If you have Parkinson’s disease or parkinsonism, your doctor might suggest Sinemet as a treatment option for you.

Sinemet is a prescription drug that’s used in adults to treat:

Sinemet is usually taken on a long-term basis for these uses.

The active ingredients in Sinemet are levodopa and carbidopa. (An active ingredient is what makes a drug work.) The drug comes as a tablet that you swallow.

For more information about Sinemet, including details about its uses, see this in-depth article on the drug.

Like other drugs, Sinemet can cause mild to serious side effects (also known as adverse effects). Keep reading to learn more.

Some people may experience mild to serious side effects during their Sinemet treatment. Examples of Sinemet’s more commonly reported side effects include:

  • dyskinesia (involuntary movements)*
  • nausea*
  • constipation
  • dizziness
  • headache

* To learn more about this side effect, see the “Side effects explained” section below.

Examples of mild side effects that have been reported with Sinemet include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have any symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Sinemet unless your doctor recommends it.

Sinemet may cause mild side effects other than the ones listed above. See the drug’s prescribing information for details.

Serious side effects that have been reported with Sinemet include:

  • dyskinesia (involuntary movements)*
  • hallucinations (seeing or hearing things that aren’t really there)
  • abnormal thoughts or behaviors, such as:
    • confusion or disorientation
    • paranoia (suspicion and mistrust)
    • delusions (believing things that aren’t true)
    • agitation or aggression
  • intense, uncontrollable urges to do certain activities, such as:
    • binge eat
    • shopping or gamble
    • have sex
  • sleepiness, including suddenly falling asleep without warning during daily activities, such as eating, talking, or driving
  • severe allergic reaction*†
  • increased risk of melanoma (a kind of skin cancer)‡
  • depression, which may lead to suicidal thoughts and behaviors

If you develop serious side effects while taking Sinemet, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Sinemet, visit MedWatch.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Sinemet. But it’s not clear whether this side effect occurred in studies.
‡ In studies, it wasn’t clear whether melanoma was caused by Sinemet or other factors, such as Parkinson’s disease itself.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

Get answers to some frequently asked questions about Sinemet’s side effects.

Do older adults have a higher risk of side effects with Sinemet?

Yes, older adults (ages 65 years and older) may have a higher risk of side effects with Sinemet than younger adults.

Sinemet causes the same side effects in older adults as in younger people taking the drug. But older adults may not clear Sinemet from their bodies as well. This may cause the drug to build up in their bodies, which can raise their risk of side effects.

Adults ages 65 years and older are also more likely to have other medical conditions or take other medications that may raise the risk of side effects with Sinemet.

Side effects of Sinemet that may be more common in older adults include:

  • hallucination (seeing or hearing things that aren’t really there)
  • confusion
  • dyskinesia (involuntary movements)
  • dizziness (which can increase the risk of falls)

If you’re concerned about your risk of side effects with Sinemet based on your age, talk with your doctor.

Does Sinemet cause long-term side effects?

No, not usually. Most of Sinemet’s side effects will resolve as your body gets used to the medication. Or they may go away quickly if your doctor reduces your dose.

But if you have sleepiness from Sinemet, this side effect may continue throughout your treatment. It may not get better even if your doctor reduces your dose. And some people have had episodes of suddenly falling asleep during daily activities as long as 1 year after starting Sinemet treatment.

If you have a side effect that doesn’t go away while you’re taking Sinemet, talk with your doctor. They may lower your dosage. But if this doesn’t help, your doctor may recommend that you stop taking Sinemet and switch to a different treatment. Sinemet side effects usually go away quickly after stopping treatment.

If you have other questions about how long side effects of Sinemet may last, talk with your doctor.

Is urinary retention a side effect of Sinemet?

It’s possible. Urinary retention (not being able to fully empty your bladder) hasn’t been reported with Sinemet. But it has been reported with other drugs containing levodopa/carbidopa (the active drugs in Sinemet). So it’s possible that urinary retention could occur with Sinemet.

If you have trouble urinating or fully emptying your bladder while taking Sinemet, talk with your doctor.

Learn more about some of the side effects Sinemet may cause.

Blood pressure changes

Sinemet can cause changes in your blood pressure, such as high or low blood pressure. It’s not known how often these blood pressure changes may occur.

Your risk of high blood pressure may be higher if you take certain other drugs with Sinemet. Examples of these include tricyclic antidepressants, such as amitriptyline.

Having high blood pressure can raise your risk of several health problems, including kidney disease and heart attack. High blood pressure doesn’t usually cause symptoms unless your blood pressure is dangerously high.

Low blood pressure can cause symptoms such as dizziness, fainting, and feeling very tired. You may have a higher risk of hypotension with Sinemet if you take certain other drugs with it. Examples of these include medications for high blood pressure, such as ramipril (Altace) and losartan (Cozaar).

Sinemet can also cause temporary drops in your blood pressure when you stand up after sitting. This is called orthostatic hypotension. It can make you feel dizzy or lightheaded when standing up. This side effect is common with Sinemet, especially when starting treatment and after a dosage increase.

What might help

If Sinemet makes you feel dizzy or lightheaded upon standing up, sit or lie down until the symptoms pass. Getting up more slowly may help, too. Orthostatic hypotension may go away as your body adjusts to the medication.

