Somatuline Depot
Somatuline Depot
Generic Name
Somatuline Depot
Mechanism
- Somatostatin receptor agonist: Octreotide selectively binds to somatostatin receptor subtypes 5 (SSTR2) and 2 (SSTR5) on pituitary somatotrophs and neuroendocrine cells.
- Inhibition of secretory pathways: Activation of these G‑protein–coupled receptors triggers ↓cAMP production and increases potassium and calcium channel activity, resulting in ↓growth hormone, insulin, glucagon, and tumor‑derived peptide secretion.
- Reduced cell proliferation: Chronic receptor activation inhibits mitogenic signaling via MAPK/ERK and PI3K/AKT cascades, decreasing tumor cell growth.
Pharmacokinetics
| Parameter | Details |
| Absorption | Subcutaneous injection; forms a drug depot that slowly releases octreotide. |
| Bioavailability | ~15 % after SC administration; >50 % for depot formulation due to reduced first‑pass. |
| Peak plasma concentration | 10–30 µM h ~3–6 h after injection. |
| Half‑life | 33–53 h (extended‑release depot). |
| Distribution | Plasma protein binding ~ 95 % (primarily to albumin). |
| Metabolism | Hydrolysis by peptidases (serine and cysteine proteases) to inactive peptides. |
| Elimination | Renal excretion of metabolites; <10 % of unchanged drug. |
| Dosing interval | Every 4–6 weeks for maintenance therapy. |
Indications
- Acromegaly: Primary and adjunctive therapy to normalize growth hormone (GH) and insulin‑like growth factor‑1 (IGF‑1) levels.
- Gastro‑enteropancreatic neuroendocrine tumors (GEP‑NETs): Control of hormone‑mediated symptoms (e.g., carcinoid syndrome) and tumor growth.
- Cerebral meningioma and other hormone‑secreting pituitary tumors: Limited indications for symptomatic control.
- Pancreatic neuroendocrine tumors (pNETs): For syndrome suppression when surgery is contraindicated or incomplete.
Contraindications
- Absolute contraindications: Known hypersensitivity to octreotide, other somatostatin analogs, or excipients.
- Pregnancy and lactation: Category X – potential for fetal growth retardation.
- Clinical warnings:
- Diabetes mellitus: Can precipitate hyperglycemia or hypoglycemia.
- Gallbladder disease: Risk of gallstones due to biliary stasis.
- Cardiac conduction abnormalities: Monitor QT interval in patients with pre‑existing arrhythmias.
- Peripheral neuropathy: Usually reversible; dose adjustment if severe.
Dosing
- Initial dose (acromegaly):
- 10 µg SC every 4 weeks; titrate to a maintenance dose of 20–30 µg.
- For GEP‑NETs:
- 10 µg SC every 4 weeks; may increase to 20–30 µg depending on response.
- Administration technique:
- Inject into the thigh, buttock, or abdomen; rotate sites to avoid lipodystrophy.
- Patient education:
- Teach self‑injection under supervision; watch for injection site reactions.
Adverse Effects
Common (≥10 %)
• Injection site reactions (erythema, induration)
• Gastro‑intestinal disturbances: nausea, abdominal pain, diarrhea, constipation
• Hyperglycemia (≈ 8 %)
Serious (≤1 %)
• Severe gallstone formation leading to cholecystitis
• Persistent hyperglycemia requiring insulin adjustment
• Hypoglycemia (particularly in patients on oral hypoglycemics)
• Fetal growth restriction if used during pregnancy
• Severe hypersensitivity reactions (anaphylaxis)
Monitoring
| Parameter | Frequency | Rationale |
| IGF‑1, serum GH | Every 3–6 months | Confirm disease control |
| Blood glucose/HbA1c | Every 3–6 months; more frequently if diabetic | Detect dysglycemia |
| Liver function tests | Every 6–12 months | Detect hepatic toxicity |
| Ultrasound of gallbladder | Every 6–12 months (especially >5 yrs) | Early gallstone detection |
| Cardiac rhythm (QTc) | Baseline; annually if arrhythmia history | Risk of conduction delays |
| Body‑weight & BMI | Every visit | Monitor for metabolic changes |
Clinical Pearls
- Pulse‑injection avoidance: Somatuline Depot’s slow‑release profile reduces the “bolus” hyper‑sensitivity seen with short‑acting octreotide; it’s ideal for patients who report nausea with rapid injections.
- Switching with NDA caution: When switching from octreotide LAR to Somatuline Depot, a bridging dose of 10 µg SC weekly for 4 weeks mitigates transient GH spikes due to delayed absorption.
- Cardiac safety check: A baseline ECG is recommended for patients >50 yrs or with coronary disease; the long‑acting depot may prolong QT in a minority, especially at 30 µg doses.
- GI prophylaxis: Co‑prescribing a proton‑pump inhibitor (PPI) lowers the incidence of drug‑induced gastritis and abdominal pain.
- Drug–drug interaction: Rifampin and St. John’s wort can reduce octreotide levels; consider dose adjustment or alternative therapy.
- Pregnancy avoidance: Married patients in reproductive age should use effective contraception for at least 6 months after the last injection, due to the drug’s long half‑life.
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• *This drug card incorporates essential pharmacology, prescribing data, and high‑yield educational points to support medical students and clinicians in evidence‑based practice.*