How does Sinemet work?

Sinemet contains two medicines: levodopa and carbidopa. Levodopa gets converted to dopamine (a naturally occurring chemical messenger) in the brain. Low dopamine levels contribute to Parkinson’s disease symptoms. Carbidopa prevents your body from breaking down levodopa. This allows more levodopa to travel to the brain.

What drugs should not be taken with Sinemet?

Certain MAOI medicines should never be taken with Sinemet. These include Marplan (isocarboxazid), methylene blue, Nardil (phenelzine), Parnate (tranylcypromine), and Zyvox (linezolid). It would be best if you stopped taking MAOI medicines at least two weeks before starting Sinemet.

How do I stop taking Sinemet?

Do not stop taking Sinemet without talking to your healthcare provider first. Abruptly stopping Sinemet can cause serious side effects, including fever, rigid muscles, unusual body movements, and confusion. If you and your healthcare provider decide that stopping treatment with Sinemet is appropriate for you, your healthcare provider will likely slowly decrease your dose to prevent side effects.

Sinemet (Carbidopa and Levodopa) - Oral: Uses, Effects

What Is Sinemet?

Sinemet (carbidopa and levodopa) is an oral prescription medication used to treat Parkinson’s disease. Healthcare providers may also prescribe Sinemet to treat Parkinson's-like symptoms after encephalitis (brain swelling) or from carbon monoxide poisoning or manganese poisoning.

Parkinson’s disease symptoms (e.g., shaking, stiffness, slowed movements) are caused by low levels of dopamine, a naturally occurring brain chemical. Levodopa (one of the medicines found in Sinemet) gets converted to dopamine in the brain. Sinemet also contains carbidopa. Carbidopa works by inhibiting the body’s breakdown of levodopa. This increases how much levodopa gets delivered to the brain.

Drug Facts

Generic Name: Carbidopa and levodopa

Brand Name(s): Sinemet

Drug Availability: Prescription

Therapeutic Classification: Decarboxylase inhibitors

Available Generically: Yes

Controlled Substance: No

Administration Route: Oral

Active Ingredient: Carbidopa and levodopa

Dosage Form(s): Tablet

What Is Sinemet Used For?

Over 10 million people around the globe have Parkinson’s disease. It’s generally more common in men. Sinemet helps treat the condition's symptoms, including tremors (shaking), stiffness, and slowed movements. Sinemet is not a cure for Parkinson’s disease, but it can help improve your mobility.

Sinemet is also useful for treating Parkinson's-like symptoms caused by certain conditions, including:

Encephalitis (brain swelling)
Carbon monoxide poisoning
Manganese poisoning

How to Take Sinemet

Sinemet is typically taken three or four times per day, evenly spaced during your awake hours. Your healthcare provider may slowly increase your dose until your symptoms are controlled. You may need to take a combination of whole tablets and half tablets to make your dose. Ask your healthcare provider or pharmacist if you are unsure how to split your tablets or how many tablets to take.

Eating foods high in protein, like meat or dairy, can decrease how much Sinemet your body absorbs. Let your healthcare provider know if your diet contains large amounts of protein or if you plan to change your diet to include more protein. Iron supplements or multivitamins containing iron can also decrease the amount of Sinemet absorbed. Let your healthcare provider know if you take any products that contain iron.

Storage

Store your Sinemet prescription at room temperature, away from light and moisture. Do not store your medication in the bathroom. Keep your medications tightly closed and out of the reach of children and pets, ideally locked in a cabinet or closet.

Avoid pouring unused and expired drugs down the drain or in the toilet. Ask your pharmacist or healthcare provider about the best ways to dispose of this medicine. Visit the FDA's website to know where and how to discard all unused and expired drugs. You can also find disposal boxes in your area. Ask your pharmacist or healthcare provider if you have any questions about the best ways to dispose of your medications.

If you travel with Sinemet, get familiar with your final destination's regulations. Make a copy of your Sinemet prescription, and keep your medication in its original container from your pharmacy with your name on the label. Ask your pharmacist or healthcare provider if you have any questions about traveling with your medicine.

Off-Label Uses

Sometimes healthcare providers prescribe medications for uses other than those approved by the FDA. This is called off-label use. Healthcare providers may prescribe Sinemet off-label to treat other degenerative neurologic conditions that cause symptoms similar to Parkinson’s disease, including:

How Long Does Sinemet Take to Work?

