La dutasterida es un azasteroide sintético que actúa como inhibidor específico de la 5a-reductasa, una enzima intracelular que convierte la testosterona en dehidrotestosterona. Se utiliza en el tratamiento de la hiperplasia benigna de próstata
Mecanismo de acción: la dutasterida inhibe la conversión de la testosterona de 5a-dehidrotestosterona, la cual es un andrógeno responsable del desarrollo inicial y de la subsiguiente hiperplasia de la glándula prostática. L
Mechanism of Action: Dutasteride inhibits the conversion of testosterone to 5a-dihydrotestosterone (DHT). DHT is the androgen primarily responsible for the initial development and subsequent enlargement of the prostate gland . Testosterone is converted to DHT by the enzyme 5a-reductase, which exists as 2 isoforms, type 1 and type 2. The type 2 isoenzyme is primarily active in the reproductive tissues while the type 1 isoenzyme is also responsible for testosterone conversion in the skin and liver .
Dutasteride is a competitive and specific inhibitor of both type 1 and type 2 5a-reductase isoenzymes, with which it forms a stable enzyme complex. Dissociation from this complex has been evaluated under in vitro and in vivo conditions and is extremely slow. Dutasteride does not bind to the human androgen receptor .
Effect on DHT and Testosterone: The maximum effect of daily doses of dutasteride on the reduction of DHT is dose dependent and is observed within 1 to 2 weeks. After 1 and 2 weeks of daily dosing with dutasteride 0.5 mg, median serum DHT concentrations were reduced by 85% and 90%, respectively. In patients with BPH treated with dutasteride 0.5 ing/day for 1 year, the median decrease in serum DHT was 94%. The median increase in serum testosterone was 19% but remained within the physiologic range .
In BPH patients 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 5793 pg/g, respectively, p<0.001). Mean prostatic tissue concentrations of testosterone were significantly higher in the dutasteride group compared with placebo (2073 and 93 pg/g, respectively, p<0.00]).
Adult males with genetically inherited type 2 5a-reductase deficiency also have decreased DHT levels. These 5a-reductase deficient males have a small prostate gland throughout life and do not develop BPH. Except for the associated urogenital defects present at birth, no other clinical abnormalities related to 5a-reductase deficiency have been observed in these individuals.
Other Effects: Plasma lipid panel and bone mineral density were evaluated following 52 weeks of dutasteride 0.5 mg once daily in healthy volunteers. There was no change in bone mineral density as measured by dual energy x-ray absorptiometry ( DEXA ) compared with either placebo or baseline . In addition, the plasma lipid profile (i.e., total cholesterol , low density lipoproteins , high density lipoproteins, and triglycerides ) was unaffected by dutasteride. No clinically significant changes in adrenal hormone responses to ACTH stimulation were observed in a subset population (n = 13) of the one-year healthy volunteer study.
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. Absolute bioavailability in 5 healthy subjects is approximately 60% (range: 40% to 94%). When the drug is administered with food, the maximum serum concentrations were reduced by 10% to 15%. This reduction is of no clinical significance.
Pharmacokinetic data following single and repeat oral doses show that dutasteride has a large volume of distribution (300 to 500 L). Dutasteride is highly bound to plasma albumin (99.0%) and alpha-1 acid glycoprotein (96.6%).
In a trial of healthy subjects (n = 26) receiving dutasteride 0.5 mg/day for 12 months, semen dutasteride concentrations averaged 3.4 ng/mL (range: 0.4 to 14 ng/mL) at 12 months and, similar to serum, achieved steady-state concentrations at 6 months. On average, at 12 months 11.5% of serum dutasteride concentrations partitioned into semen.
