The short answer
Comfrey has its own liver-safety concerns and needs review during isoniazid treatment. No direct study established that this exact combination increases liver injury, but adding a potentially hepatotoxic product is a meaningful precaution.
What this answer covers
Oral Symphytum officinale preparations containing hepatotoxic pyrrolizidine alkaloids; topical or PA-free products are different.
- Supplement or preparation
- Symphytum officinale
- Medication ingredient
- isoniazid
The medication already requires liver vigilance
Isoniazid can cause serious hepatitis, and its label calls for attention to symptoms and individual risk factors. This medicine warning does not supply an injury rate for the supplement combination.
What the original supplement evidence shows
An original report linked comfrey leaf ingestion with severe hepatic veno-occlusive disease. It did not involve this medicine. The concern is particularly about oral products containing pyrrolizidine alkaloids, not an assumed identical risk from every topical preparation.
Separate intrinsic harm from a proven interaction
The sources support concern about the specified supplement exposure itself. They do not demonstrate synergistic injury, a safe combined dose or the same effect for every preparation. A biochemical change is not automatically liver failure.
Discuss the product before adding it
Show the TB clinician the exact product and dose. Do not add an oral product with liver-injury concerns without clinical review. Seek prompt medical advice for jaundice, dark urine, persistent nausea or unusual fatigue rather than trying a spacing interval.
Evidence and practical considerations
Side effects & toxicity
Conditional hepatic co-use precaution from exact medication warning and original preparation-specific supplement liver evidence. No exact-pair increased incidence or synergistic causality established; route/preparation limits and contrary findings retained.
- Exact scope
- Oral Symphytum officinale preparations containing hepatotoxic pyrrolizidine alkaloids; topical or PA-free products are different. with Isoniazid oral tablets.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No unmeasured pair incidence, blanket class transfer or arbitrary spacing interval.
Factors that may matter: Preparation; Dose; Other medicines; Organ function.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 11, 2026
Population: People prescribed isoniazid
Hepatitis and peripheral-neuropathy warnings; pyridoxine recommended in predisposed patients; tyramine/histamine food precautions.
How this applies: Exact isoniazid RxCUI 6038 IN, with stated salt/formulation/route bridge.
Exact route and formulation apply. Label precautions do not quantify untested botanical pairs or support arbitrary supplement doses.
Source 2: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 11, 2026
Population: One23-year-old man.
Severe portal hypertension and fatal liver failure; temporal, pathological and exclusion findings supported possible causality.
How this applies: One case, no isoniazid co-use. Oral leaf/PA exposure is not topical or certified PA-free preparation.
One case, no isoniazid co-use. Oral leaf/PA exposure is not topical or certified PA-free preparation.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Research summary published | |
| Article prepared | |
| Prepared exact isoniazid article with formulation-specific evidence and uncertainty. |
Article revision: a6b8b46a2def80e1
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.