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Carbidopa and Levodopa - An Effective Therapeutic Combination for Advanced Parkinson’s Disease

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Carbidopa and Levodopa is a drug that works on the central nervous system and effectively treats advanced Parkinson's disease.

Medically reviewed by

Dr. Abhishek Juneja

Published At May 4, 2023
Reviewed AtDecember 4, 2023


Carbidopa and Levodopa are prescribed to treat Parkinson's disease and Parkinson-like symptoms. This medicine works by increasing dopamine levels in the brain. Dopamine helps reduce various symptoms of Parkinson's, such as tremors and shaking. Carbidopa and Levodopa come under central nervous system-acting drugs. Carbidopa has been specifically classified as a decarboxylase inhibitor. This property of carbidopa prevents Levodopa from breaking down in the brain.


Carbidopa and Levodopa are used for various central nervous system disorders such as Parkinson's. In such conditions of the central nervous system, dopamine levels tend to be reduced. Dopamine is a chemical secreted by the brain. Levodopa replenishes dopamine in the brain.

The various uses of this medication include,

1. Parkinson's Disease: Parkinson's disease is a condition that is caused due to deficiency of dopamine in the brain. It may present symptoms such as tremors, shaking hands and feet, stiffness, and slowing movement.

2. Parkinson Like Symptoms: Certain conditions can present with Parkinson-like symptoms. This may be caused due to certain conditions such as carbon monoxide poisoning, manganese poisoning, and encephalitis. Since the symptoms mimic Parkinson’s disease, the same line of treatment is given.

Dosage and Administration:

The various methods of this drug administration include

  1. Oral Route: The combination of carbidopa and Levodopa comes from tablets. This tablet is disintegrated orally as well as long-acting. The regular or orally disintegrating tablet must be taken three to four times daily. The long-acting tablets should be taken twice daily, depending on the requirement.

  2. Suspension Form: The suspension form of this medication is given through that it is surgically attached to the stomach. It is also administered by NJ (naso-jejunal) tube. This medication is pumped into the body with the help of special infusion pipes. The suspension form of this medication is usually given as a single morning dose (10 to 30 minutes infusion) or as an infusion that runs throughout the day.


  • One has to check for the ingredients of this medication before taking it. If one may be allergic to any of the components of the medication, it is important to inform the doctor in advance.

  • In case of pre-existing conditions such as glaucoma, breathing problems, stomach or intestinal issues, ulcers, seizures, and liver diseases, it is important to inform the doctor in advance.

  • This medication can make one dizzy and drowsy. Hence it is better to avoid driving and working with heavy medications while on this medication. One has to be very careful and alert while operating with this medication.

  • In case an individual is planning for pregnancy or thinks to get pregnant, it is advisable to consult physician before taking this medication.

  • There can be traces of this medication in breast milk. Hence one should avoid taking this medication while pregnant.

For Patients

What Is Advanced Parkinson’s Disease?

Advanced Parkinson's is an advanced and complex type of Parkinson’s disease. Advanced Parkinson's affects a person's daily life to a great extent. They may become dependent on someone else for their routine activities. In the advanced stages of Parkinson's disease, the medication dosage is increased to cater to the needs. This may end up producing a lot of side effects. The side effects can include memory issues, hallucinations, depression, and anxiety. People suffering from advanced Parkinson's disease can suffer from limited mobility.

The symptoms of advanced Parkinson's disease may include:

  1. Difficulty in walking may also require an aid such as a walker or a wheelchair.

  2. Needing assistance in day-to-day activities.

  3. Restricted to bed.

  4. Need for nursing assistance.

  5. Experiencing hallucinations and delusions.

What Is Carbidopa and Levodopa?

Carbidopa and Levodopa are prescribed to treat Parkinson's disease and Parkinson-like symptoms. This medicine works by increasing dopamine levels in the brain. Dopamine helps reduce various symptoms of Parkinson's, such as tremors and shaking. Carbidopa and Levodopa come under central nervous system-acting drugs. Carbidopa has been specifically classified as a decarboxylase inhibitor. This property of carbidopa prevents Levodopa from breaking down in the brain.

What Are the Other Uses of Carbidopa and Levodopa?

Other than Parkinson's disease, this medication is used to treat conditions that mimic its symptoms.

The other conditions that are treated by carbidopa and Levodopa include,

  1. Encephalitis or swelling of the brain.

  2. Any injury to the nervous system that causes depression in dopamine levels.

  3. Carbon monoxide poisoning.

  4. Manganese poisoning.

Who Are Advised Against the Usage of Levodopa and Carbidopa?

The following situations where the patient may be advised against this medication:

  1. Any previous history of allergy to Levodopa and carbidopa. Sometimes, the patient may also be allergic to the other ingredients that may be present in this medicine. Hence, it is advisable to check the entire list of ingredients before taking this medication.

  2. The doctor might not suggest taking Levodopa or carbidopa if the patient is on or has recently discontinued Phenelzine (a medicine used to treat depression).

What Are the Side Effects of This Medication?

  • Dizziness.

  • Loss of appetite.

  • Dryness of mouth.

  • Diarrhea.

  • Constipation.

  • Pain in the throat.

  • Altered taste.

  • Memory loss and confusion.

  • Nervousness.

  • Sleep disturbance and nightmares.

  • Weakness.

  • Constant headache.

When Should You Immediately Report to a Doctor?

All medications will come with some or the other side effects. Hence the side effects should be carefully monitored, as some are acceptable, whereas some are not. Medical opinion should be obtained earliest with the following side effects.

