Caffeine is a drug that stimulates the central nervous system.
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.
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.
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.
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.
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.
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
Arrhythmia —Any deviation from a normal heart beat.
Central nervous system —Part of the nervous system consisting of the brain, cranial nerves, and spinal cord. The brain is the center of higher processes, such as thought and emotion and is responsible for the coordination and control of bodily activities and the interpretation of information from the senses. The cranial nerves and spinal cord link the brain to the peripheral nervous system, that is the nerves present in the rest of body.
Withdrawal symptoms —A group of physical and/or mental symptoms that may occur when a person suddenly stops using a drug or other substance upon which he or she has become dependent.
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Nancy Ross-Flanigan Samuel Uretsky, PharmD