- "DHT blocker" is not one thing. It covers two different mechanisms: reducing DHT production, or blocking DHT at its receptor.
- Finasteride and dutasteride reduce production and are licensed medicines.
- RU-58841 and pyrilutamide block the receptor and are unlicensed research compounds.
- Topical delivery changes where a compound acts, not what it is. Research use only.
What DHT actually does
Dihydrotestosterone, DHT, is an androgen derived from testosterone. It binds to androgen receptors in tissues including the hair follicle. In follicles that are genetically sensitive to it, that binding drives the gradual miniaturisation that presents as pattern hair loss. The compounds people call DHT blockers all interfere with this pathway, but they do so at different points, and that difference matters more than the shared label.
"DHT blocker" means two different things
The label gets applied to two unrelated strategies. The first is to make less DHT: inhibit the enzyme that produces it. The second is to block DHT from binding: occupy the receptor so DHT has nowhere to dock. A compound in the first group changes the amount of DHT in the body. A compound in the second group leaves DHT alone and changes what it can bind to. Conflating the two is where most confusion around this category comes from.
The production reducers
Finasteride and dutasteride are 5-alpha-reductase inhibitors. They reduce the conversion of testosterone to DHT, which lowers DHT throughout the body. Both are licensed medicines with established clinical profiles, and both are systemic in their action. They are the reference point most people mean when they say DHT blocker, and they are medicines, not research compounds. Norwood Labs does not sell either one.
The receptor blockers
The topical antiandrogens take the other route. RU-58841 and pyrilutamide, KX-826, are androgen receptor antagonists. They compete with DHT for the receptor binding site without lowering DHT itself. Because the intent is local action, these are formulated for topical application, and the goal is to keep the effect at the application site rather than across the body. Both are unlicensed research compounds with limited clinical data, and both are sold strictly as reference materials for laboratory research.
Topical finasteride, explained
Topical finasteride appears in the same conversations because it shares the word topical, but it is a different thing again. It is the same licensed active compound as oral finasteride, delivered through the skin with the aim of achieving local effect at a lower systemic dose. It is still finasteride, still a medicine, and still subject to prescribing rules. It is not something Norwood Labs sells, and it is not interchangeable with the receptor blockers above simply because both are applied to the scalp.
What topical delivery changes
Topical delivery changes the pharmacokinetics of a compound: where it concentrates, how much reaches circulation, and how it distributes. It does not change the compound's identity or mechanism. A topical androgen receptor antagonist is still an androgen receptor antagonist. The practical question for any topical compound is whether it stays local enough to work where applied and absorb little enough to avoid systemic effect. For the established medicines, that question has been studied. For the research antiandrogens, it largely has not, which is part of why they remain research compounds.
The bottom line
A DHT blocker is either a production reducer or a receptor blocker, and the two could not be more different in mechanism, evidence, and legal status. Norwood Labs sits in one corner of this map: we supply the topical receptor blockers RU-58841 and pyrilutamide as batch-assayed research materials, with a public certificate of analysis for every batch. We do not sell finasteride, dutasteride, or any licensed medicine, and nothing on this site is treatment advice.