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More about Caffeine: Purpose Recommended dosage Precautions Side effects Interactions

Definition

Caffeine is a drug that stimulates the central nervous system.

Description

Caffeine is found naturally in coffee, tea, and chocolate. Colas and some other soft drinks contain it. Caffeine also comes in tablet and capsule forms and can be bought without a prescription. Over-the-counter caffeine brands include No Doz, Overtime, Pep-Back, Quick-Pep, Caffedrine, and Vivarin. Some pain relievers, medicines for migraine headaches, and antihistamines also contain caffeine.

— Nancy Ross-Flanigan

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also caf·fein n.

A bitter white alkaloid, C₈H₁₀N₄O₂, often derived from tea or coffee and used in medicine chiefly as a mild stimulant and to treat certain kinds of headache.

[German Kaffein (from Kaffee, coffee) or French caféine, both from French café, coffee. See café.]

caffeinated caf'fein·at'ed (kăf'ə-nā'tĭd) adj.

An alkaloid, formerly synthesized by methylation of theobromine isolated from cacao, but now recovered from the solvents used in the manufacture of decaffeinated coffee. Chemically, caffeine is 1,3,7-trimethylxanthine, and has the formula below. It is widely used in medicine as a stimulant for

the central nervous system and as a diuretic. It occurs naturally in tea, coffee, and yerba maté, and small amounts are found in cola nuts and cacao. Caffeine crystallizes into long, white needlelike crystals that slowly lose their water of hydration to give a white solid that melts at 235–237.2°C (455–459.0°F). It sublimes without decomposition at lower temperatures. Caffeine has an intensely bitter taste, though it is neutral to litmus. See also Alkaloid.

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Caffeine is a methylxanthine present in tea and coffee, and therefore probably is the most common drug, regularly taken, in the world. Three very similar compounds — all in this same group of alkaloids — are present in common beverages, namely caffeine, theophylline, and theobromine. The first two are found mainly in tea and coffee, and the third in cocoa. Cola beans, used in the manufacture of well-known soft drinks, also contain caffeine. The three compounds differ very little from each other: simply the number and disposition of methyl groups about the xanthine nucleus is variable. Weight for weight, the caffeine content of coffee beans (0.7-1.5%) and tea leaves (2-3%) is similar, but generally a coffee infusion is stronger than that used for tea. Thus the dose of alkaloid per usual portion of tea or coffee is very similar, namely 50-150 mg, depending on taste.

Infusions made from the leaves of Camellia sinensis (i.e. tea) have been consumed in the East for almost two millenia, and the practice reached Europe in the sixteenth century. The demand grew, and plantations were started in the Indian subcontinent. The British remain the most constant tea drinkers, with an average annual consumption of 4.5 kg, equivalent to a daily caffeine intake of 300 mg. In Japan tea is made from powdered green leaves. An elaborate tea ceremony is sometimes performed in which the tea maker performs a series of ritualized procedures in a very precise way. The green tea served at these ceremonies is usually bitter in taste.

Coffee cultivation began in the Yemen in the ninth century, the beans being obtained from a bush, Coffea arabica, and they were introduced into Europe alongside tea in the sixteenth century. The major source of coffee is now in the state of Sao Paulo, Brazil. Coffee is supposed to have been discovered by an Ethiopian holy man whose goats had eaten the berries, allowing them to frisk all night long. It was claimed that coffee ‘quickens the spirits and makes the heart lightsome’ and is ‘good against the dropsy’, but a distinguished professor of medicine at Cambridge around 1900 claimed coffee caused tremors and agitation. Explanations for all these claims can be made, particularly when allowance is made for ‘dose’. However, assuming the effects are due to caffeine, tea drinkers as well as coffee drinkers will benefit, or suffer, alike. While lethargy and irritability often result from withdrawal in drinkers, it is doubtful whether true caffeine dependency exists.

