Drug interactions
Bacillus calmette-guerin substrain tice + Isoniazid
Severity: Major
Bacillus calmette-guerin substrain tice and Isoniazid: major 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
BCG is a live attenuated Mycobacterium bovis, and isoniazid is active against mycobacteria, so it can reduce the viability and effect of intravesical BCG. This can lower the efficacy of bladder cancer immunotherapy.
What this interaction means in plain words
Bacillus calmette-guerin substrain tice and Isoniazid can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Bacillus calmette-guerin substrain tice belongs to Oncology; Isoniazid belongs to Anti Bacterial.
Why it happens
Antimycobacterial activity of isoniazid against the live BCG organisms reduces their viability and therefore immunotherapeutic activity.
What to do
Avoid giving antituberculosis drugs during intravesical BCG therapy unless needed to treat BCG infection. Use alternative non-antimycobacterial agents for local irritative symptoms.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Isoniazid
Frequently asked questions
Can I take Bacillus calmette-guerin substrain tice with Isoniazid?
MediHelp rates the interaction as major. Bacillus calmette-guerin substrain tice and Isoniazid can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. BCG is a live attenuated Mycobacterium bovis, and isoniazid is active against mycobacteria, so it can reduce the viability and effect of intravesical BCG. This can lower the efficacy of bladder cancer immunotherapy.
How serious is the interaction between Bacillus calmette-guerin substrain tice and Isoniazid?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid giving antituberculosis drugs during intravesical BCG therapy unless needed to treat BCG infection. Use alternative non-antimycobacterial agents for local irritative symptoms.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Benzhydrocodone / acetaminophen, Carbamazepine, Didanosine. The full list is on the Isoniazid page.
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