Carbidopa and levodopa and Isoniazid interaction
Carbidopa and levodopa and Isoniazid: the Carbidopa and levodopa prescribing label flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Carbidopa and levodopa (Duopa) label · effective 2026-03-19
DUOPA is contraindicated in patients who are currently taking a nonselective monoamine oxidase (MAO) inhibitor (e.g., phenelzine and tranylcypromine) or have recently (within 2 weeks) taken a nonselective MAO inhibitor.
DUOPA is contraindicated in patients taking nonselective monoamine oxidase (MAO) inhibitors ( 4 )
Monoamine Oxidase (MAO) Inhibitors The use of nonselective MAO inhibitors with DUOPA is contraindicated [see Contraindications ( 4 ) ] .
Dopamine D2 receptor antagonists, isoniazid, iron salts, and high-protein diet may reduce the effectiveness of DUOPA ( 7.3 , 7.4 , 7.5 )
Dopamine D2 Receptor Antagonists and Isoniazid Dopamine D2 receptor antagonists (e.g., phenothiazines, butyrophenones, risperidone, metoclopramide, papaverine) and isoniazid may reduce the effectiveness of levodopa.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.