This page describes pharmacological agents that may have legal restrictions, side effects, and drug interactions in your jurisdiction. Information is for educational research only — consult a clinician before considering any compound.

Browse

Topilutamide

Emerging

Fluridil / Eucapil — the most clinically validated topical AR antagonist for AGA, with hydrolytic self-quenching designed to keep activity at the scalp.

Aliases (6)

Fluridil · Eucapil · topical AR antagonist · Pyri (community shorthand for adjacent KX-826) · BP-766 · topilutamide-class

TYPICAL DOSE

2% topical solution, ~1 mL twice daily

2% solution, ~1 mL BID

ROUTE

Topical (scalp)

Topical scalp application

CYCLE

Continuous (chronic)

Continuous chronic use

STORAGE

Cool, dry, dark; avoid heat (parent molecule is…

Cool, dry, dark

Overview

What is Topilutamide?

Topilutamide (WHO INN) is the non-steroidal topical anti-androgen marketed as Fluridil / Eucapil in Czech Republic and Slovakia since ~2003 for androgenetic alopecia. It is engineered to deliver local AR blockade at scalp follicles and break down to inactive metabolites within minutes of contacting aqueous bloodstream — a chemically explicit self-quenching design that distinguishes it from older systemic anti-androgens and from research-chem RU58841. Not FDA-approved in the US; sold domestically as a research chemical (RUO).

Key Benefits

Most clinically validated topical AR antagonist for AGA — one published double-blind placebo-controlled RCT (Sovak 2002), ~20+ years Czech/Slovak commercial pharmacovigilance, no detectable systemic absorption, no perturbation of testosterone/LH/FSH at design-intent doses. Mechanistically positioned as a topical-only PFS-concern alternative to oral 5α-reductase inhibitors.

Mechanism of Action

Lipophilic non-steroidal AR antagonist applied topically; competitively binds DHT/testosterone at scalp dermal-papilla AR to halt the miniaturization driving AGA. Hydrolytically labile groups in the parent molecule cleave to inactive metabolites within minutes of contact with aqueous physiological fluid — local-active, systemically-deactivated by design. The Kintor Phase 3 disappointment for the related pyrilutamide (KX-826) is class context but does not directly retire topilutamide/fluridil, which is a different molecule with its own (modest, short, but supportive) clinical record.

Research Indications

Most Effective

What it is

Topilutamide is the WHO INN (International Nonproprietary Name) for the molecule trade-named Fluridil and marketed in central/eastern Eur…

Effective

Mechanism at the scalp follicle

1. AGA is driven by DHT (and to a lesser extent testosterone) binding the AR in genetically susceptible dermal papilla cells of scalp fol…

Investigational

The self-quenching design

The distinguishing feature of topilutamide vs. older non-steroidal anti-androgens (flutamide/nilutamide) is that the molecule was enginee…

Investigational

What topilutamide is NOT doing

- Not lowering circulating DHT (no 5α-reductase inhibition; finasteride/dutasteride do that). - Not lowering systemic testosterone (no HP…

Peptide Interactions

Minoxidil (topical, 2-5%):

Synergistic

Standard hair-loss community pairing. Different mechanisms (AR blockade vs. anagen extension / vasodilation), no PK interaction, often combined in same daily…

Finasteride or dutasteride (oral):

Synergistic

Mechanistically complementary (lower DHT systemically + block residual AR locally) but the typical topilutamide user is *avoiding* the systemic 5αRI profile.…

Topical anti-inflammatory adjuncts

Synergistic

(azelaic acid, ketoconazole 2% shampoo) — for the inflammatory component of AGA. No interaction; possibly modestly synergistic.

Microneedling (dermaroller 0.5-1.5 mm 1-2×/week):

Synergistic

Mechanically increases drug penetration; community-favored adjunct. Caveat with topilutamide specifically: because the molecule is designed to hydrolyze on c…

Topical testosterone or any topical androgen application near the scalp

Avoid

defeats the purpose by saturating local AR.

Quality Indicators

✓

Clear, ethanol-based solution; recent batch date

Topilutamide is hydrolytically labile — fresh product in cool storage with clear ethanol vehicle is the functional baseline. Look for COA / HPLC purity report ≥98%.

✓

Eucapil-grade pharmacy product

Interpharma Praha's Eucapil is a regulated pharmaceutical/cosmetic product with consistent QC; 50 mL bottle ≈ 1 month at standard dose.

Solution that has been hot-shipped or stored warm

Heat exposure accelerates parent-molecule hydrolysis; product may already be partially deactivated before opening. Check shipping season and ambient storage.

Aqueous or DMSO-heavy vehicles

Aqueous bases speed hydrolysis on the shelf; DMSO-heavy vehicles defeat the systemic-quenching design at the body. Prefer ethanol-based solutions per the published label.

✗

Past expiration or visible degradation

Cloudiness, sediment, off color, or off odor indicates degraded product — discard. Topilutamide's lability makes shelf-life shorter than RU58841.

What to Expect

Week 1
Tolerability and dose-response.
Week 2-4
Early effect window.
Week 4-8
Peak benefit assessment.
Week 8+
Cycle decision point.

Side Effects & Safety

Common (>10% in Sovak 2002): None significant beyond placebo in the trial dataset. Real-world Eucapil users sometimes report scalp dryness or mild ethanol-vehicle irritation.
Less common (1-10%):
- Scalp irritation (vehicle-related, not topilutamide-specific)
- Mild contact dermatitis (rare)
Rare-serious (<1% but worth knowing):
- Systemic anti-androgen effects (gynecomastia, libido loss, mood changes): Not reported in published trials or Czech/Slovak pharmacovigilance, and biomechanistically unlikely given the self-quenching design — but theoretically possible at very high doses, very large application areas, or with penetration-enhanced vehicles that overwhelm the hydrolysis pathway. Consistently absent from the historical record.
- Hepatotoxicity: Flutamide and nilutamide (older systemic non-steroidal anti-androgens) have a clinically significant hepatotoxic signal at systemic doses; topilutamide's design should preclude this at topical scalp doses, and no hepatotoxicity has been reported in the Czech/Slovak pharmacovigilance dataset.
- Quality-control failures from research-chem sourcing: Vendor-by-vendor variation in purity, stability of the labile parent molecule, vehicle quality, and labeling. The molecule's hydrolytic instability means storage and shelf-life are bigger concerns than for RU58841 — degraded topilutamide in a poorly stored bottle may already be the inactive metabolite before application.
- Long-term effects of decades of daily topical AR blockade in young men: The Czech/Slovak pharmacovigilance pool is real but informally tracked; the longest formal trial is 3 months. The pharmacological intuition is "should be safe given local-only design," but extrapolating from "should be safe" requires humility — the same intuition was applied to finasteride before PFS reports emerged.
Specific watch periods:
- First 4 weeks: Watch for scalp irritation, contact dermatitis. Vehicle adjustments often resolve.
- Months 1-6: Photographic check-in for response.
- Annually thereafter: Photo series; hormone panel only if any unusual symptoms develop.