What is the most appropriate initial management for a patient with hypercalcemia due to metastatic lung cancer?

The most appropriate initial management for a patient with hypercalcemia due to metastatic lung cancer is intravenous normal saline. This approach serves a dual purpose: it helps to correct volume depletion, which is often present in patients with hypercalcemia, and it promotes renal excretion of calcium. By administering isotonic saline, hydration helps dilute the serum calcium levels and encourages the kidneys to filter and excrete excess calcium more efficiently.

In a hypercalcemic state, rapid hydration can significantly improve the patient's symptoms and mitigate complications associated with high calcium levels, such as kidney stones, gastrointestinal distress, and neurological issues. The intravenous route is preferred in this situation for faster action and improved efficacy compared to oral hydration.

While other treatments like calcium antagonists, oral bisphosphonates, and dialysis may play important roles in the management of hypercalcemia in different contexts, they are not first-line treatments in this acute scenario. Calcium antagonists can be used for certain types of hypercalcemia, bisphosphonates are effective for chronic management, and dialysis is generally reserved for severe cases or when other treatments have failed. Therefore, the initial management with normal saline is rooted in both physiological principles and practical urgency in treating malignant hypercalcemia.