Which medication is potentially worsening the hyponatremia in a patient on metformin, lisinopril, lovastatin, diltiazem, Buspar (buspirone), Seroquel (quetiapine), glipizide, hydrochlorothiazide, temazepam, terbinafine, and carvedilol?

From the Guidelines

Hydrochlorothiazide is the medication most likely worsening the hyponatremia in this patient. Thiazide diuretics like hydrochlorothiazide are a common cause of hyponatremia, particularly in elderly patients, as they inhibit sodium reabsorption in the distal convoluted tubule of the kidney, increasing sodium and water excretion [ 1 ]. This mechanism can lead to excessive sodium loss relative to water, resulting in dilutional hyponatremia. Additionally, thiazides impair the kidney's ability to dilute urine, which can exacerbate the problem.

Key Points to Consider

• The European Society of Cardiology guidelines suggest stopping thiazide diuretics in patients with hyponatremia, if possible [ 1 ].
• Other medications in the patient's regimen, such as lisinopril and carvedilol, may also contribute to hyponatremia, although their effects are typically less pronounced than thiazides.
• The patient should be monitored closely during medication adjustments, with regular electrolyte checks and assessment of volume status to guide further management.

Management Approach

• Temporarily discontinuing the hydrochlorothiazide while monitoring serum sodium levels may be an appropriate initial step.
• Consider switching to a loop diuretic, if possible, as suggested by the ESC guidelines [ 1 ].
• Regular monitoring of the patient's electrolyte levels and volume status is crucial to guide further management and prevent potential complications.

From the FDA Drug Label

Dilutional hyponatremia is life-threatening and may occur in edematous patients in hot weather; appropriate therapy is water restriction rather than salt administration, except in rare instances when the hyponatremia is life-threatening. The medication that is potentially worsening the hyponatremia is hydrochlorothiazide 2, as it can cause dilutional hyponatremia, especially in edematous patients.

• Key points:
  • Hydrochlorothiazide can cause dilutional hyponatremia
  • This condition may occur in edematous patients in hot weather
  • Appropriate therapy is water restriction rather than salt administration

From the Research

Medications Potentially Worsening Hyponatremia

• Hydrochlorothiazide is a thiazide diuretic that can cause hyponatremia, as reported in several studies 3, 4, 5.
• The mechanism of thiazide-induced hyponatremia is not fully understood, but it is thought to be related to the drug's effect on the kidneys, leading to water retention and sodium loss 4.
• Studies have shown that thiazide diuretics can cause severe hyponatremia, especially in susceptible patients, and that the risk of hyponatremia is higher in patients taking thiazides compared to those not taking them 3, 5.
• The incidence of thiazide-induced hyponatremia can be as high as 30% in some patient populations, and the number needed to harm (to result in one excess case of incident hyponatremia in 5 years) is approximately 15 5.

Management of Thiazide-Induced Hyponatremia

• Immediate withdrawal of the thiazide diuretic is crucial for treatment success, as it can help to correct the hyponatremia and prevent further complications 3.
• Other treatments, such as isotonic saline, fluid restriction, and hypertonic saline, may also be effective in managing thiazide-induced hyponatremia, but the choice of treatment depends on the severity of the hyponatremia and the patient's clinical status 3.
• It is essential to monitor patients taking thiazide diuretics for signs of hyponatremia, such as weakness, nausea, and confusion, and to adjust the treatment plan accordingly 6, 7.