The pharmacological effects of caffeine are widespread and various. By inhibition of certain enzymes, it allows an increase in the concentration of the ‘second messenger’, cyclic AMP, within cells, enhancing in turn the systems which this activates. Since caffeine penetrates the blood-brain barrier it is assumed that the central stimulant effects that enhance alertness and counteract feelings of fatigue, are due to this action. Caffeine also acts on the kidneys as a mild diuretic; this combined with its stimulant actions on heart muscle provide good evidence for the claim that it is ‘good for the dropsy’, both by strengthening the force of the heart beat and by removing accumulated body fluid.

— Alan W. Cuthbert

An alkaloid (chemically trimethylxanthine) found in coffee and tea (when it is sometimes called theine). It raises blood pressure, stimulates the kidneys, and temporarily averts fatigue and tiredness, so has a stimulant action. It can also be a cause of insomnia in some people, and decaffeinated coffee and tea are commonly available.

Coffee beans contain about 1% caffeine, and the beverage contains about 70 mg/100 mL. Tea contains 1.5-2.5% caffeine, about 50-60 mg/100 mL of the beverage. Cola drinks contain 12-18 mg/100 mL, and some energy drinks may contain more.

See also coffee, decaffeinated; theobromine; xanthine.

Caffeine occurs naturally in about 60 species of plant, including coffee beans, tea leaves, and cocoa nuts. It is a constituent of chocolate bars, coffee, tea, and cola-type drinks and occurs in the following approximate amounts:

CAFFEINE PER AVERAGE	CUP OR BAR (MG)
ground coffee	90
instant coffee	60
decaffeinated coffee	3
tea	40
cola	40
chocolate bar	40

Caffeine is a mildly addictive drug. It acts as a stimulant, increasing blood pressure, and accelerating heart rate and breathing. It also makes you feel more alert and energetic.

High caffeine consumption prior to competition is banned by the International Olympic Committee because it improves performance artificially and it may be harmful if taken in excess. Concentrations above 12 micrograms per millilitre are regarded as positive indicators of doping.

Caffeine may boost athletic performance by improving muscle strength and reaction times. Drinking as little as two cups of coffee may enable athletes of average ability to run the 1500 metres several seconds faster. Coffee may also improve endurance and delay fatigue by mobilizing free fatty acids, making them more readily available as fuel. A high carbohydrate diet appears to nullify this effect.

Excessive caffeine intake can cause sleeplessness, diarrhoea, fluid loss, and stomach irritation. Many researchers have tried to link high caffeine consumption to an increased risk of certain diseases, such as cancer, high blood pressure, and heart disease. As yet, the links have not been confirmed and some of the evidence is contradictory. However, there is a well-established correlation between heart disease and those who both smoke and have high levels of caffeine consumption. Caffeine, when consumed at the same time as other foods, may also interfere with the absorption of minerals, such as calcium and iron. Loss of bone density associated with ageing in adults, may be accelerated by drinking two or more cups of coffee a day. Coffee also acts as a diuretic, increasing urine production by as much as 30 per cent.

Although there is still some uncertainty about the effects of caffeine, the general medical opinion is that between 200-250 milligrams of caffeine a day rarely cause adverse reactions in healthy adults. It also appears that caffeine consumed during exercise (rather than before or after it) has little effect on heart rate, performance, or urine production.

[ka-FEEN] An organic compound found in foods such as chocolate, coffee, cola nuts and tea. Scientific studies have shown that caffeine stimulates the nervous system, kidneys and heart, causes the release of insulin in the body and dilates the blood vessels.

(kafēn′, kaf′ē-in)
n

A white, odorless, bitter compound isolated from tea and coffee that is used as a stimulant of the central nervous system. See also aspirin, phenacetin.

Brand names: .44 Magnum™, 357 HR Magnum®, Alert®, Alertness AL®, Awake, Cafcit®, Enerjets®, Fastlene®, Keep Alert®, Keep Going®, Lucidex™, Molie®, NoDoz®, NoDoz® Maximum Strength, Overtime®, Revive®, Stay Awake, Stay Awake®, Ultra Pep-Back®, Valentine®, Verv®, Vivarin®, Wakespan®, Waykup®

Chemical formula:

Drug Forms:
• Caffeine tablets or caplets (below)
• Caffeine oral solution
• Caffeine injection

Español:
• Tabletas o "caplets" de cafeína
• Solución oral de cafeína
• Inyección de cafeína

Caffeine tablets or caplets

What are caffeine tablets or caplets?

