How to manage hypocalcemia caused by Frusemide (Furosemide)?

From the Guidelines

To manage hypocalcemia caused by Frusemide, reduce the Frusemide dose if possible and supplement with oral calcium, typically calcium carbonate 1000-1500 mg elemental calcium daily in divided doses, as Frusemide increases urinary calcium excretion through inhibition of calcium reabsorption in the loop of Henle 1.

Causes and Mechanism

Frusemide, a loop diuretic, can cause hypocalcemia by increasing urinary calcium excretion, which can lead to a decrease in serum calcium levels. This is due to the inhibition of calcium reabsorption in the loop of Henle, as seen in the mechanism of action of loop diuretics like Frusemide 1.

Management

• Reduce Frusemide dose if possible to minimize calcium loss
• Supplement with oral calcium, typically calcium carbonate 1000-1500 mg elemental calcium daily in divided doses
• For severe symptomatic hypocalcemia, administer intravenous calcium gluconate 1-2 grams over 10-20 minutes with cardiac monitoring
• Vitamin D supplementation (800-1000 IU daily) should be added to enhance calcium absorption
• Monitor serum calcium, magnesium, and potassium levels regularly, as Frusemide causes loss of multiple electrolytes
• Magnesium replacement may be necessary (typically 400-800 mg oral magnesium oxide daily) since hypomagnesemia can worsen hypocalcemia by impairing parathyroid hormone action

Alternative Diuretics

In patients requiring long-term Frusemide therapy, consider switching to a thiazide diuretic if appropriate for the clinical situation, as thiazides actually decrease urinary calcium excretion, unlike loop diuretics 1.

From the FDA Drug Label

As with any effective diuretic, electrolyte depletion may occur during furosemide therapy, especially in patients receiving higher doses and a restricted salt intake ... All patients receiving furosemide therapy should be observed for these signs or symptoms of fluid or electrolyte imbalance (hyponatremia, hypochloremic alkalosis, hypokalemia, hypomagnesemia or hypocalcemia): dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, arrhythmia, or gastrointestinal disturbances such as nausea and vomiting. Furosemide may lower serum levels of calcium (rarely cases of tetany have been reported) and magnesium. Accordingly, serum levels of these electrolytes should be determined periodically

Management of Hypocalcemia caused by Frusemide (Furosemide):

• Monitor serum calcium levels periodically in patients receiving furosemide therapy.
• Correct or avoid hypocalcemia by ensuring adequate calcium intake or supplementing with calcium if necessary.
• Be aware of the signs and symptoms of hypocalcemia, such as muscle cramps, weakness, and tetany, and manage them promptly.
• Consider temporarily withdrawing the drug or adjusting the dose if hypocalcemia occurs 2.

From the Research

Hypocalcemia Caused by Frusemide (Furosemide)

• Frusemide (Furosemide) is a loop diuretic that can cause hypocalcemia due to increased renal calcium excretion 3.
• The effect of furosemide on calcium transport molecules in distal tubules has been investigated, and it was found that furosemide enhances urinary calcium excretion, which is associated with an increase in mRNA levels of TRPV5, TRPV6, and calbindin-D28k 3.

Management of Hypocalcemia Caused by Frusemide

• To manage hypocalcemia caused by frusemide, it is essential to monitor serum calcium levels and adjust the dosage of frusemide accordingly 4.
• In some cases, frusemide may increase serum calcium levels, especially at low dosages 4.
• However, at higher dosages, frusemide may lead to urinary losses of calcium, resulting in hypocalcemia 4.
• The use of calcium supplements or other medications that can help maintain normal serum calcium levels may be necessary in some cases 5, 6.
• It is also important to note that furosemide can blunt the response to parathyroid extract, which may affect the evaluation of parathyroid function in patients taking furosemide 7.

Key Findings

• Furosemide increases renal calcium excretion, leading to hypocalcemia 3, 5, 6.
• The increase in calcium excretion is associated with an increase in mRNA levels of calcium transport molecules 3.
• Furosemide can also increase intestinal calcium absorption, which may help maintain normal serum calcium levels 6.
• The effects of furosemide on serum calcium levels and parathyroid function should be carefully monitored and managed in patients taking this medication 4, 7.