Carbidopa-Levodopa

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Apr 25, 2023

Warnings

Carbidopa-Levodopa (Sinemet) Risks, Warnings, and Complications

Carbidopa-levodopa can cause new or worsening health problems in some people. Talk to your doctor or pharmacist about other treatments for Parkinson’s disease if you are at increased risk of complications from this medication. Some of the risks of taking carbidopa-levodopa include:

SUDDEN SLEEPINESS DURING ACTIVITIES : Carbidopa-levodopa can cause sudden sleepiness during the daytime, including during activities. Avoid driving or doing anything that requires focus until you know how this medication affects you. The risk is especially high if you have a history of drowsiness or take other medications that can make you drowsy. Tell your doctor if you develop daytime sleepiness or fall asleep during activities while on this Parkinson disease medicine.
NEUROLEPTIC MALIGNANT SYNDROME: Rarely, stopping carbidopa-levodopa or a rapid dose reduction can cause symptoms similar to neuroleptic malignant syndrome (NMS), a life-threatening condition caused by certain mental health medications. Symptoms of NMS include high fever, confusion, sweating, irregular pulse, muscle stiffness, and blood pressure changes. Early diagnosis and treatment of NMS is vital. Don't stop taking carbidopa-levodopa or lower your dose without talking to your healthcare provider. They will tell you how to stop the medicine safely.
CHANGES IN BEHAVIOR AND THOUGHTS: Carbidopa-levodopa affects dopamine levels in the brain and can cause changes in behavior and thinking, such as hallucinations, delusions, paranoia, confusion, aggression, restlessness, trouble sleeping, nightmares, and decreased awareness of surroundings. These symptoms usually occur shortly after starting the medicine and go away once you stop the medicine or lower the dose. You should not take carbidopa-levodopa if you have certain mental health conditions or take certain mental health medications, such as perphenazine and haloperidol.
IMPULSIVE BEHAVIORS: Patients taking carbidopa and levodopa may develop increased sexual urges, gambling urges, urges to spend money, binge eating, and other intense urges. If such urges start to negatively impact your life, tell your provider. Your family members should know when to seek help because you may not be aware of these behavioral changes yourself.
SKIN CANCER: Parkinson's disease is associated with a higher risk of skin cancer. Make sure you have regular skin checks to detect any new or unusual growths or changes in existing moles. Tell your healthcare provider if you notice any skin changes that may be warning signs of skin cancer.

Precautions Before Starting Carbidopa-Levodopa (Sinemet)

Tell your doctor if you have ever had an allergic reaction to carbidopa-levodopa, any of the active or inactive ingredients in the various dosage forms, or any other medications. Your pharmacy can give you a list of ingredients.

Give your doctor and pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal products. This can help avoid possible drug interactions.

Give your doctor a complete medical history. Carbidopa-levodopa may not be right for people with certain medical conditions such as melanoma (skin cancer), undiagnosed skin growths, glaucoma, hormonal problems, lung diseases such as asthma and emphysema, stomach ulcers, mental illness, heart attack, diabetes, irregular heartbeat, heart disease, kidney disease, or liver disease. If you are taking the suspension, tell your doctor if you have ever had stomach surgery or a history of fainting or low blood pressure.

Precautions During Use of Carbidopa-Levodopa (Sinemet)

Keep all your appointments for laboratory tests and clinic visits. Your doctor may want to adjust your dose slowly based on therapeutic effects and clinical response. They will also want to monitor you for side effects.

Carbidopa-levodopa can cause drowsiness and make you fall asleep suddenly during regular activities such as reading, watching TV, talking, eating, or driving. Do not drive, operate machinery, work at heights, or do any other activities that can be dangerous until you know how this medicine affects you. Tell your doctor if you or your family members notice you’re suddenly falling asleep during activities or have daytime sleepiness.

Taking carbidopa-levodopa can cause orthostatic hypotension (dizziness if you arise too quickly from a lying or sitting position to standing). To avoid falls, place your feet on the ground for a few minutes before standing up, when getting out of bed.

Avoid drinking alcohol while on carbidopa-levodopa as this can make side effects worse.

This medication can lead to increased sexual urges and other urges such as gambling, spending money, or eating. Tell your provider if you or family members notice any strong urges.

Carbidopa-levodopa can make body secretions such as saliva, urine, and sweat dark in color (red, black, or brown). This is harmless, but it may stain your clothes.

The orally disintegrating tablets of carbidopa-levodopa contain phenylalanine and are not safe for people with a condition called phenylketonuria (PKU).

Tell all your healthcare providers and laboratory personnel you are on carbidopa-levodopa, especially before any surgery, including dental procedures.

Carbidopa-Levodopa (Sinemet) Drug Interactions

Certain other drugs can affect how carbidopa-levodopa works. Possible interactions between carbidopa-levodopa and other medicines can increase the risk of severe adverse reactions.

If you have taken monoamine oxidase inhibitors (MAO inhibitors), a class of antidepressants, such as phenelzine (Nardil), tranylcypromine (Parnate), selegiline (Emsam, Eldepryl, Zelapar), or isocarboxazid (Marplan) within the last 2 weeks, you should not take carbidopa-levodopa.

Concomitant use of the following medications can lead to interactions with carbidopa-levodopa:

Tricyclic antidepressants such as amitriptyline (Elavil), clomipramine (Anafranil), amoxapine (Asendin), doxepin (Adapin, Sinequan), desipramine (Norpramin), imipramine (Tofranil), protriptyline (Vivactil), nortriptyline (Aventyl, Pamelor), and trimipramine (Surmontil)
Antipsychotics such as haloperidol (Haldol)
Antihistamines
Asthma medications such as ipratropium (Atrovent)
Iron salts and vitamin pills containing iron
Antitubercular drugs such as isoniazid (INH, Nydrazid)
An antihypertensive drug
Medications used to treat irritable bowel disease
Medicines prescribed for motion sickness or nausea
Medications used to treat ulcers
Anticonvulsants such as phenytoin (Dilantin)
Medications prescribed for urinary problems
Medicines for GERD such as metoclopramide (Reglan)
Other Parkinson's disease medications such as rasagiline (Azilect) and dopamine agonists like risperidone (Risperdal)
Medications prescribed for circulation problems such as papaverine (Pavabid)
Huntington’s disease medications such as tetrabenazine (Xenazine)
Sedatives, sleeping pills, and tranquilizers

Give your doctor or pharmacist a complete list of your medications, including prescription drugs, OTC medications, dietary supplements, and herbal remedies. Also, tell your healthcare professional if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription medications.

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