| Pharmacotherapeutic group: testosterone-5-alpha-reductase inhibitors.ATC code: G04C B02.Dutasteride reduces circulating levels of dihydrotestosterone (DHT) by inhibiting both type 1 and type 2, 5α-reductase isoenzymes which are responsible for the conversion of testosterone to DHT. AVODART AS MONOTHERAPY Effects on DHT/Testosterone: Effect of daily doses of Avodart on the reduction on DHT is dose dependant and is observed within 1-2 weeks (85% and 90% reduction, respectively). In patients with BPH treated with dutasteride 0.5 mg/day, the median decrease in serum DHT was 94% at 1 year and 93% at 2 years and the median increase in serum testosterone was 19% at both 1 and 2 years. Effect on Prostate Volume: Significant reductions in prostate volume have been detected as early as one month after initiation of treatment and reductions continued through Month 24 (p<0.001). Avodart led to a mean reduction of total prostate volume of 23.6% (from 54.9 ml at baseline to 42.1 ml) at Month 12 compared with a mean reduction of 0.5% (from 54.0 ml to 53.7 ml) in the placebo group. Significant (p<0.001) reductions also occurred in prostate transitional zone volume as early as one month continuing through Month 24, with a mean reduction in prostate transitional zone volume of 17.8% (from 26.8 ml at baseline to 21.4 ml) in the Avodart group compared to a mean increase of 7.9% (from 26.8ml to 27.5 ml) in the placebo group at Month 12. The reduction of the prostate volume seen during the first 2 years of double-blind treatment was maintained during an additional 2 years of open-label extension studies. Reduction of the size of the prostate leads to improvement of symptoms and a decreased risk for AUR and BPH-related surgery.CLINICAL STUDIES Avodart 0.5 mg/day or placebo was evaluated in 4325 male subjects with moderate to severe symptoms of BPH who had prostates 30 ml and a PSA value within the range 1.5 - 10 ng/mL in three primary efficacy 2-year multicenter, multinational, placebo-controlled, double-blind studies. The studies then continued with an open-label extension to 4 years with all patients remaining in the study receiving dutasteride at the same 0.5mg dose. 37% of initially placebo-randomized patients and 40% of dutasteride-randomized patients remained in the study at 4 years. The majority (71%) of the 2,340 subjects in the open-label extensions completed the 2 additional years of open-label treatment. The most important clinical efficacy parameters were American Urological Association Symptom Index (AUA-SI), maximum urinary flow (Qmax) and the incidence of acute urinary retention and BPH-related surgery.AUA-SI is a seven-item questionnaire about BPH-related symptoms with a maximum score of 35. At baseline the average score was approx. 17. After six months, one and two years treatment the placebo group had an average improvement of 2.5, 2.5 and 2.3 points respectively while the Avodart group improved 3.2, 3.8 and 4.5 points respectively. The differences between the groups were statistically significant. The improvement in AUA-SI seen during the first 2 years of double-blind treatment was maintained during an additional 2 years of open-label extension studies.Qmax (maximum urine flow):Mean baseline Qmax for the studies was approx 10 ml/sec (normal Qmax 15 ml/sec). After one and two years treatment the flow in the placebo group had improved by 0.8 and 0.9 ml/sec respectively and 1.7 and 2.0 ml/sec respectively in the Avodart group. The difference between the groups was statistically significant from Month 1 to Month 24. The increase in maximum urinary flow rate seen during the first 2 years of double blind treatment continued throughout an additional 2 years of open-label extension studies.Acute Urinary Retention and Surgical Intervention After two years of treatment, the incidence of AUR was 4.2% in the placebo group against 1.8% in the Avodart group (57% risk reduction). This difference is statistically significant and means that 42 patients (95% CI 30-73) need to be treated for two years to avoid one case of AUR.The incidence of BPH-related surgery after two years was 4.1% in the placebo group and 2.2% in the Avodart group (48% risk reduction). This difference is statistically significant and means that 51 patients (95% CI 33-109) need to be treated for two years to avoid one surgical intervention.Hair distribution The effect of dutasteride on hair distribution was not formally studied during the phase III programme, however, 5 alpha-reductase inhibitors could reduce hair loss and may induce hair growth in subjects with male pattern hair loss (male androgenetic alopecia).Thyroid function: Thyroid function was evaluated in a one year study in healthy men. Free thyroxine levels were stable on dutasteride treatment but TSH levels were mildly increased (by 0.4 MCIU/mL) compared to placebo at the end of one year's treatment. However, as TSH levels