Caffeine Effects, Overdose and Episode 262

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Caffeine Effect and Overdose

with Lisa Booze, PharmD, CSPI

Maryland Poison Center (MDPoison.com)

Do you drink coffee, tea or cola sodas? The vast majority of us do and in some cases, maybe for most of us, the caffeine content is the main reason for drinking them. In moderation, caffeine is safe. But most people don’t realize that caffeine can be quite toxic in large doses.

We all know that caffeine is a stimulant, producing alertness, restlessness and hyperactivity, but it’s also a cardiovascular stimulant, causing tachycardia and an increase in blood pressure. The most common symptoms following the ingestion of large doses are nausea and vomiting, which can be severe and protracted. Caffeine is a diuretic so consuming large amounts can lead to dehydration. With very large doses, more serious effects can occur, including dysrhythmias such as supraventricular tachycardia, atrial fibrillation, and ventricular tachycardia, seizures, metabolic acidosis, low potassium levels and cardiovascular collapse. These serious effects can occur with overdoses of more than 1000 mg in an adult, or 40 mg/kg in a small child. The lethal dose of caffeine is 150-200 mg/kg in an adult.

Here is the caffeine content of  some foods, drinks and medications that are part of our daily lives. The amount of caffeine in a brewed or instant cup of coffee can be anywhere between 50 and 180 mg. Tea contains 20-90 mg per 5 oz cup, and a 12 oz can of a cola soft drink has 30-50 mg caffeine. Over –the- counter stimulants like No Doz® and Vivarin® contain 100 to 200 mg caffeine per tablet. For adults, the toxic dose would be equivalent to more than 10 cups of coffee or 5-10 tablets of an over-the-counter stimulant. Other OTC’s that contain smaller doses of caffeine, usually around 32 to 65 mg, include some Anacin® and Excedrin® formulations and Midol®. There are also many dietary supplements sold in stores that contain caffeine and herbal stimulants in various concentrations. These supplements are promoted for weight loss and to athletes for enhanced athletic performance.

Energy drinks usually contain caffeine and are increasing in popularity especially among our youth. Some of the better known energy drinks are Red Bull®, 5-hour Energy Shots®, Full Throttle®, Monster®, Rock Star®, Amp®, and Redline®. These energy drinks often contain the same amount of caffeine as what’s in a cup of coffee, but some have much larger amounts. Some are concentrated liquids that are added in small amounts to another beverage with as little as a teaspoonful containing more than 100 mg. One particular product contains 1,800 mg of caffeine in a 4 oz bottle! That’s equivalent to 22 ½ cans of Red Bull! Misunderstanding the directions of these concentrated products has led to ingestions of toxic amounts. Several months ago, a mother of a teen called our poison center because her son wasn’t feeling well after drinking about 3 mouthfuls of a concentrated energy drink. He didn’t read the label and didn’t realize that that maximum daily dose was 1 teaspoonful. We calculated that he swallowed approximately 9 teaspoonfuls, or 1,125 mg of caffeine.

These drinks sometimes contain a combination of herbal stimulants and supplements such as taurine, guarana, and ginseng. Many energy drinks do not list the amount of each ingredient or the amount of caffeine on the label so it’s difficult to know exactly how much it contains. Sometimes, energy drinks are used along with other stimulants to keep the person awake or to help them study, increasing the chance of them developing toxic effects.

A dangerous practice that youth are engaging in is mixing energy drinks with alcohol. Using stimulants can mask the effects of alcohol, which increases the possibility of consuming excessive amounts of alcoholic beverages. Some products are being marketed that contain caffeine premixed with alcohol and are sold in liquor stores and bars. A 2008 study of college-aged adults exiting bars shows why this is a dangerous practice. Patrons who consumed energy drinks mixed with alcohol had three times the risk of leaving a bar highly intoxicated and were four times more likely to intend to drive after drinking than bar patrons who drank alcohol only. There have been many cases of severe alcohol intoxication after drinking these combination beverages. One college in New Jersey banned these beverages after 24 of its students were hospitalized for alcohol toxicity after consuming the alcohol-energy drink mixtures. In response to public pressure, a few beverage companies have withdrawn their products that contain alcohol and stimulants.

If confronted with a patient who you suspect has caffeine toxicity, be sure to call your regional poison center at 1-800-222-1222 for help in the diagnosis and management of the patient.

Reference:

Thombs, D.L., et al., Event-level analyses of energy drink consumption and alcohol intoxication in bar patrons. Addictive Behaviors (2009), doi:10.1016/j.addbeh.2009.11.004

October 2010