What is Finasteride, and Which Finasteride is Best?

Finasteride is a drug approved by the FDA to treat benign prostate hyperplasia and androgenic alopecia. It is prescribed as a 1 mg daily tablet for men with androgenic alopecia. It is also prescribed in higher dosages for women suffering from female pattern hair loss. This ranges from 1.0-5.0 mg daily.

Finasteride is available in different formulations. The best option is determined on a patient-by-patient basis.

What Formulations of Finasteride are Available?

There are two main finasteride formulations: oral and topical. Doctors typically prescribe oral finasteride, as it’s a time-tested formulation with a high success rate. Many telehealth providers have sprouted up in recent years, offering topical and oral versions of the drug. Topical finasteride has become increasingly popular as more studies confirm its efficacy and relative safety versus oral finasteride.

As concluded in one study:

Topical finasteride significantly improves hair count compared to placebo and is well tolerated. Its effect is similar to that of oral finasteride, but with markedly lower systemic exposure and less impact on serum DHT concentrations. ^[1]https://pubmed.ncbi.nlm.nih.gov/34634163/

Clinical studies have shown that oral and topical formulations improve hair parameters equivalently in target area hair counts.^[2]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9297965/ As such, many people looking to minimize their risk of side effects from finasteride often prefer the topical formulation, and they rationalize that decision by arguing that topical finasteride (1) is just as effective as oral finasteride, and (2) remains localized to the scalp, so it must not have any systemic effects elsewhere in the body.

In reality, both of these arguments are wrong.

1. While studies do show that topical finasteride is equivalent to oral finasteride in “target area hair counts”, hair count changes outside of these target zones have not yet been measured. Therefore, it is possible that topical finasteride may not protect against hair loss wherever it isn’t applied, whereas the oral formulation tends to provide global protection across the entire scalp. In fact, if topical finasteride does offer hair loss protection in non-applied scalp regions, the most likely reason is that the drug went systemic (i.e., entered into the bloodstream), traveled throughout the body, and redistributed to those non-applied areas. In that regard…
2. Topical finasteride can go systemic, depending on the dose. Several studies show that topical finasteride also lowers blood levels of DHT, particularly for daily doses totaling greater than 0.1 mg of finasteride exposure. While the amount of drug in circulation is still far less than that of oral finasteride, people trying topical finasteride should know this, and titrate their topical formulations accordingly. Just see this chart:

Finasteride 1mg Oral Tablets

As mentioned, finasteride is typically prescribed as a once-daily 1mg tablet. At 1mg daily, finasteride is sometimes branded as Propecia®. Using more than 1mg per day isn’t likely to improve results.^[3]https://pubmed.ncbi.nlm.nih.gov/10495375/

However, it may increase the risk of side effects. Nearly all clinical studies use 1mg, as it’s the gold standard for treating male pattern baldness. 5 mg finasteride is typically used to treat men diagnosed with benign prostatic hyperplasia (under the label Proscar®).

Oral Propecia® (i.e., 1mg daily of finasteride) is prescribed under its brand name and as a generic formulation through many telehealth companies. Generic versions of the drug typically deliver similar results, and often at a fraction of the cost.

Finasteride Topical Formulations

Finasteride topicals include gels, liquid solutions, and liquid sprays. Foams are available as well.

A previous post centered on the best topical finasteride dosage determined that finasteride has a highly-sensitive and dose-dependent response curve.

In other words, 0.01 mg of finasteride barely reduces any DHT, while 0.2 mg reduces almost as much DHT as 5 mg, a much larger dose.^[4]https://onlinelibrary.wiley.com/doi/10.1111/jdv.17738 1% topical formulations essentially guarantee systemic absorption.

Those aiming to avoid the side effects may want to consider a formula with lower percentages of the active drug.

Which Finasteride Is Best for Hair Loss?

It depends on two factors: (1) the presence of side effects, and (2) whether a patient has diffuse thinning or localized hair loss.

Side effects

When weighing the pros and cons of finasteride formulas, doctors often have patients start with oral finasteride. This is because oral finasteride has the strongest clinical evidence for treating male pattern hair loss, and it provides some degree of protection across all balding-prone areas.

If side effects occur on oral finasteride at 1 mg daily, doctors may consider lowering the dose to 0.2 mg daily to see if this reduces side effects. If issues persist, other options can be explored – such as topical formulations.

Under these circumstances, users may introduce topical finasteride at a 1-2 mL daily of 0.025% to 0.3% finasteride. If side effects persist, it may be necessary to lower that dose all the way to 0.005% x 2 mL daily, and start tracking serum DHT levels to measure – as a proxy – how much finasteride is actually going systemic (as these levels vary greatly depending on the person and any adjuvant treatments that might be influencing topical absorption – i.e., retinoic acid, microneedling, etc.).

Hair loss patterning

If someone wants to use topical finasteride, they should recognize that topical formulations of the drug are most appropriate for people who have localized hair loss (i.e., hair loss only at the temples and/or crown), rather than people with diffuse thinning (i.e., hair loss throughout the entire scalp).

This is because diffuse thinners have a larger area of the scalp to cover with a topical. That requires a higher amount of mL per application daily of topical finasteride to cover all zones. When holding constance the percentage dilution of topical finasteride, the more mL applied daily, the higher likelihood some of that additional finasteride will leak into the bloodstream and cause systemic effects – thereby defeating the whole effort of the topical in the first place.

For these reasons, diffuser thinners need to take extra care to titrate down their topical finasteride doses, or perhaps consider oral formulations of finasteride to maximize their scalp coverage and thereby improve their odds of long-term success.

For those who don’t experience any sexual side effects, long-term use of oral finasteride may be advisable, given its success rate. And for those who experience adverse systemic effects of oral finasteride, or those wary about potential issues with the oral formulation, topical finasteride may be the better option.