Cimetidine and Dutasteride and tamsulosin interaction
Cimetidine and Dutasteride and tamsulosin: the Dutasteride and tamsulosin prescribing label flags 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
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).
Cimetidine Caution is advised when tamsulosin-containing products, including JALYN, are coadministered with cimetidine [see Drug Interactions (7.1) , Clinical Pharmacology (12.3) ] .
Cimetidine: Treatment with cimetidine resulted in a moderate increase in tamsulosin hydrochloride AUC (44%) [see Warnings and Precautions (5.2) , Clinical Pharmacology (12.3) ] .
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.
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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.