Tamsumax Drug Interactions

Nifedipine, Atenolol, Enalapril: In three studies in hypertensive subjects (age range 47-79 years) whose blood pressure was controlled with stable doses of Nifedipine, atenolol, or enalapril for at least three months, Tamsulosin HCl (Tamsumax) capsules 0.4 mg for seven days followed by Tamsulosin HCl (Tamsumax) capsules 0.8 mg for another seven days (n=8 per study) resulted in no clinically significant effects on blood pressure and pulse rate compared to placebo (n=4 per study). Therefore, dosage adjustments are not necessary when Tamsulosin HCl (Tamsumax) capsules are administered concomitantly with Nifedipine, atenolol, or enalapril.
Warfarin: 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. Therefore, caution should be exercised with concomitant administration of warfarin and Tamsulosin HCl (Tamsumax) capsules.
Digoxin and Theophylline: In two studies in healthy volunteers (n=10 per study; age range 19-39 years) receiving Tamsulosin HCl (Tamsumax) capsules 0.4 mg/day for two days, followed by Tamsulosin HCl (Tamsumax) capsules 0.8 mg/day for five to eight days, single intravenous doses of digoxin 0.5 mg or theophylline 5 mg/kg resulted in no change in the pharmacokinetics of digoxin or theophylline. Therefore, dosage adjustments are not necessary when a Tamsulosin HCl (Tamsumax) capsule is administered concomitantly with digoxin or theophylline.
Furosemide: The pharmacokinetic and pharmacodynamic interaction between Tamsulosin HCl (Tamsumax) capsules 0.8 mg/day (steady-state) and furosemide 20 mg intravenously (single dose) was evaluated in ten healthy volunteers (age range 21-40 years). Tamsulosin HCl (Tamsumax) capsules 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 Tamsulosin HCl (Tamsumax) capsules dosage.
Cytochrome P450 Inhibition: Cimetidine: The effects of cimetidine at the highest recommended dose (400 mg every six hours for six days) on the pharmacokinetics of a single Tamsulosin HCl (Tamsumax) capsule 0.4 mg dose was investigated in ten healthy volunteers (age range 21-38 years). Treatment with cimetidine resulted in a significant decrease (26%) in the clearance of tamsulosin hydrochloride, which resulted in a moderate increase in tamsulosin hydrochloride AUC (44%). Therefore, Tamsulosin HCl (Tamsumax) capsules should be used with caution in combination with cimetidine, particularly at doses higher than 0.4 mg.
Strong Inhibitors of CYP3A4 or CYP2D6: The effects of ketoconazole (a strong inhibitor of CYP3A4) at 400 mg every day on the pharmacokinetics of a single Tamsulosin HCl (Tamsumax) capsule 0.4 mg dose was investigated in 24 healthy volunteers (age range from 23 to 47 years). Treatment with ketoconazole resulted in a Cmax and AUC that increased by a factor of 2.2 and 2.8, respectively. Therefore, Tamsulosin HCl (Tamsumax) 0.4 mg capsules should be used with caution in combination with strong inhibitors of CYP3A4. Doses above 0.4 mg should not be used in combination with strong inhibitors of CYP3A4 (e.g., ketoconazole).
The effects of paroxetine (a strong inhibitor of CYP2D6) at 20 mg every day on the pharmacokinetics of a single Tamsulosin HCl (Tamsumax) capsule 0.4 mg dose was investigated in 23 healthy volunteers (age range from 23 to 48 years). Treatment with paroxetine resulted in a Cmax and AUC that increased by a factor of 1.3 and 1.6, respectively. Therefore, Tamsulosin HCl (Tamsumax) capsules should be used with caution in combination with strong inhibitors of CYP2D6, particularly at doses higher than 0.4 mg (e.g., 0.8 mg).