Testosterone Caproate
A medium-length hexanoate ester of testosterone, historically a component of some combination testosterone injectables and depot preparations. Pharmacologically it is bioidentical testosterone with a release rate between propionate and enanthate. It is uncommon as a standalone product and is best known as one of the esters blended into legacy multi-ester testosterone mixtures.
01 Overview
Testosterone caproate (hexanoate) is testosterone esterified with caproic acid, giving a half-life intermediate between the fast propionate and the longer enanthate. It featured in older combination preparations designed to smooth testosterone release using several esters of different chain lengths, and as a depot component in some formulations.
Because the active steroid is plain testosterone, its effects and risks are those of the parent hormone: aromatisation to oestradiol, 5-alpha reduction to DHT, erythropoiesis and HPG-axis suppression. As a standalone ester it is rarely encountered today, and specific pharmacokinetic data on the caproate are limited compared with enanthate or cypionate.
02 Mechanism
Hydrolysed to free testosterone, which agonises the androgen receptor; aromatised to oestradiol and reduced to DHT, producing the standard testosterone profile.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Therapeutic (as component) | 50–100 mg/wk | IM | Typically used as part of a multi-ester blend rather than alone. |
| Estimated | 250–500 mg/wk | IM | As a testosterone base; behaves like other mid-length esters. |
Ester comparison
| Ester | Half-life | Injection freq. | Testosterone by mass |
|---|
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Increased lean muscle massAs bioidentical testosterone, dose-dependent gains in fat-free mass, per the wider testosterone literature. | Clinical | ||
| Restored libido and moodStandard testosterone replacement effects in hypogonadal men. | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Oestrogenic effectsWater retention and gynaecomastia from aromatisation. | Moderate | Common | Clinical | |
| PolycythaemiaRaised haematocrit increasing thrombotic risk. | Moderate | Common | Clinical | |
| HPTA suppressionSuppresses LH/FSH and endogenous testosterone. | Severe | Universal | Clinical |