Carbidopa/Levodopa
- PO (Adults ): Immediate-release (IR) or orally disintegrating tablets: 25 mg carbidopa/100 mg levodopa 3 times daily; may be ↑ every 1–2 days until desired effect is achieved (max = 8 tablets of 25 mg carbidopa/100 mg levodopa/day).
- Enteral(Adults ): Patients must be converted to and be on stable dose of PO IR carbidopa/levodopa tablets before initiation of enteral suspension therapy. Morning dose for Day 1 (mL) (to be administered over 10–30 min) = (Amount of levodopa [in mg] in first dose of IR carbidopa/levodopa taken by patient on previous day * 0.8); Continuous dose for Day 1 (mL) (to be administered over 16 hr) = Determine amount of levodopa (in mg) patient received from IR carbidopa/levodopa doses throughout 16 waking hr of previous day (do not include doses of IR carbidopa/levodopa taken at night when calculating the levodopa amount). Then, subtract amount of first levodopa dose (in mg) taken by patient on previous day. Divide result by 20 to obtain the # of mL to be administered over 16 hr. Do not exceed dose of 2000 mg. At end of daily 16-hr infusion, patients will disconnect the pump from feeding tube and take their nighttime dose of oral IR carbidopa/levodopa tablets. Total daily dose can be titrated after Day 1 based on patient response and tolerability.
Carbidopa/Levodopa Extended-Release (ER) (doses of all other dosage forms of carbidopa/levodopa and Rytary are not interchangeable)
- PO (Adults ): Patients not currently receiving levodopa (Sinemet CR): 50 mg carbidopa/200 mg levodopa twice daily (minimum of 6 hr apart) initially. Patients not currently receiving levodopa (Rytary): 23.75 mg carbidopa/95 mg levodopa 3 times daily for 3 days; then 36.25 mg carbidopa/145 mg levodopa 3 times daily. May continue to ↑ dose as needed (max dose = 97.5 mg carbidopa/390 mg levodopa 3 times daily). May also ↑ frequency of administration up to 5 times daily (max dose = 612.5 mg carbidopa/2450 mg levodopa/day). Patients not currently receiving levodopa (Crexont): 35 mg carbidopa/140 mg levodopa twice daily for 3 days. May then gradually ↑ dose as needed to max dose of 525 mg carbidopa/2100 mg levodopa/day in up to 4 divided doses.Conversion from IR carbidopa/levodopa to Sinemet CR: Initiate therapy with at least 10% more levodopa content/day (may need up to 30% more) given at 4–8 hr intervals while awake. Allow 3 days between dosage changes; some patients may require larger doses and shorter dosing intervals. Conversion from IR carbidopa/levodopa to Rytary: If taking 400–549 mg/day of IR levodopa, give 3 capsules of Rytary 23.75 mg carbidopa/95 mg levodopa 3 times daily. If taking 550–749 mg/day of IR levodopa, give 4 capsules of Rytary 23.75 mg carbidopa/95 mg levodopa 3 times daily. If taking 750–949 mg/day of IR levodopa, give 3 capsules of Rytary 36.25 mg carbidopa/145 mg levodopa 3 times daily. If taking 950–1249 mg/day of IR levodopa, give 3 capsules of Rytary 48.75 mg carbidopa/195 mg levodopa 3 times daily. If taking ≥1250 mg/day of IR levodopa, give 4 capsules of Rytary 48.75 mg carbidopa/195 mg levodopa 3 times daily or 3 capsules of Rytary 61.25 mg carbidopa/245 mg levodopa 3 times daily; may then titrate as needed (max daily dose = 612.5 mg carbidopa/2450 mg levodopa). Conversion from IR carbidopa/levodopa to Crexont: If taking <500 mg/day of IR levodopa and most frequent single dose of IR levodopa is 100 mg, give Crexont 70 mg carbidopa/280 mg levodopa twice daily. If taking <500 mg/day of IR levodopa and most frequent single dose of IR levodopa is 150 mg, give 2 capsules of Crexont 52.5 mg carbidopa/210 mg levodopa twice daily. If taking <500 mg/day of IR levodopa and most frequent single dose of IR levodopa is 200 mg, give 2 capsules of Crexont 70 mg carbidopa/280 mg levodopa twice daily. If taking ≥500 mg/day of IR levodopa and most frequent single dose of IR levodopa is 100 mg, give Crexont 70 mg carbidopa/280 mg levodopa 3 times daily. If taking ≥500 mg/day of IR levodopa and most frequent single dose of IR levodopa is 150 mg, give 2 capsules of Crexont 52.5 mg carbidopa/210 mg levodopa 3 times daily. If taking ≥500 mg/day of IR levodopa and most frequent single dose of IR levodopa is 200 mg, give 2 capsules of Crexont 70 mg carbidopa/280 mg levodopa 3 times daily. If taking ≥500 mg/day of IR levodopa and most frequent single dose of IR levodopa is >200 mg, give 2 capsules of Crexont 87.5 mg carbidopa/350 mg levodopa 3 times daily. Conversion from Rytary to Crexont: Initiate Crexont on an approximately 1:1 mg basis using the levodopa component for conversion.
Therapeutic Classification: antiparkinson agents
Pharmacologic Classification: dopamine agonists
Absorption: Well absorbed following oral administration.
Distribution: Widely distributed. Levodopa: enters the CNS in small concentrations. Carbidopa: does not cross the blood-brain barrier but does cross the placenta.
Metabolism/Excretion: Levodopa: mostly metabolized by the GI tract and liver. Carbidopa: 30% excreted unchanged by the kidneys.
Half-Life: Levodopa: 1 hr; carbidopa: 1–2 hr.
KAR-bi-doe-pa/LEE-voe-doe-pa