From the FDA Drug Label
Hyponatremia: Severe and symptomatic hyponatremia can occur in patients receiving sulfamethoxazole and trimethoprim, particularly for the treatment of P. jirovecii pneumonia. Evaluation for hyponatremia and appropriate correction is necessary in symptomatic patients to prevent life-threatening complications Bactrim and Hyponatremia:
- Bactrim can cause severe and symptomatic hyponatremia, especially in patients being treated for P. jirovecii pneumonia.
- It is essential to evaluate and correct hyponatremia in symptomatic patients to prevent life-threatening complications. 1
From the Research
Bactrim (trimethoprim-sulfamethoxazole) can cause hyponatremia, particularly in elderly patients or those with predisposing conditions, and clinicians should monitor serum sodium levels and be aware of the risk of electrolyte disturbances, as highlighted in a recent study 2.
Causes and Risk Factors
The trimethoprim component of Bactrim inhibits sodium reabsorption in the distal tubule of the kidney, acting similarly to potassium-sparing diuretics, which can lead to hyponatremia. The risk of hyponatremia increases with higher doses and longer treatment duration, and patients with baseline electrolyte abnormalities or those taking other medications that can lower sodium levels are at higher risk.
Symptoms and Diagnosis
Symptoms of hyponatremia include headache, confusion, nausea, seizures, and in severe cases, coma. Clinicians should be aware of these symptoms and consider hyponatremia in patients taking Bactrim, especially if they have predisposing conditions. A study published in 2022 2 found that hyponatremia induced by TMP/SMX manifested as nausea, vomiting, or asymptomatic hyponatremia, and the median serum sodium concentration was 118 mmol/L.
Treatment and Management
If hyponatremia develops, consider discontinuing Bactrim and providing appropriate sodium replacement based on the severity of the condition, as recommended in a review of hyponatremia diagnosis and management 3. For patients requiring continued antimicrobial therapy, switching to an alternative antibiotic without this side effect profile may be necessary. The hyponatremia typically resolves within days after discontinuation of the medication.
Key Considerations
- Monitor serum sodium levels in patients taking Bactrim, especially in high-risk patients.
- Be aware of the risk of electrolyte disturbances caused by Bactrim.
- Consider hyponatremia in patients taking Bactrim who present with symptoms such as headache, confusion, or nausea.
- Discontinue Bactrim and provide appropriate sodium replacement if hyponatremia develops.
- Switch to an alternative antibiotic if necessary to prevent further electrolyte disturbances.