Theophylline Toxicity Workup

Updated: Nov 29, 2023
  • Author: Christopher P Holstege, MD; Chief Editor: Stephen L Thornton, MD  more...
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Laboratory Studies

Obtain a serum theophylline level upon presentation and then every 2 hours until the level falls significantly. This is especially important following ingestion of extended-release formulations. Theophylline capsules can form bezoars, resulting in ongoing absorption and toxicity despite gastrointestinal decontamination.

Order electrolytes and glucose tests to evaluate for the following:

  • Hypokalemia (serial testing of serum potassium levels may be required)
  • Hyperglycemia
  • Metabolic acidosis (lactate)
  • Hypocalcemia/hypercalcemia
  • Hypophosphatemia
  • Ketosis

Other tests to obtain include the following:

  • Pregnancy test in women of childbearing age
  • Acetaminophen (paracetamol) level in sucidal ingestions
  • Aspirin (ASA) level, particularly in patients with history and findings suggestive of aspirin toxicity, including but not limited to metabolic acidosis, respiratory alkalosis, and change of mental status

On a complete  blood cell count, the white blood cell count may be elevaed, as a result of increased catecholamine activity.


Imaging Studies

A computed tomography (CT) scan of the brain is indicated if seizures occur.


Other Tests

An electrocardiogram (ECG) is performed to look for evidence of dysrhythmias from electrolyte abnormalities. The ECG should also be used to evaluate for the signs of other cardioactive drug toxicity, especially in cases of suicidal overdose.

Lumbar puncture may be required for the evaluation of altered mental status and/or new-onset seizures.