Theophylline Toxicity: A Differential to Consider in Patients on Long-Term Theophylline Presenting With Nonspecific Symptoms

Theophylline has been used for decades as a bronchodilator to treat asthma and chronic obstructive pulmonary disease (COPD). The precise mode of action is still uncertain. Since beta-2 agonists are at least as effective as theophylline as a bronchodilator while having fewer side effects, theophylline has become less popular in recent clinical practice as the first-line treatment in patients with airway obstruction due to its narrow therapeutic window, which necessitates frequent level monitoring, severe side effects that can be fatal, and interactions with other medications. Patients with a chronic theophylline overdose often present with nonspecific gastrointestinal symptoms, which can result in misdiagnosis for a variety of gastrointestinal conditions. Convulsions that may be fatal can occur as a result of a theophylline overdose. Therefore, it is important to manage individuals who have been taking theophylline for a long period and have nonspecific cardiac or gastrointestinal symptoms with a high index of suspicion for theophylline toxicity. We present a case of a COPD patient who had no regular theophylline level monitoring for two years. He presented with vague gastrointestinal symptoms for the past six months and was initially suspected of having gastrointestinal cancer due to weight loss caused by decreased oral intake due to nausea and vomiting. He was suspected of having theophylline toxicity because he was on long-term theophylline and did not have frequent theophylline level monitoring. His theophylline level was measured and found to be high at 28.9 mL/L (normal level, 15 mL/L). He was given conservative treatment, including intravenous fluid and electrolyte replacements, and close monitoring of his theophylline levels.