Prozelax Drug Interactions

Cytochrome P450 Inhibition: Strong and Moderate Inhibitors of CYP3A4 or CYP2D6: Tamsulosin is extensively and mainly metabolized by CYP3A4 and CYP2D6 isoenzymes.
Concomitant administration of ketoconazole, a strong inhibitor of CYP3A4 isoenzyme, may increase the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. Combined use is not recommended.
The effect of concomitant administration of moderate inhibitors of CYP3A4 (e.g., erythromycin) on the pharmacokinetics of tamsulosin have not been studied.
Concomitant administration of paroxetine, a strong inhibitor of CYP2D6 isoenzyme, may increase the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Similarly, an increase in exposure was identified in poor metabolizers of CYP2D6 compared to extensive metabolizers of CYP2D6. Since CYP2D6 poor metabolizers cannot be readily identified and the potential for significant increase in tamsulosin exposure exists when tamsulosin is co-administered with strong CYP3A4 inhibitors in these patients, the use of strong CYP3A4 inhibitors in CYP2D6 poor metabolizers are not recommended.
The effect of concomitant administration of moderate inhibitors of CYP2D6 (e.g., terbinafine) on the pharmacokinetics of tamsulosin have not been evaluated.
Concomitant administration of both CYP3A4 and CYP2D6 inhibitors with tamsulosin has not been evaluated. A potential significant increase in tamsulosin exposure, however, is expected when tamsulosin is administered with a combination of strong inhibitors of both CYP3A4 and CYP2D6.
Alpha-adrenergic Blocking Agents: Pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-adrenergic blocking agents have not been determined. Do not use tamsulosin in combination with these agents since interactions may be expected.
PDE5 Inhibitors: Concomitant administration of alpha-adrenergic blocking agents and PDE5 inhibitors may lower blood pressure and cause hypotension due to their vasodilating effects. Caution is advised when these drugs are given concomitantly.
Warfarin: Warfarin may increase the elimination rate of tamsulosin in vitro. Exercise caution when tamsulosin is administered concomitantly with warfarin.
Nifedipine, Atenolol, Enalapril: There is no clinically significant effects on blood pressure and pulse rate when nifedipine, atenolol or enalapril are taken together with tamsulosin. Concomitant administration with tamsulosin requires no dosage adjustment.
Digoxin and Theophylline: Orally administered tamsulosin taken concomitantly with digoxin and theophylline resulted in no change in the pharmacokinetics of digoxin or theophylline. No dosage adjustments are necessary when these drugs are taken concomitantly.
Furosemide: Orally administered tamsulosin taken concomitantly with furosemide 20 mg single IV dose had no effect on the pharmacodynamics of furosemide. Although furosemide reduced the maximum concentration (Cmax) and AUC of tamsulosin, dosage adjustment is not required since these changes are expected to be clinically insignificant.
Cimetidine: Tamsulosin's clearance was significantly decreased by 26% which resulted in a moderate increase in AUC (44%) with concomitant treatment with cimetidine. Use tamsulosin with caution when used in combination with cimetidine.
Other in vitro findings: Diazepam, propranolol, trichlormethiazide, chlormadinone, amitriptyline, diclofenac, glibenclamide, simvastatin, salbutamol, finasteride, and warfarin did not change the free fraction of tamsulosin in human plasma in vitro.
Laboratory Findings: There are no known laboratory test interactions with the use of tamsulosin. Tamsulosin treatment for up to 3 months has been shown to have no significant effect on prostate specific antigen (PSA).