carbidopa/levodopa
Brand names: Sinemet
This medicine contains carbidopa, levodopa, and entacapone. It is used to treat Parkinson's disease.
Drug Pricing (NADAC)
Brand Price
$1.29/unit
Generic Available
No
ORGANON
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine treats Parkinson's disease.
Common side effects
Uncontrolled movements, Diarrhea, Nausea
Key warnings
This medicine can make you fall asleep suddenly, even when you feel awake.
How It Works
Levodopa turns into dopamine in your brain, helping to control movement. Carbidopa helps levodopa get to your brain. Entacapone helps levodopa work longer.
How to Take It
Take this medicine exactly as your doctor tells you. Do not split or crush the tablets. The right dose varies for each person. Your doctor may change your dose to find what works best for you.
Pregnancy & Breastfeeding
This medicine may harm your unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is not known if this medicine passes into breast milk.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store at room temperature, away from heat and moisture.
Side Effects (from patient reports)
Based on 30,161 FDA adverse event reports.
Serious Warnings
This medicine can make you fall asleep suddenly, even when you feel awake. Be careful when driving or doing other activities where you need to be alert. Stopping this medicine suddenly can cause serious problems like fever and confusion.
Known Drug Interactions
7 DRUG INTERACTIONS Drugs metabolized by COMT: use with caution ( 5.10 , 7.2 ) Anti-hypertensive agents: dose adjustment may be required ( 7.3 ) Tricyclic antidepressants: risk of hypertension and dyskinesia reported during concomitant use with carbidopa/levodopa ( 7.4 ) Dopamine D2 receptor antagonists, isoniazid, phenytoin, papaverine and iron salts: may reduce efficacy of carbidopa, levodopa and entacapone tablets ( 7.5 , 7.6 , 7.7 , 7.8 , 7.9 ) Drugs that interfere with biliary excretion, glucuronidation and intestinal beta-glucuronidase: dose adjustment of carbidopa, levodopa and entac...
Mechanism: These drugs can interfere with how your body breaks down certain medicines, which may change how well your blood thinner works.
What to do: Your doctor should check your blood clotting tests more frequently and may need to adjust your warfarin dose.
7 DRUG INTERACTIONS Drugs metabolized by COMT: use with caution ( 5.10 , 7.2 ) Anti-hypertensive agents: dose adjustment may be required ( 7.3 ) Tricyclic antidepressants: risk of hypertension and dyskinesia reported during concomitant use with carbidopa/levodopa ( 7.4 ) Dopamine D2 receptor antagonists, isoniazid, phenytoin, papaverine and iron salts: may reduce efficacy of carbidopa, levodopa and entacapone tablets ( 7.5 , 7.6 , 7.7 , 7.8 , 7.9 ) Drugs that interfere with biliary excretion, glucuronidation and intestinal beta-glucuronidase: dose adjustment of carbidopa, levodopa and entac...
Mechanism: Entacapone is designed to block the enzyme that breaks down levodopa, which helps the medicine stay in your system longer. This can increase the effects of the levodopa on your brain and body.
What to do: Use this combination with caution as directed by your doctor. Your healthcare provider may need to adjust your dose to prevent side effects.
7.2 Drugs Metabolized by Catechol-O-Methyltransferase (COMT) Drugs known to be metabolized by COMT, such as isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, alpha-methyldopa, apomorphine, isoetherine, and bitolterol should be administered with caution in patients receiving entacapone regardless of the route of administration (including inhalation), as their interaction may result in increased heart rates, possibly arrhythmias, and excessive changes in blood pressure [ see Warnings and Precautions (5.10) ].
Mechanism: Both of these drugs are processed by the same enzyme in the body. Taking them together can cause the drugs to build up, which may lead to a fast heart rate or changes in blood pressure.
What to do: Use these medicines together with caution. Your doctor should monitor your heart rate and blood pressure closely during treatment.
7.2 Drugs Metabolized by Catechol-O-Methyltransferase (COMT) Drugs known to be metabolized by COMT, such as isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, alpha-methyldopa, apomorphine, isoetherine, and bitolterol should be administered with caution in patients receiving entacapone regardless of the route of administration (including inhalation), as their interaction may result in increased heart rates, possibly arrhythmias, and excessive changes in blood pressure [ see Warnings and Precautions (5.10) ].
Mechanism: These drugs are broken down by the same enzyme, so taking them at the same time can lead to higher drug levels. This can cause dangerous changes in blood pressure or an irregular heartbeat.
What to do: Your doctor should use caution when giving these drugs together. They will likely monitor your heart rhythm and blood pressure for any problems.
7 DRUG INTERACTIONS Drugs metabolized by COMT: use with caution ( 5.10 , 7.2 ) Anti-hypertensive agents: dose adjustment may be required ( 7.3 ) Tricyclic antidepressants: risk of hypertension and dyskinesia reported during concomitant use with carbidopa/levodopa ( 7.4 ) Dopamine D2 receptor antagonists, isoniazid, phenytoin, papaverine and iron salts: may reduce efficacy of carbidopa, levodopa and entacapone tablets ( 7.5 , 7.6 , 7.7 , 7.8 , 7.9 ) Drugs that interfere with biliary excretion, glucuronidation and intestinal beta-glucuronidase: dose adjustment of carbidopa, levodopa and entac...
Mechanism: These medications compete for the same enzyme that clears them from your body. This can cause the drugs to reach high levels, potentially leading to heart rhythm issues or blood pressure spikes.
What to do: Use this combination with extreme caution. Your healthcare provider may need to adjust your doses and monitor your heart health closely.
Common Questions
Can I drive while taking this medicine?
What should I do if I feel dizzy?
Can I drink alcohol while taking this medicine?
Will this medicine cure my Parkinson's disease?
How long does it take for this medicine to start working?
Can I stop taking this medicine on my own?
What if I have side effects?
Can I take other medicines with this one?
What should I do if my symptoms get worse?
How many tablets can I take each day?
What are the common side effects of carbidopa/levodopa?
Does carbidopa/levodopa interact with other medications?
What drug class is carbidopa/levodopa?
Is carbidopa/levodopa safe during pregnancy?
Related Medications in Dopamine Precursor Combination
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Medication Guides
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What the FDA Data Shows for carbidopa/levodopa
The FDA label for carbidopa/levodopa (sold under brand names such as Sinemet) classifies it as a prescription-only medication in the Dopamine Precursor Combination class. This medicine treats Parkinson's disease. Official labeling lists 7 commonly reported side effects, including Uncontrolled movements, Diarrhea, Nausea.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 30,161 voluntary reports. The database also lists 13 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated moderate severity. NADAC pricing from CMS.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: November 5, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages