Isoniazid and Levodopa Oral Inhalation: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Isoniazid
No brand names on recordLevodopa Oral Inhalation
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Excess catecholamine stimulation and/or reduced efficacy of levodopa, an increased risk of exacerbating psychosis (or symptoms of Parkinson's disease: delusion, confusion, agitation, etc.)
Interaction Deep Dive
Concomitant use of isoniazid with levodopa may produce symptoms of excess catecholamine stimulation (agitation, flushing, palpitations) or lack of levodopa effect2. DOPamine D2 receptor antagonists, such as isoniazid, may reduce the therapeutic effects of levodopa 3. Concomitant isoniazid and levodopa therapy has resulted in agitation, flushing, palpitations, severe non-parkinsonian tremor, and elevated blood pressure 64. Monitor patients for worsening of Parkinson's disease 1.
Why it happens (mechanism)
Antagonism of DOPamine effects
Literature reports
2 reports — tap to read
a) A 55-year-old man with idiopathic parkinsonism stabilized on levodopa-carbidopa for six years developed tuberculosis (TB) which was treated with a combination of isoniazid, rifAMPin, ethambutol, and pyridoxine. Within one week, symptomatic control of Parkinson's disease deteriorated and the patient spontaneously stopped his antitubercular therapy. Over the next month, he again stabilized. When TB therapy was reinstituted without pyridoxine, control was again lost within two weeks. Subsequently, the patient volunteered for a "levodopa challenge" pharmacokinetic and clinical evaluation during combination therapy with rifAMPin 600 mg-isoniazid 300 mg, and again 33 days after TB drugs were withdrawn. While on levodopa alone, latency from ingestion to "on" was 11 minutes, and the total "on" period was 440 minutes. During concurrent TB therapy, latency was prolonged to 27 minutes, and total time under control was only 251 minutes. Activities of daily living were rated best during monotherapy; motor performance assessments were not significantly different. Plasma levodopa levels during concurrent TB treatment were reduced by 33%, while time to peak levels, half-life, and AUC were all increased by 37% to 104%. Further analysis of levodopa metabolite concentrations suggested INH inhibition of both peripheral and central dopa decarboxylase activity; potential effects of rifAMPin on hepatic metabolism of levodopa were not determined 4.
b) Concomitant administration of isoniazid with levodopa resulted in a worsening of parkinsonian symptoms for 20 patients with Parkinson's disease; this presumably occurred from antagonism of the therapeutic effects of levodopa 5.
Common questions
Can I take Isoniazid and Levodopa Oral Inhalation together?
Excess catecholamine stimulation and/or reduced efficacy of levodopa, an increased risk of exacerbating psychosis (or symptoms of Parkinson's disease: delusion, confusion, agitation, etc.) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Isoniazid and Levodopa Oral Inhalation interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Isoniazid or Levodopa Oral Inhalation need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (6)
- Product Information: CREXONT(TM)oral extended-release capsules, carbidopa, levodopa oral extended-release capsules. Amneal Specialty (per FDA), Bridgewater, NJ, 2024. DailyMed
- Product Information: RIFATER(R) oral tablets, rifampin, isoniazid, pyrazinamide oral tablets. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
- Product Information: STALEVO(R) oral tablets, carbidopa, levodopa and entacapone oral tablets. Novartis Pharmaceuticals Corporation, East Hanover, NJ, 2010. DailyMed
- Wenning GK, O'Connell MT, Patsalos PN, et al: A clinical and pharmacokinetic case study of an interaction of levodopa and antituberculous therapy in parkinson's disease. Move Disorder 1995; 10(5):664-667. PubMed
- Gershanik OS, Luquin MR, Scipioni O, et al: Isoniazid therapy in Parkinson's disease. Movement Disorders 1988; 3:133-139. DOI
- Morgan JP: Isoniazid and levodopa. (letter). Ann Intern Med 1980; 92(3):434. PubMed
Keep reading about Isoniazid
Keep reading about Levodopa Oral Inhalation
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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