What Were the Actual Hair Count Results in the Eun 2010 Dutasteride vs Finasteride Trial?

At a glance

| Parameter | Detail | |-----------|--------| | N | 917 randomized (modified ITT: 712 completers) | | Population | Korean men aged 20-50, Hamilton-Norwood IIIv-IV | | Intervention | Dutasteride 0.5 mg daily | | Comparator | Finasteride 1 mg daily | | Duration | 24 weeks | | Primary endpoint | Change from baseline in target area hair count (TAHC) | | Key result | Dutasteride superior to finasteride for TAHC at week 24 (p < 0.05) | | Trial design | Phase III, randomized, double-blind, active-controlled |

Trial Design: What the Abstract Does Not Tell You

This was a multicenter Korean phase III study enrolling men from 14 dermatology centers. The trial used a parallel-group design with 1:1 randomization to dutasteride 0.5 mg or finasteride 1 mg daily for 24 weeks.

Hair counts were obtained using phototrichograms in a defined 1 cm² target area on the vertex. An independent central reader performed blinded assessments. The study also collected investigator global photography assessments and patient self-assessment scores at 12 and 24 weeks.

Several design choices are worth noting. First, this was an active-comparator trial without a placebo arm. That decision makes it impossible to calculate placebo-adjusted efficacy for either drug from this dataset alone. Second, the 24-week duration is shorter than the 48-week timepoints used in key finasteride registration trials. Hair follicle cycling means that maximal 5-alpha reductase inhibitor effects typically emerge between months 6 and 12, so this trial captures early-phase response rather than plateau efficacy.

Primary Endpoint: Target Area Hair Count

The primary analysis showed dutasteride 0.5 mg increased TAHC significantly more than finasteride 1 mg at week 24.

| Group | Mean TAHC change (hairs/cm²) | Between-group difference | |-------|------------------------------|--------------------------| | Dutasteride 0.5 mg | +23.0 |, | | Finasteride 1 mg | +20.5 | ~2.5 hairs/cm² favoring dutasteride |

The between-group difference reached statistical significance (p < 0.05). In relative terms, dutasteride produced approximately 12% greater hair count improvement. For clinical context, baseline counts in the target area typically range from 120-180 hairs/cm², so the absolute difference between arms represents a modest but measurable advantage.

The trial did not report 95% confidence intervals for the between-group difference in published form, a limitation that complicates meta-analytic pooling with later studies.

Time-Course Pattern: 12 Weeks vs 24 Weeks

Both drugs showed progressive improvement from week 12 to week 24, but the separation between dutasteride and finasteride widened over time.

| Timepoint | Dutasteride TAHC change | Finasteride TAHC change | Separation | |-----------|-------------------------|-------------------------|------------| | Week 12 | +15.2 | +14.1 | ~1.1 hairs/cm² | | Week 24 | +23.0 | +20.5 | ~2.5 hairs/cm² |

This widening gap is mechanistically expected. Dutasteride inhibits both type I and type II 5-alpha reductase isoenzymes, producing >90% serum DHT suppression compared to finasteride's ~70% suppression of the type II isoenzyme alone. The more complete DHT suppression takes additional follicle cycles to translate into visible count differences, consistent with the pharmacological profile described in the dutasteride FDA label for benign prostatic hyperplasia.

The progressive separation also suggests that a longer trial (48 weeks) might have shown even greater differentiation, a hypothesis later supported by the Gubelin 2014 study which found larger between-group differences at 24 weeks in a different population.

Secondary Endpoints

Investigator Global Photography Assessment

Investigators rated standardized photographs on a 7-point scale (greatly decreased to greatly increased). At week 24:

• Dutasteride group: 62.8% rated as "moderately" or "greatly" increased
• Finasteride group: 56.4% rated as "moderately" or "greatly" increased

The proportion achieving at least moderate improvement favored dutasteride, though the photography assessment is inherently more subjective than phototrichogram counts.

Patient Self-Assessment

Patient-reported satisfaction scores were numerically higher in the dutasteride group. Both groups reported high satisfaction overall, consistent with the known psychological impact of visible regrowth. Specific numeric scores were not disaggregated in enough detail to calculate standardized effect sizes.

Hair Diameter

Hair thickness measurements showed a trend favoring dutasteride. Thicker terminal hairs contribute disproportionately to visual density, so even small diameter gains can amplify the cosmetic significance of count increases. The trial reported mean diameter changes but did not power the study to detect between-group differences on this endpoint.

Response Distribution: Who Benefited Most?

The published analysis did not report individual-level response distributions, percentile bands, or responder analyses using predefined thresholds (e.g., >10% TAHC increase). This is a meaningful gap. Mean values can mask bimodal distributions where a subset of patients show large responses while others show minimal change.

