1. Clinical Overview
Triptorelin is a synthetic decapeptide analogue of Gonadotropin-Releasing Hormone (GnRH). The 11.25mg formulation is a long-acting, sustained-release depot injection used for the palliative treatment of advanced hormone-dependent prostate cancer and for the management of central precocious puberty. It acts as a potent GnRH agonist, initially stimulating then profoundly suppressing pituitary gonadotropin secretion, leading to a medical castration or suppression of puberty.
| Onset | Duration | Bioavailability |
|---|---|---|
| Initial stimulation (flare): Within 1-3 days. Therapeutic suppression: Achieved within 2-4 weeks of the first injection. | Sustained for 3 months (84 days) per 11.25mg depot injection. | Approximately 53% after intramuscular injection (depot formulation). |
2. Mechanism of Action
Triptorelin is a superagonist of the endogenous GnRH receptor. Continuous, non-pulsatile stimulation of pituitary GnRH receptors leads to an initial flare (upregulation) followed by profound downregulation and desensitization of these receptors. This inhibits the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In males, the suppression of LH leads to a dramatic reduction in testicular testosterone production (medical castration). In central precocious puberty, it halts the premature activation of the hypothalamic-pituitary-gonadal axis.
3. Indications & Uses
- Palliative treatment of advanced hormone-dependent prostate carcinoma (Stage C or D)
- Management of Central Precocious Puberty (CPP) in children (both sexes)
4. Dosage & Administration
Adult Dosage: Prostate Cancer: 11.25mg as a single intramuscular (IM) injection into the gluteal region every 3 months (84 days). Pre-treatment with an oral anti-androgen for at least 2 weeks before and 2-4 weeks after the first injection is recommended.
Administration: For IM use only. Reconstitute the microsphere powder with the provided sterile diluent (typically 2mL). Shake well to form a uniform milky suspension. Adminish immediately via deep IM injection into the upper outer quadrant of the gluteus. Do not inject intravenously. Rotate injection sites.
5. Side Effects
Common side effects may include:
- Hot flashes (flushes)
- Injection site reactions (pain, induration, erythema)
- Loss of libido
- Erectile dysfunction
- Fatigue
- Headache
- Increased weight
- Arthralgia/myalgia
- Initial disease flare in prostate cancer (worsening bone pain, urinary symptoms)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Bicalutamide, Flutamide | Concomitant use is standard to block the initial testosterone flare. Synergistic therapeutic effect. | Major (Beneficial) |
| Corticosteroids (e.g., Dexamethasone) | May suppress ACTH and reduce the efficacy of triptorelin. Monitor. | Moderate |
| Drugs that prolong QT interval (e.g., Class IA/III antiarrhythmics, certain antipsychotics, antibiotics) | Additive risk of QT prolongation. Monitor ECG and electrolytes. | Moderate |
| Sex hormones (androgens, estrogens) | Counteracts the therapeutic effect of triptorelin. Contraindicated. | Major |
7. Patient Counselling
- Do report any new or worsening bone pain, difficulty urinating, or neurological symptoms (leg weakness, numbness) immediately after the first injection.
- Do keep all scheduled 3-month injection appointments to maintain suppression.
- Do discuss bone health (calcium, vitamin D, exercise) with your doctor.
- Don't stop the medication without consulting your doctor.
- Don't miss the recommended pre-treatment with anti-androgen tablets (for prostate cancer).
8. Toxicology & Storage
Overdose: Acute overdose is unlikely due to depot administration. Symptoms would be an exaggeration of pharmacologic effects: severe hot flashes, profound hypotension, nausea, vomiting, and potentially increased severity of the initial disease flare in cancer patients.
Storage: Store unopened vials in a refrigerator between 2°C and 8°C. Do not freeze. Protect from light. After reconstitution, the suspension is stable for up to 24 hours if refrigerated (2°C-8°C), but should be administered immediately for optimal sterility. Do not use if the suspension has separated and cannot be reconstituted into a homogeneous milky liquid.