Risk of toxicity in patients with elevated theophylline levels.

Toxic side effects of elevated theophylline levels range from minor symptoms to life-threatening complications. We investigated the incidence of life-threatening events in patients with elevated levels in order to identify those at low risk for significant theophylline toxicity. Five hundred ten episodes of elevated levels were reviewed in 214 hospitalized patients. Four seizures occurred in patients with prior seizures, while two had new onset seizures with levels of 27 and 30 micrograms/mL. All eight episodes of ventricular tachycardia occurred in patients who had a history of arrhythmias or who were critically ill. Seven patients had new supraventricular arrhythmias with levels of 21 to 40 micrograms/mL. Life-threatening events may occur in critically ill patients or patients with past seizures or arrhythmias with mildly elevated levels, although the extent to which theophylline toxicity contributes to morbidity or mortality in these patients is unclear. Patients who are otherwise healthy are unlikely to have significant theophylline toxicity with levels less than 25 micrograms/mL.