Dutasteride and tamsulosin and Ketoconazole interaction
Dutasteride and tamsulosin and Ketoconazole: 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 Dutasteride and tamsulosin (Jalyn) label · effective 2026-03-09
Do not use JALYN with strong inhibitors of cytochrome P450 (CYP) 3A4 (e.g., ketoconazole).
Drug-Drug Interactions Strong Inhibitors of Cytochrome P450 (CYP) 3A4 Tamsulosin-containing products, including JALYN, should not be coadministered with strong CYP3A4 inhibitors (e.g., ketoconazole) as this can significantly increase tamsulosin exposure [see Drug Interactions (7.1) , Clinical Pharmacology (12.3) ].
Since CYP2D6 PMs cannot be readily identified and the potential for significant increase in tamsulosin exposure exists when tamsulosin 0.4 mg is coadministered with strong CYP3A4 inhibitors in CYP2D6 PMs, tamsulosin 0.4 mg capsules should not be used in combination wıth strong inhibitors of CYP3A4 (e.g., ketoconazole).
Use caution in combination with moderate CYP3A4 inhibitors (e.g., erythromycin) or strong (e.g., paroxetine) or moderate CYP2D6 inhibitors, a combination of both CYP3A4 and CYP2D6 inhibitors, or known poor metabolizers of CYP2D6.
Moderate Inhibitors of CYP3A4, Inhibitors of CYP2D6, or a Combination of Both CYP3A4 and CYP2D6 Inhibitors Tamsulosin-containing products, including JALYN, should be used with caution when coadministered with moderate inhibitors of CYP3A4 (e.g., erythromycin), strong (e.g., paroxetine) or moderate (e.g., terbinafine) inhibitors of CYP2D6, a combination of both…
From the Ketoconazole label · effective 2026-07-07
Alpha Blockers tamsulosin Analgesics methadone alfentanil, buprenorphine IV and sublingual, fentanyl, oxycodone, sufentanil Methadone: The potential increase in plasma concentrations of methadone when coadministered with ketoconazole tablets may increase the risk of serious cardiovascular events including QT prolongation and torsade de pointes, or respiratory…
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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.