What commonly used medications cause hypercalcemia and how?
Vitamin D toxicity, which usually develops in vitamin faddists, manifests clinically with hypercalcemia. In general, serum 25D levels above 80 ng/mL are necessary for vitamin D toxicity, though much higher levels are typically seen in symptomatic hypercalcemia.
Hypercalcemia also occurs in CKD patients treated for secondary hyperparathyroidism with pharmacologic doses of active vitamin D, like calcitriol (1,25D) or synthetic analogs (paricalcitol, doxercalciferol, etc.). Hypercalcemia is dose-dependent and transient, resolving within a few days of the drug being discontinued.
Vitamin A intoxication, more commonly seen today with dermatologic or oncologic use of vitamin A analogues, causes hypercalcemia via osteoclast-mediated bone resorption.
Thiazide diuretics reduce urinary calcium excretion via the sodium-calcium exchanger in the distal tubule. However, hypercalcemia from thiazide diuretics occurs mainly in patients with underlying mild primary hyperparathyroidism.
Lithium interferes with CaSR, resulting in an increase in the set point at which calcium is suppressed. Patients on chronic lithium therapy can develop mild hypercalcemia, which subsides when medication is stopped in most cases.
Hypercalcemia, a condition characterized by elevated levels of calcium in the blood, can be caused by various medications. Some commonly used medications that may lead to hypercalcemia include:
- Thiazide Diuretics: Thiazide diuretics, commonly prescribed for high blood pressure and edema, can reduce calcium excretion by the kidneys, leading to increased calcium levels in the blood.
- Calcium Supplements: Taking excessive amounts of calcium supplements can lead to hypercalcemia, especially if not prescribed or monitored by a healthcare professional.
- Vitamin D Supplements: High doses of vitamin D supplements can increase the absorption of calcium from the intestines, potentially causing hypercalcemia.
- Lithium: Lithium, a medication used to treat bipolar disorder, can cause hypercalcemia by various mechanisms, including direct effects on the parathyroid glands.
- Certain Antacids: Some antacid medications, particularly those containing calcium carbonate, can contribute to elevated calcium levels in the blood if used excessively.
- Calcitriol: Calcitriol is an active form of vitamin D used to treat conditions like hypocalcemia and certain kidney disorders. However, excessive use of calcitriol can lead to hypercalcemia.
- Teriparatide: Teriparatide is a medication used to treat osteoporosis by promoting bone formation. However, it can increase calcium levels in the blood.
- Tamoxifen: Tamoxifen, a medication used in breast cancer treatment, can rarely cause hypercalcemia as a side effect.
It’s important to note that not everyone taking these medications will experience hypercalcemia. The development of hypercalcemia may depend on factors such as individual susceptibility, dosage, duration of treatment, and any underlying medical conditions.
If you are taking any of these medications and experience symptoms of hypercalcemia, such as excessive thirst, frequent urination, nausea, vomiting, constipation, weakness, or confusion, it’s essential to inform your healthcare provider immediately. Prompt evaluation and management are necessary to prevent complications associated with high calcium levels.