From the Guidelines
Carbidopa-levodopa is a medication combination used to treat Parkinson's disease, with a therapeutic effect of alleviating symptoms by increasing dopamine levels in the brain 1.
Key Points
- The carbidopa component helps prevent levodopa conversion to dopamine outside the brain, allowing more levodopa to reach the brain, where it is converted to dopamine to help alleviate symptoms of Parkinson's disease 1.
- The recommended starting dose is 25/100 mg, taken three times a day, with a maximum daily dose of 200/2000 mg, and it is essential to take this medication exactly as prescribed, with food to reduce nausea, and to gradually increase the dose as needed and under medical supervision 1.
- Regular monitoring by a healthcare provider is necessary to adjust the dose and manage potential side effects, such as nausea, vomiting, abdominal pain, dyspepsia, constipation, weight decrease, dry mouth, diarrhea, anorexia, and GI disorders 1.
- Patients with Parkinson's disease are at increased risk of malnutrition and weight loss, and nutritional status should be monitored routinely throughout the natural history of the disease 1.
- The use of levodopa may be associated with impaired nutritional status and risk for malnutrition, and increasing doses of levodopa and levodopa equivalent doses have also been found to be related to increased risk for malnutrition 1.
- Carbidopa-levodopa can also cause hyperhomocysteinemia, which may be associated with cardiovascular diseases, dementia, and depression 1.
- The medication can be effective in treating ocular symptoms of Parkinson's disease, including blurred vision or impaired convergence, due to the presence of the L-type amino acid transporter 1 (LAT1) on the blood-retinal barrier (BRB) and blood-brain barrier (BBB) 1.
From the FDA Drug Label
Carbidopa and levodopa tablets are indicated in the treatment of Parkinson's disease, post-encephalitic parkinsonism, and symptomatic parkinsonism that may follow carbon monoxide intoxication or manganese intoxication. Carbidopa allows patients treated for Parkinson's disease to use much lower doses of levodopa. Some patients who responded poorly to levodopa have improved on carbidopa and levodopa tablets. This is most likely due to decreased peripheral decarboxylation of levodopa caused by administration of carbidopa rather than by a primary effect of carbidopa on the nervous system.
The therapeutic effect of Carbidopa-Levodopa is to treat Parkinson's disease and other related conditions, by reducing symptoms. The combination allows for lower doses of levodopa to be used, and may also reduce nausea and vomiting. This is achieved through the decreased peripheral decarboxylation of levodopa caused by carbidopa, rather than a direct effect on the nervous system 2, 3.
- Key benefits:
- Treatment of Parkinson's disease and related conditions
- Reduced symptoms
- Lower doses of levodopa required
- Reduced nausea and vomiting
From the Research
Therapeutic Effect of Carbidopa-Levodopa
The combination of Carbidopa and Levodopa is a well-established treatment for Parkinson's disease (PD) [(4,5)]. The therapeutic effect of this combination can be summarized as follows:
- Symptom management: Carbidopa-Levodopa is effective in managing symptoms of PD, such as tremors, rigidity, and bradykinesia [(4,5)].
- Dopamine replacement: Levodopa, a dopamine precursor, crosses the blood-brain barrier and is converted to dopamine, replacing the deficient dopamine in the brain 4.
- Reduction of motor fluctuations: The combination of Carbidopa and Levodopa can reduce motor fluctuations, such as "on" and "off" episodes, in advanced PD patients [(4,6)].
- Inhibition of T cell activation: Carbidopa has been shown to inhibit T cell activation and autoimmunity, which may have implications for the treatment of PD 7.
Administration and Dosage
The administration and dosage of Carbidopa-Levodopa can be tailored to individual patient needs, including:
- Oral administration: Carbidopa-Levodopa can be administered orally, with or without food 4.
- Enteral suspension: Carbidopa-Levodopa enteral suspension (CLES) is a formulation that can be delivered directly into the jejunum through a PEG-J tube, providing continuous delivery of the medication 8.
- Titration: The dosage of Carbidopa-Levodopa can be titrated to achieve optimal therapeutic effect, with careful monitoring of patient response and adjustment of dosage as needed 8.