Isoniazid and Rifampicin: Drug Interaction Guide
Quick answer: This combination requires caution. Isoniazid and Rifampicin can be used together with adjustments and monitoring.
How Isoniazid interacts with Rifampicin
Rifampicin induces hepatic CYP enzymes that increase production of hepatotoxic isoniazid metabolites; combined regimen raises the risk of drug-induced hepatitis.
What you should do
Monitor LFTs at baseline, 2 weeks, then monthly. Discontinue both drugs if ALT rises above 3× ULN with symptoms or above 5× ULN asymptomatic.
Key facts
Severity
Moderate — caution required
Mechanism
Rifampicin induces hepatic CYP enzymes that increase production of hepatotoxic isoniazid metabolites; combined regimen r...
Action
Monitor LFTs at baseline, 2 weeks, then monthly. Discontinue both drugs if ALT rises above 3× ULN with symptoms or above...
Frequently asked questions
Can I take Isoniazid and Rifampicin together?
With caution. Monitor LFTs at baseline, 2 weeks, then monthly. Discontinue both drugs if ALT rises above 3× ULN with symptoms or above 5× ULN asymptomatic.
What is the severity of this interaction?
The interaction between Isoniazid and Rifampicin is classified as Moderate — caution required. Rifampicin induces hepatic CYP enzymes that increase production of hepatotoxic isoniazid metabolites; combined regimen raises the risk of drug-induced hepatitis.
What should I do if I'm prescribed both?
Monitor LFTs at baseline, 2 weeks, then monthly. Discontinue both drugs if ALT rises above 3× ULN with symptoms or above 5× ULN asymptomatic. Always consult your prescribing clinician — do not stop or change medications without medical guidance.
Last reviewed: by iMedic Medical Editorial Team. Our editorial process.