Ethylestrenol
A weakly androgenic oral 19-nortestosterone derivative that lacks the 3-keto group, marketed under names such as Maxibolin and Orabolin for wasting and as a veterinary agent. It is essentially a prodrug-like relative of norethandrolone and is considered mild but hepatotoxic due to 17-alpha-alkylation.
01 Overview
Ethylestrenol is a 17-alpha-ethyl estrane steroid closely related to norethandrolone but lacking the 3-keto oxygen, which reduces its intrinsic androgen-receptor binding. It was sold for human use (Maxibolin, Orabolin) for cachexia, geriatric weakness and paediatric failure to thrive, and has a long history in veterinary medicine, particularly for debilitated dogs and cats.
Because of its weak androgenic profile it was promoted as a gentle anabolic, but human efficacy data are sparse and largely vintage. As a 17-alpha-alkylated oral it still burdens the liver, and its 19-nor structure gives it progestogenic character. Its metabolism partly overlaps with norethandrolone. It has largely disappeared from human pharmacies but persists in some veterinary and grey markets.
02 Mechanism
A weak androgen receptor agonist; the absence of the 3-keto group lowers receptor affinity relative to testosterone, while the estrane (19-nor) backbone contributes progestogenic activity. 17-alpha-ethylation provides oral bioavailability.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Vintage clinical | 4–12 mg/day | Oral | Historical human dosing for wasting; not a current regimen. |
Ester comparison
| Ester | Half-life | Injection freq. | Testosterone by mass |
|---|
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Mild nitrogen retentionModest anabolic effect reported in vintage wasting and geriatric use. | Observational | ||
| Appetite and weight supportUsed in debilitated human and veterinary patients to support weight. | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| HepatotoxicityLiver enzyme elevation and cholestasis risk from 17-alpha-alkylation. | Moderate | Class effect of 17aa orals | Observational | |
| Progestogenic and virilising effectsLibido changes, gynecomastia risk, and virilisation in women. | Moderate | Inherent to 19-nor | Anecdotal | |
| HPTA suppressionSuppression of endogenous testosterone via negative feedback. | Moderate | Expected | Observational |