Generic Name: dutasteride
Dosage Form: capsule, liquid filled
FULL PRESCRIBING INFORMATION
Indications and Usage for Avodart
Monotherapy
Avodart® (dutasteride) Soft Gelatin Capsules are indicated for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate to:
- improve symptoms,
- reduce the risk of acute urinary retention (AUR), and
- reduce the risk of the need for BPH-related surgery.
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.
1.3 Limitations of Use
Avodart is not approved for the prevention of prostate cancer.
Avodart Dosage and Administration
The capsules should be swallowed whole and not chewed or opened, as contact with the capsule contents may result in irritation of the oropharyngeal mucosa. Avodart may be administered with or without food.
Monotherapy
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.
Dosage Forms and Strengths
0.5-mg, opaque, dull yellow, gelatin capsules imprinted with “GX CE2” in red ink on one side.
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 (5.4), Use in Specific Populations (8.1)].
- Women of childbearing potential [see Warnings and Precautions (5.4), Use in Specific Populations (8.1)].
- Pediatric patients [see Use in Specific Populations (8.4)].
- Patients with previously demonstrated, clinically significant hypersensitivity (e.g., serious skin reactions, angioedema) to Avodart or other 5 alpha-reductase inhibitors [see Adverse Reactions (6.2)].
Warnings and Precautions
5.1 Effects on Prostate-Specific Antigen (PSA) and the Use of PSA in Prostate Cancer Detection
In clinical studies, Avodart reduced serum PSA concentration by approximately 50% within 3 to 6 months of treatment. This decrease was predictable over the entire range of PSA values in patients with symptomatic BPH, although it may vary in individuals. Avodart may also cause decreases in serum PSA in the presence of prostate cancer. To interpret serial PSAs in men taking Avodart, a new PSA baseline should be established at least 3 months after starting treatment and PSA monitored periodically thereafter. Any confirmed increase from the lowest PSA value while on Avodart may signal the presence of prostate cancer and should be evaluated, even if PSA levels are still within the normal range for men not taking a 5 alpha-reductase inhibitor. Noncompliance with Avodart may also affect PSA test results.
To interpret an isolated PSA value in a man treated with Avodart for 3 months or more, the PSA value should be doubled for comparison with normal values in untreated men.
The free-to-total PSA ratio (percent free PSA) remains constant, even under the influence of Avodart. If clinicians elect to use percent free PSA as an aid in the detection of prostate cancer in men receiving Avodart, no adjustment to its value appears necessary.
Coadministration of dutasteride and tamsulosin resulted in similar changes to serum PSA as dutasteride monotherapy.
5.2 Increased Risk of High-grade Prostate Cancer
In men aged 50 to 75 years with a prior negative biopsy for prostate cancer and a baseline PSA between 2.5 ng/mL and 10.0 ng/mL taking Avodart in the 4-year Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial, there was an increased incidence of Gleason score 8-10 prostate cancer compared with men taking placebo (Avodart 1.0% versus placebo 0.5%) [see Indications and Usage (1.3), Adverse Reactions (6.1)]. 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%).
5 alpha-reductase inhibitors may increase the risk of development of high-grade prostate cancer. Whether the effect of 5 alpha-reductase inhibitors to reduce prostate volume, or study-related factors, impacted the results of these studies has not been established.
Evaluation for Other Urological Diseases
Lower urinary tract symptoms of BPH can be indicative of other urological diseases, including prostate cancer. Patients should be assessed to rule out prostate cancer and other urological diseases prior to treatment with Avodart and periodically thereafter.
Exposure of Women—Risk to Male Fetus
Avodart Capsules should not be handled by a woman who is pregnant or who could become pregnant. Dutasteride is absorbed through the skin and could result in unintended fetal exposure. If a woman who is pregnant or who could become pregnant comes in contact with leaking dutasteride capsules, the contact area should be washed immediately with soap and water [see Use in Specific Populations (8.1)].
Blood Donation
Men being treated with Avodart should not donate blood until at least 6 months have passed following their last dose. The purpose of this deferred period is to prevent administration of dutasteride to a pregnant female transfusion recipient.
Effect on Semen Characteristics
The effects of dutasteride 0.5 mg/day on semen characteristics were evaluated in normal volunteers aged 18 to 52 (n = 27 dutasteride, n = 23 placebo) throughout 52 weeks of treatment and 24 weeks of post-treatment follow-up. At 52 weeks, the mean percent reductions from baseline in total sperm count, semen volume, and sperm motility were 23%, 26%, and 18%, respectively, in the dutasteride group when adjusted for changes from baseline in the placebo group. Sperm concentration and sperm morphology were unaffected. After 24 weeks of follow-up, the mean percent change in total sperm count in the dutasteride group remained 23% lower than baseline. While mean values for all semen parameters at all time-points remained within the normal ranges and did not meet predefined criteria for a clinically significant change (30%), 2 subjects in the dutasteride group had decreases in sperm count of greater than 90% from baseline at 52 weeks, with partial recovery at the 24-week follow-up. The clinical significance of dutasteride’s effect on semen characteristics for an individual patient’s fertility is not known.