  • Uncontrolled mouth, tongue, head, arms, or leg movements.

  • Racing heartbeat with or without chest pain.

  • A sudden increase in sweating.

  • Depressive mood.

  • Thoughts of self-harm.

  • Experiencing hallucinations. This means that the person sees or hears things that others do not.

  • Sudden facial swelling or another body part that may resemble an allergic reaction.

  • Sudden hoarseness of the voice.

  • Sudden difficulty in swallowing or breathing.

  • Loss of sensation in the foot and fingers. Loss of sensation can also be accompanied by weakness of the extremities.

  • Infection in the site of tube entry. This happens when this medication is administered through tubes in suspension form.

  • Dark stools.

  • Blood in stools.

  • Blood in vomit.

  • Nausea and vomiting.

  • Fever with abdominal pain.

What to Do in the Case of a Missed Dosage?

  • In the case of a missed dosage, orally disintegrating tablet, extended-release (long-acting) tablet, or extended-release (long-acting) capsule, it is advisable to take the medication as soon as one remembers. If the time for the next dose is near, then it is advisable to take the next dosage directly. Never take two tablets to compensate for the missed dose.

  • In the case of the usage of pumps for suspension, it is advisable to disconnect the pump for short durations in between the doses. Other than that, the pump should be discontinued at night. However, the pump discontinuation should be done only on the doctor's advice. If the pump is discontinued for more than two hours and any dosage has to be administered in this period, this can be given as oral and long-acting tablets.

Storage and Disposal:

This medicine can be stored and disposed of in the following manner:

  • This medicine should be kept in its appropriate container, and the box should be firmly closed. This medicine is to be stored at room temperature. Direct contact with sunlight should be avoided. Store tapes containing Levodopa and carbidopa enteral suspension in the cooler in their unique container shielded from light. Try not to freeze the suspension.

  • Unnecessary drugs should be discarded in unusual ways to keep them out of children and pets. In any case, one should wait to wash this drug away forever. The best way to discard unused medications is through medical reclaim. Through this program, the pharmacist usually takes back the prescribed medication and provides a refund or replenishes it with the latest prescription. The doctor or the pharmacist can guide the patient regarding this.

For Doctors


  • When blended in with Levodopa, carbidopa hinders the fringe transformation of Levodopa to dopamine and the decarboxylation of oxitriptan to serotonin by fragrant L-amino corrosive decarboxylase. This outcome is an expanded measure of Levodopa and oxitriptan accessible for transport to the focal sensory system. Carbidopa likewise restrains the digestion of Levodopa in the GI plot, thus expanding the bioavailability of Levodopa.

  • The presence of extra units of flowing Levodopa can build the viability of the still functional dopaminergic neurons, and lightening side effects for a time have been shown. The activity of carbidopa is vital as Levodopa can cross the blood-mind obstruction while dopamine cannot. Subsequently, the organization of carbidopa is fundamental to forestall the change of outer Levodopa to dopamine before arriving at the primary activity site in the cerebrum.

  • The coadministration of carbidopa with Levodopa has been displayed to expand the half-existence of Levodopa more than 1.5 times while expanding the plasma level and diminishing leeway. The mixed treatment has likewise shown an increment of the recuperation of Levodopa in the urine excreted rather than dopamine, demonstrating decreased digestion. A huge decrease has profoundly seen this impact in Levodopa necessities and a critical decrease within sight of secondary effects like sickness. It has been found that the action of carbidopa is not dependent on the portion that is administered.

Mechanism of Action:

Carbidopa, a DDC inhibitor, hinders the fringe digestion of Levodopa. DDC is vital in the biosynthesis of L-tryptophan to serotonin and the adjustment of L-DOPA to dopamine.

DDC can be found in the body's outskirts and the blood-mind hindrance. The activity of carbidopa is centered around fringe DDC as this medication cannot cross the blood-mind obstruction. Thus, it will forestall the digestion of Levodopa in the fringe; however, it will not have any movement on the age of dopamine in the cerebrum.


This drug shows an absorption rate of 40 to 70 %. When absorbed, this drug has a bioavailability of about 58 %.


This drug is eliminated through the urine. About 66 % of this drug gets excreted in the urine. About 10 % of the absorbed dosage also gets excreted via the feces.


The reported half-life of carbidopa and Levodopa is around 107 minutes.

Adverse Drug Reactions:

  • Dizziness.

  • Loss of appetite.

  • Diarrhea.

  • Dryness of mouth.

  • Pain in the throat.

  • Constipation.

  • Altered taste sensation in the mouth.

  • Confusion and loss of memory.

  • Nervousness.

  • Nightmares.

  • Difficulty falling asleep or staying asleep.

  • Weakness.

  • Headaches.


  • Antipsychotic medications such as Haloperidol can interact with this medication. Antihypertensive medications can also interfere with this medication.

  • This medication may result in false results in certain tests such as ketone and glucose tests.

  • Using MAO inhibitors (Monoamine Oxidase inhibitors) with these medications can cause severe drug reactions. MAO inhibitors should be discontinued for at least two weeks prior to this medication.

Levodopa vs Carbidopa:

  • Levodopa:

  1. They are central nervous system agents.

  2. Used to treat conditions such as Parkinson’s disease.

  3. It produces dopamine in the brain.

  • Carbidopa:

  1. They are decarboxylase inhibitors.

  2. Used to treat conditions such as Parkinson’s disease.

  3. This prevents the breakdown of Levodopa.

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Dr. Abhishek Juneja
Dr. Abhishek Juneja



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