CAFFEINE (Enerjets®, NoDoz®, Snap-Back®, Stay-Alert®, Vivarin®) acts as a central nervous system (CNS) or brain stimulant, increasing alertness in people who are tired or sleepy. Caffeine occurs naturally in tea, coffee, cocoa, and chocolate, and is added to many soft drinks. Generic forms of caffeine are available, and can be obtained without a prescription.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
• anxiety
• diabetes
• heart disease or irregular heartbeat
• high blood pressure
• kidney disease
• liver disease
• panic attacks
• peptic ulcer disease or colitis
• seizure disorder
• thyroid disease
• trouble sleeping
• an unusual or allergic reaction to caffeine, aminophylline, theophylline, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should I take this medicine?

Take caffeine tablets or caplets by mouth. Follow the directions on the prescription label. Swallow with a drink of water; do not take with grapefruit juice. If you are taking an extended-release form of caffeine, swallow whole, do not crush or chew. If you are taking chewable tablets, chew well and swallow. Do not take your medicine more often than directed. Do not stop taking except on your prescriber's advice.

Contact your pediatrician or health care professional regarding the use of this medicine in children. Special care may be needed.

What drug(s) may interact with caffeine?

• cimetidine
• ciprofloxacin
• clarithromycin
• clozapine
• ephedra, Ma huang
• erythromycin
• female hormones, like estrogen or birth control pills
• fluvoxamine
• grapefruit juice
• guarana
• ketoconazole
• lithium
• medicines called MAO inhibitors-phenelzine, tranylcypromine, isocarboxazid, selegiline
• medicines for colds and breathing difficulties
• medicines for sleep
• medicines for weight loss
• phenobarbital
• phenytoin
• rifampin
• stimulants like amphetamine, dextroamphetamine, methylphenidate
• tacrine
• terbinafine
• theophylline

Tell your prescriber or health care professional about all other medicines you are taking, including non-prescription medicines, nutritional supplements, or herbal products. Also tell your prescriber or health care professional if you are a frequent user of drinks with caffeine or alcohol, if you smoke, or if you use illegal drugs. These may affect the way your medicine works. Check with your health care professional before stopping or starting any of your medicines.

What should I watch for while taking caffeine?

Caffeine is not intended for long-term use. Do not use caffeine products regularly to make up for lost sleep. Do not increase the dose if tolerance develops; your body will not develop a tolerance to the harmful side effects of caffeine. See your prescriber or health care professional if you continue to experience tiredness or constant sleepiness; this may indicate a problem needing medical attention.

Do not take caffeine close to bedtime. It may prevent you from sleeping.

If you have been a regular caffeine user you can get withdrawal symptoms if you stop taking caffeine. Symptoms include tiredness, dizziness, headache, anxiety, or nervousness. This can be a weekend effect for people who drink a lot of coffee during their working week.

If you are taking caffeine as a part of a medical treatment, avoid food and drinks that contain additional caffeine, like coffee, tea, colas and chocolate.

Do not take caffeine with other non-prescription medicines, especially cold and allergy medicines, without asking your prescriber or health care professional for advice.

Do not take caffeine with grapefruit juice, this can increase the effects of caffeine.

What side effects may I notice from taking caffeine?

Side effects that you should report to your prescriber or health care professional as soon as possible:
• anxiety or panic reactions
• confusion
• dizziness, lightheadedness, or fainting spells
• fast or irregular breathing or heartbeat (palpitations)
• muscle twitching
• nausea and vomiting
• seizures (convulsions)
• trembling

Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):
• diarrhea
• frequent passing of urine
• headache
• nervousness, restlessness
• stomach upset
Reduce your intake of caffeine if you get any of these side effects. Let your prescriber or health care professional know about them if they do not go away or if they annoy you.

Where can I keep my medicine?

Keep out of the reach of children in a container that small children cannot open.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Throw away any unused medicine after the expiration date.