were variable, median TSH ranges (1.4 - 1.9 MCIU/mL ) remained within normal limits (0.5 - 5/6 MCIU/mL), free thyroxine levels were stable within the normal range and similar for both placebo and dutasteride treatment, the changes in TSH were not considered clinically significant. In all the clinical studies, there has been no evidence that dutasteride adversely affects thyroid function. Breast neoplasia: In the 2 year clinical trials, providing 3374 patient years of exposure to dutasteride, and at the time of registration in the 2 year open label extension, there were 2 cases of breast cancer reported in dutasteride-treated patients and 1 case in a patient who received placebo.However, the relationship between breast cancer and dutasteride is not clear.Effects on male fertility The effects of dutasteride 0.5mg/day on semen characteristics were evaluated in healthy 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 reduction 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 parameters at all time points remained within the normal ranges and did not meet the predefined criteria for a clinically significant change (30%), two 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 possibility of reduced male fertility cannot be excluded.AVODART IN COMBINATION WITH THE ALPHA-BLOCKER TAMSULOSINAvodart 0.5 mg/day (n = 1,623), tamsulosin 0.4 mg/day (n = 1,611) or the combination of Avodart 0.5 mg plus tamsulosin 0.4 mg (n = 1,610) were evaluated in male subjects with moderate to severe symptoms of BPH who had prostates 30 ml and a PSA value within the range 1.5 - 10 ng/mL in a multicentre, multinational, randomized double-blind, parallel group study. Approximately 53% of subjects had previous exposure to 5-alpha reductase inhibitor or alpha-blocker treatment. The primary efficacy endpoint during the first 2 years of treatment was change in International Prostate Symptom Score (IPSS), an 8-item instrument based on AUA-SI with an additional question on quality of life. Secondary efficacy endpoints at 2 years included maximum urine flow rate (Qmax) and prostate volume. The primary efficacy endpoint at 4 years of treatment was time to first event of AUR or BPH-related surgery. After 4 years of treatment, combination therapy statistically significantly reduced the risk of AUR or BPH-related surgery (65.8% reduction in risk p<0.001 [95% CI 54.7% to 74.1%]) compared to tamsulosin monotherapy. The incidence of AUR or BPH-related surgery by Year 4 was 4.2% for combination therapy and 11.9% for tamsulosin (p<0.001). Compared to Avodart monotherapy, combination therapy reduced the risk of AUR or BPH-related surgery by 19.6% (p=0.18 [95% CI -10.9% to 41.7%]). The incidence of AUR or BPH-related surgery by Year 4 was 4.2% for combination therapy and 5.2% for Avodart. Secondary efficacy endpoints after 4 years of treatment included time to clinical progression (defined as a composite of: IPSS deterioration by 4 points, BPH-related events of AUR, incontinence, urinary tract infection (UTI), and renal insufficiency) change in International Prostate Symptom Score (IPSS), maximum urine flow rate (Qmax) and prostate volume. IPSS is an 8-item instrument based on the AUA-SI with an additional question on quality of life. Results following 4 years of treatment are presented below: |
Parameter | Time-point | Combination | Avodart | Tamsulosin | AUR or BPH related surgery (%) | Incidence at Month 48 | 4.2 | 5.2 | 11.9a | Clinical progression* (%) | Month 48 | 12.6 | 17.8b | 21.5a | IPSS (units) | [Baseline] Month 48 (Change from Baseline) | [16.6] -6.3 | [16.4] -5.3b | [16.4] -3.8a | Qmax (mL/sec) | [Baseline] Month 48 (Change from Baseline) | [10.9] 2.4 | [10.6] 2.0 | [10.7] 0.7a | Prostate Volume (ml) | [Baseline] Month 48 (% Change from Baseline) | [54.7] -27.3 | [54.6] -28.0 | [55.8] +4.6a | Prostate Transition Zone Volume (ml)# | [Baseline] Month 48 (% Change from Baseline) | [27.7] -17.9 | [30.3] -26.5 | [30.5] 18.2a | BPH Impact Index (BII) (units) | [Baseline] Month 48 (Change from Baseline) | [5.3] -2.2 | [5.3] -1.8b | [5.3] -1.2a | IPSS Question 8 (BPH-related Health Status) (units) | [Baseline] Month 48 (Change from Baseline) | [3.6] -1.5 | [3.6] -1.3b | [3.6] -1.1a | Baseline values are mean values and changes from baseline are adjusted mean changes.* Clinical progression was defined as a composite of: IPSS deterioration by 4 points, BPH-related events of AUR, incontinence, UTI, and renal insufficiency.# Measured at selected sites (13% of randomized patients)a. Combination achieved significance (p<0.001) vs. tamsulosin at Month 48b. Combination achieved significance (p<0.001) vs. Avodart at Month 48Cardiac failure: In this 4 year BPH study the incidence of the composite term cardiac failure in the combination group (14/1610, 0.9%) was higher than in either monotherapy group: Avodart, (4/1623, 0.2%) and tamsulosin, (10/1611, 0.6%) (see section 4.4). | |