Both finasteride and dutasteride are 5-alpha reductase inhibitors — oral medications that work by reducing dihydrotestosterone (DHT), the hormone responsible for follicle miniaturisation in androgenetic alopecia. But they’re not the same drug, and the differences matter when choosing between them.
This guide breaks down how each medication works, compares their efficacy, discusses side effect profiles, and explains how to track either one effectively.
To understand finasteride and dutasteride, you need to understand DHT.
Dihydrotestosterone (DHT) is a potent androgen derived from testosterone via the enzyme 5-alpha reductase. In men with the genetic predisposition to male pattern baldness, DHT binds to androgen receptors in scalp hair follicles, causing them to shrink progressively over successive growth cycles — a process called follicle miniaturisation.
There are two types of 5-alpha reductase:
This distinction is critical for understanding why finasteride and dutasteride produce different results.
Finasteride (Propecia, generic) selectively inhibits 5-alpha reductase type II. At the 1 mg dose used for hair loss, it reduces scalp DHT by approximately 60–70% and serum (blood) DHT by approximately 70%.
Because finasteride targets type II — which is highly expressed in hair follicles — it’s an efficient, targeted approach.
Standard dose: 1 mg/day oral FDA-approved: Yes, for male pattern baldness
Dutasteride (Avodart) is a dual inhibitor, blocking both type I and type II 5-alpha reductase. This broader blockade reduces serum DHT by approximately 90% — significantly more than finasteride.
This greater DHT suppression translates to measurably better outcomes in head-to-head studies, at the cost of a broader hormonal effect.
Standard dose: 0.5 mg/day or 0.5 mg/week (off-label) FDA-approved: For benign prostatic hyperplasia, not hair loss (prescribed off-label for hair loss)
Multiple studies have compared finasteride and dutasteride for hair loss:
| Study | Duration | Dutasteride Result | Finasteride Result |
|---|---|---|---|
| Harcha et al. (2014) | 24 weeks | +12.2 hairs/cm² | +7.3 hairs/cm² |
| Boyapati et al. (2022) | 12 months | Superior regrowth | — |
| Phase III trials | 12 months | Hair count: +109.7/cm² | Hair count: +75.6/cm² |
The consensus across available evidence is that dutasteride produces more hair regrowth than finasteride, particularly at the vertex, due to its deeper DHT suppression.
However, finasteride has decades of safety data and remains the first-line pharmacological treatment recommended by most dermatologists.
Both medications share a class of side effects related to sexual function — reduced libido, erectile dysfunction, reduced ejaculate volume — because DHT plays a role in sexual function.
| Side Effect | Finasteride | Dutasteride |
|---|---|---|
| Sexual dysfunction | ~2–4% | ~4–6% |
| Breast tenderness | Rare | Rare |
| Depression | Small increased risk | Similar |
| Post-discontinuation persistence | PFS reported (rare) | Reported, less studied |
| Onset of sexual SE | Weeks to months | Weeks to months |
For most men, side effects are mild or absent. It’s worth noting that clinical trial rates of sexual dysfunction in placebo arms are often similar to active treatment arms, suggesting significant nocebo effect.
Important: Discuss your medical history, including any cardiovascular conditions or prostate issues, with a prescribing physician before starting either medication. Do not self-prescribe.
The pharmacokinetic difference between these drugs is dramatic and affects how quickly effects wear off if you stop:
| Finasteride | Dutasteride | |
|---|---|---|
| Half-life | ~6 hours | ~5 weeks |
| DHT recovery after stopping | Days to weeks | Months |
Dutasteride’s long half-life means it takes significantly longer to clear your system. This is relevant if you experience unwanted side effects and want to stop quickly.
This is a decision for you and your prescribing physician. Some considerations:
Finasteride may be preferred if:
Dutasteride may be preferred if:
Regardless of which medication you choose, tracking is essential. Both finasteride and dutasteride take 6–24 months to show their full effect — and without before-and-after photos, it’s nearly impossible to objectively assess progress.
Here’s how to track your 5-ARI regimen with Track Hair:
Start tracking your hair loss treatment. Download Track Hair and set up your finasteride or dutasteride schedule today.
| *Related reading: How to Track Minoxidil Progress | Understanding the Norwood Scale | Finasteride Guide* |