Denosumab is a bone anti-resorptive drug used for the treatment of the following:
Denosumab is a total human IgG2 monoclonal antibody that binds to receptor activator of NF kappa B ligand (RANKL) and competitively inhibits its binding to receptor activator of NF kappa B (RANK). Soluble RANKL is a trimer and a member of the tumor necrosis factor (TNF) family of ligands. Each RANKL trimer can bind and oligomerize up to three receptors. When bound to RANK, RANKL potentiates osteoclast differentiation from hematopoietic stem cells and activates and prolongs the survival of mature osteoclasts. Osteoclasts primary function then is to promote bone resorption. Denosumab binds to RANKL with high affinity and blocks it from binding to and oligomerizing its receptor RANK, thus inhibiting osteoclast maturation and bone resorption.
Administer via subcutaneous injection only and should not be administered via intravenously or intramuscularly. Injection sites include the upper arm, upper thigh, or abdomen. No observation or premedication is required. Dosing is prescribed as 120 mg/1.7 mL (70 mg/mL) solution in a single-dose vial or as a single-use pre-filled syringe containing 60 mg in a 1 mL solution. Administer vitamin D and calcium as necessary to treat or prevent hypocalcemia — no dosing adjustments required for hepatic or renal impairment. The distribution and timing of doses depend on the pathology as shown below.
Adverse effects include the following based on body systems:
Central nervous system:
Hematologic and oncologic:
Neuromuscular and skeletal:
Possible pregnancy should be evaluated before initiation of treatment. Obtaining vitamin D level and clearance from a dentist is suggested before the initiation of therapy. Within the first few weeks of treatment, recommended monitoring of serum creatinine, calcium, phosphorus, and magnesium. Monitor for signs and symptoms of hypocalcemia as well as hypercalcemia upon discontinuation of denosumab. A dental exam should is recommended if osteonecrosis of the jaw is suspected. The evaluation of bone mineral density should occur anywhere between one to two years after initiating treatment. The recommendation is for periodic monitoring of vitamin D and serum calcium throughout treatment duration.
Atypical bone fractures: Although the incidence remains low, an association with atypical bone fractures exists with prolonged bisphosphonate therapy. However, these fractures have also been observed in those receiving denosumab for osteoporosis or metastatic bone disease. These fractures are usually located in the subtrochanteric region or along the shaft of the femur. Patients tend to feel prodromal pain from weeks to months leading up to the fracture. Fractures commonly occur with little to no trauma in the area. Experts are unsure at this time if the atypical fractures occur secondary to denosumab toxicity or the patient’s underlying osteoporosis. Patients should receive counseling regarding the potential for new hip or thigh pain and the contralateral limb examined if an atypical fracture is suspected. Upon diagnosis of an atypical fracture, possible discontinuation of denosumab is an option. If discontinued, consider initiating a different osteoporosis therapy due to an increased risk of fracture.
Hypersensitivity: Clinically severe and anaphylactic reactions have been reported. Symptoms may include rash, pruritus, urticaria, facial edema, airway edema, and possibly hypotension. If these symptoms occur, initiate appropriate treatment and subsequently discontinue denosumab.
Hypocalcemia: Due to its anti-resorptive effects, denosumab has the potential to cause hypocalcemia. Severe, even fatal, cases of denosumab-induced hypocalcemia have been documented. Those with severe renal dysfunction may have an increased risk of developing hypocalcemia. Serum calcium should be obtained, and preexisting hypocalcemia corrected at the initiation of treatment. In patients with preexisting hypocalcemia, serum calcium should be monitored more frequently. Use denosumab with caution in those who have predisposing conditions to hypocalcemia.
Osteonecrosis of the jaw (ONJ): Reports of ONJ have been observed in those receiving denosumab. Symptoms may include jaw pain, tooth infection, bone, and gingival erosion, toothache. An increased risk of being diagnosed with ONJ correlates directly to the duration of denosumab exposure. Those with predisposing factors, such as poor dentition and recent tooth extraction, are at a higher risk. If ONJ is suspected, make arrangements for a thorough dental exam. Risk of ONJ is considerably higher in patients with malignancy receiving denosumab than in patients with osteoporosis receiving denosumab. Denosumab should not be initiated until dental health is optimized. While on denosumab for cancer therapy, dental procedures are contraindicated. If ONJ is suspected, denosumab should be discontinued.
Dermatologic reactions: Reports of dermatitis, eczema, and rash have been observed. If symptoms are severe, consider discontinuation of denosumab.
Healthcare workers including primary care physicians and nurse practitioners who prescribe denosumab should monitor the patients. Pharmacists should assist in monitoring for side effects. The patient should get a baseline evaluation from the dentist prior to initiating treatment. At regular intervals, the patient's electrolytes and renal function should also be monitored. The most severe complication of therapy is osteonecrosis of the jaw, and thus an oral exam is necessary at each visit. Periodic bone density evaluation every 1-2 years is recommended. Only through close monitoring of the patient can the morbidity of this agent be decreased.