On March 20, 2026, the FDA issued a Warning (here) notifying healthcare providers and patients that Carbidopa/Levodopa drug products can cause vitamin B6 deficiency and vitamin B6 deficiency-associated seizures. The warning instructs healthcare providers to monitor B6 levels in their patients taking the combination therapy, and recommends taking a baseline B6 level at the beginning of treatment. B6 supplementation should be instituted when appropriate.
The warning was precipitated by the FDA’s investigation of fourteen cases of seizures linked to B6 deficiency in patients taking Carbidopa/Levodopa. The FDA surmises that there may be additional unreported cases and noted that the fourteen case it reviewed “involved levodopa doses exceeding 1,000 mg daily, with higher doses (>1,500 mg levodopa) associated with shorter duration from treatment initiation to identification of vitamin B6 deficiency.” The warning notice includes additional information regarding the investigation that led the Agency to issue the warning and mandate labeling changes to all products containing the two components. (Note: There are several products, aside from carbidopa/levodopa, for which labels should contain the new warning, i.e., Carbidopa; Entacapone; Levodopa.)
Today, the FDA published approved label revisions for NDA products under its Drug Safety Label Changes for many of the products requiring the new warning. An example of the changes that FDA is requiring can be found here. Makers of generic versions of these products are now on notice to revise their labeling accordingly.
