COMPOUND

Compounds / TRT and hormones

Test Undecanoate (Inj)

Testosterone Undecanoate Injection (Aveed in US, Nebido outside US)

TRT and hormones IM FDA approved

Ultra-long-acting injectable testosterone in castor oil. Dosed every 10-14 weeks after loading. Carries an FDA boxed warning for pulmonary oil microembolism (POME) and anaphylaxis. REMS-restricted to certified healthcare settings with 30-minute post-injection observation.

At a glance

Half-life
~82 days Mean terminal t½ ~82 days IM (Aveed label, NDA 022219). Steady state reached after ~3 doses. Castor oil vehicle drives the slow release, NOT just the ester.
Routes
IM
Vial sizes
750 mg · 1000 mg
Evidence base
3 studies 3 human

Mechanism

11-carbon ester dissolved in refined castor oil (NOT sesame oil) for slow lymphatic absorption from the IM depot. The combination of long ester chain and castor oil vehicle gives the longest depot duration of any approved T ester (~70-90 day terminal t½). Once absorbed, lymphatic transport bypasses first-pass metabolism, then esterases release free testosterone systemically.

Dosing

Any amounts shown here are reported from published studies only. 3 of 3 catalogued studies involved human subjects. COMPOUND does not publish its own dosing guidance.

Published evidence

  1. Human RCT 2023

    Cardiovascular Safety of Testosterone-Replacement Therapy

    Lincoff AM, Bhasin S, Flevaris P, et al. N Engl J Med

    TRAVERSE class CV safety data applies; AF/PE signals extend to undecanoate use.

    PMID 37326322

  2. Human RCT 2008

    Long acting testosterone undecanoate therapy in men with hypogonadism (Aveed pivotal trial)

    Morgentaler A, Dobs AS, Kaufman JM, et al. J Urol

    Pivotal Phase 3 supporting Aveed approval: 84% of men maintained T in normal range with 10-week dosing after 6-week loading.

    PMID 18930255

  3. Human observational 2020

    Occurrence of Pulmonary Oil Microembolism After Testosterone Undecanoate Injection: A Postmarketing Safety Analysis

    Pastuszak AW, Hu Y, Freid JD Sex Med

    POME spontaneous reporting rate <0.1% per injection across 633 case safety reports. Quantifies BBW risk in real-world use.

    PMID 32184081

Reported side effects

Pulmonary oil microembolism (POME)
Rare Serious · FDA BOXED WARNING. Cough, dyspnea, chest pain, syncope during or immediately after injection. Postmarketing rate <0.1%/injection but clinically significant. Drives REMS observation requirement (30 min post-injection).
Anaphylaxis
Rare Serious · FDA BOXED WARNING. Reported even after initial uneventful injections. Drives REMS observation requirement.
Polycythemia / hematocrit elevation
Very common Moderate · Occurs but somewhat less peak-driven than weekly esters due to flat PK.
Acne / oily skin
Common Mild
Injection site pain
Common Mild · Large volume (3-4 mL of viscous castor oil) injection.
Estradiol elevation / gynecomastia
Common Mild
HPTA suppression / fertility loss
Very common Moderate · Universal. HCG add-on protocol harder to time given 10-week injection cadence.
Hepatic dysfunction
Rare Moderate · Minor LFT elevations, generally clinically insignificant.

Interactions

  • Anastrozole Synergy

    AI for E2 management. Less commonly needed than with weekly esters due to flatter PK.

  • HCG Synergy

    HPTA preservation adjunct possible but adherence is harder when primary T is q10wk.

  • Self injection Contraindicated

    Aveed REMS program prohibits home self-administration. Must be injected by certified healthcare provider with 30-min observation post-injection due to POME and anaphylaxis BBW.

Reconstitution and storage

Not applicable: single-dose 3 mL vial of castor oil solution (250 mg/mL). Slow injection (60-90 sec) into gluteal muscle is critical for POME risk reduction.

Room temperature 20-25°C, protect from light.

Open the reconstitution calculator for Test Undecanoate (Inj)