Version July 2025
Dosage guidance:
Safety: Consult a neurology specialist for all management decisions; choice of therapy must be carefully individualized (Ref).
Clinical considerations: Foslevodopa/foscarbidopa replaces levodopa-containing medications and catechol-O-methyl transferase (COMT) inhibitors; other pharmacologic classes for treatment of Parkinson disease may be taken concurrently, if needed. A reduction in concomitant Parkinson disease medications, followed by an adjustment in foslevodopa/foscarbidopa dosage, may be considered during therapy.
Parkinson disease:
Note: For use in advanced levodopa-responsive Parkinson disease.
Optional loading dose:
Note: To quickly achieve symptomatic control if in an "off" state or if the base continuous infusion has been off for >3 hours, may administer a loading dose immediately prior to starting or re-starting the base continuous hourly infusion. Loading doses may be administered with either foslevodopa/foscarbidopa or oral IR carbidopa/levodopa; calculate loading dose from the first morning dose of oral IR levodopa the patient took before starting foslevodopa/foscarbidopa therapy.
SUBQ: Administer calculated foslevodopa/foscarbidopa loading dose as a single dose followed by continuous infusion.
Loading dose calculation:
Foslevodopa/foscarbidopa loading dose (mL) = ([oral IR levodopa first morning dose (mg)] × 1.3) ÷ 240
Note: 1 mL of foslevodopa/foscarbidopa contains 240 mg of foslevodopa. The 1.3 conversion factor takes into account the molecular weight and bioavailability of foslevodopa compared to levodopa. The Vyafuser pump can deliver a loading dose range of foslevodopa/foscarbidopa 0.1 to 3 mL in increments of 0.1 mL.
Continuous infusion:
SUBQ: Administer calculated initial continuous infusion rate in mL/hour based on total levodopa dosage (TLD). Administer over patient’s waking hours or over 24 hours. Adjust the hourly infusion rate based on response and tolerability in increments of 0.01 mL/hour (foslevodopa 2.4 mg/hour, equivalent to levodopa ~1.7 mg/hour). Maximum: foslevodopa/foscarbidopa 14.69 mL/day (foslevodopa 3.525 g/day, equivalent to levodopa ~2.5 g/day).
Continuous infusion calculation:
Hourly base continuous infusion rate (mL/hour) = [(TLD × 1.3) ÷ 240] ÷ [number of hours the patient is typically awake (eg, 16 hours)]
Note: Calculate the TLD for the levodopa-containing medications that foslevodopa/foscarbidopa will be replacing; convert all doses to the equivalent IR levodopa to obtain the TLD. Adjust the TLD for COMT inhibitor use. Do not include rescue or as-needed levodopa or any other anti-Parkinsonian medication or therapy, including medications taken outside of awake time (eg, night-time dosing) in calculation (Ref). One mL of foslevodopa/foscarbidopa contains 240 mg of foslevodopa. The 1.3 conversion factor takes into account the molecular weight and bioavailability of foslevodopa compared to levodopa (Ref). Recommended conversion factors vary globally (may vary per region; consult product labeling).
Alternative flow rates: Two alternative hourly infusion rates (low/high) may be preprogrammed by the provider if needed. Patients or caregivers may select alternative flow rates based on changes in functional demand (eg, lowering dosage at night, increasing dose for prolonged intense activity).
Extra doses: If enabled by the provider and programmed into the pump, patients or caregivers may administer an extra dose to manage acute "off" symptoms. Maximum: 1 extra dose/hour. If ≥2 extra doses are used in a 24-hour period, consider adjusting the base continuous infusion rate.
|
Foslevodopa/Foscarbidopa extra dose volume (mL) |
Foslevodopa dose (mg) |
Levodopa dose equivalent (LE) (mg) |
|---|---|---|
|
0.1 mL |
24 mg |
~17 mg LE |
|
0.15 mL |
36 mg |
~25.5 mg LE |
|
0.2 mL |
48 mg |
~34 mg LE |
|
0.25 mL |
60 mg |
~42.5 mg LE |
|
0.3 mL |
72 mg |
~51 mg LE |
Discontinuation of therapy: Discontinuation of therapy may result in neuroleptic malignant-like syndrome (Ref). Avoid sudden discontinuation or rapid dose reduction. If infusion is interrupted for >3 hours, the patient or caregiver may administer a loading dose (if instructed by health care provider). Consider making access to an alternative carbidopa/levodopa oral product available if delivery of foslevodopa/foscarbidopa is interrupted. If previously discontinued, foslevodopa/foscarbidopa therapy may be resumed at any time by following initiation instructions.
