-release product is approximately 70% for levodopa and 50% for carbidopa. Levodopa time to peak is approximately 1–4.5 hours and elimination half-life approximately 1.9 hours. Levodopa volume of distribution is 0.9–1.6 L/kg; protein binding 10%–30% (carbidopa approximately 36%). Metabolism includes decarboxylation and O-methylation; metabolites are excreted in urine. High-fat/high-calorie meals may delay levodopa absorption by approximately 2 hours, while high-protein meals may reduce or delay absorption.

Hypersensitivity to carbidopa, levodopa, or any formulation component; concurrent use of a nonselective monoamine oxidase inhibitor or use within the preceding 14 days.

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No formal pregnancy category is assigned. Human pregnancy data are limited; levodopa crosses the placenta, whereas fetal exposure to carbidopa appears low. Carbidopa/levodopa has more reported pregnancy outcomes than other antiparkinson therapies, but treatment should be individualized after maternal–fetal benefit–risk assessment.

No formal lactation category is assigned. Levodopa is present in human milk; carbidopa milk data are unavailable. Levodopa may suppress prolactin and inhibit lactation. Consider infant exposure, breastfeeding benefits, and the mother’s clinical need before continuing therapy.

Reported oral-formulation incidences vary by product and study population: nausea 2%–21%, dizziness 2%–19%, headache 1%–17%, dyskinesia 2%–17%, insomnia 1%–9%, vomiting 1%–5%, hallucinations 5%, and orthostatic hypotension 1%–68%. Clinically important events include sudden sleep onset, psychiatric or impulse-control disorders, severe dyskinesia, withdrawal-associated parkinsonism–hyperpyrexia syndrome, and vitamin B6 deficiency with neuropathy or seizures. Evaluate vitamin B6 before treatment, periodically, and when deficiency symptoms occur; supplement when indicated. The 2026 FDA review identified reported seizures primarily with high levodopa exposure, especially >1,000 mg/day.

1. Levodopa-naave adult:
Initial carbidopa/levodopa 23.75/95 mg orally three times daily for 3 days; on day 4, may increase to 36.25/145 mg three times daily. Further increases may be made according to response and tolerability, generally in levodopa 50 mg increments at intervals of at least 1 week.

2. Use of the requested 48.75/195 mg strength when converting from immediate-release carbidopa/levodopa:
- Current levodopa 950–1,249 mg/day: 3 capsules of 48.75/195 mg three times daily.
- Current levodopa 1,250 mg/day: 4 capsules of 48.75/195 mg three times daily, or an alternative equivalent extended-release regimen

3. Extended-release capsules are not interchangeable with immediate-release or controlled-release products on a 1:1 basis. Titrate after conversion according to response and tolerability.

4. Maximum recommended total: carbidopa 612.5 mg/levodopa 2,450 mg/day; dosing frequency may be increased to no more than five times daily.

5. Administer with or without food. Swallow whole; do not chew, divide, or crush. If swallowing is difficult, open the capsule and sprinkle the entire contents on 1–2 tablespoons of applesauce; consume immediately without chewing and do not store.

6. Avoid abrupt discontinuation or rapid dose reduction because of parkinsonism–hyperpyrexia/neuroleptic malignant-like syndrome risk.

No pediatric dosing recommendation is available; safety and effectiveness have not been established.

No dosage adjustment is likely necessary for any degree of kidney impairment. No adjustment is likely necessary for intermittent hemodialysis, peritoneal dialysis, CRRT, or PIRRT. When a scheduled dose coincides with hemodialysis, administer at least 1 hour before dialysis or after completion.

No specific dosage recommendation is available; use cautiously and monitor clinical response and hepatic function.

Store oral capsules at 20°C–25°C; permitted excursions 15°C–30°C. Protect from light and moisture. Keep in a tight container.