Metabolism and Elimination
Dutasteride is extensively metabolized in humans. In vitro studies showed that dutasteride is metabolized by the CYP3A4 and CYP3A5 isoenzymes. Both of these isoenzymes produced the 4'-hydroxydutasteride, 6-hydroxydutasteride, and the 6,4'-dihydroxydutasteride metabolites. In addition, the 15-hydroxydutasteride metabolite was formed by CYP3A4. Dutasteride is not metabolized in vitro by human cytochrome P450 isoenzymes CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1. In human serum following dosing to steady state, unchanged dutasteride, 3 major metabolites (4'-hydroxydutasteride, 1,2-dihydrodutasteride, and 6-hydroxydutasteride), and 2 minor metabolites (6,4'-dihydroxydutasteride and 15-hydroxydutasteride), as assessed by mass spectrometric response, have been detected. The absolute stereochemistry of the hydroxyl additions in the 6 and 15 positions is not known. In vitro, the 4'-hydroxydutasteride and 1,2-dihydrodutasteride metabolites are much less potent than dutasteride against both isoforms of human 5 alpha-reductase. The activity of 6β-hydroxydutasteride is comparable to that of dutasteride.
Dutasteride and its metabolites were excreted mainly in feces. As a percent of dose, there was approximately 5% unchanged dutasteride (~1% to ~15%) and 40% as dutasteride-related metabolites (~2% to ~90%). Only trace amounts of unchanged dutasteride were found in urine ( < 1%). 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. The average steady-state serum dutasteride concentration was 40 ng/mL following 0.5 mg/day for 1 year. Following daily dosing, dutasteride serum concentrations achieve 65% of steady-state concentration after 1 month and approximately 90% after 3 months. 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.
Pediatric: Dutasteride pharmacokinetics have not been investigated in subjects younger than 18 years.
Geriatric: No dose adjustment is necessary in the elderly. The pharmacokinetics and pharmacodynamics of dutasteride were evaluated in 36 healthy male subjects aged between 24 and 87 years following administration of a single 5-mg dose of dutasteride. In this single-dose trial, dutasteride half-life increased with age (approximately 170 hours in men aged 20 to 49 years, approximately 260 hours in men aged 50 to 69 years, and approximately 300 hours in men older than 70 years). Of 2,167 men treated with dutasteride in the 3 pivotal trials, 60% were age 65 and over and 15% were age 75 and over. No overall differences in safety or efficacy were observed between these patients and younger patients.
Gender: AVODART is contraindicated in pregnancy and women of childbearing potential and is not indicated for use in other women [see CONTRAINDICATIONS, WARNINGS AND PRECAUTIONS]. The pharmacokinetics of dutasteride in women have not been studied.
Race: The effect of race on dutasteride pharmacokinetics has not been studied.
Renal Impairment: The effect of renal impairment on dutasteride pharmacokinetics has not been studied. However, less than 0.1% of a steady-state 0.5-mg dose of dutasteride is recovered in human urine, so no adjustment in dosage is anticipated for patients with renal impairment.
Hepatic Impairment: The effect of hepatic impairment on dutasteride pharmacokinetics has not been studied. Because dutasteride is extensively metabolized, exposure could be higher in hepatically impaired patients.
Animal Toxicology and/or Pharmacology
arcinogenesis, Mutagenesis, Impairment of Fertility
A 2-year carcinogenicity study was conducted in B6C3F1 mice at doses of 3, 35, 250, and 500 mg/kg/day for males and 3, 35, and 250 mg/kg/day for females; an increased incidence of benign hepatocellular adenomas was noted at 250 mg/kg/day (290-fold the MRHD of a 0.5-mg daily dose) in female mice only. Two of the 3 major human metabolites have been detected in mice. The exposure to these metabolites in mice is either lower than in humans or is not known.
In a 2-year carcinogenicity study in Han Wistar rats, at doses of 1.5, 7.5, and 53 mg/kg/day in males and 0.8, 6.3, and 15 mg/kg/day in females, there was an increase in Leydig cell adenomas in the testes at 135-fold the MRHD (53 mg/kg/day and greater). An increased incidence of Leydig cell hyperplasia was present at 52-fold the MRHD (male rat doses of 7.5 mg/kg/day and greater). A positive correlation between proliferative changes in the Leydig cells and an increase in circulating luteinizing hormone levels has been demonstrated with 5 alpha-reductase inhibitors and is consistent with an effect on the hypothalamic-pituitary-testicular axis following 5 alpha-reductase inhibition. At tumorigenic doses, luteinizing hormone levels in rats were increased by 167%. In this study, the major human metabolites were tested for carcinogenicity at approximately 1 to 3 times the expected clinical exposure.
