FDA has required label updates for carbidopa/levodopa Parkinson’s drugs after identifying seizures linked to vitamin B6 deficiency in post-marketing cases.
Written By: Vikas Londhe,
Chief Editor and Patient Safety Expert
The U.S. Food and Drug Administration (FDA) has required new safety warnings for Parkinson’s disease medicines containing carbidopa and levodopa after identifying cases of vitamin B6 deficiency–associated seizures in treated patients.
In a recent drug safety communication on 20 March 2026 directed to health care professionals, patients, and manufacturers, FDA said the prescribing information for all carbidopa/levodopa-containing products must be updated to include warnings about the risk of vitamin B6 (pyridoxine) deficiency and associated seizures. These medicines are widely used for the management of symptoms in patients with Parkinson’s disease.
According to the FDA review, 14 cases of seizures linked to vitamin B6 deficiency were identified in patients treated with carbidopa/levodopa products. The cases included 13 reports from post-marketing safety data and one case described in the medical literature. Several patients experienced focal seizures that progressed to generalized seizures or status epilepticus, and two deaths were reported.
The agency also noted additional clinical evidence consistent with vitamin B6 deficiency, including elevated homocysteine levels in four cases, microcytic or normocytic anemia in three cases, and neuropsychiatric symptoms in four cases.
The agency noted that the combination of carbidopa and levodopa can reduce available vitamin B6 levels. Carbidopa binds to the active form of vitamin B6, while levodopa metabolism also utilizes the vitamin, which may result in clinically significant depletion in some patients. Severe deficiency can disrupt neuronal function and increase the risk of seizures.
Many of the reported cases occurred in patients receiving high daily doses of levodopa, often exceeding 1,000 mg per day, and several had additional risk factors for vitamin B6 deficiency such as poor nutrition or underlying medical conditions.
Significantly, the FDA said that vitamin B6 supplementation resolved seizures in several patients, including cases where seizures did not respond adequately to standard anti-seizure medications.
Based on these findings, the FDA is requiring manufacturers to update prescribing information for all carbidopa/levodopa-containing products to include warnings about vitamin B6 deficiency and seizure risk. The agency also advises clinicians to consider monitoring vitamin B6 levels and supplementing when appropriate, particularly in patients receiving high doses or long-term therapy.
Carbidopa/levodopa products are considered the standard of care for symptomatic treatment of Parkinson’s disease, helping restore dopamine levels in the brain and improve motor symptoms such as tremor, rigidity, and bradykinesia. However, the FDA emphasized that healthcare providers should remain aware of potential nutritional deficiencies that may arise during treatment.
The updated labeling requirement is intended to improve clinician awareness and ensure early recognition and management of vitamin B6 deficiency–related neurological complications in patients receiving these widely used Parkinson’s therapies.
Reference
FDA Is Requiring Warning about Vitamin B6 Deficiency and Associated Seizures for Drug Products Containing Carbidopa/Levodopa, 20 March 2026, https://www.fda.gov/drugs/drug-safety-and-availability/fda-requiring-warning-about-vitamin-b6-deficiency-and-associated-seizures-drug-products-containing
FDA Is Requiring Warning about Vitamin B6 Deficiency and Associated Seizures for Drug Products Containing Carbidopa/Levodopa, 20 March 2026, https://www.fda.gov/media/191605/download?attachment
Vikas Londhe is the Chief Editor and a subject matter expert in patient safety and drug safety. He has a deep understanding of pharmacology, medication-related risks, patient and drug-related errors, and global drug regulatory frameworks. Through his work, he focuses on translating complex medical and regulatory information into clear, evidence-based insights that support safer medication use and informed healthcare decisions.
