Drug interactions
Isoniazid + Saquinavir
Severity: Moderate
Isoniazid and Saquinavir: moderate 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 is a weak CYP3A4 inhibitor, so a major rise in saquinavir levels is unlikely. Saquinavir/ritonavir carries QT and PR prolongation risk and both agents can affect the liver.
What this interaction means in plain words
Isoniazid and Saquinavir can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Weak CYP3A4 inhibition by isoniazid; additive hepatotoxic potential.
What to do
Monitor liver enzymes during co-treatment. Obtain a baseline ECG for saquinavir and avoid rifampicin, which is contraindicated with ritonavir-boosted saquinavir.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Isoniazid
Frequently asked questions
Can I take Isoniazid with Saquinavir?
MediHelp rates the interaction as moderate. Isoniazid and Saquinavir can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Isoniazid is a weak CYP3A4 inhibitor, so a major rise in saquinavir levels is unlikely. Saquinavir/ritonavir carries QT and PR prolongation risk and both agents can affect the liver.
How serious is the interaction between Isoniazid and Saquinavir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor liver enzymes during co-treatment. Obtain a baseline ECG for saquinavir and avoid rifampicin, which is contraindicated with ritonavir-boosted saquinavir.
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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