Laboratory Studies

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.

The following laboratory studies are indicated in patients with moderate-to-severe symptoms of caffeine toxicity (ie, hemodynamic instability, dysrhythmias, seizures, altered mental status).

A complete blood cell count (CBC) 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.
Serum electrolyte, glucose, blood urea nitrogen (BUN), and creatinine concentrations should be checked. Pay particular attention to potassium concentrations and the anion gap. Hypokalemia is a classic feature of caffeine overdose. An increased anion gap (resulting from lactic acidosis) and hyperglycemia are also common findings in severe toxicity.
Routine screening for other potentially treatable toxins (eg, acetaminophen, salicylate) is recommended. Such testing is essential if the patient ingested analgesic medications containing caffeine combined with other drugs (eg, Excedrin, Cafergot, Fiorinal or Fioricet, Midol, Anacin).
Measure total creatine kinase (CK) concentrations to check for rhabdomyolysis, which is occasionally associated with severe caffeine toxicity. A CK concentration greater than 5 times the upper limit of normal indicates clinically significant rhabdomyolysis. Include the CK-MB fraction and troponin level if myocardial ischemia is suspected.
Results of dipstick urinalysis may give a rapid indication of rhabdomyolysis, myoglobinuria, or both. Glucosuria and ketonuria are also common findings.
A rapid urine drug screen may help in identifying co-ingested substances. Illicit drugs, such as ecstasy or methamphetamine, often contain caffeine as a substitute or co-ingredient. Standard urine drug tests usually cannot detect ecstasy or methamphetamines.
Consider checking serum ethanol concentrations and osmolality in cases of unknown ingestion or suspected co-ingestion.
A serum pregnancy test is indicated in all women of childbearing age.
Thyroid studies should be considered because thyrotoxicosis can mimic caffeine toxicity.
Arterial blood gas analysis is indicated in patients with respiratory compromise, with altered mental status, or with a need for mechanical ventilation.

Serum caffeine concentration determinations do not influence management. Consider the following:

Caffeine tests are generally available only at reference or research laboratories and are not clinically useful.
Serum theophylline concentrations are more rapidly and widely available than caffeine determinations. Because theophylline is a minor metabolite of caffeine, a positive theophylline assay may be helpful in confirming suspected caffeine toxicity.^[24]
Patients with severe caffeine toxicity have had serum theophylline concentrations in the therapeutic range (10-20 mg/L).

Imaging Studies

Patients with only mild symptoms without any hemodynamic instability do not require imaging studies. Obtain a chest radiograph in patients with chest pain, fever, altered mental status, or respiratory complaints. In patients with seizures or altered mental status despite initial resuscitation, consider obtaining a nonenhanced head CT scan.

Other Tests

Patients with chest pain, palpitations, tachycardia, or an irregular heart rhythm should be evaluated with an electrocardiogram (ECG) and telemetry monitoring.

Treatment & Management

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Media Gallery

Caffeine content of various foods, beverages, medications, and supplements. Caffeine content is approximate for brewed beverages and chocolate).
Chemical structure of caffeine.

of 2

Table 1. Reported Caffeine Content of Common Beverages^[4]

Table 1. Reported Caffeine Content of Common Beverages ^[4]

Item	Amount	Caffeine Content, mg
Milk chocolate	8 oz	5
Dark semi-sweet chocolate	1 oz	20
Brewed green tea	8 oz	20
Anacin	1 tablet	32
Coca-Cola Classic	12 oz	35
Pepsi cola	12 oz	38
Espresso	1 oz	40
Fiorinal/Fioricet	1 tablet	40
Mountain Dew	12 oz	54
Brewed Coffee, generic	8 oz	57
Midol	1 felcap	60
Excedrin pain reliever	1 tablet	65
Brewed black tea, generic	8 oz	45-74
Dexatrin Natural	1 tablet	80
Jolt cola	12 oz	80
Red Bull Regular	8.4 oz	80
Monster energy drink	16 oz	80
Jolt caffeine energy gum	2 pieces	100
Penguin caffeinated mints	6 pieces	100
No Doz	1 tablet	100
Rockstar	16 oz	160
Monster Energy	16 oz	160
Espresso, generic	1 oz	170
Vivarin	1 tablet	200
Alani Nu	12 oz	200
5 Hour Energy	1.9 oz	200
Ripped Fuel Extreme Ephedra Free	2 capsules	220
Taiwanese Milk Tea	24 oz	226
NOS	16 oz	280
Bang Energy	16 oz	300
Starbucks Tall Americano	16 oz	330

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Author

David Yew, MD Assistant Clinical Professor, Department of Surgery, University of Hawaii, John A Burns School of Medicine; Medical Director and Flight Physician, Hawaii Life Flight, AirMed International

David Yew, MD is a member of the following medical societies: American College of Emergency Physicians, Air Medical Physician Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John G Benitez, MD, MPH Associate Professor, Department of Medicine, Medical Toxicology, Vanderbilt University Medical Center; Managing Director, Tennessee Poison Center

John G Benitez, MD, MPH is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, American College of Medical Toxicology, American College of Preventive Medicine, Undersea and Hyperbaric Medical Society, Wilderness Medical Society, American College of Occupational and Environmental Medicine

Disclosure: Nothing to disclose.

Chief Editor

Michael A Miller, MD Clinical Professor of Emergency Medicine, Medical Toxicologist, Department of Emergency Medicine, Texas A&M Health Sciences Center; CHRISTUS Spohn Emergency Medicine Residency Program

Michael A Miller, MD is a member of the following medical societies: American College of Medical Toxicology

Disclosure: Nothing to disclose.

Additional Contributors

James E Keany, MD, FACEP Associate Medical Director, Emergency Services, Mission Hospital Regional Medical Center, Children's Hospital of Orange County at Mission

James E Keany, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians, American College of Sports Medicine, California Medical Association

Disclosure: Nothing to disclose.

China N Byrns Department of Cell and Molecular Biology, University of Hawaii at Manoa

China N Byrns is a member of the following medical societies: Phi Beta Kappa

Disclosure: Nothing to disclose.

Sophie Kim Boston College

Disclosure: Nothing to disclose.

Acknowledgements

Jeffrey T Laczek, MD Gastroentology Fellow, Walter Reed Army Medical Center

Disclosure: Nothing to disclose.