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling.
There are no dosage adjustments provided in the manufacturer's labeling.
Refer to adult dosing.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Adverse reactions reported in adults.
>10%:
Local: Infusion-site reaction (62%; infusion-site infection: 28%)
Nervous system: Hallucination (12%)
Neuromuscular & skeletal: Dyskinesia (11%)
1% to 10%:
Cardiovascular: Peripheral edema (5%)
Gastrointestinal: Constipation (5%)
Nervous system: Agitation (4%), balance impairment (5%), insomnia (4%), on-off phenomenon (8%), psychosis (4%; including delusion, paranoid ideation)
Respiratory: Dyspnea (4%)
US labeling: Concurrent use with nonselective monoamine oxidase inhibitors (MAOIs) or use within the last 2 weeks.
Canadian labeling: Hypersensitivity to foslevodopa, levodopa, foscarbidopa, carbidopa, or any component of the formulation; concurrent use with nonselective MAOIs or use within the last 14 days (however, may be administered concomitantly with the manufacturer's recommended dose of an MAOI with selectivity for MAO type B); narrow angle glaucoma; clinical or laboratory evidence of uncompensated cardiovascular, cerebrovascular, endocrine, hepatic, hematologic, pulmonary (eg, bronchial asthma), or renal disease; concomitant administration of a sympathomimetic amine (eg, epinephrine, norepinephrine, isoproterenol); undiagnosed skin lesions or history of melanoma; conditions in which medication with adrenergic activity is contraindicated (eg, pheochromocytoma, hyperthyroidism, Cushing disease).
Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Concerns related to adverse effects:
• Dyskinesias: May cause or exacerbate dyskinesias; may require dose adjustment of Parkinson disease treatment(s).
• Hallucinations/Psychosis: Hallucinations and psychosis have been reported; hallucinations may occur shortly after treatment initiation and may respond to dose reduction of foslevodopa/foscarbidopa or other concomitant medications. A higher incidence of hallucinations may occur in patients receiving concomitant dopamine agonist agents and dopaminergic treatments containing levodopa. Lower nighttime infusion rates may be considered to reduce hallucinations (Aldred 2023; Fung 2024).
• Impulse control disorders: Dopamine agonists used for Parkinson disease have been associated with compulsive behaviors and/or loss of impulse control, which has manifested as pathological gambling, increased sexual urges, intense urges to spend money, binge or compulsive eating, and other intense urges. Dose reduction or discontinuation of therapy has been reported to reverse these behaviors in some, but not all cases.
• Infusion-site reactions: Infusion-site reactions and infections have been reported, including bruising, cellulitis, edema, erythema, extravasation, hematoma, hemorrhage, induration, inflammation, mass, nodule, pain, pallor, pruritus, rash, swelling, and warmth. If infection is suspected at infusion site, remove the cannula from the infusion site; in cases of prolonged interruption, prescribe an oral carbidopa/levodopa until therapy can be resumed.
• Melanoma: Risk for melanoma development is increased in patients with Parkinson disease; drug causation or factors contributing to risk have not been established. Patients should be monitored closely and periodic skin examinations should be performed.
• Polyneuropathy: Polyneuropathy, including peripheral neuropathy, decreased vibratory sense, neuralgia, and sensory disturbance/loss, has been reported; symptoms may include numbness, tingling, decreased sensation, weakness, and pain in legs, feet, and extremities. Use with caution in patients with risk factors for polyneuropathy, including patients with vitamin B12 or B6 deficiencies, diabetes mellitus, and/or hypothyroidism. Patients with symptoms of peripheral neuropathy and low vitamin concentrations and elevated homocysteine or methylmalonic acid may benefit from vitamin supplementation. May consider benefit/risk of continued treatment and possible dose adjustment.
• Somnolence: Somnolence and falling asleep while engaged in activities of daily living (including operation of motor vehicles) have been reported with levodopa; some cases reported that there were no warning signs for the onset of symptoms. Prior to treatment initiation, evaluate for factors that may increase these risks, such as concomitant sedating medications and the presence of sleep disorders. Use with caution with concomitant sedating medication or preexisting sleep disorder. There is insufficient information to suggest that dose reductions will eliminate these symptoms. Caution patients about performing tasks that require mental alertness (eg, operating machinery, driving). Patients who experienced somnolence or an episode of sudden sleep onset during specific activities should not participate in those activities during therapy.