Last updated: 7/1/2002

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

Description

Caffeine is a drug that stimulates the central nervous system (CNS). Caffeine is found naturally in coffee, Kola seed kernels or nuts (Cola nidtida), and a variety of teas. Other foods and beverages, such as chocolate and soft drinks, also contain caffeine, and the drug can be purchased in over-the-counter tablet and capsule form (No Doz, Overtime, Pep-Back, Quick-Pep, Caffedrine, and Vivarin). Some prescription pain relievers, medicines for migraine headaches, and antihistamines also contain caffeine.

General Use

Caffeine makes people more alert, less drowsy, and improves coordination. It is sometimes included in athletes' diets to improve physical performance. In addition, one recent study found that older people who were given a cup of caffeinated coffee in the morning had fewer late-day memory problems than those who were given decaffeinated coffee. Combined with certain pain relievers or medicines for treating migraine headache, caffeine makes those drugs work more quickly and effectively. Caffeine alone can also help relieve headaches. Antihistamines are sometimes combined with caffeine to counteract the drowsiness caused by those drugs. Caffeine is also sometimes used to treat other conditions, including breathing problems in newborns and in young babies after surgery.

Preparations

Kola can be prepared in decoction or tincture form. To prepare a decoction, mix 1-2 tsp of powdered kola nut in a cup of water. After bringing the water to a boil, simmer the decoction on low heat for 10-15 minutes. Tinctures of kola nut can be purchased at many health food stores or mail order suppliers. A tincture is an herbal preparation made by diluting the herb in alcohol, glycerin, or vinegar. Dosage of kola tincture varies by formula and the symptoms or illness it is supposed to treat, but an average recommended dosage might be 1-4 ml three times daily. Powdered kola nut and kola tinctures should be stored in airtight containers away from direct light to maintain potency.

For over-the-counter caffeine preparations, adults and children age 12 years and older should take 100-200 mg no more than every 3-4 hours. In timed-release form, the dose is 200-250 mg once a day. Timed-release forms should not be taken less than 6 hours before bedtime. Caffeine pills or tablets are typically not recommended for children under 12 years of age.

Precautions

If caffeine is administered in a kola preparation, kola should always be obtained from a reputable source that observes stringent quality control procedures and industry-accepted good manufacturing practices. Consumers should look for the designations "U.S.P." (U.S. Pharmacopeia) or "NF" (National Formulary) on kola nut labeling. Herbal preparations prepared under USP or NF guidelines meet nationally recognized strength, quality, purity, packaging, and labeling standards as recommended by the United States Food and Drug Administration (FDA).

CAFFEINE CONTENT OF COMMON DIETARY AND MEDICINAL SOURCES
Source	Standard amount in milligrams (mg)
Bottled beverages (12 oz)
Red bull	115.5
Jolt	72
Mountain Dew	55
Diet Coke	45
Dr. Pepper	41
Coca Cola Classic	34
Coffee (8 oz)
Brewed	80–135
Instant	65–100
Decaf brew	3–4
Tea (8 oz)
Iced	47
Brewed	40–60
Instant	30
Green	15
Chocolate
Hot cocoa (8 oz)	14
Chocolate milk (6 oz)	4
Chocolate bar (1 oz)	3–6
Medications (per tablet)
Vivarin	200
No-Doz	100
Midol, Maximum Strength	65
Anacin	32
Dristan	30

Avoid taking too much caffeine when it is being taken as an over-the-counter drug. Consider how much caffeine is being taken in from coffee, tea, chocolate, soft drinks, and other foods that contain caffeine. Check with a pharmacist or healthcare professional to find out how much caffeine is safe to use.

Caffeine cannot replace sleep and should not be used regularly to stay awake as the drug can lead to more serious sleep disorders, like insomnia.

People who use large amounts of caffeine over long periods build up a tolerance to it. When that happens, they have to use more and more caffeine to get the same effects. Heavy caffeine use can also lead to dependence. If an individual stops using caffeine abruptly, withdrawal symptoms may occur, including headache, fatigue, drowsiness, yawning, irritability, restlessness, vomiting, or runny nose. These symptoms can go on for as long as a week. In addition, caffeine dependence is not confined to the adult population. A study published in 2002 found that American teenagers have a high rate of caffeine dependence, partly because they consume large amounts of carbonated beverages that contain caffeine.