Dutasteride was tested for genotoxicity in a bacterial mutagenesis assay (Ames test), a chromosomal aberration assay in CHO cells, and a micronucleus assay in rats. The results did not indicate any genotoxic potential of the parent drug. Two major human metabolites were also negative in either the Ames test or an abbreviated Ames test.
Impairment of Fertility
Treatment of sexually mature male rats with dutasteride at 0.1- to 110-fold the MRHD (animal doses of 0.05, 10, 50, and 500 mg/kg/day for up to 31 weeks) resulted in dose- and time-dependent decreases in fertility; reduced cauda epididymal (absolute) sperm counts but not sperm concentration (at 50 and 500 mg/kg/day); reduced weights of the epididymis, prostate, and seminal vesicles; and microscopic changes in the male reproductive organs. The fertility effects were reversed by recovery week 6 at all doses, and sperm counts were normal at the end of a 14-week recovery period. The 5 alpha-reductase–related changes consisted of cytoplasmic vacuolation of tubular epithelium in the epididymides and decreased cytoplasmic content of epithelium, consistent with decreased secretory activity in the prostate and seminal vesicles. The microscopic changes were no longer present at recovery week 14 in the low-dose group and were partly recovered in the remaining treatment groups. Low levels of dutasteride (0.6 to 17 ng/mL) were detected in the serum of untreated female rats mated to males dosed at 10, 50, or 500 mg/kg/day for 29 to 30 weeks.
In a fertility study in female rats, oral administration of dutasteride at doses of 0.05, 2.5, 12.5, and 30 mg/kg/day resulted in reduced litter size, increased embryo resorption, and feminization of male fetuses (decreased anogenital distance) at 2- to 10-fold the MRHD (animal doses of 2.5 mg/kg/day or greater). Fetal body weights were also reduced at less than 0.02-fold the MRHD in rats (0.5 mg/kg
Central Nervous System Toxicology Studies
In rats and dogs, repeated oral administration of dutasteride resulted in some animals showing signs of non-specific, reversible, centrally-mediated toxicity without associated histopathological changes at exposures 425- and 315-fold the expected clinical exposure (of parent drug), respectively.
INDICACIONES Y POSOLOGIA
Combination With Alpha Adrenergic Antagonist
AVODART in combination with the alpha adrenergic antagonist, tamsulosin, is indicated for the treatment of symptomatic BPH in men with an enlarged prostate.
The recommended dose of AVODART is 1 capsule (0.5 mg) taken once daily.
Combination With Alpha Adrenergic Antagonist
The recommended dose of AVODART is 1 capsule (0.5 mg) taken once daily and tamsulosin 0.4 mg taken once daily.
Pregnancy Category X. AVODART is contraindicated for use in women of childbearing potential and during pregnancy. AVODART is a 5 alpha-reductase inhibitor that prevents conversion of testosterone to dihydrotestosterone (DHT), a hormone necessary for normal development of male genitalia. In animal reproduction and developmental toxicity studies, dutasteride inhibited normal development of external genitalia in male fetuses. 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.
Abnormalities in the genitalia of male fetuses is an expected physiological consequence of inhibition of the conversion of testosterone to DHT by 5 alpha-reductase inhibitors. These results are similar to observations in male infants with genetic 5 alpha-reductase deficiency. Dutasteride is absorbed through the skin. To avoid potential fetal exposure, women who are pregnant or could become pregnant should not handle AVODART Soft Gelatin Capsules. If contact is made with leaking capsules, the contact area should be washed immediately with soap and water [see WARNINGS AND PRECAUTIONS]. Dutasteride is secreted into semen. The highest measured semen concentration of dutasteride in treated men was 14 ng/mL. Assuming exposure of a 50-kg woman to 5 mL of semen and 100% absorption, the woman's dutasteride concentration would be about 0.0175 ng/mL. This concentration is more than 100 times less than concentrations producing abnormalities of male genitalia in animal studies. 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 female rats, oral administration of dutasteride at doses 10 times less than the maximum recommended human dose (MRHD) of 0.5 mg daily resulted in abnormalities of male genitalia in the fetus (decreased anogenital distance at 0.05 mg/kg/day), nipple development, hypospadias, and distended preputial glands in male offspring (at all doses of 0.05, 2.5, 12.5, and 30 mg/kg/day). An increase in stillborn pups was observed at 111 times the MRHD, and reduced fetal body weight was observed at doses of about 15 times the MRHD (animal dose of 2.5 mg/kg/day). Increased incidences of skeletal variations considered to be delays in ossification associated with reduced body weight were observed at doses about 56 times the MRHD (animal dose of 12.5 mg/kg/day).
