Drug interactions
Efavirenz + Tolbutamide
Severity: Moderate
Efavirenz and Tolbutamide: 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
Efavirenz affects CYP2C9, and the effect on tolbutamide exposure is uncertain, with possible changes in glucose control. Tolbutamide dose requirements may change after starting or stopping efavirenz.
What this interaction means in plain words
Efavirenz and Tolbutamide 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.
Efavirenz belongs to Anti Virals; Tolbutamide belongs to Endocrine.
Why it happens
Efavirenz modulates CYP2C9 activity, altering tolbutamide metabolism.
What to do
Monitor blood glucose when starting or stopping efavirenz, and watch for hypoglycemia or hyperglycemia; adjust the tolbutamide dose.
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 Efavirenz
- Cobimetinib + Efavirenz Contraindicated
- Dienogest / estradiol valerate + Efavirenz Contraindicated
- Dihydroergotamine intranasal + Efavirenz Contraindicated
- Dihydroergotamine + Efavirenz Contraindicated
- Doravirine + Efavirenz Contraindicated
- Efavirenz + Elbasvir / grazoprevir Contraindicated
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 Efavirenz with Tolbutamide?
MediHelp rates the interaction as moderate. Efavirenz and Tolbutamide 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. Efavirenz affects CYP2C9, and the effect on tolbutamide exposure is uncertain, with possible changes in glucose control. Tolbutamide dose requirements may change after starting or stopping efavirenz.
How serious is the interaction between Efavirenz and Tolbutamide?
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 blood glucose when starting or stopping efavirenz, and watch for hypoglycemia or hyperglycemia; adjust the tolbutamide dose.
What other medicines interact with Efavirenz?
MediHelp also lists interactions of Efavirenz with, for example, Cobimetinib, Dienogest / estradiol valerate, Dihydroergotamine intranasal. The full list is on the Efavirenz page.
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