Sinemet starts to work 30 minutes after taking your dose. Your healthcare provider will adjust your dose based on your symptoms and side effects until they find the best amount for you.

What Are the Side Effects of Sinemet?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

Some people may develop side effects while taking Sinemet. Inform your healthcare provider if you experience any side effects that bother you or don’t go away.

Common side effects include:

Constipation
Dizziness
Dry mouth
Headache
Nausea
Nightmares
Tiredness
Trouble sleeping
Uncontrollable body movements (dyskinesia)
Vomiting

After taking Sinemet, you may notice that your saliva, urine, or sweat turns a dark color (red, brown, or black). This is not harmful, but it can stain your clothes.

Severe Side Effects

Rarely, Sinemet may cause severe side effects. Call your healthcare provider right away if you develop any severe reactions. Call 911 if your symptoms feel life-threatening or if you think you have a medical emergency. Serious side effects and their symptoms include the following:

A fast or abnormal heartbeat
Chest pain or pressure
Confusion, agitation, aggression, or paranoia
Fever, sweating, or stiff muscles
Hallucinations (seeing or hearing things that are not there)
Intense urges that are hard to control, such as gambling, sexual urges, binge eating, or spending money
New or worsening changes in mood, depression, or suicidal thoughts
Signs of an allergic reaction including a rash, itching, trouble breathing, or swelling of the mouth, tongue, or throat
Signs of high or low blood pressure (such as a bad headache, dizziness, fainting, or changes in eyesight)
Skin changes like a new lump or growth or a mole that has changed size or color
Stomach pain; black, tarry, or bloody stools; or vomit that contains blood or that looks like coffee grounds
Sudden onset of sleep
Uncontrollable body movements (dyskinesia)

Long-Term Side Effects

Long-term side effects are unclear.

Report Side Effects

Sinemet may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program online or by phone (800-332-1088).

(800) 332-1088

Dosage: How Much Sinemet Should I Take?

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For Parkinson's disease:
- For oral dosage form (extended-release capsules):
  - Adults—
    - For patients starting on carbidopa and levodopa treatment: At first, one capsule 3 times a day for the first 3 days. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 10 capsules per day.
    - For patients taking carbidopa and levodopa already: At first, 3 or 4 capsules 3 times a day. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 10 capsules per day.
  - Children—Use and dose must be determined by your doctor.
- For oral dosage form (disintegrating tablets):
  - Adults—
    - For patients starting on carbidopa and levodopa treatment: At first, one tablet 3 or 4 times a day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 8 tablets per day.
    - For patients taking levodopa already: Levodopa should be discontinued at least 12 hours before starting Parcopa®. The starting dose is one tablet 3 or 4 times a day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 8 tablets per day.
  - Children—Use and dose must be determined by your doctor.
- For oral dosage form (sustained release tablets):
  - Adults—
    - For patients switching from Sinemet® to Sinemet® CR: The starting dose is based on the amount of Sinemet® you are currently taking per day. Your doctor may adjust your dose as needed.
    - For patients taking levodopa already: Levodopa should be discontinued at least 12 hours before starting Sinemet® CR. The starting dose is one tablet 2 times a day. Your doctor may adjust your dose as needed.
    - For patients not taking levodopa: At first, one tablet 2 times a day. Your doctor may adjust your dose as needed.
  - Children—Use and dose must be determined by your doctor.
- For oral dosage form (tablets):
  - Adults—
    - For patients starting on carbidopa and levodopa treatment: At first, one tablet 3 or 4 times a day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 200 mg per day.
    - For patients taking levodopa already: Levodopa should be discontinued at least 12 hours before starting Lodosyn® plus levodopa or Sinemet®. The starting dose is one tablet 3 or 4 times a day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 200 mg per day.
    - For patients taking carbidopa and levodopa already: 25 milligrams (mg) of Lodosyn® per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 200 mg per day.
  - Children—Use and dose must be determined by your doctor.
For Parkinson's disease, parkinsonism caused by encephalitis, or parkinsonism caused by carbon monoxide or manganese poisoning:
- For oral dosage form (tablets):
  - Adults—At first, 25 milligrams (mg) carbidopa and 100 mg levodopa (1 tablet) 3 times a day. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 8 whole tablets per day.
  - Children—Use and dose must be determined by your doctor.