Adverse Reactions
Clinical Trials Experience
Because 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:
- The most common adverse reactions reported in subjects receiving Avodart were impotence, decreased libido, breast disorders (including breast enlargement and tenderness), and ejaculation disorders. The most common adverse reactions reported in subjects receiving combination therapy (Avodart plus tamsulosin) were impotence, decreased libido, breast disorders (including breast enlargement and tenderness), ejaculation disorders, and dizziness. Ejaculation disorders occurred significantly more in subjects receiving combination therapy (11%) compared with those receiving Avodart (2%) or tamsulosin (4%) as monotherapy.
- Study withdrawal due to adverse reactions occurred in 4% of subjects receiving Avodart, and 3% of subjects receiving placebo in placebo-controlled trials with Avodart. The most common adverse reaction leading to study withdrawal was impotence (1%).
- In the clinical trial evaluating the combination therapy, study withdrawal due to adverse reactions occurred in 6% of subjects receiving combination therapy (Avodart plus tamsulosin) and 4% of subjects receiving Avodart or tamsulosin as monotherapy. The most common adverse reaction in all treatment arms leading to study withdrawal was erectile dysfunction (1% to 1.5%).
Monotherapy: Over 4,300 male subjects with BPH were randomly assigned to receive placebo or 0.5-mg daily doses of Avodart in three identical 2-year, placebo-controlled, double-blind, Phase 3 treatment studies, 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.
| a Includes breast tenderness and breast enlargement. | ||||
| Adverse Reaction | Adverse Reaction Time of Onset | |||
| Months 0-6 | Months 7-12 | Months 13-18 | Months 19-24 | |
| Avodart (n) | (n = 2,167) | (n = 1,901) | (n = 1,725) | (n = 1,605) |
| Placebo (n) | (n = 2,158) | (n = 1,922) | (n = 1,714) | (n = 1,555) |
| Impotence | ||||
| Avodart | 4.7% | 1.4% | 1.0% | 0.8% |
| Placebo | 1.7% | 1.5% | 0.5% | 0.9% |
| Decreased libido | ||||
| Avodart | 3.0% | 0.7% | 0.3% | 0.3% |
| Placebo | 1.4% | 0.6% | 0.2% | 0.1% |
| Ejaculation disorders | ||||
| Avodart | 1.4% | 0.5% | 0.5% | 0.1% |
| Placebo | 0.5% | 0.3% | 0.1% | 0.0% |
| Breast disordersa | ||||
| Avodart | 0.5% | 0.8% | 1.1% | 0.6% |
| Placebo | 0.2% | 0.3% | 0.3% | 0.1% |
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%) [see Indications and Usage (1.3), Warnings and Precautions (5.2)]. 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 study. 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.
| Adverse Reaction | Adverse Reaction Time of Onset | ||||
| Year 1 | Year 2 | Year 3 | Year 4 | ||
| Months 0-6 | Months 7-12 | ||||
| Combinationa | (n = 1,610) | (n = 1,527) | (n = 1,428) | (n = 1,283) | (n = 1,200) |
| Avodart | (n = 1,623) | (n = 1,548) | (n = 1,464) | (n = 1,325) | (n = 1,200) |
| Tamsulosin | (n = 1,611) | (n = 1,545) | (n = 1,468) | (n = 1,281) | (n = 1,112) |
| Ejaculation disordersb | |||||
| Combination | 7.8% | 1.6% | 1.0% | 0.5% | <0.1% |
| Avodart | 1.0% | 0.5% | 0.5% | 0.2% | 0.3% |
| Tamsulosin | 2.2% | 0.5% | 0.5% | 0.2% | 0.3% |
| Impotencec | |||||
| Combination | 5.4% | 1.1% | 1.8% | 0.9% | 0.4% |
| Avodart | 4.0% | 1.1% | 1.6% | 0.6% | 0.3% |
| Tamsulosin | 2.6% | 0.8% | 1.0% | 0.6% | 1.1% |
| Decreased libidod | |||||
| Combination | 4.5% | 0.9% | 0.8% | 0.2% | 0.0% |
| Avodart | 3.1% | 0.7% | 1.0% | 0.2% | 0.0% |
| Tamsulosin | 2.0% | 0.6% | 0.7% | 0.2% | <0.1% |
| Breast disorderse | |||||
| Combination | 1.1% | 1.1% | 0.8% | 0.9% | 0.6% |
| Avodart | 0.9% | 0.9% | 1.2% | 0.5% | 0.7% |
| Tamsulosin | 0.4% | 0.4% | 0.4% | 0.2% | 0.0% |
| Dizziness | |||||
| Combination | 1.1% | 0.4% | 0.1% | <0.1% | 0.2% |
| Avodart | 0.5% | 0.3% | 0.1% | <0.1% | <0.1% |
| Tamsulosin | 0.9% | 0.5% | 0.4% | <0.1% | 0.0% |
a Combination = Avodart 0.5 mg once daily plus tamsulosin 0.4 mg once daily.
