Patients may be unaware that some products contain caffeine or that high doses of caffeine can be harmful. Patients may ingest caffeine-containing analgesics for headaches, over-the-counter (OTC) caffeine-containing medications for dieting, or OTC medications for improving alertness while studying or working. Certain medications, such as cytochrome inhibitors (eg, cimetidine) and oral contraceptives, impair caffeine metabolism. Caffeine clearance is increased in smokers. With smoking cessation, serum caffeine concentrations can double even if caffeine consumption remains stable.
CNS findings on physical examination include:
The patient's signs and symptoms should guide the use of laboratory studies. In hemodynamically stable patients with mild symptoms who give a clear history of caffeine ingestion, no laboratory studies are indicated. Among other studies, in patients with moderate to severe symptoms of caffeine toxicity (ie, hemodynamic instability, dysrhythmias, seizures, altered mental status), a complete blood cell count should be checked to evaluate for infection. Mild leukocytosis (11-16 × 109 L [11,000-16,000/mL]) can be present in caffeine toxicity; however, infectious processes should be excluded.
Although most patients with caffeine toxicity improve with supportive care, life-threatening complications can result from severe overdoses. Fatalities are generally related to cardiac dysrhythmias. Other factors contributing to mortality include seizures, myocardial infarction, hypotension, electrolyte disturbances, rhabdomyolysis, and aspiration (secondary to an inability to protect the airway). Caffeine acts as a bronchodilator and generally does not result in respiratory compromise, if the patient can protect his or her airway.
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This Fast Five Quiz was excerpted and adapted from the Medscape Drugs & Diseases articles Caffeine Toxicity and Neurologic Effects of Caffeine.