A significant difference was seen by Month 9 and continued through Month 48. Dutasteride is highly protein bound in human semen (greater than 96%), which may reduce the amount of dutasteride available for vaginal absorption.In an embryo-fetal development study in rats, oral administration of dutasteride at 10 times less than the MRHD of 0.5 mg daily (based on average blood levels in men) resulted in feminization of male genitalia in the fetus (decreased anogenital distance at 0.05 mg/kg/day, with a lack of a no-effect level) in the absence of maternal toxicity. Visit the Copyright © 2020 by RxList Inc. RxList does not provide medical advice, diagnosis or treatment. Histological evaluation of the genital papilla of fetuses revealed evidence of feminization of the male fetus as well as fused skull bones and increased placental weights at all doses in the absence of maternal toxicity.
A few months may be required before benefits occur.

No feminization of male external genitalia of monkey offspring was observed. Dutasteride is not metabolized in vitro by human cytochrome P450 isoenzymes CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1. No clinically significant changes in adrenal hormone responses to adrenocorticotropic hormone (ACTH) stimulation were observed in a subset population (n = 13) of the 1-year healthy volunteer trial.Following administration of a single 0.5-mg dose of a soft gelatin capsule, time to peak serum concentrations (Tmax) of dutasteride occurs within 2 to 3 hours. Due to the long half-life of dutasteride, serum concentrations remain detectable (greater than 0.1 ng/mL) for up to 4 to 6 months after discontinuation of treatment.Dutasteride pharmacokinetics have not been investigated in subjects younger than 18 years.No dose adjustment is necessary in the elderly. The median increase in serum testosterone was 19% at both 1 and 2 years, 26% at 3 years, and 22% at 4 years, but the mean and median levels remained within the physiologic range.In patients with BPH treated with 5 mg/day of dutasteride or placebo for up to 12 weeks prior to transurethral resection of the prostate, mean DHT concentrations in prostatic tissue were significantly lower in the dutasteride group compared with placebo (784 and 5,793 pg/g, respectively, P <0.001). Therefore, on average, the dose unaccounted for approximated 55% (range: 5% to 97%).The terminal elimination half-life of dutasteride is approximately 5 weeks at steady state. Trial entry criteria were similar to the double-blind, placebo-controlled monotherapy efficacy trials described in Section 14.1. Subjects were randomized to receive placebo (n = 4,126) or 0.5-mg daily doses of AVODART (n = 4,105) for up to 4 years. At Month 24 the mean changes from baseline (±SD) in IPSS total symptom scores were -6.2 (±7.14) for combination, -4.9 (±6.81) for AVODART, and -4.3 (±7.01) for tamsulosin, with a mean difference between combination and AVODART of -1.3 units (P <0.001; [95% -1.69, -0.86]), and between combination and tamsulosin of -1.8 units (P <0.001; [95% -2.23, -1.40]). 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 The administration of AVODART in combination with tamsulosin or terazosin has no effect on the steady-state pharmacokinetics of either alpha-adrenergic antagonist.

No cases of breast cancer were reported in any treatment group in the 4-year CombAT trial or the 4-year REDUCE trial.The relationship between long-term use of dutasteride and male breast neoplasia is currently unknown.Over 4,800 male subjects with BPH were randomly assigned to receive 0.5-mg AVODART, 0.4-mg tamsulosin, or combination therapy (0.5-mg AVODART plus 0.4-mg tamsulosin) administered once daily in a 4-year double-blind trial. For more information, ask your doctor or pharmacist.Call your doctor for medical advice about side effects.


These data suggest that AVODART arrests the disease process of BPH in men with an enlarged prostate.The efficacy of combination therapy (AVODART 0.5 mg/day plus tamsulosin 0.4 mg/day, n = 1,610) was compared with AVODART alone (n = 1,623) or tamsulosin alone (n = 1,611) in a 4-year multicenter, randomized, double-blind trial.