Hyponatremia is a common adverse effect of many drugs (diuretics, antipsychotic agents, carbamazepine, and others). Among the uncommon causes of hyponatremia are theophylline and trimethoprim. We describe a woman who presented with severe symptomatic hyponatremia following treatment with anhydrous theophylline and developed trimethoprim-induced severe hyponatremia 6 months later.
A 78-year-old woman was admitted to the hospital because of severe hyponatremia (plasma sodium level, 117 mmol/L), weakness, abdominal pain, nausea, and vomiting. Her medical history included arterial hypertension, hypercholesterolemia, bronchial asthma, occasional abdominal pain, and dizziness, for which she was treated with cilazapril, albuterol sulfate, budesonide, famotidine, and mebeverine hydrochloride. One week before admission, she was treated with trimethoprim-sulfamethoxazole for a presumptive urinary tract infection.
Dreiher J, Porath A. Severe Hyponatremia Induced by Theophylline and Trimethoprim. Arch Intern Med. 2001;161(2):291-292. doi: