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Avodart (Dutasteride) - Drug Interactions, Contraindications, Overdosage, etc

 
 



DRUG INTERACTIONS

Cytochrome P450 3A Inhibitors

Dutasteride 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 AVODART to patients taking potent, chronic CYP3A4 enzyme inhibitors (e.g., ritonavir) [see Clinical Pharmacology].

Alpha Adrenergic Antagonists

The administration of AVODART in combination with tamsulosin or terazosin has no effect on the steady-state pharmacokinetics of either alpha adrenergic antagonist. The effect of administration of tamsulosin or terazosin on dutasteride pharmacokinetic parameters has not been evaluated.

Calcium Channel Antagonists

Coadministration of verapamil or diltiazem decreases dutasteride clearance and leads to increased exposure to dutasteride. The change in dutasteride exposure is not considered to be clinically significant. No dose adjustment is recommended [see Clinical Pharmacology].

Cholestyramine

Administration of a single 5-mg dose of AVODART followed 1 hour later by 12 g of cholestyramine does not affect the relative bioavailability of dutasteride [see Clinical Pharmacology].

Digoxin

AVODART does not alter the steady-state pharmacokinetics of digoxin when administered concomitantly at a dose of 0.5 mg/day for 3 weeks [see Clinical Pharmacology].

Warfarin

Concomitant administration of AVODART 0.5 mg/day for 3 weeks 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].

OVERDOSAGE

In volunteer studies, single doses of dutasteride up to 40 mg (80 times the therapeutic dose) for 7 days have been administered without significant safety concerns. In a clinical study, daily doses of 5 mg (10 times the therapeutic dose) were administered to 60 subjects for 6 months with no additional adverse effects to those seen at therapeutic doses of 0.5 mg.

There is no specific antidote for dutasteride. Therefore, in cases of suspected overdosage symptomatic and supportive treatment should be given as appropriate, taking the long half-life of dutasteride into consideration.

CONTRAINDICATIONS

AVODART is contraindicated for use in:

  • Pregnancy. In animal reproduction and developmental toxicity studies, dutasteride inhibited development of male fetus external genitalia. Therefore, AVODART may cause fetal harm when administered to a pregnant woman. If AVODART is used during pregnancy or if the patient becomes pregnant while taking AVODART, the patient should be apprised of the potential hazard to the fetus [see Warnings and Precautions Use in Specific Populations].
  • Women of childbearing potential [see Warnings and Precautions Use in Specific Populations].
  • Pediatric patients [see Use in Specific Populations].
  • Patients with previously demonstrated, clinically significant hypersensitivity (e.g., serious skin reactions, angioedema) to AVODART or other 5 alpha-reductase inhibitors [see Adverse Reactions].

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