Decapeptyl (Triptorelin): Clinical Uses and Administration
Primary Indications
Decapeptyl (triptorelin) is a GnRH agonist indicated for advanced prostate cancer, central precocious puberty, and off-label for uterine fibroids, with multiple formulations allowing flexible dosing intervals from 1 to 6 months. 1
Prostate Cancer
Standard Treatment Approach
- Triptorelin is equivalent to surgical castration (bilateral orchiectomy) and other LHRH agonists for metastatic hormone-naive prostate cancer. 2
- Available formulations include 3.75 mg (monthly), 11.25 mg (3-month), and 22.5 mg (6-month) administered intramuscularly. 2, 1
- The 6-month formulation achieves castrate testosterone levels (<50 ng/dL) in 97.5% of patients by day 29 and maintains suppression in 93% through 12 months. 3
Administration Protocol
- Antiandrogen therapy (flutamide, bicalutamide, or nilutamide) must be initiated 1 week before or coadministered with the first LHRH agonist injection and continued for at least 7 days to prevent testosterone flare in patients with metastatic disease or those at risk for spinal cord compression. 2
- For patients at high risk of immediate complications from metastases (e.g., spinal cord compression), avoid LHRH agonists initially; use bilateral orchiectomy, antiandrogen monotherapy, or LHRH antagonist instead. 2
- Testosterone levels increase transiently during the first week, peaking on days 2-4, before declining to castrate levels by weeks 3-4. 1
Monitoring Requirements
- Measure serum testosterone at baseline and every 4 weeks initially to confirm castration (<50 ng/dL). 1, 3
- Monitor PSA at baseline, then at 12-week intervals. 3
- Continue androgen deprivation therapy lifelong once initiated, even after progression to castration-resistant disease. 2
Critical Warnings
- Tumor flare phenomenon occurs in the first 2-3 weeks, potentially causing worsening bone pain, urinary obstruction, hematuria, or spinal cord compression with paralysis. 2, 1
- Monitor for cardiovascular events (myocardial infarction, stroke, sudden cardiac death), which have increased risk with GnRH agonists. 1
- Check baseline and periodic ECGs in patients with congenital long QT syndrome, heart failure, or electrolyte abnormalities, as triptorelin may prolong QT/QTc interval. 1
- Screen for metabolic syndrome: monitor lipids, glucose, and HbA1c periodically, as androgen deprivation increases risk of diabetes and cardiovascular disease. 1
Central Precocious Puberty (CPP)
Diagnostic Criteria
- CPP is defined as onset of secondary sexual characteristics before age 8 in girls or age 9 in boys, with bone age advancement ≥1 year over chronological age. 4
- Confirm diagnosis with GnRH stimulation test showing pubertal LH response (stimulated LH >5 IU/L). 4
Treatment Protocol
- Triptorelin 22.5 mg (6-month formulation) administered intramuscularly every 24 weeks is effective and safe for CPP. 4
- Alternative shorter-acting formulations (1-month or 3-month) are also available but require more frequent injections. 5, 4
- Treatment achieves LH suppression to prepubertal levels (stimulated LH ≤5 IU/L) in 93.2% of patients at 6 months and 97.7% at 12 months. 4
Monitoring Efficacy
- Urinary FSH from nocturnal spontaneous urine (≤5.24 IU/L), diurnal stimulated urine (≤6.94 IU/L), or nocturnal stimulated urine (≤5.78 IU/L) measured by immunochemiluminometric assay provides a non-invasive method to assess treatment efficacy. 6
- Perform triptorelin stimulation test (100 μg) at 3-month intervals to confirm adequate suppression. 6
- Monitor bone age, growth velocity, and pubertal staging at each visit. 4
Adverse Effects
- Hot flushes are the most common side effect (71.7% of patients). 3
- Local injection site reactions occur in 3.6% of patients. 1
- No unexpected adverse events have been reported in pediatric populations. 4
Uterine Fibroids (Off-Label Use)
Rationale and Duration
- GnRH agonists including triptorelin induce a hypoestrogenic state, causing fibroid shrinkage and symptom relief. 5
- Treatment duration should be limited to 3-6 months due to bone density loss from prolonged hypoestrogenism. 5
- Typically used as preoperative therapy to reduce fibroid size and vascularity before myomectomy or hysterectomy. 5
Formulation Selection
- Use 3.75 mg monthly or 11.25 mg 3-month formulations for short-term preoperative therapy. 2
- The 6-month formulation is less practical for this indication given the limited treatment duration. 5
Practical Administration Details
Injection Technique
- Reconstitute with 2 mL sterile water for injection immediately before use. 1
- Administer deep intramuscular injection into the gluteal muscle. 1, 7
- Subcutaneous administration is equally effective and well-tolerated for the depot formulation. 7
Cost Considerations
- Triptorelin (Trelstar) costs approximately $1,696 per 6 months across all formulations (3.75 mg monthly, 11.25 mg quarterly, or 22.5 mg biannually), with 340B pricing ranging from $97-$127 per dose. 2
- The 6-month formulation reduces injection frequency, potentially improving compliance and patient comfort. 5, 3
Common Pitfalls to Avoid
- Failing to provide antiandrogen coverage before initiating LHRH agonist therapy in patients with metastatic prostate cancer or high tumor burden risks catastrophic tumor flare with spinal cord compression. 2
- Discontinuing androgen deprivation therapy after progression to castration-resistant disease; castrate testosterone levels must be maintained lifelong. 2
- Using antiandrogen monotherapy as primary treatment for metastatic prostate cancer; it is inferior to castration. 2
- Overlooking cardiovascular risk assessment before initiating therapy; patients with pre-existing cardiac disease require closer monitoring. 1
- Neglecting to correct electrolyte abnormalities before treatment in patients at risk for QT prolongation. 1
- Treating uterine fibroids with GnRH agonists for >6 months without bone density monitoring or add-back hormone therapy. 5