Drug interactions
Isoniazid + Tolbutamide
Severity: Minor
Isoniazid and Tolbutamide: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Isoniazid can impair glucose tolerance and may reduce the glucose-lowering effect of tolbutamide in some patients. The effect is inconsistent and usually modest.
What this interaction means in plain words
Isoniazid and Tolbutamide have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Isoniazid belongs to Anti Bacterial; Tolbutamide belongs to Endocrine.
Why it happens
Isoniazid may cause hyperglycemia or impaired glucose tolerance, opposing the hypoglycemic effect; the mechanism is not well defined.
What to do
Monitor blood glucose when isoniazid is started or stopped in patients taking tolbutamide, and adjust the antidiabetic dose if control changes.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Isoniazid
Other interactions of Tolbutamide
- Glyburide-metformin + Tolbutamide Major
- Insulin degludec-liraglutide + Tolbutamide Major
- Aceclofenac + Tolbutamide Moderate
- Acemetacin + Tolbutamide Moderate
- Acetylsalicylic acid + Tolbutamide Moderate
- Albiglutide + Tolbutamide Moderate
Frequently asked questions
Can I take Isoniazid with Tolbutamide?
MediHelp rates the interaction as minor. Isoniazid and Tolbutamide have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Isoniazid can impair glucose tolerance and may reduce the glucose-lowering effect of tolbutamide in some patients. The effect is inconsistent and usually modest.
How serious is the interaction between Isoniazid and Tolbutamide?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood glucose when isoniazid is started or stopped in patients taking tolbutamide, and adjust the antidiabetic dose if control changes.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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