Disease-related concerns:
• Cardiovascular disease: Use with caution in patients with severe cardiovascular disease, including a history of myocardial infarction (MI) and/or cardiac arrhythmias; MI and arrhythmia have been reported in patients taking carbidopa/levodopa.
• Glaucoma: Use with caution in patients with glaucoma; may increase intraocular pressure.
• Psychiatric disorders: Use with caution in patients with a history of psychotic disorders.
Other warnings/precautions:
• Discontinuation of therapy: Dopaminergic agents have been associated with a syndrome resembling neuroleptic malignant syndrome (eg, altered consciousness, autonomic instability, muscular rigidity, elevated temperature) upon rapid dose reduction, changes in dopaminergic therapy, or abrupt withdrawal.
Vyalev (foscarbidopa 12 mg/foslevodopa 240 mg per 1 mL injection): FDA approved October 2024; anticipated availability currently unknown. Information pertaining to this product within the monograph is pending revision. Vyalev is approved for the treatment of motor fluctuations in adults with advanced Parkinson disease. Consult the prescribing information for additional information.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Subcutaneous [preservative free]:
Vyalev: Foscarbidopa 12 mg and foslevodopa 240 mg per mL (10 mL)
No
Solution (Vyalev Subcutaneous)
12-240 mg/mL (per mL): $39.30
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Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Subcutaneous:
Vyalev: Foscarbidopa 12 mg and foslevodopa 240 mg per mL (10 mL)
SUBQ: Administer by SUBQ infusion using the Vyafuser infusion pump; do not administer IV or IM. Do not dilute or mix with other products. May administer over patient’s waking hours (eg, 16 hours) or over 24 hours. Prior to initiating therapy, train patients/caregivers on proper use of foslevodopa/foscarbidopa and the delivery system. Administer into abdomen (avoiding the 2-inch area around the navel); infusion set may remain in place for up to 3 days; rotate infusion site and use a new infusion set at least every 3 days. New infusion sites should be at least 1-inch from sites previously used in the last 12 days. Do not administer into skin that is tender, bruised, red, or hard to the touch. Advise patients not to swim, bathe, or shower with the pump. Administration may be interrupted for a short period of time (eg, patient is taking a shower); if infusion is interrupted for >1 hour, change infusion set (tubing and cannula) and rotate to a different infusion site.
An FDA-approved patient medication guide, which is available with the product information and as follows, must be dispensed with this medication:
Vyalev: https://www.rxabbvie.com/pdf/vyalev_medguide.pdf
Parkinson disease: Treatment of motor fluctuations in adults with advanced levodopa-responsive Parkinson disease.
Foslevodopa/Foscarbidopa may be confused with Carbidopa/Levodopa.
The Institute for Safe Medication Practices (ISMP) includes this medication among its list of drug classes (anti-Parkinson agent) which have a heightened risk of causing significant patient harm when used in error (High-Alert Medications in Long-Term Care Settings).
Refer to individual components.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Alfuzosin: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Alizapride: May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk X: Avoid
Amifostine: Blood Pressure Lowering Agents may increase hypotensive effects of Amifostine. Management: When used at chemotherapy doses, hold blood pressure lowering medications for 24 hours before amifostine administration. If blood pressure lowering therapy cannot be held, do not administer amifostine. Use caution with radiotherapy doses of amifostine. Risk D: Consider Therapy Modification
Amisulpride (Injection): May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk X: Avoid
Amisulpride (Oral): Anti-Parkinson Agents (Dopamine Agonist) may decrease therapeutic effects of Amisulpride (Oral). Amisulpride (Oral) may decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk X: Avoid
Antipsychotic Agents (First Generation [Typical]): May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Management: Avoid concomitant therapy if possible. If antipsychotic use is necessary, consider using atypical antipsychotics such as clozapine, quetiapine, or ziprasidone at lower initial doses, or a non-dopamine antagonist (eg, pimavanserin). Risk D: Consider Therapy Modification
Antipsychotic Agents (Second Generation [Atypical]): May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Management: Consider avoiding atypical antipsychotic use in patients with Parkinson disease. If an atypical antipsychotic is necessary, consider using clozapine, quetiapine, or ziprasidone at lower initial doses, or a non-dopamine antagonist (eg, pimavanserin). Risk D: Consider Therapy Modification
