A 22-year-old woman with no past medical history presented to the emergency department with palpitations. She reported that she had ingested a handful of caffeine tablets with a large glass of wine two hours earlier. She reported feeling "stressed out" and wanting to hurt herself. The patient was alert but appeared anxious on arrival at the ED.
Her blood pressure was 90/49 mm Hg, heart rate was 115 beats/min, respiratory rate was 20 breaths/min, and SPO2 was 100% on room air. An ECG showed sinus tachycardia at 120 beats/min with normal intervals. Shortly after arrival, her blood pressure dropped to 83/42 mm Hg, and she appeared drowsy.
Comparing Caffeinated Products
Type of Coffee Size Caffeine
Brewed 8 oz. (237 mL) 95-200 mg
Brewed, decaffeinated 8 oz. (237 mL) 2-12 mg
Brewed, single-serve 8 oz. (237 mL) 75-150 mg
Brewed, single-serve, 8 oz. (237 mL) 2-4 mg
Espresso, restaurant-style 1 oz. (30 mL) 47-75 mg
Espresso, restaurant-style 1 oz. (30 mL) 0-15 mg
Instant 8 oz. (237 mL) 27-173 mg
Instant, decaffeinated 8 oz. (237 mL) 2-12 mg
Specialty drink (latte 8 oz. (237 mL) 63-175 mg
Adapted from Journal of Food Science, 2010; Pediatrics, 2011; USDA National Nutrient Database for Standard Reference, Release 26; Journal of Analytical Toxicology, 2006; Starbucks, 2014; Food and Chemical Toxicology, 2014; Keurig, 2014.
Over-the-counter caffeine tablets are available as 100 mg and 200 mg doses. There are also powdered caffeine products that may contain up to 100 percent caffeine, and a teaspoon may be equal to drinking 25-28 cups of coffee. A single tablet of Fioricet contains 40 mg of caffeine.
Acute caffeine toxicity is dose-dependent. Plasma concentrations over30 mg/L are associated with symptoms of toxicity. Serum levels above 80 mg/L and doses around 150-200 mg/kg are associated with death.
Mechanisms of Caffeine Toxicity
Toxicity may affect multiple organ systems. Caffeine is nearly 100 percent bioavailable, and peak concentrations occur within 30-60 minutes following oral ingestion. Caffeine exerts its toxicity via adenosine antagonism and stimulating the release of catecholamines, and it is a phosphodiesterase inhibitor.
Gastrointestinal symptoms typically include nausea and vomiting. Sinus tachycardia is typically seen in caffeine-toxic patients. Tachydysrhythmias and hypotension may also occur in these patients. Hypokalemia seen in caffeine toxicity due to beta-adrenergic agonism causes the shift of potassium intracellularly. Pulmonary toxicity includes hyperventilation, respiratory alkalosis, and acute lung injury. Neurotoxicity may manifest as tremors, anxiety, agitation, delirium, and seizures. Patients may also be hyperthermic from increased metabolic activity and muscle hyperactivity.
Managing Caffeine Toxicity
Diagnostic testing may include an ECG, serum electrolytes, and creatinine kinase. Caffeine levels are likely not readily available in the acute setting. Most caffeine overdoses can be managed with supportive care, and cardiac monitoring should be initiated to evaluate for dysrhythmias and hypotension. Gastrointestinal decontamination with activated charcoal may be considered if administered early, but symptoms of vomiting and altered mental status as well as the risk of seizures may preclude its use.
There is no antidote for caffeine toxicity. Benzodiazepines may be administered for agitation and seizures. IV fluids should be administered for hypotension. Phenylephrine or norepinephrine should be considered. Beta1-selective beta antagonists such as esmolol may also be considered to treat refractory hypotension to target the beta-adrenergic mediated vasodilation and tachycardia. Hemodialysis may also be considered in patients who have ingested massive amounts of caffeine and have persistent signs of severe toxicity (seizures, dysrhythmias, hypotension) despite these measures.
The patient in this case received IV normal saline boluses, and her blood pressure improved. She was monitored in the emergency department and remained hemodynamically stable. Psychiatry was consulted and admitted her to their service.