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Caffeine is a drug that stimulates the central nervous system.


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.


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.

Recommended dosage

Adults and children age 12 years and over

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 six hours before bedtime.

Children under 12 years

Not recommended.

Other considerations

People should avoid taking much caffeine when it is being used as an over-the-counter drug and should consider how much caffeine is being taken in from coffee, tea, chocolate, soft drinks, and other foods that contain caffeine. A pharmacist or physician should be consulted 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, such as insomnia.
People who use large amounts of caffeine over long periods build up a tolerance to it. When this 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. As of 2004, caffeine withdrawal has been officially recognized as a disorder classification manual.
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.

Special conditions

Caffeine may cause problems for people with certain medical conditions or who are taking certain medicines.
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.
BREASTFEEDING. 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 breastfeeding 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)
USE OF CERTAIN MEDICINES. Using caffeine with certain other drugs may interfere with the effects of the drugs or cause unwanted—and possibly serious—side effects.

Side effects

At recommended doses, caffeine can cause rest-lessness, irritability, nervousness, shakiness, headache, lightheadedness, 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. High caffeine consumption can lead to benign breast disease, which also can increase risk of breast cancer.


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.

Key terms

Arrhythmia — Abnormal heart rhythm.
Central nervous system — The brain and spinal cord.
Fetus — A developing baby inside the womb.
Palpitation — Rapid, forceful, throbbing, or fluttering heartbeat.
Withdrawal symptoms — A group of physical or mental symptoms that may occur when a person suddenly stops using a drug to which he or she has become dependent.
Serious side effects are possible when caffeine is combined with certain drugs. For example, taking caffeine with the decongestant phenylpropanolamine can raise blood pressure. And 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. A pharmacist or physician should be consulted 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. Those trying to withdraw from caffeine are advised to do reduce their consumption slowly over time by substituting decaffeinated or non-caffeinated products for some of the caffeinated products.



"Caffeine Withdrawal Recognized as Disorder." Ascribe Health News Service September 29, 2004.
"High Caffeine Intake May Increase Risk of Benign Breast Disease." Womenós Health Weekly September 16, 2004: 32.


a purine compound found in most bodily tissues and fluids; it is a precursor of uric acid. Methylated xanthine compounds such as caffeine, theobromine, and theophylline are used for their bronchodilator effects.


(kaf'ēn), Although this word was originally pronounced in three syllables, modern usage has fused the second and third syllables into one. Avoid the mispronunciation kaf-ēn'.
An alkaloid obtained from the dried leaves of Thea sinensis, tea, or the dried seeds of Coffea arabica, coffee; used as a central nervous system stimulant, diuretic, circulatory and respiratory stimulant.
Synonym(s): guaranine, thein


/caf·feine/ (kă-fēn´) (kaf´ēn) a xanthine found in coffee, tea, chocolate, and colas; it is a central nervous system stimulant, diuretic, striated muscle stimulant, and acts on the cardiovascular system. As the base or the citrate salt, it is used as a central nrvous system stimulant and as an adjunct in treating neonatal apnea; as the base it is also used in the treatment of vascular headaches and as an adjunct to analgesics.




(kă-fēn′, kăf′ēn′)
A bitter white alkaloid, C8H10N4O2, found in certain plants such as cacao, coffee, kola, and tea, that stimulates the central nervous system and body metabolism and is used in medicine, usually in combination with other drugs, to relieve headaches and treat respiratory conditions in premature infants.


[kafēn′, kaf′ē·in]
Etymology: Ar, qahwah, coffee
a central nervous system stimulant.
indications It is prescribed to counteract migraine, drowsiness, and mental fatigue.
contraindications It is used with caution in patients with heart disease and peptic ulcer. Known hypersensitivity to this drug prohibits its use.
adverse effects Among the most serious adverse reactions are tachycardia and diuresis. GI distress, restlessness, and insomnia are common.


A methylxanthine that is the most widely used psychoactive substance on the planet.
Caffeine-bearing substances
Coffee, tea, maté, soft drinks, cocoa, Excedrin, NoDoz, colas, Red Bull, kola nuts, guarana products.

Low-dose (20–200 mg) effects
Positive subjective effects, feelings of well-being, alertness, energy.