In a rabbit embryo-fetal study, doses 28- to 93-fold the MRHD (animal doses of 30, 100, and 200 mg/kg/day) were administered orally during the period of major organogenesis (gestation days 7 to 29) to encompass the late period of external genitalia development. Histological evaluation of the genital papilla of fetuses revealed evidence of feminization of the male fetus at all doses. A second embryo-fetal study in rabbits at 0.3- to 53-fold the expected clinical exposure (animal doses of 0.05, 0.4, 3.0, and 30 mg/kg/day) also produced evidence of feminization of the genitalia in male fetuses at all doses.
In an oral pre- and post-natal development study in rats, dutasteride doses of 0.05, 2.5, 12.5, or 30 mg/kg/day were administered. Unequivocal evidence of feminization of the genitalia (i.e., decreased anogenital distance, increased incidence of hypospadias, nipple development) of male offspring occurred at 14- to 90-fold the MRHD (animal doses of 2.5 mg/kg/day or greater). At 0.05-fold the expected clinical exposure (animal dose of 0.05 mg/kg/day), evidence of feminization was limited to a small, but statistically significant, decrease in anogenital distance. Animal doses of 2.5 to 30 mg/kg/day resulted in prolonged gestation in the parental females and a decrease in time to vaginal patency for female offspring and a decrease in prostate and seminal vesicle weights in male offspring. Effects on newborn startle response were noted at doses greater than or equal to 12.5 mg/kg/day. Increased stillbirths were noted at 30 mg/kg/day.
In an embryo-fetal development study, pregnant rhesus monkeys were exposed intravenously to a dutasteride blood level comparable to the dutasteride concentration found in human semen. Dutasteride was administered on gestation days 20 to 100 at doses of 400, 780, 1,325, or 2,010 ng/day (12 monkeys/group). The development of male external genitalia of monkey offspring was not adversely affected. Reduction of fetal adrenal weights, reduction in fetal prostate weights, and increases in fetal ovarian and testis weights were observed at the highest dose tested in monkeys. Based on the highest measured semen concentration of dutasteride in treated men (14 ng/mL), these doses represent 0.8 to 16 times the potential maximum exposure of a 50-kg human female to 5 mL semen daily from a dutasteride-treated man, assuming 100% absorption. (These calculations are based on blood levels of parent drug which are achieved at 32 to 186 times the daily doses administered to pregnant monkeys on a ng/kg basis). Dutasteride is highly bound to proteins in human semen (greater than 96%), potentially reducing the amount of dutasteride available for vaginal absorption. It is not known whether rabbits or rhesus monkeys produce any of the major human metabolites.
Estimates of exposure multiples comparing animal studies to the MRHD for dutasteride are based on clinical serum concentration at steady state.
AVODART is contraindicated for use in women of childbearing potential, includin
ytochrome 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].
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].
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].
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
ecause clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trial of another drug and may not reflect the rates observed in practice.
From clinical trials with AVODART as monotherapy or in combination with tamsulosin:
Over 4,300 male subjects with BPH were randomly assigned to receive placebo or 0.5-mg daily doses of AVODART in 3 identical 2-year, placebo-controlled, double-blind, Phase 3 treatment trials, each followed by a 2-year open-label extension. During the double-blind treatment period, 2,167 male subjects were exposed to AVODART, including 1,772 exposed for 1 year and 1,510 exposed for 2 years. When including the open-label extensions, 1,009 male subjects were exposed to AVODART for 3 years and 812 were exposed for 4 years. The population was aged 47 to 94 years (mean age: 66 years) and greater than 90% were Caucasian. Table 1 summarizes clinical adverse reactions reported in at least 1% of subjects receiving AVODART and at a higher incidence than subjects receiving placebo.
