Can any of these medications cause hyponatremia and hypochloremia?

Carbamazepine is the Culprit for Hyponatremia and Hypochloremia

Among the medications listed, carbamazepine is definitively causing the low sodium and chloride levels through the syndrome of inappropriate antidiuretic hormone secretion (SIADH). 1

Mechanism and Evidence for Carbamazepine

Carbamazepine directly causes hyponatremia through SIADH, and the risk is dose-related. 1 The FDA drug label explicitly states: "Hyponatremia can occur as a result of treatment with carbamazepine. In many cases, the hyponatremia appears to be caused by the syndrome of inappropriate antidiuretic hormone secretion (SIADH)." 1

• At the patient's dose of 600 mg daily (200 mg three times daily), carbamazepine-induced hyponatremia occurs with a frequency ranging from 4.8% to 40% depending on the patient population 2
• The mechanism involves altered sensitivity of hypothalamic osmoreceptors to serum osmolality and potentially increased renal tubular sensitivity to circulating ADH 2
• Carbamazepine causes both hyponatremia AND hypochloremia together, as documented in clinical cases 3

Risk Factors Present in This Patient

Elderly patients and those treated with diuretics are at greater risk of developing hyponatremia with carbamazepine. 1 While we don't have complete patient demographics, several risk factors may apply:

• Age >40 years increases risk 4
• Female gender increases risk 4
• Concomitant use of medications associated with hyponatremia 4
• The dose-dependent nature means even therapeutic dosing can cause this effect 1

Clinical Significance and Symptoms

Signs and symptoms of carbamazepine-induced hyponatremia include headache, new or increased seizure frequency, difficulty concentrating, memory impairment, confusion, weakness, and unsteadiness leading to falls. 1

• Patients with carbamazepine-induced hyponatremia have a 7-fold increased risk of developing adverse effects during treatment 5
• Common symptoms include dizziness (28%), tiredness (22%), instability (19%), and diplopia (16%) 5
• Severe hyponatremia (≤128 mEq/L) causes symptoms in 83% of patients 5

Other Medications: Minimal to No Risk

The remaining medications on this list have negligible risk for causing hyponatremia:

• Atorvastatin: No established association with hyponatremia 6
• Sotalol: Not listed among medications causing hyponatremia in cardiovascular guidelines 6
• Montelukast: No documented association with electrolyte disturbances
• Aspirin: Not associated with hyponatremia 6
• Zolpidem: Not documented to cause hyponatremia
• CBD gummies: Insufficient evidence for hyponatremia risk

Management Recommendations

Consider discontinuing carbamazepine in patients with symptomatic hyponatremia. 1

• Check serum sodium and chloride levels immediately 1
• If sodium is <130 mmol/L, treatment should be initiated 6
• For symptomatic hyponatremia: discontinue carbamazepine and provide supportive care with fluid restriction or hypertonic saline depending on severity 1
• Hyponatremia is rapidly reversible after carbamazepine discontinuation 3
• Alternative antiepileptic medications should be considered if seizure control is needed 3

Critical Pitfall to Avoid

Do not rapidly correct severe hyponatremia to avoid central pontine myelinolysis. 6 After initial rapid correction to attenuate symptoms (5 mmol/L in the first hour), serum sodium should not increase more than 8 mmol/L per day. 6