If taken too close to bedtime, caffeine can interfere with sleep. Even if it does not prevent a person from falling asleep, it may disturb sleep during the night.

The notion that caffeine helps people sober up after drinking too much alcohol is a myth. In fact, using caffeine and alcohol together is not a good idea. The combination can lead to an upset stomach, nausea, and vomiting.

Older people may be more sensitive to caffeine and thus more likely to have certain side effects, such as irritability, nervousness, anxiety, and sleep problems. Recent findings also suggest that people with insulin-dependent diabetes should monitor their caffeine intake. One study published in 2002 found that caffeine appears to decrease insulin sensitivity by about 15%.

Allergies

Anyone with allergies to foods, dyes, preservatives, or to the compounds aminophylline, dyphylline, oxtriphylline, theobromine, or theophylline should check with a physician before using caffeine. Anyone who has ever had an unusual reaction to caffeine should also check with a physician before using it again.

Pregnancy

Caffeine can pass from a pregnant woman's body into the developing fetus. Although there is no evidence that caffeine causes birth defects in people, it does cause such effects in laboratory animals given very large doses (equal to human doses of 12-24 cups of coffee a day). In humans, evidence exists that doses of more than 300 mg of caffeine a day (about the amount of caffeine in 2-3 cups of coffee) may cause miscarriage or problems with the baby's heart rhythm. Women who take more than 300 mg of caffeine a day during pregnancy are also more likely to have babies with low birth weights. Any woman who is pregnant or planning to become pregnant should check with her physician before using caffeine.

Breast-Feeding

Caffeine passes into breast milk and can affect the nursing baby. Nursing babies whose mothers use 600 mg or more of caffeine a day may be irritable and have trouble sleeping. Women who are breast-feeding should check with their physicians before using caffeine.

Other Medical Conditions

Caffeine may cause problems for people with these medical conditions:

• peptic ulcer
• heart arrhythmias or palpitations
• heart disease or recent heart attack (within a few weeks)
• high blood pressure
• liver disease
• insomnia (trouble sleeping)
• anxiety or panic attacks
• agoraphobia (fear of being in open places)
• premenstrual syndrome (PMS)

Side Effects

At recommended doses, caffeine can cause restlessness, irritability, nervousness, shakiness, headache, light-headedness, sleeplessness, nausea, vomiting, and upset stomach. At higher than recommended doses, caffeine can cause excitement, agitation, anxiety, confusion, a sensation of light flashing before the eyes, unusual sensitivity to touch, unusual sensitivity of other senses, ringing in the ears, frequent urination, muscle twitches or tremors, heart arrhythmias, rapid heartbeat, flushing, and convulsions.

Interactions

Using caffeine with certain other drugs may interfere with the effects of the drugs or cause unwanted—and possibly serious—side effects. Certain drugs interfere with the breakdown of caffeine in the body. These include oral contraceptives that contain estrogen, the antiarrhythmia drug mexiletine (Mexitil), the ulcer drug cimetidine (Tagamet), and the drug disulfiram (Antabuse), used to treat alcoholism.

Caffeine interferes with drugs that regulate heart rhythm, such as quinidine and propranolol (Inderal). Caffeine may also interfere with the body's absorption of iron. Anyone who takes iron supplements should take them at least an hour before or two hours after using caffeine.

Serious side effects are possible when caffeine is combined with certain drugs. For example, taking caffeine with the decongestant phenylpropanolamine can raise blood pressure. Very serious heart problems may occur if caffeine and monoamine oxidase inhibitors (MAO) are taken together. These drugs are used to treat Parkinson's disease, depression, and other psychiatric conditions. Consult with a pharmacist or physician about which drugs can interact with caffeine.

Because caffeine stimulates the nervous system, anyone taking other central nervous system stimulants should be careful about using caffeine.

Resources

Books

Hoffman, David. The Complete Illustrated Herbal. New York: Barnes & Noble Books, 1999.

Medical Economics Corporation. The PDR for Herbal Medicines. Montvale, NJ: Medical Economics Corporation, 1998.