Arginine: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Barbiturates: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Biperiden: May increase adverse/toxic effects of Levodopa-Foslevodopa. Specifically, the risk of choreic movements or dyskinesias may be increased. Risk C: Monitor
Blood Pressure Lowering Agents: May increase hypotensive effects of Hypotension-Associated Agents. Risk C: Monitor
Blood Pressure Lowering Agents: May increase hypotensive effects of Levodopa-Foslevodopa. Risk C: Monitor
Bornaprine: May increase adverse/toxic effects of Levodopa-Foslevodopa. Specifically, dyskinesia may be increased. Risk C: Monitor
Brimonidine (Topical): May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Brivudine: May increase adverse/toxic effects of Anti-Parkinson Agents (Dopamine Agonist). Specifically, the risk of chorea may be increased. Risk C: Monitor
Bromopride: May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk C: Monitor
Bromperidol: May decrease hypotensive effects of Blood Pressure Lowering Agents. Blood Pressure Lowering Agents may increase hypotensive effects of Bromperidol. Risk X: Avoid
BuPROPion: Anti-Parkinson Agents (Dopamine Agonist) may increase adverse/toxic effects of BuPROPion. Risk C: Monitor
Diazoxide: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Droxidopa: Foscarbidopa may decrease therapeutic effects of Droxidopa. Foscarbidopa may increase serum concentration of Droxidopa. Foscarbidopa may decrease active metabolite exposure of Droxidopa. Risk C: Monitor
DULoxetine: Blood Pressure Lowering Agents may increase hypotensive effects of DULoxetine. Risk C: Monitor
Fluorodopa F18: Coadministration of Anti-Parkinson Agents (Dopamine Agonist) and Fluorodopa F18 may alter diagnostic results. Management: Discontinue medications used to treat Parkinson disease, including dopamine agonists, 12 hours prior to fluorodopa F 18 administration if these medications can be safely withheld. Risk D: Consider Therapy Modification
Fosphenytoin-Phenytoin: May decrease therapeutic effects of Levodopa-Foslevodopa. Risk C: Monitor
Glycopyrrolate (Systemic): May decrease serum concentration of Levodopa-Foslevodopa. Risk C: Monitor
Herbal Products with Blood Pressure Lowering Effects: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Hypotension-Associated Agents: Blood Pressure Lowering Agents may increase hypotensive effects of Hypotension-Associated Agents. Risk C: Monitor
Isoniazid: May decrease therapeutic effects of Levodopa-Foslevodopa. Risk C: Monitor
Kava Kava: May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Kava Kava may increase adverse/toxic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk C: Monitor
Levodopa-Foslevodopa: Blood Pressure Lowering Agents may increase hypotensive effects of Levodopa-Foslevodopa. Risk C: Monitor
Lormetazepam: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Macimorelin: Coadministration of Levodopa-Foslevodopa and Macimorelin may alter diagnostic results. Risk X: Avoid
MATE1/2-K Substrates (Clinically Relevant with Inhibitors): Foslevodopa may increase serum concentration of MATE1/2-K Substrates (Clinically Relevant with Inhibitors). Risk C: Monitor
Metergoline: May increase adverse/toxic effects of Levodopa-Foslevodopa. Management: Consider the need for possible reductions in levodopa dose with initiation of or increasing doses of metergoline. Monitor for evidence of increased levodopa adverse effects with use of the combination. Risk D: Consider Therapy Modification
Methotrimeprazine: May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Anti-Parkinson Agents (Dopamine Agonist) may decrease therapeutic effects of Methotrimeprazine. Risk X: Avoid
Metoclopramide: May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk X: Avoid
Molsidomine: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Monoamine Oxidase Inhibitors (Type B): Levodopa-Foslevodopa may increase orthostatic hypotensive effects of Monoamine Oxidase Inhibitors (Type B). Risk C: Monitor
Monoamine Oxidase Inhibitors: Levodopa-Foslevodopa may increase adverse/toxic effects of Monoamine Oxidase Inhibitors. Of particular concern is the development of hypertensive reactions when levodopa is used with nonselective MAOI. Risk X: Avoid
Multivitamins/Fluoride (with ADE): May decrease therapeutic effects of Levodopa-Foslevodopa. Management: Concurrent use of a multivitamin and levodopa (without carbidopa) should be avoided. Risk D: Consider Therapy Modification
Multivitamins/Minerals (with AE, No Iron): May decrease therapeutic effects of Levodopa-Foslevodopa. Management: Concurrent use of a multivitamin and levodopa (without carbidopa) should be avoided. Risk D: Consider Therapy Modification
Naftopidil: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Nicergoline: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Nicorandil: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Nitroprusside: Blood Pressure Lowering Agents may increase hypotensive effects of Nitroprusside. Risk C: Monitor
