Risk of vitamin B6 deficiency and associated seizures with carbidopa/levodopa or benserazide/levodopa

Levodopa, a metabolic precursor to dopamine, is the cornerstone replacement therapy for Parkinson’s disease, a neurodegenerative disorder characterised by the loss of dopamine-producing neurons. As levodopa is converted into dopamine via decarboxylation both centrally and peripherally, this limits the amount of levodopa available for delivery across the blood-brain barrier. To enhance its central bioavailability and reduce adverse effects, levodopa is typically co-administered with a peripheral decarboxylase inhibitor, such as carbidopa or benserazide, to prevent the peripheral conversion of levodopa to dopamine.

There are currently 14 products containing levodopa in combination with a peripheral decarboxylase inhibitor registered locally since 1990. Post-market cases of seizures, some with fatal outcomes, have been reported overseas and in published literature in patients using combination products containing levodopa and a peripheral decarboxylase inhibitor. To date, no cases have been reported locally.

Example of a case report published in the literature