Periodicals

Bernstein, G. A., M. E. Carroll, P. D. Thuras, et al. "Caffeine Dependence in Teenagers." Drug and Alcohol Dependence 66 (March 2002): 1-6.

Keijzers, G. B., B. E. De Galan, et al. "Caffeine Can Decrease Insulin Sensitivity in Humans." Diabetes Care 25 (February 2002): 399-400.

Maughan, R. "The Athlete's Diet: Nutritional Goals and Dietary Strategies." Proceedings of the Nutrition Society 61 (February 2002): 87-96.

Ryan L., C. Hatfield, and M. Hostetter. "Caffeine Reduces Time-of-Day Effects on Memory Performance in Older Adults." Psychological Science 13 (January 2002): 68-71.

Organizations

Office of Dietary Supplements. National Institutes of Health. Building 31, Room 1B25, 31 Center Drive, MSC 2086, Bethesda, MD 20892-2086. (301) 435-2920. Fax: (301) 480-1845. http://odp.od.nih.gov/ods/ (Includes on-line access to International Bibliographic Information on Dietary Supplements (IBIDS), a database of published, international scientific literature on dietary supplements and botanicals).

[Article by: Paula Ford-Martin; Rebecca J. Frey, PhD]

Definition

Caffeine is a drug that stimulates the central nervous system.

Description

Caffeine is found naturally in coffee, tea, and chocolate. Colas and some other soft drinks contain it. Caffeine also comes in tablet and capsule forms and can be bought without a prescription. Over-the-counter caffeine brands include No Doz, Overtime, Pep-Back, Quick-Pep, Caffedrine, and Vivarin. Some pain relievers, medicines for migraine headaches, and antihistamines also contain caffeine.

General Use

Caffeine makes people more alert, less drowsy, and improves coordination. Combined with certain pain relievers or medicines for treating migraine headache, caffeine makes those drugs work more quickly and effectively. Caffeine alone can also help relieve headaches. Antihistamines are sometimes combined with caffeine to counteract the drowsiness that those drugs cause. Caffeine is also sometimes used to treat other conditions, including breathing problems in newborns and in young babies after surgery.

Precautions

Caffeine cannot replace sleep and should not be used regularly for staying awake as the drug can lead to serious sleep disorders, like insomnia.

People who use large amounts of caffeine over long periods build up a tolerance to it. When that happens, they have to use more and more caffeine to get the same effects. Heavy caffeine use can also lead to dependence. If the person then stops using caffeine abruptly, withdrawal symptoms may occur. These can include throbbing headaches, fatigue, drowsiness, yawning, irritability, restlessness, vomiting, or runny nose. These symptoms can go on for as long as a week if caffeine is avoided. Then the symptoms usually disappear.

If taken too close to bedtime, caffeine can interfere with sleep. Even if it does not prevent a person from falling asleep, it may disturb sleep during the night.

The notion that caffeine helps people sober up after drinking too much alcohol is a myth. In fact, using caffeine and alcohol together is not a good idea. The combination can lead to an upset stomach, nausea, and vomiting.

Older people may be more sensitive to caffeine and thus more likely to have certain side effects, such as irritability, nervousness, anxiety, and sleep problems.

Children under the age of 12 should normally avoid caffeine.

Side Effects

Although caffeine is used to treat headaches, regular consumption of large quantities of caffeine containing beverages can cause severe headaches.

Excess use of caffeine by children leads to decreased nighttime sleep, but increased daytime sleep.

Interactions

Certain drugs interfere with the breakdown of caffeine in the body. These include oral contraceptives that contain estrogen, the antiarrhythmia drug mexiletine (Mexitil), and the ulcer drug cimetidine (Tagamet).

Caffeine interferes with drugs that regulate heart rhythm, such as quinidine and propranolol (Inderal). Caffeine may also interfere with the body's absorption of iron. Anyone who takes iron supplements should take them at least an hour before or two hours after using caffeine.

Serious side effects are possible when caffeine is combined with certain drugs. For example, taking caffeine with the decongestant phenylpropanolamine can raise blood pressure. Very serious heart problems may occur if caffeine and monoamine oxidase (MAO) inhibitors are taken together. These drugs are used to treat Parkinson's disease, depression, and other psychiatric conditions. People who use these drugs should consult a pharmacist or physician about which drugs can interact with caffeine.