If this side effect is bothersome or doesn’t go away, or you have other symptoms of low blood pressure, talk with your doctor. They may lower your Sinemet dosage, which can help reduce these symptoms.

Your doctor will likely monitor your blood pressure while you’re taking Sinemet. If you develop high or low blood pressure, they may reduce your Sinemet dosage.

Dyskinesia

Some people may experience dyskinesia (involuntary movements) while taking Sinemet. These movements can affect any part of your body. Dyskinesia is one of the most common side effects of Sinemet.

Symptoms of dyskinesia may include:

  • tremor*
  • twitching
  • head bobbing
  • fidgeting
  • rocking or swaying

You may have a higher risk of dyskinesia with Sinemet if you take it with certain other drugs. Examples of these include tricyclic antidepressants, such as amitriptyline.

* Tremor is also a symptom of Parkinson’s disease, which Sinemet is used to treat.

What might help

If you develop new or worsening symptoms of dyskinesia while taking Sinemet, talk with your doctor. They may lower your dosage of Sinemet, which may reduce your symptoms. Or they may recommend other ways to manage this side effect.

Nausea

Some people may have nausea while taking Sinemet. Nausea is one of the most common side effects of this medication.

What might help

If you have nausea with Sinemet, it may help to:

  • take the medication with food
  • get plenty of fresh air
  • take frequent sips of water
  • drink ginger or peppermint tea
  • eat little and often rather than three large meals
  • avoid greasy and sugary foods

If you have nausea that’s bothersome or severe, talk with your doctor. They may lower your Sinemet dosage, which may reduce the nausea. Or they may prescribe other medications to help reduce this side effect.

Allergic reaction

Like most drugs, Sinemet can cause an allergic reaction in some people. But it’s not clear whether this side effect occurred in studies.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Sinemet, they’ll decide whether you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Sinemet, they may have you switch to a different treatment.

Keeping track of side effects

During your Sinemet treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Sinemet affects you. They can then use this information to adjust your treatment plan if needed.

Sinemet may not be right for you if you have certain medical conditions. These are known as drug-condition interactions. Other factors may also affect whether Sinemet is a good treatment option for you.

Talk with your doctor about your health history before starting Sinemet. Factors to consider include those described below.

Glaucoma. Sinemet can increase the pressure in your eye. This side effect could be dangerous if you have closed-angle glaucoma, so your doctor will likely not prescribe Sinemet. You can ask them what other medications are better options for you.

If you have open-angle glaucoma, your doctor may prescribe Sinemet. During your treatment, they’ll likely monitor the pressure in your eyes to make sure Sinemet is not making your condition worse.

Heart or blood pressure problems. Sinemet can cause changes in your blood pressure, such as high or low blood pressure. These changes may be dangerous if you already have heart or blood pressure problems, such as an irregular heartbeat or high or low blood pressure. Talk with your doctor about whether Sinemet is right for you.

Allergic reaction. If you’ve had an allergic reaction to Sinemet or any of its ingredients, your doctor will likely not prescribe Sinemet. Ask them what other medications are better options for you.

Sleep disorders. Sinemet can cause sleepiness, including falling asleep without warning during daily activities. If you have a sleep disorder such as sleep apnea or narcolepsy, you may have a higher risk of this side effect. If you have other conditions that make you feel sleepy during the day, you may also have a higher risk of this side effect. Talk with your doctor about whether Sinemet is right for you.

Mental health conditions. Sinemet can cause hallucinations (seeing or hearing things that aren’t really there). It can also cause abnormal thinking and behavior, including psychosis (loss of touch with reality). If you have a mental health condition such as schizophrenia, you may have a higher risk of these side effects. Talk with your doctor about whether Sinemet is safe for you.

Peptic ulcer. If you’ve had a peptic ulcer before, taking Sinemet may raise your risk of stomach bleeding. Talk with your doctor about whether Sinemet is right for you.

Alcohol and Sinemet

Your doctor will likely recommend that you avoid alcohol or limit how much alcohol you drink while taking Sinemet.

This is because drinking alcohol with Sinemet could raise your risk of certain side effects, especially sleepiness and suddenly falling asleep without warning. Other side effects that could be worsened by alcohol include nausea, dizziness, and headache.

If you drink alcohol, talk with your doctor about how much (if any) may be safe to drink during your Sinemet treatment.

Pregnancy and breastfeeding while taking Sinemet

It’s not known if Sinemet is safe to take during pregnancy.

It’s also not known if it’s safe to take the drug while breastfeeding. Levodopa, one of the active ingredients* in Sinemet, can pass into breast milk. Levodopa’s use while breastfeeding hasn’t been studied, but the drug could cause harm to a child who’s breastfed.

If you’re pregnant or breastfeeding, or planning to become pregnant or to breastfeed, talk with your doctor before taking Sinemet.

* An active ingredient is what makes a drug work.

If you still have questions about Sinemet’s side effects, talk with your doctor. Examples of questions you might want to ask include:

  • Do my other medications or health conditions raise my risk of side effects from Sinemet?
  • How do the side effects of Sinemet compare with those of extended-release carbidopa/levodopa (Rytary)?
  • Does Sinemet cause sexual side effects?

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.