Drug interactions
Erythromycin lactobionate + Ketoconazole
Severity: Major
Erythromycin lactobionate and Ketoconazole: major interaction.
Last updated Sources: UK SmPC
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 prolong the QT interval, and each inhibits CYP3A4, so erythromycin concentrations may rise. The combination increases the risk of torsades de pointes, particularly with intravenous erythromycin.
What this interaction means in plain words
Erythromycin lactobionate and Ketoconazole 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.
Erythromycin lactobionate belongs to Anti Bacterial; Ketoconazole belongs to Anti Fungals.
Why it happens
Additive QT prolongation combined with mutual CYP3A4 inhibition.
What to do
Avoid if possible and choose a non-macrolide antibiotic. If combined, use ECG monitoring and correct potassium and magnesium.
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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References
- Erythromycin 1g Powder for Solution for Infusion - SmPC sections 4.3/4.5 (names the partner; "losporine, hexobarbiton, colchicine, methylprednisolone, midazolam, omeprazole, tacrolimus, valproate, vinblastine, antimycotics such as fluconazole, ketoconazo") — electronic medicines compendium (UK SmPC)
Other interactions of Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Other interactions of Erythromycin lactobionate
- Cisapride + Erythromycin lactobionate Contraindicated
- Dihydroergotamine + Erythromycin lactobionate Contraindicated
- Dronedarone + Erythromycin lactobionate Contraindicated
- Eletriptan + Erythromycin lactobionate Contraindicated
- Ergotamine + Erythromycin lactobionate Contraindicated
- Erythromycin lactobionate + Flibanserin Contraindicated
Frequently asked questions
Can I take Erythromycin lactobionate with Ketoconazole?
MediHelp rates the interaction as major. Erythromycin lactobionate and Ketoconazole 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. Both drugs prolong the QT interval, and each inhibits CYP3A4, so erythromycin concentrations may rise. The combination increases the risk of torsades de pointes, particularly with intravenous erythromycin.
How serious is the interaction between Erythromycin lactobionate and Ketoconazole?
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 if possible and choose a non-macrolide antibiotic. If combined, use ECG monitoring and correct potassium and magnesium.
What other medicines interact with Ketoconazole?
MediHelp also lists interactions of Ketoconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Ketoconazole page.
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