Why More Finasteride Isn't Better: A Compounding Pharmacist's Case for Low-Concentration Topical Foam

By Harminder Mathroo, Hair Compounding Pharmacist & Formulationist, Beyond Health & Pharmacy

There is a quiet arms race in the topical finasteride market. Every few months a product appears at a higher concentration than the last (1%, 2%, and now 2.5% gels), marketed on a simple, intuitive premise: stronger must work better. Alongside them sit “liposomal” formulations promising that their delivery technology keeps the drug locked in your scalp and out of your bloodstream.

I formulate and compound topical finasteride for a living. I want to walk through what the pharmacology and the published data actually say, because on close reading the intuitive premise falls apart. More concentration does not buy more hair. What it reliably buys is a larger reservoir of a potent drug sitting on your skin, and, in the case of the highest-strength gels, more systemic exposure for no additional benefit.

This is not a marketing piece dressed up as science. Where the evidence is strong, I will show it. Where a claim rests on mechanism or on a manufacturer's own in-house testing, I will say so plainly.

First, what finasteride actually does

Pattern hair loss (androgenetic alopecia) is driven largely by DHT, or dihydrotestosterone, a hormone that gradually miniaturizes genetically susceptible hair follicles until they stop producing visible hair. DHT is made from testosterone by an enzyme called 5-alpha-reductase type II.

Finasteride works by blocking that enzyme. Less enzyme activity means less DHT, which means follicles are no longer being pushed to shrink. That is the entire mechanism, whether the drug is swallowed or applied to the scalp.

The key insight for everything that follows is this: an enzyme is a finite target. Once you have inhibited most of the 5-alpha-reductase in the scalp, adding more drug has very little left to do. This is why a dose-response curve for finasteride does not keep climbing. It flattens out, or plateaus. Hold onto that idea.

Topical versus oral: same job at the follicle, very different exposure everywhere else

Oral finasteride is effective and well established. Its drawback is that a daily tablet suppresses DHT throughout your entire body, typically reducing circulating (serum) DHT by around 60 to 70%. For most men that is uneventful, but a minority experience systemic effects tied to that body-wide DHT drop.

The logic of topical finasteride is to put the drug where the follicles are and limit how much reaches the rest of the body. The pivotal evidence here is a Phase III randomized controlled trial (Piraccini and colleagues, JEADV, 2022) comparing a 0.25% topical finasteride spray against oral finasteride 1 mg and placebo over 24 weeks. Two findings matter:

• Scalp efficacy was comparable. Hair count increased by roughly the same amount in the topical and oral groups (about +20 hairs/cm² each), and both clearly beat placebo.
• Systemic exposure was not comparable at all. Peak plasma finasteride levels were more than 100 times lower with the topical, and serum DHT fell about 34.5% with topical versus 55.6% with oral.

Read that again: roughly the same hair result, at a fraction of the whole-body drug exposure. That is the entire value proposition of topical finasteride, and it is well supported. It also quietly demolishes the idea that you need to flood the scalp with drug to get a result.

Why 0.1% is enough: the plateau, in the data

If efficacy plateaus, the practical question becomes: how little drug do you actually need to sit on that plateau? Here the dose-finding work is unusually clear.

In a controlled study (Caserini and colleagues, 2016), researchers applied escalating volumes of 0.25% topical finasteride and measured DHT in two places: the scalp (where you want the effect) and the serum (where you don't). The pattern was striking:

• Scalp DHT suppression plateaued almost immediately. Low application volumes already produced near-maximal scalp DHT reduction (roughly 47 to 52%), and applying substantially more drug did not meaningfully increase it.
• Serum DHT suppression, by contrast, kept climbing with dose, rising from about 24% at the lowest volume to nearly 48% at the highest.

This is the whole argument in one experiment. Past a modest dose, escalating the amount of finasteride on the scalp adds systemic exposure while adding essentially no scalp benefit. The authors concluded that the sweet spot, maximum scalp effect with minimum systemic effect, sits at the low end of dosing.

