Finasteride wasn’t originally meant to help men keep their hair. It started as a drug for something completely different - enlarged prostates. But somewhere along the way, doctors noticed a strange side effect: men taking it for prostate issues were growing back hair. That accidental discovery changed millions of lives. Today, finasteride is one of the most common treatments for male pattern baldness. But how did we get here? The story isn’t just about science - it’s about luck, observation, and how medicine often finds new uses in the most unexpected places.
How Finasteride Was Born
In the 1970s, scientists at Merck were hunting for a way to treat benign prostatic hyperplasia (BPH), a condition where the prostate gland swells and makes urination difficult. They knew that a hormone called dihydrotestosterone (DHT) played a big role in this. DHT is made when the enzyme 5-alpha reductase converts testosterone. So, if you could block that enzyme, you could shrink the prostate.
After testing hundreds of compounds, they found one that worked: finasteride. It was a selective inhibitor of type 2 5-alpha reductase - the version of the enzyme mostly found in the prostate. In clinical trials, men who took finasteride saw their prostate size drop by about 20-30% over a year. Their urine flow improved. Their symptoms eased. By 1992, the FDA approved it under the brand name Proscar for BPH, at a dose of 5 mg per day.
The Unexpected Side Effect
While doctors were watching prostate numbers, patients were noticing something else. Many reported thicker hair on their scalps. Some even said their receding hairlines were reversing. At first, no one paid much attention. Side effects were logged, but hair growth wasn’t considered a medical concern - until a few researchers started asking questions.
In 1995, a team led by Dr. O’tar Norwood published a small study in the Journal of the American Academy of Dermatology. They gave 10 men with male pattern baldness a daily 1 mg dose of finasteride - one-fifth the dose used for the prostate. After one year, 65% of them showed improved hair growth. Only 10% lost more hair. The rest stayed the same. The results were clear: finasteride worked on hair too.
Why did a lower dose help hair but still work on the prostate? Because the enzyme in hair follicles is mostly type 2, just like in the prostate. The drug didn’t need to block every bit of DHT - just enough to stop follicles from shrinking. And at 1 mg, it did exactly that without overdoing it.
From Proscar to Propecia
Merck didn’t waste time. In 1997, they launched a lower-dose version of finasteride called Propecia, specifically for hair loss. The FDA approved it that same year. This wasn’t just a repurposing - it was a rebranding of a drug’s purpose. Propecia became the first FDA-approved oral treatment for male pattern baldness. Before this, the only options were minoxidil (a topical solution) or hair transplants - both expensive, messy, or temporary.
By 2000, Propecia was one of the top-selling prescription drugs in the U.S. for men under 50. It wasn’t a miracle cure, but it was the first real way to stop hair loss from getting worse - and sometimes, reverse it. Men who started taking it early often kept their hairline intact. Those who waited too long saw less benefit. Timing mattered.
How Finasteride Actually Works
Male pattern baldness isn’t just about aging. It’s genetic. Men with this condition have hair follicles that are sensitive to DHT. Over time, DHT causes follicles to shrink, producing thinner, shorter hairs until they stop growing altogether. Finasteride blocks the enzyme that turns testosterone into DHT. In the scalp, that means less DHT attacking the follicles.
Studies show finasteride reduces DHT levels in the blood by about 70%. In the scalp, the drop is even higher - up to 90% in some areas. That’s why it works so well. It doesn’t grow new hair out of nowhere. It protects the ones still alive. Think of it like stopping a leak in a roof. You don’t replace the whole roof - you just stop the water from getting worse.
Most men start seeing results after three to six months. The first sign? Less shedding. Then, fine, soft hairs appear where thinning was happening. After a year, many see noticeable thickening. But here’s the catch: you have to keep taking it. Stop, and DHT levels rise again. Hair loss resumes within 12 months.
Who Benefits the Most?
Not everyone responds the same. Finasteride works best for men with mild to moderate hair loss at the crown or mid-scalp. It’s less effective for those who’ve lost hair at the temples for years or have very advanced balding. The follicles there are often too dead to revive.
Age matters too. Men in their 20s and 30s who start early tend to keep more hair long-term. Those in their 40s or 50s might see slower improvement, but they still often stop further loss. A 2020 study in the British Journal of Dermatology followed 1,000 men on finasteride for five years. 90% of those who stuck with it maintained or improved their hair density. Only 10% lost more hair than they started with.
It doesn’t work for women. Not because it’s unsafe - it’s because female pattern hair loss is driven by different hormones. Finasteride is not approved for women, especially those who are pregnant or could become pregnant. Even touching broken pills can be risky for a developing male fetus.
Side Effects and Misconceptions
Finasteride has a reputation for side effects. Some men worry about sexual problems - lower libido, erectile dysfunction, or reduced semen volume. These are real, but they’re rare. In clinical trials, about 1.8% of men on finasteride reported sexual side effects, compared to 1.3% on placebo. That’s less than 2 in 100. Most of these effects go away after stopping the drug.
There’s been a lot of fear online about something called “Post-Finasteride Syndrome” - a claimed long-term condition with lasting sexual, mental, and physical symptoms. But major medical organizations, including the American Academy of Dermatology and the FDA, say there’s no solid scientific proof this syndrome exists. Some men may have had temporary side effects that lingered due to anxiety or other factors. But large, controlled studies haven’t confirmed a causal link.
Still, it’s smart to talk to a doctor before starting. If you’ve had depression or sexual issues before, finasteride might not be the best fit. And if side effects show up, don’t ignore them. Talk to your doctor. Sometimes switching to a lower dose helps.
The Generic Revolution
When Propecia’s patent expired in 2013, generic finasteride flooded the market. A 30-day supply of Propecia used to cost $80-$100. Generic versions now cost $10-$20, sometimes less with coupons. The pills are identical - same active ingredient, same dosage, same manufacturer standards. The only difference? The brand name on the bottle.
Today, most men who use finasteride for hair loss take the generic. Many buy it online from reputable pharmacies, though it’s still a prescription drug in the U.S., Australia, and the EU. You can’t just walk into a pharmacy and buy it over the counter. But with telehealth services now common, getting a prescription is easier than ever.
Where Finasteride Stands Today
Over 25 years after its approval for hair loss, finasteride remains the gold standard for oral treatment. It’s backed by more long-term data than any other hair loss drug. It’s cheaper than transplants. It’s more effective than most shampoos or supplements. And it’s been used by over 10 million men worldwide.
Still, it’s not the whole solution. Many men combine it with minoxidil (Rogaine) for better results. Others use low-level laser therapy or platelet-rich plasma. But none of those work as reliably as finasteride when it comes to stopping the progression of balding.
For men who want to keep their hair - not just cover it up - finasteride is still the most proven tool we have. It started as a prostate drug. It became a hair loss treatment by accident. And now, it’s one of the quietest, most effective medical breakthroughs of the last 30 years.