Modifications

The following modifications should be kept in mind when using Sinemet:

Severe allergic reaction: Avoid using Sinemet if you have a known allergy to it or its ingredients. Ask your pharmacist or healthcare provider for a complete list of the ingredients if you're unsure.

Pregnancy: In animal studies, Sinemet was found to have adverse effects on the fetus. We don't know enough about the safety and effectiveness of Sinemet in pregnant people and their unborn fetuses. Discuss with your healthcare provider if you plan to become pregnant or are pregnant, and weigh the benefits and risks of taking Sinemet during pregnancy.

Breastfeeding: Sinemet is present in breast milk in people who take it. We don't know enough about the safety of Sinemet in human breast milk and nursing babies. Talk with your healthcare provider to weigh the benefits and risks of taking Sinemet while nursing and how to feed your baby if you plan to breastfeed.

Adults over 65: Although older adults didn't respond differently than younger adults in a clinical study, older adults might be more sensitive to Sinemet's side effects. Older adults with several medical conditions or taking several medications should use caution with Sinemet.

Children: The safety and effectiveness of Sinemet have not been established in children. Avoid use in this age group.

Missed Dose

If you accidentally forgot your Sinemet dose, take it as soon as you remember. If it's already close to your next scheduled dose, skip the missed dose and take the following dose at your next scheduled dosing time. Don't try to double up to make up for the missed dose.

Find ways to help yourself remember to keep your appointments and take your medication. If you miss too many doses, Sinemet might be less effective at treating your condition.

Overdose: What Happens If I Take Too Much Sinemet?

Taking too much Sinemet can cause serious problems, including agitation, hallucinations, confusion, a fast or abnormal heartbeat, or low blood pressure. Because multiple tablets of Sinemet are typically taken three to four times per day, it's essential to keep track of your doses. If you're unsure how much Sinemet to take, talk with your healthcare provider or pharmacist.

If you think you're experiencing an overdose or life-threatening symptoms, seek immediate medical attention.

What Happens If I Overdose on Sinemet?

If you think you or someone else may have overdosed on Sinemet, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Sinemet, call 911 immediately.

911

Precautions

It is very important that your doctor check your progress at regular visits to allow changes in your dose. Blood and urine tests may be needed to check for any unwanted effects.

Do not take this medicine together with non-selective MAO inhibitor (eg, phenelzine, linezolid, tranylcypromine, Nardil®, Parnate®, Zyvox®) in the past 2 weeks.

Do not stop taking this medicine without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are taking before stopping completely.

Check with your doctor right away if you are having convulsions (seizures), difficulty with breathing, a fast heartbeat, a high fever, high or low blood pressure, increased sweating, loss of bladder control, severe muscle stiffness, unusually pale skin, or tiredness. These could be symptoms of a serious condition called neuroleptic malignant syndrome (NMS).

This medicine may cause dizziness, drowsiness, trouble in controlling movements, or trouble concentrating, or seeing clearly. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

It is important that your doctor check your skin regularly for signs of a skin cancer called melanoma. If you notice any unusual red, brown, or black spots on your skin, talk to your doctor right away.

If you develop any unusual or strange thoughts and behavior while receiving this medicine, be sure to discuss it with your doctor. Other changes might be confusion, worsening of depression, visual hallucinations (seeing things that are not there), suicidal thoughts, and unusual excitement, nervousness, or irritability.

It is possible that a dark color (red, brown, or black) may appear in saliva, urine, or sweat after taking this medicine. The color may cause some of your garments to become discolored. This is normal and nothing to worry about.

It is possible that you may become nauseous, especially when you are first starting your medicine.

This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. Also tell your doctor if you have sudden or strong feelings, such as feeling nervous, angry, restless, violent, or scared. If you, your child, or your caregiver notice any of these adverse effects, tell your doctor or your child's doctor right away.

Some people who have used this medicine had unusual changes in their behavior. Talk with your doctor right away if you start having problems with gambling or an increased interest in sex while using this medicine.

This medicine may cause uncontrolled sudden movements (dyskinesia) or make such movements you already have worse or more frequent. Tell your doctor if this happens.

Before you have any medical tests, tell the medical doctor in charge that you are taking this medicine. The results of some tests may be affected by this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Sinemet?