That is precisely why I cap our formulation at 0.1% and offer microdose strengths below it. A well-formulated 0.1% foam, with the drug fully dissolved and thermodynamically active (more on that term below), places you on the efficacy plateau. Everything above that is not a stronger treatment. It is a bigger dose of side-effect risk chasing a benefit that isn't there.

The 2.5% gel problem: doing the math out loud

Now to the high-concentration gels. Let me put the numbers on the table, because they are genuinely startling once written down.

A 2.5% w/w gel contains 2.5 grams of finasteride per 100 grams of product, which is 2,500 mg per tube. For scale:

• Against the standard 1 mg hair-loss tablet, that is 2,500 tablets' worth of finasteride in a single 100 g tube.
• Against the 5 mg tablet used for prostate enlargement, it is 500 tablets' worth.
• Against our 0.1% foam (100 mg per 100 g), it is a 25-fold higher drug concentration.

The marketing implication is that 25 times the concentration means a dramatically stronger, faster result. The pharmacology says otherwise, for two reasons.

Reason one: you cannot force more drug across skin just by adding more powder

Finasteride is poorly soluble. In any gel base, only the fraction of drug that is actually dissolved is available to cross the skin. Pharmacologists call this the thermodynamically active fraction. Once the base is saturated with dissolved finasteride, any additional drug you pack in doesn't dissolve; it simply sits as suspended powder. It raises the number on the label but not the driving force pushing drug into the skin.

Put plainly: above a certain point, a “stronger” gel is not delivering more medicine to your follicles. It is carrying a large payload of undissolved drug that rides on the surface, contributes nothing extra to the effect, and washes, rubs, or transfers off.

Reason two: the 2.5% product's own data says it isn't better

This is the part I find most telling. The patent filing behind a 2.5% w/w topical finasteride composition reports its own pharmacodynamic results. After treatment, it documents a serum DHT reduction of approximately 31% (with a range spanning 0 to 53%) and an individual peak plasma finasteride level of 13.9 ng/mL.

Sit with that. A gel at ten times the concentration of the trial-validated 0.25% spray produced a serum DHT reduction (~31%) that is no greater than the 0.25% product's ~34.5%, and in fact slightly lower. Meanwhile the peak plasma level it reports (13.9 ng/mL) is in the range of, and can exceed, the peak levels typical of a 1 mg oral tablet. By its own filing, this is a product delivering oral-range systemic exposure in some users while showing no advantage on the very hormone finasteride is meant to suppress.

That is the opposite of the “targeted, local, minimal absorption” promise. It is the plateau problem made concrete: the extra concentration didn't improve the scalp result, it just raised the systemic load.

Reason three: it is a handling hazard with no upside to justify it

There is a safety dimension that gets almost no airtime. Finasteride is a known teratogen. It is contraindicated in pregnancy because it can interfere with normal genital development in a male fetus. Regulators are explicit that women who are or may become pregnant should not even handle finasteride, and this includes contact with a partner's product.

A low-strength foam that absorbs and dries cleanly is a very different household object from a 2.5% gel carrying 2,500 mg of a teratogen that can transfer on skin contact, pillowcases, or shared surfaces. When a formulation delivers no additional benefit but multiplies the drug reservoir in your home 25-fold, the risk-benefit math is not close. In my professional assessment, that is the specific and defensible sense in which these ultra-high-concentration gels are a problem: not because “strong is bad,” but because this strength buys exposure without benefit.

“Liposomal finasteride keeps it out of your bloodstream”: where the evidence actually stands

Liposomal and other nanocarrier formulations are marketed on an appealing mechanistic story: tiny lipid vesicles ferry the drug down the follicle and into scalp tissue, keeping it “local” and out of systemic circulation. As a delivery concept it is genuinely plausible. Liposomal drugs exist and work well in other areas of medicine.

