Newer agents for the treatment of malignant hypercalcemia

Electrolyte complications of malignancy

A thorough working knowledge of the diagnosis and treatment of life-threatening electrolyte abnormalities in cancer patients, especially hyponatremia, hypoglycemia, and hypercalcemia, is essential to the successful practice of emergency medicine. Although most minor abnormalities have no specific treatment, severe clinical manifestations of several notable electrolytes occur with significant frequency in the setting of malignancy. The treatment of life-threatening electrolyte abnormalities is reviewed here. Promising future treatments directed at the underlying physiology are also introduced.

Paraneoplastic syndromes associated with bronchogenic carcinoma

Paraneoplastic syndromes associated with lung cancer are diverse in their presentation, pathophysiology, and implications. They can be seen as a diagnostic and therapeutic challenge or as an opportunity to detect an otherwise asymptomatic malignancy. Unraveling the mechanisms that produce these syndromes will lead to insight into tumor biology that will be translated into novel approaches for early detection and therapy.

Use of pamidronate in the management of acute cancer-related hypercalcemia in children

PURPOSE

To determine whether pamidronate is a safe and effective agent for the treatment of severe hypercalcemia of malignancy in children.

MATERIALS AND METHODS

A retrospective review of the charts of five children treated with pamidronate 1-2 mg/kg for severe, refractory hypercalcemia of malignancy. All children failed conventional therapy. Statistical analysis was done utilizing the two-tailed Student's t-test.

RESULTS

All five children had complete resolution of their hypercalcemia in a predictable pattern within 24-48 hours. The average decrease in serum calcium was 1.63 mmol/L (6.54 mg/dl). (P < .01) The adverse effects were mild and transient, and consisted of hypocalcemia, hypophosphatemia, and hypomagnesemia.

CONCLUSIONS

Pamidronate at a dose of 1 mg/kg is a safe and effective treatment for severe, refractory hypercalcemia of malignancy in children.

Immobilization hypercalcemia in incomplete paraplegia: successful treatment with pamidronate

Immobilization hypercalcemia (IH) occurs in adolescent patients with high-level complete tetraplegia, but it has not been reported in patients with incomplete paraplegia. We describe two adolescent patients with low-level incomplete paraplegia who developed IH during comprehensive rehabilitation. Conventional therapies with hydration, diuresis, and calcitonin were not effective. Finally, a single-dose infusion of pamidronate, an amino-bisphosphonate, completely resolved the hypercalcemia. Although it has a pharmacologic profile similar to etidronate, pamidronate is more potent, being effective in a single dose, has fewer adverse effects, and has a longer action than etidronate. These features make pamidronate more suitable for the treatment of severe IH in rehabilitation settings. It is reasonable to consider immobilization as the cause of hypercalcemia in low-level incomplete paraplegic patients who have other contributing factors.

Preparation and evaluation of chitosan microspheres containing bisphosphonates

Local implantation or injection of microspheres containing bisphosphonates for site-specific therapy may aid in treating several pathological conditions associated with bone destruction. Chitosan microspheres containing two antiresorption and anticalcification agents, pamidronate and suberoylbisphosphonate (SuBP), were prepared from a w/o emulsion. Various formulation variables were studied for their effect on the release rate profile of these bone-seeking agents. Polymer coating of micromatrices yielded microspheres with the most retarded release rate, and the drug delivery system was found biocompatible in endothelial cell culture. The microspheres were examined in vitro and in vivo for release kinetics and drug disposition. The release of bisphosphonate from the microspheres was faster in vitro than in vivo. Drug disposition following implantation of microspheres in the tibialis muscle resulted in a relatively increased disposition in the adjacent tibia while injection of drug solution in the tibialis muscle resulted in uniform disposition of the drug in the femorae and tibiae. Bisphosphonate released from chitosan microspheres effectively inhibited bioprosthetic tissue calcification in the rat subdermal model.

Hypercalcemia and electrolyte disturbances in malignancy

Hypercalcemia and electrolyte abnormalities are common problems in patients with malignancy. In this article we discuss the pathophysiology, clinical features, and management of hypercalcemia, which is the most common metabolic abnormality. We also analyze the electrolyte disturbances that occur in association with malignancy, including hyponatremia, hypokalemia, hypomagnesemia, hypophosphatemia, and hyperkalemia. Recognition and treatment of these disturbances are important parts of the management of patients with malignant disease.

The management of hypercalcemia of malignancy

Hypercalcemia (HCM) occurs in 10-15% of all malignancies, predominantly in patients with solid tumors. This metabolic complication leads to significant morbidity and impairment of quality of life. Recent insights into the pathophysiology of HCM include an understanding of the role of parathyroid-hormone-related peptide and several cytokines secreted by tumors. The osteoclast plays a central role as the final common pathway through which these hormones and cytokines act to cause bone lysis. These findings have led to the development of new treatment strategies. Foremost among these has been the introduction of agents such as the newer bisphosphonates and gallium nitrate, which are potent inhibitors of osteoclast-mediated bone resorption. The clinician can now choose from an array of therapeutic approaches based on a consideration of the mechanisms of action, individual clinical circumstances, efficacy, toxicities and costs of available agents. In addition to their use in the management of HCM, non-toxic drugs that effectively inhibit osteoclast function, such as the bisphosphonates, are playing an emerging role in the palliative treatment of the more common clinical problems of painful lytic bone metastases and osteoporosis.