1. Clinical Overview
Testosterone is a naturally occurring androgenic anabolic steroid hormone, primarily secreted by the Leydig cells of the testes. In its exogenous form, as a 250mg injectable preparation, it is a long-acting ester (typically testosterone enanthate or cypionate) used for testosterone replacement therapy (TRT) in males. It is a Schedule H drug in India, requiring strict medical supervision. It corrects the symptoms and signs of hypogonadism by restoring physiological testosterone levels.
| Onset | Duration | Bioavailability |
|---|---|---|
| Gradual, with symptomatic improvement often noted within 3-6 weeks of initiating therapy. | Approximately 2-4 weeks for a single 250mg intramuscular injection of testosterone enanthate/cypionate, depending on the individual's metabolism. | Approximately 100% for intramuscular injection, as it bypasses first-pass metabolism. |
2. Mechanism of Action
Testosterone is the primary endogenous androgen. Exogenous testosterone exerts its effects by binding to and activating the intracellular androgen receptor (AR). The hormone-receptor complex translocates to the nucleus, binds to specific DNA sequences (androgen response elements), and modulates the transcription of target genes, leading to the synthesis of proteins responsible for its effects.
3. Indications & Uses
- Male Hypogonadism (Primary and Hypogonadotropic)
- Delayed Male Puberty (with clear diagnostic criteria)
4. Dosage & Administration
Adult Dosage: For testosterone replacement in hypogonadism: 250mg intramuscularly every 2 to 4 weeks. Dose and interval MUST be individualized based on trough serum testosterone levels measured just before the next injection. Typical target range: 400-700 ng/dL.
Administration: For deep intramuscular (IM) injection only, typically into the gluteus maximus (upper outer quadrant) or vastus lateralis. Use a 21-23 gauge needle, 1-1.5 inches long. Aspirate before injection to avoid intravascular administration. Rotate injection sites. The oil-based solution should be at room temperature before administration.
5. Side Effects
Common side effects may include:
- Injection site pain, swelling, or erythema
- Acne or oily skin
- Increased frequency of erections or libido
- Headache
- Gynecomastia (breast tenderness/enlargement)
- Fluid retention (edema)
- Increased hematocrit and hemoglobin
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin / Oral Anticoagulants | Testosterone may potentiate anticoagulant effect by increasing synthesis of clotting factors? Actually, it can increase or decrease effect unpredictably; more commonly, it increases risk of bleeding by unknown mechanisms. INR must be monitored closely. | Major |
| Corticosteroids (e.g., Prednisolone) | Enhanced risk of severe fluid retention and edema. | Major |
| Insulin, Oral Hypoglycemics | Testosterone may decrease blood glucose and insulin requirements. Monitor blood glucose closely. | Moderate |
| Cyclosporine, Tacrolimus | Testosterone may inhibit metabolism of these drugs, increasing risk of toxicity. Monitor drug levels. | Moderate |
| Propranolol | Testosterone may increase clearance of propranolol, reducing its effect. | Moderate |
| Oxyphenbutazone | Increased serum levels of oxyphenbutazone. | Moderate |
7. Patient Counselling
- DO report for regular follow-up and blood tests (Testosterone, Hematocrit, PSA, Lipids).
- DO rotate injection sites as instructed.
- DO inform all your doctors (including surgeons and dentists) that you are on testosterone therapy.
- DON'T share your medication with anyone, especially athletes or bodybuilders.
- DON'T adjust the dose or frequency without consulting your doctor.
- DON'T use if the solution is discolored or contains particles.
8. Toxicology & Storage
Overdose: Symptoms are an extension of its pharmacologic effects: severe nausea, vomiting, headache, anxiety, priapism, excessive virilization, hypercalcemia (lethargy, confusion), severe polycythemia, hepatotoxicity, and uncontrolled hypertension. In women, profound virilization.
Storage: Store below 25°C. Protect from light. Do not freeze. Keep the vial in the outer carton. Keep out of reach and sight of children. Do not use after the expiry date printed on the label.