USFDA Flags Seizure Risk in Parkinson's Drugs, Orders Label Updates

The drugs containing the ingredients carbidopa or levodopa should state that they ‌can cause ⁠vitamin ⁠B6 deficiency and seizures associated with it, the health regulator said.

Carbidopa ​and levodopa are almost always taken together to treat symptoms of Parkinson's ​disease, a progressive nervous system disorder that occurs when brain cells produce insufficient dopamine, leading to tremors, stiffness and slow movement.

The ​FDA said it conducted a ⁠safety review ‌and identified 14 cases of seizures linked to ​vitamin ​B6 deficiency in patients using these drugs. These ⁠seizures usually start in one part of the brain ​and then spread, potentially becoming severe ​and prolonged.

Healthcare professionals should evaluate vitamin B6 levels before starting patients on these drugs and consider whether supplementation is necessary, the regulator said.

Levodopa turns into dopamine in the brain, replenishing the diminished levels seen in Parkinson's disease and ‌improving movement. Carbidopa helps ensure more levodopa reaches the brain by preventing its premature breakdown in the ​body.

Drugs containing ​these ingredients ⁠can deplete vitamin B6 levels during the process by which levodopa is converted into dopamine. Carbidopa binds to the active form of ​vitamin B6, resulting in additional functional loss of the vitamin, the FDA said.

Amneal, AbbVie, Organon and Novartis manufacture drugs containing carbidopa or levodopa. The companies did not immediately respond to Reuters' requests for comment.

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