Testosterone decanoate is a steroid used in testosterone replacement therapy (TRT) to treat hypogonadism, which can arise from conditions like testicular failure, hypopituitarism, or osteoporosis. Testosterone decanoate was developed in the mid-20th century as a long-acting injectable testosterone ester to improve the pharmacokinetics of testosterone replacement therapy. Before its creation, earlier forms of therapy required frequent injections or carried a risk of liver toxicity.
BRAND NAMES
Sustanon 250, Testomix.
The formulation is an oil-based solution for deep intramuscular injection. The concentration of testosterone decanoate is 100 mg per millilitre.
MECHANISM OF ACTION
Testosterone decanoate is a long-acting prodrug of testosterone that works by releasing free testosterone into the bloodstream after intramuscular injection. The added decanoate ester slows the hormone's absorption and prolongs its effect, creating a sustained "depot" of testosterone that the body can use over an extended period. The fundamental mechanism is the same as naturally produced testosterone, in which the hormone and its active metabolites bind to androgen receptors.
PHARMACOKINETICS
Absorption
Testosterone decanoate, commonly formulated as the long-acting ester testosterone undecanoate, is absorbed through the lymphatic system when taken orally with food, thereby avoiding first-pass metabolism by the liver. It is also available as an intramuscular (IM) injection, which offers a prolonged depot effect. After absorption, enzymes cleave the undecanoate, releasing active testosterone into the bloodstream, which helps maintain elevated testosterone levels over an extended period.
Distribution
There is no published volume of distribution (Vd) value specifically for testosterone decanoate, but it is expected to be very high. This is due to its lipophilic (fat-soluble) properties, which cause it to accumulate extensively in the body's fatty tissues and muscles after injection.
Metabolism
Testosterone decanoate, whether injected or taken orally, is metabolized into active testosterone, but the process differs significantly based on the route of administration. With intramuscular injections, the compound is released slowly from a depot in the muscle and then broken down by enzymes in the bloodstream, resulting in stable, long-lasting testosterone levels.
Excretion
When injected, it is slowly released into the bloodstream and converted into active testosterone, which is then primarily metabolized in the liver and eliminated through the kidneys.
PHARMACODYNAMICS
As an androgen and anabolic-androgenic steroid (AAS), testosterone decanoate functions as a prodrug for testosterone. Administered via intramuscular injection, it is not used as a single-ingredient drug but is a component of the Sustanon® formulation, which contains a blend of four different testosterone esters.
ADMINISTRATION
Testosterone decanoate is an injectable form of testosterone that is part of the combination drug Sustanon 250. Sustanon 250 is a multi-component medication delivered via deep intramuscular injection.
DOSAGE AND STRENGTH
Testosterone decanoate is most commonly found as a component of the intramuscular injection.
Each milliliter of Sustanon 250 contains 250 mg of testosterone esters, comprising 100 mg of testosterone decanoate and 150 mg from a blend of three additional esters.
DRUG INTERACTIONS
Testosterone decanoate, often found in combination drugs like Sustanon, can interact significantly with several medications. It can increase the effects of blood thinners, such as warfarin or apixaban, raising the risk of bleeding. Co-administration with corticosteroids, like prednisone, can lead to increased fluid retention, which is especially concerning for individuals with pre-existing heart, liver, or kidney disease. In diabetic patients, testosterone may enhance the blood sugar-lowering effects of insulin and other diabetes medications, potentially requiring dosage adjustments.
FOOD INTERACTIONS
No food interactions are reported for testosterone decanoate, which is an injectable medication. Food interactions are relevant for oral medications, but testosterone decanoate is an intramuscular injection that bypasses the digestive system.
CONTRAINDICATIONS
Testosterone decanoate and other testosterone products are contraindicated in patients with known or suspected prostate or male breast cancer, as well as those with severe heart, liver, or kidney diseases. Additionally, they should not be used by women who are pregnant, breastfeeding, or planning to become pregnant. Pre-existing conditions like benign prostatic hyperplasia, high blood pressure, elevated red blood cell counts, sleep apnea, and known allergies to ingredients also require careful consideration or prohibit its use. In children, it is contraindicated due to the risk of premature growth plate closure.
SIDE EFFECTS
Skin problems.
Fluid retention.
Breast swelling.
Mood and behavioural changes.
Increased red blood cell count.
Urological changes.
Cardiovascular events.
Worsening sleep apnea.
Liver issues.
Prostate cancer.
Fertility impairment.
OVER DOSE
Many of the symptoms of an overdose are heightened versions of the drug's typical side effects.
Mental and mood changes.
Cardiovascular issues.
Fluid retention.
Prolonged erections.
Reproductive system effects.
Gynecomastia.
Hair and skin changes.
High red blood cell count.
TOXICITY
Testosterone decanoate toxicity is primarily associated with misuse or chronic overuse, as is common with anabolic-androgenic steroid abuse. While acute intramuscular overdose has very low toxicity, long-term abuse can lead to serious adverse effects affecting the cardiovascular, hepatic, and psychiatric systems.