Because caffeine stimulates the nervous system, anyone taking other central nervous system (CNS) stimulants should be careful about using caffeine.

Parental Concerns

Moderate amounts of caffeine are not normally associated with adverse effects. As a rule, a daily intake of 300 milligrams should not present a problem. The following list gives the estimated amount of caffeine in common foods, but actual concentrations may be higher or lower.

• coffee, 115 mg
• black tea, 40 mg
• cola and other soft drinks, 18 mg
• chocolate milk, 5 mg
• milk chocolate (1 ounce) 6 mg

Resources

Books

Beers, Mark H., and Robert Berkow, eds. The Merck Manual, 2nd home ed. West Point, PA: Merck & Co., 2004.

Mcevoy, Gerald, et al. AHFS Drug Information 2004. Bethesda, MD: American Society of Healthsystems Pharmacists, 2004.

Siberry, George K., and Robert Iannone, eds. The Harriet Lane Handbook, 15th ed. Philadelphia: Mosby Publishing, 2000.

Periodicals

Hering-Hanit, R., and N. Gadoth. "Caffeine-induced headache in children and adolescents." Cephalalgia 23, no. 5 (June 2003): 332–5.

Pollak Charles P., and David Bright. "Caffeine consumption and weekly sleep patterns in U.S. seventh, eighth, and ninth graders." Pediatrics 111, no. 1 (January 2003): 42–6.

Steer, P. A., and D. J. Henderson-Smart. "Caffeine versus theophylline for apnea in preterm infants." Cochrane Database of Systematic Review 2 (2000): CD000273.

Organizations

Baylor College of Medicine USDA/ARS Children's Nutrition Research Center. 1100 Bates Street, Houston, TX 77030.

University of Minnesota Extension Service. Office of the Director, 240 Coffey Hall, 1420 Eckles Ave. St. Paul, MN 55108–6068.

Web Sites

"Caffeine." Center for the Evaluation of Risks to Human Reproduction. Available online at (accessed October 16, 2004).

"Questions and Answers about Caffeine and Health." International Food Information Council. Available online at www.ific.org/publications/qa/caffqa.cfm (accessed October 16, 2004).

[Article by: Nancy Ross-Flanigan Samuel Uretsky, PharmD]

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For more information on caffeine, visit Britannica.com.

A mildly addictive central nervous system stimulant. It is a constituent of many common products including chocolate bars, coffee, tea, and cola-type drinks. A cup of ordinary percolated coffee contains about 100-150 mg of caffeine. Caffeine may enhance the performance of endurance activities by improving the mobilization of fatty acids, enabling the more efficient use of fat as fuel and sparing glycogen reserves. The caffeine also lowers an endurance athlete's perception of effort at a given work rate, potentially enabling the athlete to work harder for the same perceived effort. In addition, caffeine enhances physical performances requiring speed and strength. It improves reaction times and alertness immediately after it is taken, but these improvements may be followed by feelings of mild fatigue and depression. Caffeine consumed before a physical activity acts as a diuretic drug, increasing the risk of dehydration, but its diuretic effect seems to be absent when the caffeine is taken during the activity. Chronic, excessive caffeine intake can lead to insomnia, diarrhoea, fluid and weight loss, stomach irritation, ulcers, and hypertension. In 2004, caffeine was taken off the World Anti-Doping Agency (WADA) List of Prohibited substances, but in 2005 WADA was considering putting caffeine back on the list after several Australian athletes, including the national rugby union captain, George Gregan, admitted to taking it to enhance performance.

Caffeine

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A central nervous system stimulant from coffee, tea, guarana and maté; it also acts as a mild diuretic. The production of more effective drugs has led to caffeine being discarded as an analeptic. It has even been bypassed by the persons who dope horses, especially because it is readily detectable in urine for up to 10 days after its administration.

IN BRIEF: A substance which is a stimulant that is found in coffee, tea, and cola drinks.

That soda had no caffeine in it.