Table 1: Adverse Reactions Reported in ≥ 1% of Subjects Over a 24-Month Period and More Frequently in the Group Receiving AVODART Than the Placebo Group (Randomized, Double-Blind, Placebo-Controlled Trials Pooled) by Time of Onset
Long-Term Treatment (Up to 4 Years)
High-Grade Prostate Cancer: The REDUCE trial was a randomized, double-blind, placebo-controlled trial that enrolled 8,231 men aged 50 to 75 years with a serum PSA of 2.5 ng/mL to 10 ng/mL and a negative prostate biopsy within the previous 6 months. 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. The mean age was 63 years and 91% were Caucasian. Subjects underwent protocol-mandated scheduled prostate biopsies at 2 and 4 years of treatment or had “for-cause biopsies” at non-scheduled times if clinically indicated. There was a higher incidence of Gleason score 8-10 prostate cancer in men receiving AVODART (1.0%) compared with men on placebo (0.5%) [seeINDICATIONS AND USAGE, WARNINGS AND PRECAUTIONS]. In a 7-year placebo-controlled clinical trial with another 5 alpha-reductase inhibitor (finasteride 5 mg, PROSCAR), similar results for Gleason score 8-10 prostate cancer were observed (finasteride 1.8% versus placebo 1.1%).
No clinical benefit has been demonstrated in patients with prostate cancer treated with AVODART.
Reproductive and Breast Disorders
In the 3 pivotal placebo-controlled BPH trials with AVODART, each 4 years in duration, there was no evidence of increased sexual adverse reactions (impotence, decreased libido, and ejaculation disorder) or breast disorders with increased duration of treatment. Among these 3 trials, there was 1 case of breast cancer in the dutasteride group and 1 case in the placebo group. 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.
Combination With Alpha-Blocker Therapy (CombAT)
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. Overall, 1,623 subjects received monotherapy with AVODART; 1,611 subjects received monotherapy with tamsulosin; and 1,610 subjects received combination therapy. The population was aged 49 to 88 years (mean age: 66 years) and 88% were Caucasian. Table 2 summarizes adverse reactions reported in at least 1% of subjects in the combination group and at a higher incidence than subjects receiving monotherapy with AVODART or tamsulosin.
Table 2: Adverse Reactions Reported Over a 48-Month Period in ≥ 1% of Subjects and More Frequently in the Coadministration Therapy Group Than the Groups Receiving Monotherapy With AVODART or Tamsulosin (CombAT) by Time of Onset
Cardiac Failure: In CombAT, after 4 years of treatment, the incidence of the composite term cardiac failure in the combination therapy group (12/1,610; 0.7%) was higher than in either monotherapy group: AVODART, 2/1,623 (0.1%) and tamsulosin, 9/1,611 (0.6%). Composite cardiac failure was also examined in a separate 4-year placebo-controlled trial evaluating AVODART in men at risk for development of prostate cancer. The incidence of cardiac failure in subjects taking AVODART was 0.6% (26/4,105) compared with 0.4% (15/4,126) in subjects on placebo. A majority of subjects with cardiac failure in both trials had comorbidities associated with an increased risk of cardiac failure. Therefore, the clinical significance of the numerical imbalances in cardiac failure is unknown. No causal relationship between AVODART alone or in combination with tamsulosin and cardiac failure has been established. No imbalance was observed in the incidence of overall cardiovascular adverse events in either trial.
The following adverse reactions have been identified during post-approval use of AVODART. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These reactions have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to AVODART.
Neoplasms: Male breast cancer.
Psychiatric Disorders: Depressed mood.
Reproductive System and Breast Disorders: Testicular pain and testicular swelling.
Read the Avodart (dutasteride) Side Effects Center for a complete guide to possible side effects »
Monografía creada el 18 de noviembre de 2009. Equipo de Redacción de IQB