But plausible is not the same as demonstrated, and the specific claim being sold (reduced systemic absorption in humans) is where the marketing outruns the data. Here is what the evidence base for these hair-loss products actually consists of:

• In-vitro skin-permeation testing.Much of the supporting data comes from Franz diffusion cell studies, a laboratory apparatus using excised skin or a membrane. These measure flux across a barrier in glassware. They do not measure what reaches a living person's bloodstream.
• Manufacturer-generated, manufacturer-reviewed reports.A good deal of the “clinical data” cited for these systems is produced and reviewed in-house by the companies selling them. That is not automatically wrong, but it is not independent evidence, and it should be read with the same caution as any result an interested party grades for itself.
• Review literature that openly flags the gap. Even sympathetic scientific reviews of liposomal delivery for hair loss describe major translational gaps (reproducibility, stability, and the absence of standardized human models) as unresolved.

What is missing is the thing that would actually settle the question: an independent, adequately powered human pharmacokinetic study showing that a liposomal finasteride product produces lower systemic exposure than a conventional topical of the same strength. To my knowledge, that study does not yet exist. And separately, the broader literature is consistent that all topical finasteride is absorbed systemically to some degree. The Phase III data show measurable plasma drug and a real, if smaller, serum DHT drop.

So when a product states categorically that “you don't absorb it systemically,” the honest scientific response is that the burden of proof lies with the claimant, and that burden has not been met with independent clinical data. A plausible mechanism and a favourable in-vitro flux curve are a reason to keep studying something. They are not a licence to promise a patient a systemic-safety outcome that hasn't been measured in humans.

How we formulate at Beyond Health, and why

Our approach follows directly from the evidence above rather than from what markets well:

• Lowest effective strength, by design.We formulate topical finasteride from a 0.01% microdose up to a 0.1% ceiling, the range that the dose-finding data place squarely on the efficacy plateau, so you get the scalp effect without paying for systemic exposure you don't need.
• The active is fully dissolved and thermodynamically activein our Trichofoam base, because, as we covered, it's the dissolved fraction that treats you, not the number on the label.
• Propylene glycol-free. We leave out the solvent most associated with the greasy, stinging feel that drives people to abandon treatment, and which is itself a penetration enhancer that can nudge absorption upward.
• A licensed pharmacist confirms the gentlest effective strength for you, and every request is reviewed by a practitioner before anything is dispensed.

The goal is not to win a concentration contest. It is to give you the result the follicle actually responds to, with the smallest drug footprint on the rest of your body and in your home.

The bottom line

Finasteride's effect on hair plateaus once scalp DHT is suppressed, and that plateau is reached at low doses. The published trial evidence shows a 0.25% topical matching oral finasteride for hair count at a fraction of the systemic exposure, and the dose-finding data show that piling on more drug adds systemic suppression, not scalp benefit. High-concentration 2.5% gels demonstrate this vividly in their own filings: no advantage on DHT, oral-range plasma levels in some users, and a 25-fold larger reservoir of a teratogen to keep in your home. And the “liposomal means no systemic absorption” claim, however appealing, rests on in-vitro and in-house data that no independent human study has yet confirmed.

More concentration is not a stronger treatment. It is, at best, wasted drug, and at worst, added risk marketed as an upgrade. The better question is never how much finasteride we can put in the tube, but how little we need to sit on the plateau. That is the formulation I'd want for my own scalp, and it's the one we make.

References

• Piraccini BM, et al. Efficacy and safety of topical finasteride spray solution for male androgenetic alopecia: a phase III, randomized, controlled clinical trial. J Eur Acad Dermatol Venereol. 2022.
• Caserini M, et al. Effects of a novel finasteride 0.25% topical solution on scalp and serum dihydrotestosterone in healthy men with androgenetic alopecia. 2016.
• United States Patent No. 11,786,466, topical finasteride composition (2.5% w/w), reported pharmacokinetic and pharmacodynamic data.
• Review literature on liposomal and nanocarrier delivery of 5-alpha-reductase inhibitors for androgenetic alopecia, noting unresolved translational gaps (reproducibility, stability, standardized human models).
• FDA prescribing information for finasteride: pregnancy contraindication and handling precautions.

This article is educational and reflects the professional assessment of the author. It is not individual medical advice. Topical finasteride is a prescription treatment; suitability is determined by a licensed practitioner following assessment. Comparisons above address formulation categories and published or publicly filed data, not any individual product's overall quality.