High-dose effects
Nervousness, anxiety.


Pharmacology A methylxanthine that is the most widely used psychoactive substance; it is present in coffee, tea, maté, soft drinks, cocoa, Excedrin, NoDoz, kola nuts, guarana products; low doses–20–200 mg produce positive subjective effects, feelings of well-being, alertness, energy; higher doses have adverse effects–eg, nervousness, anxiety. See Coffee.


An alkaloid obtained from the dried leaves of Thea sinensis, tea, or the dried seeds of Coffea arabica, coffee; used as a central nervous system stimulant, diuretic, circulatory and respiratory stimulant, and adjunct in the treatment of headaches.


One of the most popular and widely used drugs of mild addiction. Caffeine is used, in the form of coffee, tea and Cola-flavoured drinks, by about half the population of the world. It elevates mood, controls drowsiness, decreases fatigue and increases capacity for work. Caffeine is incorporated in various drug formulations such as Cafergot and Migril for the treatment of MIGRAINE.


a bitter purine derivative found especially in coffee beans, tea leaves and cacao beans, and as an ingredient of soft drinks and aspirin tablets. It acts as a stimulant of the CENTRAL NERVOUS SYSTEM and as a DIURETIC. It is a BASE ANALOGUE and therefore likely to be a MUTAGEN.


An alkaloid obtained from the dried leaves of Thea sinensis, tea, or the dried seeds of Coffea arabica, coffee; used as a central nervous system stimulant, diuretic, and circulatory and respiratory stimulant.


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.

Patient discussion about caffeine

Q. Am I addicted to caffeine? I love coffee! I can't start my day without it. I drink about 5 cups a day. How do I know if I am addicted?

A. When your body starts shaking, your heartbeat flutters, you feel lightheaded, you want to mow the lawn at 1 a.m., they are symptons I've had of a caffeine overdose. Drink lots of water and hydrating drinks! Stay away from Mountain Dew!!!!

Q. What is safer than caffeine but works just as well?

A. :? i fail to see what is so wrong with caffeine. as long as you don't over use it - it's fine. but if you insist of giving it up:
eat a light breakfast, orange juice.
at noon when you get tired- take a nap (less than 30 min. more than 15) after 2 weeks you won't understand how you lived without it.
exercise regularly, walk 40 min a day , 5 days a week.
that should do it.

Q. Whats the harm in drinking coffee? I drink coffee all day long and love it! My friends say I'm addicted and should cut back. But what is the harm in drinking coffee?

A. drinking coffee doesn't cause any significant damage, the only thing I can think of, is that when it is too much, coffe relax your exofagus esfinter, and stomach content could come out causing heartburn.

More discussions about caffeine
References in periodicals archive ?
According to David G Munoz, MD of the University of Toronto in Canada, who authored an accompanying editorial about the study, said the people with more severe stages of Parkinson's did not have lower levels of caffeine in their blood, suggesting the decrease only occured in the earliest stages of the disease.
Their blood was tested for caffeine and for 11 byproducts the body makes as it metabolizes caffeine.
Caffeine can be considered as a non-caloric thermogenic agent that is commonly consumed in many beverages.
The highly individual variations in the caffeine metabolism response and the lack of sufficient evidence regarding caffeine as an ergogenic aid potentially attributable to testing of untrained subjects and habitual versus non-habitual caffeine users formed the basis of this research.
Caffeine administration and collection of tissue samples: 5 rats were used as a control group.
Espresso, restaurant style decaffeinated *: 0-15 mg caffeine
It must also be noted that some people are more sensitive to caffeine than other people.
The study found that average caffeine consumption among school- going adolescents from Delhi is very high.
Another consideration beyond the direct effects of caffeine is that it is usually coupled with sugary substances like those found in syrups used in Starbucks drinks, chocolate candy, and energy drinks.
Since caffeine can remain in your system for several hours, drinking super-caffeinated beverages later in the day may contribute to insomnia.
The caffeinerich solution can again be passed through the carbon filter to remove the caffeine and the now caffeine-free green coffee bean extract can be used once more to remove the caffeine from yet another fresh batch of green coffee beans.