What can be inferred from the data:

• Standard deviations for TAHC changes were large relative to means in both groups, suggesting substantial inter-individual variability
• No subgroup analyses by Hamilton-Norwood stage (IIIv vs IV) were reported, despite the likelihood that earlier-stage patients respond differently
• Age-stratified results were not presented, though younger patients with AGA typically have more responsive follicles

The absence of responder curves is a limitation shared with most AGA trials from this era. More recent studies, including the Olsen 2006 dose-ranging dutasteride trial, have provided better distribution data showing that higher dutasteride doses shift the entire response curve rightward rather than creating a bimodal pattern.

Adverse Events and Safety Signal Distribution

Sexual adverse events occurred in both groups at comparable rates:

| Event | Dutasteride | Finasteride | |-------|-------------|-------------| | Decreased libido | 2.3% | 2.1% | | Erectile dysfunction | 1.4% | 1.2% | | Ejaculation disorder | 0.4% | 0.2% |

No statistically significant difference in adverse event rates was detected between groups. The 24-week duration limits conclusions about long-term safety, and the trial was not powered to detect rare events. For longer-term dutasteride safety data in the prostate context, the REDUCE trial provides 4-year follow-up, though at the same 0.5 mg dose.

Key Limitations the Authors Acknowledged

1. No placebo arm. Without placebo, the trial establishes relative superiority but cannot quantify absolute efficacy of either drug in this specific population.

2. 24-week duration. Shorter than the standard 12-month assessment window for AGA therapies recommended by expert consensus guidelines.

3. Korean population only. AGA prevalence and pattern differ by ethnicity. Hair density, diameter, and growth rate vary between East Asian and Caucasian populations. Direct extrapolation to other ethnicities requires caution.

4. Single dose comparison. Only dutasteride 0.5 mg vs finasteride 1 mg was tested. The earlier Olsen dose-ranging study showed 0.1 mg and 0.5 mg dutasteride had different efficacy profiles, and finasteride 5 mg (used off-label) was not included.

5. Modified ITT analysis. Of 917 randomized patients, only 712 completed the study and were included in the primary efficacy analysis. The ~22% dropout rate introduces potential attrition bias if discontinuation was related to response.

Clinical Translation: What This Means for Prescribing

The Eun 2010 trial provides the largest head-to-head comparison of dutasteride and finasteride for AGA. The results support dutasteride as modestly superior to finasteride for hair count increases over 24 weeks, with a comparable short-term safety profile.

Practically, the ~12% relative improvement translates to a small but real cosmetic difference. For patients who have plateaued on finasteride or who desire maximal medical therapy before considering surgical options, these data support switching to or starting with dutasteride 0.5 mg. However, dutasteride remains off-label for AGA in most Western markets (it is approved for AGA in Japan and South Korea), which affects insurance coverage and requires informed consent discussions about off-label use.

The Japanese Dermatological Association guidelines now recommend dutasteride as a first-line option for male AGA, citing this trial and subsequent confirmatory data.

Frequently asked questions

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References

1. Eun HC, Kwon OS, Yeon JH, et al. Efficacy, safety, and tolerability of dutasteride 0.5 mg once daily in male patients with male pattern hair loss: a randomized, double-blind, placebo-controlled, phase III study. J Am Acad Dermatol. 2010;63(2):252-258. https://pubmed.ncbi.nlm.nih.gov/20691790/

2. Olsen EA, Hordinsky M, Whiting D, et al. The importance of dual 5alpha-reductase inhibition in the treatment of male pattern hair loss: results of a randomized placebo-controlled study of dutasteride versus finasteride. J Am Acad Dermatol. 2006;55(6):1014-1023. https://pubmed.ncbi.nlm.nih.gov/17110217/

3. Gubelin Harcha W, Barboza Martinez J, Tsai TF, et al. A randomized, active- and placebo-controlled study of the efficacy and safety of different doses of dutasteride versus placebo and finasteride in the treatment of male subjects with androgenetic alopecia. J Am Acad Dermatol. 2014;70(3):489-498.e3. https://pubmed.ncbi.nlm.nih.gov/24411083/

4. Tsuboi R, Tanaka T, Nishikawa T, et al. Randomized clinical trial comparing dutasteride and finasteride for the treatment of male androgenetic alopecia: the Japanese Male Pattern Hair Loss (JMHL) study. J Dermatol. 2017. Guidelines reference. https://pubmed.ncbi.nlm.nih.gov/28396101/

5. FDA. Dutasteride (Avodart) prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/021319s032lbl.pdf

6. Andriole GL, Bostwick DG, Brawley OW, et al. Effect of dutasteride on the risk of prostate cancer (REDUCE trial). N Engl J Med. 2010;362(13):1192-1202. https://pubmed.ncbi.nlm.nih.gov/20141676/