Ketoconazole and Olanzapine and fluoxetine interaction
Ketoconazole and Olanzapine and fluoxetine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Ketoconazole label · effective 2026-07-07
This may potentiate and prolong hypnotic and sedative effects, especially with repeated dosing or chronic administration of these agents.
…methadone when coadministered with ketoconazole tablets may increase the risk of serious cardiovascular events including QT prolongation and torsade de pointes, or respiratory or CNS depression [See CONTRAINDICATIONS .] Fentanyl: The potential increase in plasma concentrations of fentanyl when coadministered with ketoconazole tablets may increase the risk of…
Antipsychotics, Anxiolytics and Hypnotics Lurasidone, alprazolam, oral midazolam, pimozide, triazolam aripiprazole, buspirone, haloperidol, midazolam IV, quetiapine, ramelteon, risperidone The increase in plasma concentrations of lurasidone when coadministered with ketoconazole tablets may increase the risk of serious side effects (See CONTRAINDICATIONS ).
From the Olanzapine and fluoxetine label · effective 2026-03-31
Use olanzapine and fluoxetine capsules with caution in combination with other drugs that prolong the QT interval ( 4.2 , 5.20 , 7.7 , 7.8 ) 7.1 Monoamine Oxidase Inhibitors (MAOIs) [See Dosage and Administration ( 2.4 , 2.5 ), Contraindications ( 4.1 ), and Warnings and Precautions ( 5.6 )] .
Drugs Metabolized by CYP3A — In vitro studies utilizing human liver microsomes suggest that olanzapine has little potential to inhibit CYP3A.
In addition, in vitro studies have shown ketoconazole, a potent inhibitor of CYP3A activity, to be at least 100 times more potent than fluoxetine or norfluoxetine as an inhibitor of the metabolism of several substrates for this enzyme, including astemizole, cisapride, and midazolam.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.