Ketoconazole (cortisol use)
Ketoconazole is an antifungal that, at higher doses, potently inhibits several cytochrome P450 steroidogenic enzymes, lowering both cortisol and testosterone. This off-label steroidogenesis inhibition (marketed as Ketoconazole HRA in Europe for Cushing's) makes it a cortisol-lowering agent. Its major liabilities are hepatotoxicity and suppression of testosterone — the latter making it counterproductive for physique goals.
01 Overview
By inhibiting enzymes including 17-alpha-hydroxylase, 11-beta-hydroxylase and 17,20-lyase, ketoconazole broadly suppresses adrenal and gonadal steroid synthesis. This lowers cortisol (useful in Cushing's syndrome) but also lowers testosterone, and it has historically been used as a chemical anti-androgen in prostate cancer for the same reason.
The critical safety issue is idiosyncratic hepatotoxicity, which led regulators to restrict oral ketoconazole's systemic use to specialist indications; it requires liver-function monitoring. For an athlete the combination of cortisol suppression plus testosterone suppression and liver risk makes it a poor and hazardous choice; there is no legitimate physique rationale.
02 Mechanism
Inhibits multiple steroidogenic cytochrome P450 enzymes (17-alpha-hydroxylase, 11-beta-hydroxylase, 17,20-lyase), reducing cortisol and testosterone synthesis.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Cushing's (off-label) | 400–1200 mg/day | Oral | Divided doses titrated to cortisol; requires liver monitoring. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Reduced cortisol synthesisLowers cortisol in Cushing's syndrome via P450 enzyme inhibition. | dose-dependent | Clinical | |
| Reduced testosteroneSimultaneously suppresses testosterone — counterproductive for muscle/physique goals. | marked | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| HepatotoxicityIdiosyncratic liver injury, occasionally severe or fatal, prompting regulatory restriction. | Severe | Idiosyncratic | Clinical | |
| Hypogonadism / low libidoLow testosterone causing reduced libido and, over time, gynaecomastia. | Moderate | Common in men | Clinical | |
| Adrenal insufficiencyExcessive cortisol suppression can precipitate adrenal insufficiency. | Severe | Dose-dependent | Clinical |