Finasteride 1mg Three Times Weekly vs. Daily Dosing for DHT Suppression
No, 1mg of finasteride three times per week (Monday, Wednesday, Friday) is NOT as effective at lowering DHT levels as 1mg daily, though the difference may be clinically modest given finasteride's prolonged pharmacodynamic effects.
Pharmacokinetic and Pharmacodynamic Rationale
The key to understanding this question lies in finasteride's unique pharmacological properties:
A single dose of finasteride suppresses serum DHT levels for up to 4 days, which is considerably longer than would be predicted by its serum elimination half-life of 4.7 to 7.1 hours 1
This prolonged DHT suppression occurs because finasteride has extremely high affinity for the 5-alpha-reductase enzyme, creating a persistent pharmacodynamic effect that outlasts its presence in serum 1
At therapeutic doses, finasteride produces rapid and pronounced DHT reduction, with doses below 0.5mg/day producing minimal DHT suppression, while doses above 5mg/day offer little additional benefit 1
DHT Suppression Data with Standard Dosing
With daily 1mg dosing in normal male volunteers:
Serum DHT is reduced by approximately 70% at steady state 2
Prostatic tissue DHT is reduced by 80-90% with daily finasteride administration 2
DHT levels return to pretreatment values within 14 days of discontinuing treatment 3
Critical Gap in Evidence
There are no published studies directly comparing 1mg three times weekly versus 1mg daily for DHT suppression. The available evidence only addresses:
- Daily dosing regimens at various doses 1, 3, 2
- Single-dose pharmacodynamics showing 4-day DHT suppression 1
- The dose-response relationship showing minimal effect below 0.5mg/day 1
Clinical Implications and Practical Considerations
Given the pharmacological data:
Three times weekly dosing (Monday/Wednesday/Friday) creates gaps of 2-3 days between doses, which falls within the 4-day window of DHT suppression from a single dose 1
However, steady-state DHT suppression would likely be less consistent compared to daily dosing, with potential fluctuations in DHT levels between doses
The clinical significance of these fluctuations is unknown for androgenetic alopecia treatment in reproductive-age men
Important Caveats
Sexual dysfunction risks remain present regardless of dosing frequency, occurring in approximately 2-4% more patients taking finasteride compared to placebo 4, 5
PSA monitoring considerations: After 1 year of 5-ARI therapy, measured serum PSA values should be doubled to accurately assess prostate cancer risk, though this applies primarily to the 5mg dose used for BPH 5, 6
For reproductive-age men concerned about fertility: The 1mg dose has inconclusive evidence regarding fertility impact, while the 5mg dose is associated with reduced semen volume 4
Recommendation for Clinical Practice
If cost or adherence is a concern, three times weekly dosing may provide partial benefit, but daily 1mg dosing remains the evidence-based standard for consistent DHT suppression. The lack of direct comparative data means three times weekly dosing represents an off-label modification without proven equivalence.