Drug interactions
Efavirenz + Fentanyl iontophoretic transdermal system
Severity: Moderate
Efavirenz and Fentanyl iontophoretic transdermal system: 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 causes CNS effects such as dizziness and somnolence, which can add to the sedation and respiratory depression of fentanyl. Efavirenz is also a CYP3A4 inducer and may lower fentanyl exposure, but the on-demand, short-term use of this system limits that effect.
What this interaction means in plain words
Efavirenz and Fentanyl iontophoretic transdermal system 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
Additive CNS depression; efavirenz also induces CYP3A4, which metabolizes fentanyl.
What to do
Monitor for sedation and respiratory depression, and for inadequate analgesia. Titrate analgesia to effect.
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
Frequently asked questions
Can I take Efavirenz with Fentanyl iontophoretic transdermal system?
MediHelp rates the interaction as moderate. Efavirenz and Fentanyl iontophoretic transdermal system 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 causes CNS effects such as dizziness and somnolence, which can add to the sedation and respiratory depression of fentanyl. Efavirenz is also a CYP3A4 inducer and may lower fentanyl exposure, but the on-demand, short-term use of this system limits that effect.
How serious is the interaction between Efavirenz and Fentanyl iontophoretic transdermal system?
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 sedation and respiratory depression, and for inadequate analgesia. Titrate analgesia to effect.
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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