NutriStack
Levodopa/Carbidopa and Vitamin B6, a caution.
Vitamin B6 (pyridoxine) is a cofactor for DOPA decarboxylase, which converts levodopa to dopamine peripherally before it reaches the brain. While carbidopa blocks peripheral decarboxylation, high-dose B6 (>50mg/day) may partially overcome carbidopa's inhibition, reducing levodopa's efficacy.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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From the interaction database
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At a glance
- Substances
- Levodopa/Carbidopa and Vitamin B6
- Pair type
- Caution
- Evidence (highest tier)
- Strong
- Source citations
- 1 source
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Strong evidence
Caution
What is happening. Vitamin B6 (pyridoxine) is a cofactor for DOPA decarboxylase, which converts levodopa to dopamine peripherally before it reaches the brain. While carbidopa blocks peripheral decarboxylation, high-dose B6 (>50mg/day) may partially overcome carbidopa's inhibition, reducing levodopa's efficacy.
Mechanism. Pyridoxal 5'-phosphate (active B6) is the essential cofactor for aromatic L-amino acid decarboxylase (AADC/DOPA decarboxylase). High-dose B6 increases peripheral AADC activity, potentially overwhelming carbidopa's competitive inhibition and converting levodopa to dopamine before it crosses the blood-brain barrier.
Recommendation. Avoid high-dose vitamin B6 supplements (>50mg/day) while on levodopa/carbidopa. Standard multivitamin doses of B6 (2-10mg) are generally safe when carbidopa is included. If you need higher B6 doses, consult your neurologist.
Stack Score
How this pair moves the number.
Effect on the composite score
If both Levodopa/Carbidopa and Vitamin B6 are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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