Simlosin Drug Interactions

No interactions occurred when tamsulosin hydrochloride was coadministered with atenolol, enalapril, or theophylline. Co-administration with cimetidine increased the plasma concentration of tamsulosin hydrochloride, while it decreased for furosemide. However, since it was still within the normal posology range, no dose adjustment was required. There was no change in plasma-free fraction of tamsulosin hydrochloride when co-administered with diazepam. Propanolol, trichlormethiazide, chlormadinone, amitriptyline, diclofenac, glibenclamide, simvastatin, and warfarin. Likewise, tamsulosin hydrochloride did not change the free fraction of diazepam, propanolol, trichlormethiazide, and chlormadinone. There was no interaction at the level of hepatic metabolism with the hepatic microsomal fraction (representing the group of drugs related to the cytochrome P450 metabolizing enzyme system), involving amitriptyline, salbutamol, glibenclamide, and finasteride. However, diclofenac and warfarin may increase the elimination rate of tamsulosin hydrochloride. Concomitant use of tamsulosin hydrochloride with strong antagonists of CYP3A4 might increase the effects of tamsulosin hydrochloride. Concomitant use with ketoconazole (known to be a strong antagonist of CYP3A4) led to an increase in AUC of tamsulosin. Tamsulosin hydrochloride should not be combined with strong CYP3A4 antagonists in patients with CYP2D6 metabolizing deficiency. Tamsulosin hydrochloride should be administered with caution when combined with strong and moderate strength CYP3A4 antagonists. Co-administration of tamsulosin hydrochloride with paroxetine which is a strong antagonist of CYP2D6 resulted in an increase in Cmax and AUC of tamsulosin hydrochloride, but not clinically significant. Co-administration with other α-adrenoreceptor antagonists may cause hypotensive effects.