Obinutuzumab: May increase hypotensive effects of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Risk D: Consider Therapy Modification
Papaverine: May decrease therapeutic effects of Levodopa-Foslevodopa. Papaverine may increase hypotensive effects of Levodopa-Foslevodopa. Risk C: Monitor
Pentoxifylline: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Pholcodine: Blood Pressure Lowering Agents may increase hypotensive effects of Pholcodine. Risk C: Monitor
Phosphodiesterase 5 Inhibitors: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Prostacyclin Analogues: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Pyridoxine: May decrease therapeutic effects of Levodopa-Foslevodopa. Management: The concomitant use of pyridoxine and levodopa (in the absence of a dopa decarboxylase inhibitor (DDI)) should be avoided. Use of a DDI (eg, carbidopa) with levodopa will essentially eliminate the risk of this interaction. Risk D: Consider Therapy Modification
Quinagolide: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Reserpine: Levodopa-Foslevodopa may increase hypotensive effects of Reserpine. Reserpine may decrease therapeutic effects of Levodopa-Foslevodopa. Management: Consider alternatives to the coadministration of levodopa and reserpine. If combined, monitor for reduced levodopa efficacy and hypotension. Risk D: Consider Therapy Modification
Sapropterin: May increase adverse/toxic effects of Levodopa-Foslevodopa. Risk C: Monitor
Silodosin: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Solriamfetol: May increase adverse/toxic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk C: Monitor
Sulpiride: May decrease therapeutic effects of Anti-Parkinson Agents (Dopamine Agonist). Risk X: Avoid
Tiapride: Levodopa-Foslevodopa may decrease therapeutic effects of Tiapride. Tiapride may decrease therapeutic effects of Levodopa-Foslevodopa. Risk X: Avoid
Vesicular Monoamine Transporter 2 (VMAT2) Inhibitors: May decrease therapeutic effects of Levodopa-Foslevodopa. Management: Consider alternatives to the coadministration of levodopa and vesicular monoamine transporter 2 (VMAT2) inhibitors. If combined, monitor for reduced levodopa efficacy. Risk D: Consider Therapy Modification
Foslevodopa and foscarbidopa are prodrugs converted to levodopa and carbidopa. Refer to the Carbidopa and Levodopa monograph for additional information.
Foslevodopa and foscarbidopa are prodrugs converted to levodopa and carbidopa. Levodopa is present in breast milk.
According to the manufacturer, the decision to breastfeed during therapy should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and the benefits of treatment to the mother.
Refer to the Carbidopa and Levodopa monograph for additional information.
Some products may contain sodium.
Hepatic, renal, hematopoietic, cardiovascular evaluation (periodically throughout therapy; for patients with history of myocardial infarction or atrial nodal or ventricular arrhythmia, also monitor carefully during therapy initiation); BP (in patients receiving antihypertensive medications), signs/symptoms of infusion-site reaction/infection (eg, redness, pain, swelling at infusion site [monitor throughout therapy]); mental status changes, signs/symptoms of impulse control disorders; intraocular pressure (in patients with glaucoma [monitor periodically throughout therapy]); risk factors for neuropathy (vitamin B12, vitamin B6, homocysteine, methylmalonic acid, and folic acid plasma concentrations; presence of diabetes mellitus, hypothyroidism [monitor at baseline and periodically throughout therapy]), signs and symptoms of neuropathy (periodically throughout therapy); skin examinations (periodically throughout therapy); drowsiness or sleepiness (periodically throughout therapy).
Parkinson disease symptoms are due to a lack of striatal dopamine. Foscarbidopa and foslevodopa are prodrugs of carbidopa and levodopa, respectively. Foscarbidopa and foslevodopa are rapidly converted to carbidopa and levodopa by ubiquitous alkaline phosphatases. Levodopa circulates in the plasma and crosses the blood-brain-barrier (BBB), where it is converted by striatal enzymes to dopamine. Carbidopa inhibits the peripheral plasma breakdown of levodopa by inhibiting its decarboxylation, increasing available levodopa at the BBB.
Protein binding: Foscarbidopa and foslevodopa: 24% to 26%.
Metabolism:
Foscarbidopa and foslevodopa: Rapidly converted to carbidopa and levodopa via alkaline phosphatases.
Levodopa: Two major pathways (decarboxylation and O-methylation) and 2 minor pathways (transamination and oxidation) of metabolism.
Carbidopa: Metabolized to 2 main metabolites.
Half-life elimination: Carbidopa: ~2 hours; levodopa: 1.5 hours (when administered with carbidopa).
Excretion: Carbidopa: Urine (30% as unchanged drug; also as metabolites).
