Denosumab

# denosumab ## Overview - **Classification**: Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) Inhibitor, Monoclonal Antibody. - **Mechanism**: Binds to RANKL, preventing it from activating RANK on osteoclast precursors and osteoclasts, thereby inhibiting osteoclast formation, function, and survival, leading to decreased bone resorption. ## Primary Indications 1. **Osteoporosis**: Treatment of postmenopausal women and men at high risk of fracture. 2. **Prevention of Skeletal-Related Events (SREs)**: In patients with multiple myeloma and bone metastases from solid tumors. 3. **Treatment of Giant Cell Tumor of Bone (GCTB)**: For unresectable GCTB or where surgical resection would result in severe morbidity. 4. **Treatment of Hypercalcemia of Malignancy (HCM)**: Refractory to bisphosphonate therapy. ## Adult Dosing ### Standard Dosing **Osteoporosis (Prolia)** - **Dose**: **60 mg** - **Frequency**: Every **6 months** - **Route**: Subcutaneous (SC) injection - **Duration**: Long-term, typically continued unless intolerable side effects. **Prevention of Skeletal-Related Events (SREs) (Xgeva)** - **Dose**: **120 mg** - **Frequency**: Every **4 weeks** - **Route**: Subcutaneous (SC) injection - **Special Considerations**: Administer with calcium **500 mg** and vitamin D **400-1000 IU** daily. **Giant Cell Tumor of Bone (GCTB) (Xgeva)** - **Dose**: **120 mg** - **Frequency**: Days **1, 8, 15, and 29** of first month, then every **4 weeks** thereafter. - **Route**: Subcutaneous (SC) injection - **Special Considerations**: Administer with calcium **500 mg** and vitamin D **400-1000 IU** daily. **Hypercalcemia of Malignancy (HCM) (Xgeva)** - **Dose**: **120 mg** - **Frequency**: Days **1, 8, 15, and 29** of first month, then every **4 weeks** thereafter (dose may vary based on clinical response). - **Route**: Subcutaneous (SC) injection - **Special Considerations**: Administer with calcium **500 mg** and vitamin D **400-1000 IU** daily if not hypercalcemic. ### Dose Adjustments - **Renal Impairment**: No dose adjustment is required. However, patients with severe renal impairment (CrCl < 30 mL/min) or on dialysis are at significantly increased risk of severe hypocalcemia. - **Hepatic Impairment**: No dose adjustment is required. - **Elderly Patients**: No specific dose adjustment. Monitor closely for adverse effects, especially hypocalcemia. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: Not indicated. - **Special Notes**: Safety and efficacy have not been established. ### Infants (1-12 months) - **Dose**: Not indicated. - **Special Notes**: Safety and efficacy have not been established. ### Children (1-12 years) - **Dose**: Generally **not indicated** for osteoporosis. For Giant Cell Tumor of Bone (GCTB), use in this age group is usually **off-label** and reserved for severe, refractory cases. - **Frequency**: For GCTB, typically follows adult protocol: **120 mg** on Days 1, 8, 15, 29, then every 4 weeks. - **Maximum**: **120 mg** - **Special Notes**: Use only after multidisciplinary consultation. Risk of growth plate suppression is a concern in skeletally immature children. Closely monitor calcium and vitamin D levels. ### Adolescents (13-18 years) - **Giant Cell Tumor of Bone (GCTB)**: For skeletally mature adolescents (12 years and older) with unresectable GCTB. - **Dose**: **120 mg** - **Frequency**: Days **1, 8, 15, and 29** of first month, then every **4 weeks** thereafter. - **Route**: Subcutaneous (SC) injection - **Osteoporosis**: Not indicated for osteoporosis in this age group. - **Maximum**: **120 mg** per dose. - **Special Notes**: Verify skeletal maturity before administration. Administer with calcium **500 mg** and vitamin D **400-1000 IU** daily. ## Safety Information ### Contraindications - **Absolute**: Hypocalcemia (must be corrected prior to initiation). - **Absolute**: Hypersensitivity to denosumab or any component of the formulation. - **Absolute**: Pregnancy (for osteoporosis indication). - **Absolute**: Lactation (for osteoporosis indication). ### Common Adverse Effects - **Very Common (>10%)**: Hypocalcemia, back pain, pain in extremity, musculoskeletal pain, arthralgia. - **Common (1-10%)**: Osteonecrosis of the jaw (ONJ), rash, cellulitis, hypercholesterolemia, cystitis. - **Serious but Rare**: Atypical femoral fractures, severe symptomatic hypocalcemia, serious infections (e.g., cellulitis), new primary malignancies, severe allergic reactions (anaphylaxis). ### Key Drug Interactions - **Immunosuppressants**: Increased risk of serious infections. Avoid co-administration if possible. - **Chemotherapy/Radiotherapy**: Increased risk of osteonecrosis of the jaw (ONJ). - **Other Bone Resorption Inhibitors (e.g., bisphosphonates)**: Concomitant use is not recommended due to additive effects and potential for increased toxicity. ## Monitoring & Follow-up - **Before Treatment**: - Verify normal serum calcium and correct hypocalcemia if present. - Dental exam (especially for cancer indications). - Baseline renal function. - **During Treatment**: - Serum calcium: Monitor frequently (e.g., weekly for first month for Xgeva, more often if at high risk of hypocalcemia). - Dental exam: Routine exams, especially if risk factors for ONJ. - Renal function: Periodically, especially in patients with severe impairment. - Signs/symptoms of hypocalcemia, ONJ, atypical femoral fracture. - **Clinical Signs**: Muscle cramps, twitching, spasms, numbness/tingling (hypocalcemia), jaw pain, swelling, non-healing sores (ONJ), new or unusual thigh/groin pain (atypical femoral fracture). ## Clinical Pearls - 💡 **Calcium/Vitamin D Supplementation**: Crucial for all patients to minimize hypocalcemia risk, especially with Xgeva. - 💡 **Injection Technique**: Administer SC into the upper arm, upper thigh, or abdomen. Do not inject into areas of skin that are tender, bruised, or hardened. - 💡 **Oral Hygiene**: Emphasize good oral hygiene and regular dental check-ups, especially for patients receiving Xgeva. - 💡 **Discontinuation Risks**: Rapid bone loss and increased fracture risk can occur after Prolia discontinuation. Rebound vertebral fractures are a concern. Consider alternative anti-resorptive therapy. - 💡 **Patient Counseling**: Instruct patients to report any new or unusual thigh/groin pain or jaw pain/swelling promptly. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.