History

If acute caffeine ingestion is suspected, patients or their family members should be questioned about their use of prescription medications, over-the-counter (OTC) drugs, and illicit drugs. Patients and family members should be queried about the use of any of the following drugs:

Cocaine
Amphetamines
Methamphetamine
Phencyclidine (PCP)
Antidepressants
Asthma medications
Thyroid medications
Anticholinergics (eg, OTC allergy medications)

The patient and family members or friends may be able to give a history of recent caffeine ingestion (eg, ingestion of alertness-promoting OTC medications, caffeinated beverages, or diet medications) or a history of recent behavior compatible with such use (eg, the patient was trying to lose weight or taking stimulants to aid in working or studying). In an acute overdose, pill bottles found at the scene may provide a clue to what the patient ingested.

When ingested chronically in excessive amounts, caffeine produces a specific toxidrome (caffeinism), which consists of primarily central nervous system (CNS), cardiovascular, and gastrointestinal (GI) hyperstimulation.

CNS features include the following:

Headache
Lightheadedness
Anxiety, agitation
Tremulousness, perioral and extremity tingling (resulting from tachypnea-induced respiratory alkalosis)
Confusion, psychosis
Seizures

Cardiovascular features include the following:

Palpitations or racing heart rate
Chest pain

GI features include the following:

Nausea and vomiting
Abdominal pain
Diarrhea, bowel incontinence
Anorexia

Physical Examination

Vital signs may include tachypnea and tachycardia. On blood pressure measurement, a characteristic finding is widened pulse pressure due to the positive inotropic effect as well as the vasodilatory effect of caffeine. Hypotension may be present.

CNS findings on physical examination include the following:

Anxiety, agitation
Tremors
Seizures
Altered mental status

The pupils are dilated but reactive to light. The thyroid should be examined because thyrotoxicosis may mimic caffeine toxicity.

GI findings include the following:

Vomiting
Abdominal cramping
Hyperactive bowel sounds

Differential Diagnoses

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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.