Testosterone isocaproate

BRAND NAMES

Sustanon 100, Sustanon 250, and Omnadren 250. These are oil-based solutions for intramuscular injection.

MECHANISM OF ACTION

Testosterone isocaproate is a prodrug that is slowly released from an intramuscular injection site. Enzymes in the body then cleave off the isocaproate ester, freeing testosterone. This testosterone binds to androgen receptors, influencing gene transcription and causing anabolic effects like muscle growth and androgenic effects like the development of male characteristics. Some of the freed testosterone is also converted to dihydrotestosterone (DHT) and estrogen, which have their own effects. 

PHARMACOKINETICS

Absorption

Testosterone isocaproate is a prodrug that is absorbed slowly after an intramuscular injection, providing a sustained release of testosterone over an intermediate period. The "absorption" in this context refers to the gradual release of the testosterone ester from the oily depot formed in the muscle tissue, not a rapid uptake into the bloodstream. 

Distribution

There is no distinct volume of distribution (Vd) for testosterone isocaproate because it is a prodrug that is rapidly hydrolyzed into free testosterone upon entering systemic circulation. 

Metabolism

Testosterone isocaproate is a prodrug that is hydrolyzed by esterase enzymes to release active testosterone. This esterification enables a slow and sustained release of the hormone into the bloodstream from the site of intramuscular injection. Once freed, the active testosterone is then metabolized in the body, primarily in the liver. The main metabolic pathways include conversion into the more potent androgen dihydrotestosterone (DHT) through the 5-alpha-reductase enzyme and transformation into estradiol (estrogen) via the aromatase enzyme.

Excretion

Testosterone isocaproate is an esterified variant of testosterone that is not excreted in its original form. After intramuscular injection, esterase enzymes in the blood rapidly hydrolyze it into free, active testosterone and isocaproic acid. 

PHARMACODYNAMICS

Testosterone isocaproate is a moderately long-acting ester of testosterone that acts as a prodrug for testosterone. It is not active on its own; its pharmacodynamic effects are produced only after it is converted into active, un-esterified testosterone in the body. 

ADMINISTRATION

Testosterone isocaproate is not available as a single-ingredient product but is one of four testosterone esters found in the blend medication Sustanon. The administration involves a deep intramuscular (IM) injection, and the specific dosage and frequency are determined by a healthcare professional. 

DOSAGE AND STRENGTH

This medication is administered by deep intramuscular injection. The dosage and strength vary based on the particular formulation of the mixture.

DRUG INTERACTIONS

Testosterone isocaproate can interact with several medications, similar to other testosterone esters. Key interactions include increased bleeding risk when taken with anticoagulants like warfarin, and potential alterations in blood sugar that may require dosage adjustments for insulin or other diabetes medications. The combination with corticosteroids can heighten the risk of fluid retention, especially in those with heart, liver, or kidney conditions. Additionally, as the body processes testosterone, it can affect drugs metabolized by the liver and alter the results of thyroid function tests.

FOOD INTERACTIONS

Because testosterone isocaproate is an injectable medication, it bypasses the digestive system, meaning there are no specific food interactions that affect its absorption. However, individuals should be mindful if their medication is a combination product, like Sustanon, which contains peanut oil and should be avoided by those with a peanut allergy. While not direct interactions, a balanced diet rich in zinc and vitamin D can support overall hormonal health, while a high-fat diet could potentially complicate liver issues.

CONTRAINDICATIONS

Testosterone isocaproate should be avoided in men with prostate or breast cancer, women with confirmed or suspected breast cancer, and in pregnant or breastfeeding individuals. It should also be avoided in patients with severe congestive heart failure, uncontrolled high blood pressure, severe liver or kidney disease, elevated red blood cell levels, and in those who wish to conceive.

SIDE EFFECTS

• Skin issues.

• Injection site reactions.

• Weight changes.

• Fluid retention.

• Breast changes.

• Headaches.

• Mood fluctuations.

• Increased or decreased libido.

• Changes in blood work.

• Mental health.

• Fertility impairment.

OVER DOSE

• Cardiovascular events.

• Mental and emotional changes.

• Fluid retention.

• Polycythemia.

• Liver problems.

• Sexual and reproductive issues.

• Liver damage and tumors.

• Increased risk of certain cancers, including prostate cancer.

TOXICITY

Testosterone isocaproate can cause a range of serious health risks, particularly when abused at high doses. These risks are often connected to systemic hormonal imbalances and include cardiovascular events, liver damage, psychiatric issues, and complications from overdose.