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Sinemet

Generic Name: carbidopa and levodopa (KAR bi DOE pa and LEE voe DOE pa)
Brand Name: Sinemet, Sinemet CR

Medically reviewed by Philip Thornton, DipPharm. Last updated on March 31, 2021.

What is Sinemet?

Sinemet contains a combination of carbidopa and levodopa.

Sinemet is used to treat symptoms of Parkinson's disease, such as muscle stiffness, tremors, spasms, and poor muscle control. Parkinson's disease may be caused by low levels of a chemical called dopamine (DOE pa meen) in the brain.

Sinemet is also used to treat Parkinson symptoms caused by carbon monoxide carbon monoxide poisoning or manganese intoxication.

Warnings

You should not use Sinemet if you have narrow-angle glaucoma.

Do not use Sinemet if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine.

Before taking this medicine

You should not use Sinemet if you are allergic to carbidopa or levodopa, or if you have:

  • narrow-angle glaucoma.

Do not use Sinemet if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

To make sure Sinemet is safe for you, tell your doctor if you have:

People with Parkinson's disease may have a higher risk of skin cancer (melanoma). Talk to your doctor about this risk and what skin symptoms to watch for.

Tell your doctor if you are pregnant or breastfeeding.

The disintegrating tablet may contain phenylalanine. Tell your doctor if you have phenylketonuria (PKU).

How should I take Sinemet?

Take Sinemet exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose.

If you already take levodopa, you must stop taking it at least 12 hours before you start taking Sinemet.

Sinemet can be taken with or without food. Take your doses at regular intervals to keep a steady amount of the drug in your body at all times. Get your prescription refilled before you run out of medicine completely.

The tablet is sometimes broken in half to give the correct dose. Always swallow a whole or half tablet without chewing or crushing.

It may take up to several weeks of using Sinemet before your symptoms improve. For best results, keep using the medication as directed. Talk with your doctor if your symptoms do not improve after a few weeks of treatment. Also tell your doctor if the effects of this medication seem to wear off quickly in between doses.

If you use Sinemet long-term, you may need frequent medical tests at your doctor's office.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using Sinemet.

Do not stop using Sinemet suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.

Store at room temperature away from moisture, heat, and light.

Dosing information

Usual Adult Dose for Parkinson's Disease:

Optimum dosage is determined by careful individual titration: All doses expressed as CARBIDOPA-LEVODOPA

Immediate-release tablets:
Initial dose: 25 mg-100 mg orally three times a day or 10 mg-100 mg orally 3 or 4 times a day
-Increase by 1 tablet every day or every other day as needed until a dose of 8 tablets is reached; may use a combination of tablets from both ratios (1:4 or 1:10) to provide the optimum dose.
Conversion from LEVODOPA:
-Levodopa should be discontinued at least 12 hours before starting carbidopa-levodopa; initiate with approximately 25% of the previous levodopa dose.
-Suggested dose for patients receiving less than levodopa 1500 mg per day: 25 mg-100 mg orally 3 or 4 times a day.
-Suggested dose for patients receiving more than levodopa 1500 mg per day: 25 mg-250 mg orally 3 or 4 times a day.

Sustained-Release Tablets (Sinemet CR):
-Initial dose (levodopa-naive): 50 mg-200 mg orally twice a day; initial dosage should be given at intervals of more than 6 hours
-Dose and dosing interval may be increased or decreased at intervals of at least 3 days based on therapeutic response
-Dose range: Most patients will require levodopa 400 to 1600 mg/day in divided doses every 4 to 8 hours during waking hours; doses of 2400 mg/day at intervals of less than 4 hours have been used, but are generally not recommended.
Conversion from IMMEDIATE-RELEASE levodopa with or without a decarboxylase inhibitor:
-For patients receiving levodopa with a decarboxylase inhibitor: Dosage with Sinemet CR should be approximately 10% higher than previous levodopa dosage; this may need to be increased to up to 30% higher depending on clinical response.
-For patients receiving levodopa without a decarboxylase inhibitor: Dosage with sustained release should be approximately 25% of previous levodopa dosage; levodopa should be discontinued at least 12 hours before starting carbidopa-levodopa.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking Sinemet?

Avoid driving or hazardous activity until you know how Sinemet will affect you. Your reactions could be impaired. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Avoid taking iron supplements or eating a diet that is high in protein (protein sources include meat, eggs, and cheese). These things can make it harder for your body to digest and absorb carbidopa and levodopa. Talk with your doctor or nutrition counselor about the best foods to eat while you are taking this medicine.

Sinemet side effects

Get emergency medical help if you have signs of an allergic reaction to Sinemet: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • uncontrolled muscle movements in your face (chewing, lip smacking, frowning, tongue movement, blinking or eye movement);

  • worsening of tremors (uncontrolled shaking);

  • severe or ongoing vomiting or diarrhea;

  • confusion, hallucinations, unusual changes in mood or behavior;

  • depression or suicidal thoughts; or

  • severe nervous system reaction - very stiff (rigid) muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, feeling like you might pass out.

Some people taking Sinemet have fallen asleep during normal daytime activities such as working, talking, eating, or driving. Tell your doctor if you have any problems with daytime sleepiness or drowsiness.

You may have increased sexual urges, unusual urges to gamble, or other intense urges while taking this medicine. Talk with your doctor if this occurs.

You may notice that your sweat, urine, or saliva appears dark in color, such as red, brown, or black. This is not a harmful side effect, but it may cause staining of your clothes or bed sheets.

Common Sinemet side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Sinemet?

Other drugs may interact with carbidopa and levodopa, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Frequently asked questions

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Sinemet only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.