Certain situations can increase your risk of developing complications from Sinemet. Do not take Sinemet if you:

Are allergic to carbidopa, levodopa, or any other ingredient in Sinemet
Have narrow-angle glaucoma

Take specific monoamine oxidase inhibitor (MAOI) medicines, including:

Marplan (isocarboxazid)
Methylene blue
Nardil (phenelzine)
Parnate (tranylcypromine)
Zyvox (linezolid)

It would be best if you stopped taking MAOI medicines at least two weeks before starting Sinemet.

What Other Medications Interact With Sinemet?

Many medications may interact with Sinemet. Inform your healthcare provider and pharmacist about all the medicines you take, including over-the-counter, nonprescription products.

Some drugs should never be taken with Sinemet. These include certain MAOI medicines. It would be best if you stopped taking MAOI medication at least two weeks before starting Sinemet. MAOI drugs include:

Marplan (isocarboxazid)
Methylene blue
Nardil (phenelzine)
Parnate (tranylcypromine)
Zyvox (linezolid)

Other drugs can increase your risk of developing side effects from Sinemet or affect how well Sinemet works. Let your healthcare provider know if you take:

Antipsychotic medicines like Risperdal (risperidone), Abilify (aripiprazole), chlorpromazine, Haldol (haloperidol), and perphenazine
Dilantin (phenytoin)
High blood pressure medicines
Iron supplements or multivitamins containing iron
Reglan (metoclopramide)
Tricyclic antidepressants, such as amitriptyline, Tofranil (imipramine), and Pamelor (nortriptyline)
Xenazine (tetrabenazine)
Zelapar (selegiline)

This is not a complete list of all the medicines that may interact with Sinemet. Always keep an up-to-date list of all the medicines you take, and let your healthcare provider and pharmacist know any time there are changes.

Talk with your healthcare provider about any other medicines you take or plan to take, including over-the-counter, nonprescription products, vitamins, herbs, or plant-based medicines.

What Medications Are Similar?

A similar medication is the dopamine precursor for Parkinson's, levodopa, an ingredient in Sinemet. An example would be Inbrija, an inhalation powder containing levodopa. Lodosyn has carbidopa, which is also an ingredient in Sinemet.

Frequently Asked Questions

What is Sinemet used for?

Sinemet helps treat the symptoms of Parkinson’s disease, including stiffness, shaking, and slowed movements. Sinemet can also be used to treat conditions that cause Parkinson's-like symptoms, including encephalitis (brain swelling), carbon monoxide poisoning, and manganese poisoning.
How does Sinemet work?

Sinemet contains two medicines: levodopa and carbidopa. Levodopa gets converted to dopamine (a naturally occurring chemical messenger) in the brain. Low dopamine levels contribute to Parkinson’s disease symptoms. Carbidopa prevents your body from breaking down levodopa. This allows more levodopa to travel to the brain.
What drugs should not be taken with Sinemet?

Certain MAOI medicines should never be taken with Sinemet. These include Marplan (isocarboxazid), methylene blue, Nardil (phenelzine), Parnate (tranylcypromine), and Zyvox (linezolid). It would be best if you stopped taking MAOI medicines at least two weeks before starting Sinemet.
What are the side effects of Sinemet?

The most common side effects of Sinemet are nausea and vomiting. Other side effects include constipation, dizziness, dry mouth, headache, nightmares, tiredness, trouble sleeping, and uncontrollable body movements (dyskinesia). Sinemet can also turn your saliva, sweat, or urine a dark color (red, brown, or black). This is harmless, but it can stain your clothes.
How do I stop taking Sinemet?

Do not stop taking Sinemet without talking to your healthcare provider first. Abruptly stopping Sinemet can cause serious side effects, including fever, rigid muscles, unusual body movements, and confusion. If you and your healthcare provider decide that stopping treatment with Sinemet is appropriate for you, your healthcare provider will likely slowly decrease your dose to prevent side effects.

How Can I Stay Healthy While Taking Sinemet?

Parkinson’s disease is a progressive condition and can’t be cured. Fortunately, medications are available to improve your symptoms and mobility. Sinemet can help decrease the stiffness, shaking, and slowed movements you may be experiencing. Pay close attention to your prescription instructions. Your dose will likely be adjusted quite a bit in the beginning to find the best dose for you—one that gives you the most benefit while limiting side effects.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

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By Christina Varvatsis, PharmD
Christina Varvatsis is a hospital pharmacist and freelance medical writer. She is passionate about helping individuals make informed healthcare choices by understanding the benefits and risks of their treatment options.

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