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Trimethoprim-sulfamethoxazole-induced hyponatremia
Rebecca L Dunn1, Winter J Smith, Mark A Stratton
1Department of Pharmacy: Clinical and Administrative Sciences, University of Oklahoma Health Sciences Center College of Pharmacy, Oklahoma City, Oklahoma.
Summary
Trimethoprim-sulfamethoxazole (TMP-SMX) can cause hyponatremia, a rare adverse drug reaction. This case highlights TMP-SMX-induced hyponatremia occurring independently of hyperkalemia, confirmed by a rechallenge.
Area of Science:
- Pharmacology
- Nephrology
- Internal Medicine
Background:
- Hyponatremia is a common electrolyte imbalance, often associated with various medications.
- Trimethoprim-sulfamethoxazole (TMP-SMX) is an antibiotic frequently used for urinary tract infections and other bacterial infections.
- While TMP-SMX is generally well-tolerated, rare adverse drug reactions, including electrolyte disturbances, have been reported.
Observation:
- An 86-year-old male presented with hyponatremia during TMP-SMX therapy.
- Symptoms and serum sodium levels improved upon TMP-SMX discontinuation.
- A subsequent inadvertent rechallenge with TMP-SMX led to recurrent hyponatremia and similar symptoms.
Findings:
- This case demonstrates TMP-SMX-induced hyponatremia independent of hyperkalemia, a rare presentation.
- The Naranjo probability scale assigned a score of 7, indicating a probable link between TMP-SMX and hyponatremia.
- The challenge-rechallenge pattern strongly supports TMP-SMX as the causative agent.
Implications:
- Healthcare providers should consider TMP-SMX as a potential cause of hyponatremia, even without hyperkalemia.
- Monitoring of serum electrolytes and renal function is recommended during TMP-SMX treatment.
- This case adds to the understanding of rare adverse drug reactions associated with TMP-SMX.
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