e is extensively metabolized in humans by the CYP3A4 and CYP3A5 isoenzymes. The effect of potent CYP3A4 inhibitors on dutasteride has not been studied. Because of the potential for drug-drug interactions, use caution when prescribing a dutasteride-containing product, including JALYN, to patients taking potent, chronic CYP3A4 enzyme inhibitors (e.g., ritonavir) [see Clinical Pharmacology (12.3)].
Tamsulosin:Strong and Moderate Inhibitors of CYP3A4 or CYP2D6: Tamsulosin is extensively metabolized, mainly by CYP3A4 or CYP2D6.
Concomitant treatment with ketoconazole (a strong inhibitor of CYP3A4) resulted in increases in the Cmax and AUC of tamsulosin by factors of 2.2 and 2.8, respectively. Concomitant treatment with paroxetine (a strong inhibitor of CYP2D6) resulted in increases in the Cmax and AUC of tamsulosin by factors of 1.3 and 1.6, respectively. A similar increase in exposure is expected in poor metabolizers (PM) of CYP2D6 as compared to extensive metabolizers (EM). Since CYP2D6 PMs cannot be readily identified and the potential for significant increase in tamsulosin exposure exists when tamsulosin 0.4mg is coadministered with strong CYP3A4 inhibitors in CYP2D6 PMs, tamsulosin 0.4mg capsules should not be used in combination with strong inhibitors of CYP3A4 (e.g., ketoconazole). The effects of coadministration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have not been eva luated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin 0.4mg is coadministered with a combination of both CYP3A4 and CYP2D6 inhibitors [see Warnings and Precautions (5.2), 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)].
7.2 Warfarin
Dutasteride: Concomitant administration of dutasteride 0.5mg/day for 3weeks with warfarin does not alter the steady-state pharmacokinetics of the S- or R-warfarin isomers or alter the effect of warfarin on prothrombin time [see Clinical Pharmacology (12.3)].
Tamsulosin: A definitive drug-drug interaction study between tamsulosin hydrochloride and warfarin was not conducted. Results from limited in vitro and in vivo studies are inconclusive. Caution should be exercised with concomitant administration of warfarin and tamsulosin-containing products, including JALYN [see Warnings and Precautions (5.2), Clinical Pharmacology (12.3)].
7.3 Nifedipine, Atenolol, Enalapril
Tamsulosin: Dosage adjustments are not necessary when tamsulosin is administered concomitantly with nifedipine, atenolol, or enalapril [see Clinical Pharmacology (12.3)].
7.4 Digoxin and Theophylline
Dutasteride: Dutasteride does not alter the steady-state pharmacokinetics of digoxin when administered concomitantly at a dose of 0.5mg/day for 3weeks [see Clinical Pharmacology (12.3)].
Tamsulosin: Dosage adjustments are not necessary when tamsulosin is administered concomitantly with digoxin or theophylline [see Clinical Pharmacology (12.3)].
7.5 Furosemide
Tamsulosin: Tamsulosin had no effect on the pharmacodynamics (excretion of electrolytes) of furosemide. While furosemide produced an 11% to 12% reduction in tamsulosin hydrochloride Cmax and AUC, these changes are expected to be clinically insignificant and do not require adjustment of the dose of tamsulosin [see Clinical Pharmacology (12.3 |