b Includes anorgasmia, retrograde ejaculation, semen volume decreased, orgasmic sensation decreased, orgasm abnormal, ejaculation delayed, ejaculation disorder, ejaculation failure, and premature ejaculation.
c Includes erectile dysfunction and disturbance in sexual arousal.
d Includes libido decreased, libido disorder, loss of libido, sexual dysfunction, and male sexual dysfunction.
e Includes breast enlargement, gynecomastia, breast swelling, breast pain, breast tenderness, nipple pain, and nipple swelling.
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 studies had co-morbidities 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 study.
Postmarketing Experience
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.
Immune System Disorders: Hypersensitivity reactions, including rash, pruritus, urticaria, localized edema, serious skin reactions, and angioedema.
Neoplasms: Male breast cancer.
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 (12.3)].
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 (12.3)].
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 (12.3)].
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 (12.3)].
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 (12.3)].
USE IN SPECIFIC POPULATIONS
Pregnancy
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 (5.4)]. 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.
Nursing Mothers
Avodart is contraindicated for use in women of childbearing potential, including nursing women. It is not known whether dutasteride is excreted in human milk.
Pediatric Use
Avodart is contraindicated for use in pediatric patients. Safety and effectiveness in pediatric patients have not been established.
Geriatric Use
Of 2,167 male subjects treated with Avodart in 3 clinical studies, 60% were aged 65 years and older and 15% were aged 75 years and older. No overall differences in safety or efficacy were observed between these subjects and younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out [see Clinical Pharmacology (12.3)].
Renal Impairment
No dose adjustment is necessary for Avodart in patients with renal impairment [see Clinical Pharmacology (12.3)].
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. However, in a clinical study where 60 subjects received 5 mg (10 times the therapeutic dose) daily for 24 weeks, no additional adverse events were observed compared with those observed at the therapeutic dose of 0.5 mg [see Clinical Pharmacology (12.3)].
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.
Avodart Description
Avodart is a synthetic 4-azasteroid compound that is a selective inhibitor of both the type 1 and type 2 isoforms of steroid 5 alpha-reductase, an intracellular enzyme that converts testosterone to DHT.
Dutasteride is chemically designated as (5α,17β)-N-{2,5 bis(trifluoromethyl)phenyl}-3-oxo-4-azaandrost-1-ene-17-carboxamide. The empirical formula of dutasteride is C27H30F6N2O2, representing a molecular weight of 528.5 with the following structural formula:
Dutasteride is a white to pale yellow powder with a melting point of 242° to 250°C. It is soluble in ethanol (44 mg/mL), methanol (64 mg/mL), and polyethylene glycol 400 (3 mg/mL), but it is insoluble in water.
Each Avodart Soft Gelatin Capsule, administered orally, contains 0.5 mg of dutasteride dissolved in a mixture of mono-di-glycerides of caprylic/capric acid and butylated hydroxytoluene. The inactive excipients in the capsule shell are ferric oxide (yellow), gelatin (from certified BSE-free bovine sources), glycerin, and titanium dioxide. The soft gelatin capsules are printed with edible red ink.
Avodart - Clinical Pharmacology
Mechanism of Action
Dutasteride inhibits the conversion of testosterone to 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 5 alpha-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 5 alpha-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.
Pharmacodynamics
Effect on 5 Alpha-Dihydrotestosterone 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 mg/day for 4 years, the median decrease in serum DHT was 94% at 1 year, 93% at 2 years, and 95% at both 3 and 4 years. 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). Mean prostatic tissue concentrations of testosterone were significantly higher in the dutasteride group compared with placebo (2,073 and 93 pg/g, respectively, P<0.001).
Adult males with genetically inherited type 2 5 alpha-reductase deficiency also have decreased DHT levels. These 5 alpha-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 5 alpha-reductase deficiency have been observed in these individuals.
Effects on Other Hormones: In healthy volunteers, 52 weeks of treatment with dutasteride 0.5 mg/day (n = 26) resulted in no clinically significant change compared with placebo (n = 23) in sex hormone-binding globulin, estradiol, luteinizing hormone, follicle-stimulating hormone, thyroxine (free T4), and dehydroepiandrosterone. Statistically significant, baseline-adjusted mean increases compared with placebo were observed for total testosterone at 8 weeks (97.1 ng/dL, P<0.003) and thyroid-stimulating hormone at 52 wee
No comments:
Post a Comment