Which Has Less Effect on Erection: Proscar or Avodart?
Based on the available evidence, finasteride (Proscar) and dutasteride (Avodart) have essentially equivalent effects on erectile function, with no clinically meaningful difference between the two medications. 1, 2, 3
Direct Comparative Evidence
The most relevant head-to-head comparison comes from the EPICS trial, which directly compared dutasteride 0.5 mg versus finasteride 5 mg in men with BPH over 12 months. 2 This study found:
- Both medications produced similar percentages of adverse events, including sexual side effects 2
- No clinically significant difference existed between the adverse event profiles of the two drugs 3
- The safety profiles were comparable throughout the study period 2
Magnitude of Erectile Dysfunction Risk
Both medications carry similar risks for erectile dysfunction:
- Erectile dysfunction occurs in approximately 2-4% more patients compared to placebo with either medication 4, 5
- In longer-term studies (7 years), finasteride showed 67.4% cumulative ED versus 61.5% with placebo (relative risk 1.10), though this includes high baseline dysfunction in older populations 1, 4
- Mid-term studies (1-2 years) show ED rates ranging from 4.2% to 15.8% depending on the population studied 5
Mechanism and Clinical Context
The theoretical difference in mechanism does not translate to clinical differences:
- Dutasteride inhibits both Type 1 and Type 2 5-alpha-reductase enzymes, while finasteride only inhibits Type 2 3
- Despite dutasteride producing greater DHT suppression than finasteride, this does not result in different sexual side effect profiles 3
- The magnitude of sexual dysfunction from either medication is clinically modest: only 3.21 points on a 0-100 scale, compared to 1.26 points for each year of aging 4, 5
Important Clinical Considerations
When counseling patients about either medication:
- Sexual side effects (ED, decreased libido, ejaculatory dysfunction) decrease over time and remain statistically significant but clinically small after the first year 5
- Baseline sexual dysfunction is extremely common in BPH populations (46% in some studies), making attribution to medication challenging 5
- Discontinuation rates due to adverse events are approximately 6-7% for both finasteride and placebo groups, indicating the side effect burden is similar to placebo 5, 6
Bottom Line for Clinical Practice
Choose between finasteride and dutasteride based on factors other than erectile function impact, such as cost, formulary availability, or other efficacy considerations, as their effects on erections are equivalent. 1, 2, 3 The 2003 AUA guidelines note that dutasteride has similar efficacy and comparable safety profile to finasteride 1, and subsequent comparative trials confirm no meaningful difference in sexual adverse events between the two medications. 2, 3