Drug interactions
Cycloserine + Isoniazid
Severity: Moderate
Cycloserine and Isoniazid: 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
Both drugs can cause central nervous system toxicity, and used together they may increase the risk of dizziness, drowsiness, confusion, psychosis and seizures. This matters because they are commonly combined in tuberculosis regimens.
What this interaction means in plain words
Cycloserine and Isoniazid 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.
Cycloserine belongs to Anti Bacterial; Isoniazid belongs to Anti Bacterial.
Why it happens
Additive neurotoxicity; isoniazid may also contribute to CNS effects by interfering with pyridoxine and GABA synthesis.
What to do
Monitor for neurological and psychiatric symptoms and give pyridoxine prophylactically. Reduce the cycloserine dose or stop it if CNS toxicity develops.
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 Cycloserine
Other interactions of Isoniazid
Frequently asked questions
Can I take Cycloserine with Isoniazid?
MediHelp rates the interaction as moderate. Cycloserine and Isoniazid 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. Both drugs can cause central nervous system toxicity, and used together they may increase the risk of dizziness, drowsiness, confusion, psychosis and seizures. This matters because they are commonly combined in tuberculosis regimens.
How serious is the interaction between Cycloserine and Isoniazid?
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 for neurological and psychiatric symptoms and give pyridoxine prophylactically. Reduce the cycloserine dose or stop it if CNS toxicity develops.
What other medicines interact with Cycloserine?
MediHelp also lists interactions of Cycloserine with, for example, Ethionamide, Sodium picosulfate / magnesium oxide / anhydrous citric acid. The full list is on the Cycloserine page.
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