Duoflow Drug Interactions

Dutasteride: α-Adrenergic Blocking Agents: Concomitant administration of dutasteride with α-adrenergic blocking agents (i.e., tamsulosin, terazosin) has no effect on the steady-state pharmacokinetics of either α-adrenergic blocker. However, the effect of tamsulosin or terazosin on dutasteride pharmacokinetic parameters has not been evaluated.
Calcium-channel Blocking Agents: Concomitant administration of dutasteride with calcium-channel blocking agents that inhibit cytochrome P-450 (CYP) 3A4 isoenzymes (i.e., diltiazem, verapamil) decreases dutasteride clearance resulting in increased exposure to dutasteride. However, dosage adjustment of dutasteride is not recommended since the change in dutasteride exposure is not considered to be clinically important.
Drugs Affecting Hepatic Microsomal Enzymes: Potential pharmacokinetic interaction (decreased clearance and increased serum concentrations of dutasteride) with potent, chronic inhibitors of the CYP3A4 and CYP3A5 isoenzymes. However, the clinical effect of potent CYP3A4 inhibitors on dutasteride has not been studied. Because of the potential for drug interactions, care should be taken if dutasteride is administered with such drugs (e.g., ritonavir, ketoconazole, verapamil, diltiazem, cimetidine, ciprofloxacin).
Cholestyramine: Administration of a single 5-mg dose of dutasteride followed by a 12-g dose of cholestyramine one hour later did not affect the relative bioavailability of dutasteride.
Digoxin: Concomitant administration of dutasteride at a dosage of 0.5 mg daily for 3 weeks with digoxin did not alter the steady-state pharmacokinetics of digoxin.
Warfarin: Concomitant administration of dutasteride at a dosage of 0.5 mg daily for 3 weeks with warfarin did not alter the steady-state pharmacokinetics of R- or S-warfarin or alter the effect of warfarin on prothrombin time.
Tamsulosin: α-Adrenergic Blocking Agents: Additive effects; concomitant use not recommended.
Atenolol: No change in blood pressure or pulse rate; dosage adjustment not necessary.
Cimetidine: Increased plasma tamsulosin concentrations. Use with caution, particularly with dose >0.4 mg.
Enalapril: No change in blood pressure or pulse rate; dosage adjustment not necessary.
Furosemide: Decreased plasma tamsulosin concentrations; not clinically important.
Nifedipine: No change in blood pressure of pulse rate; dosage adjustment not necessary.
Warfarin: Possible pharmacokinetic interaction. Available data inconclusive; use with caution.
Food Interactions: Dutasteride: Maximum serum concentrations reduced by 10% to 15% when taken with food; not clinically significant. Management: Administer without regards to meals.
Tamsulosin: Fasting increases bioavailability by 30% and peak concentration 40% to 70%. Administer 30 minutes after the same meal each day.