1. Clinical Overview
Testosterone is the primary endogenous androgen, a steroid hormone synthesized from cholesterol in the Leydig cells of the testes (95%), and to a lesser extent in the adrenal cortex and ovaries. In the Indian market, the 1000mg strength is formulated as a long-acting intramuscular injection (Testosterone Undecanoate) for testosterone replacement therapy (TRT). It is a controlled-release depot preparation designed to maintain physiological testosterone levels for 10-14 weeks, significantly improving compliance compared to shorter-acting esters.
| Onset | Duration | Bioavailability |
|---|---|---|
| Gradual increase over 7 days, with steady-state levels achieved after the 2nd injection (loading dose). | Approximately 10 to 14 weeks per 1000mg injection. | Intramuscular: ~100% (systemic availability from depot). |
2. Mechanism of Action
Testosterone is the principal male sex hormone. Its effects are mediated through activation of the androgen receptor (AR), a ligand-dependent transcription factor. Upon binding, the receptor complex dimerizes, translocates to the nucleus, and binds to specific androgen response elements (AREs) on DNA, modulating gene transcription.
3. Indications & Uses
- Male hypogonadism (primary and secondary) confirmed by clinical symptoms and consistently low morning serum testosterone levels on at least two separate occasions.
- Delayed male puberty (under specialist supervision).
4. Dosage & Administration
Adult Dosage: For hypogonadism: 1000 mg intramuscularly, followed by a second 1000 mg injection after 6 weeks. Maintenance: 1000 mg every 10-14 weeks thereafter. Dose must be individualized based on serum testosterone trough levels (measured just before next injection), clinical response, and tolerability.
Administration: For DEEP INTRAMUSCULAR GLUTEAL INJECTION ONLY (upper outer quadrant). Must be administered by a healthcare professional. The vial must be warmed in hand for 1-2 minutes. Inject SLOWLY (over 1-2 minutes) to minimize pain and oil leakage. Patient should remain lying down for observation for 30 seconds post-injection. Rotate injection sites.
5. Side Effects
Common side effects may include:
- Injection site pain, swelling, or irritation
- Headache
- Increased hematocrit and hemoglobin (polycythemia)
- Acne or oily skin
- Increased frequency of erections
- Gynecomastia (due to aromatization)
- Fluid retention (edema)
- Mood swings, aggression ('roid rage' in susceptible individuals)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin/Anticoagulants | Testosterone may potentiate anticoagulant effect by reducing clotting factors; increased INR/bleeding risk. | Major |
| Corticosteroids (e.g., Prednisolone) | Increased risk of severe edema due to synergistic sodium and water retention. | Major |
| Insulin, Oral Hypoglycemics | Testosterone may decrease blood glucose; risk of hypoglycemia. Dose adjustment may be needed. | Moderate |
| Cyclosporine, Tacrolimus | Testosterone may inhibit CYP3A4, increasing levels of these drugs and risk of toxicity. | Moderate |
| ACTH, Corticotropin | Enhanced edema formation. | Moderate |
| Opioids, GnRH agonists | Can suppress testosterone production, potentially affecting TRT requirements. | Moderate |
7. Patient Counselling
- DO report for all scheduled injections and blood tests (Testosterone, Hematocrit, PSA, Lipids).
- DO inform all treating doctors (including dentists) that you are on testosterone therapy.
- DO practice safe handling. If a caregiver administers, they must wear gloves. Keep used vials/syringes away from children/pets.
- DON'T share this medicine with anyone. It is a controlled substance prescribed specifically for you.
- DON'T use it for bodybuilding or athletic performance enhancement.
- DON'T adjust the dose or interval without consulting your doctor.
8. Toxicology & Storage
Overdose: Symptoms are an extension of pharmacological effects: severe nausea/vomiting, priapism, aggressive behavior, significant fluid retention leading to heart failure, severe polycythemia, hypercalcemia (in metastatic disease), and jaundice.
Storage: Store below 25°C. Do not freeze. Keep the vial in the outer carton to protect from light. Keep out of reach and sight of children. After use, dispose of the vial and syringe as per biomedical waste guidelines. Do not reuse or recap needles.