The World of Caffeine (59 page)

Caffeine is useful in averting hypotension after eating among the elderly, especially that which occurs after eating breakfast. Patients with hypotension related to autonomic failure are advised to consume 200–250 mg of caffeine, or about two cups of coffee, with their breakfast.
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Older people often complain of cold hands and feet. Frequently, the cause is often undetermined and their condition may not be serious. Possible causes include poor circulation owing to diseased arteries, a side effect of certain medications, stress, or Raynaud’s disease (a disorder that affects the flow of blood to the fingers and sometimes the toes). For people suffering from cold hands and feet, it may be important to avoid caffeine, which constricts blood vessels and could exacerbate the underlying condition.

One happy note: A recent University of Michigan study suggested that, for older people, caffeine may have aphrodisiac powers, because its researchers found that the elderly were more likely to have remained sexually active if they were coffee drinkers.

Caffeine may affect your eyes by constricting blood vessels, thereby increasing intraocular pressure and, with it, increasing your risk of developing glaucoma. Although no one has suggested that caffeine can in and of itself be regarded as a cause of glaucoma, one study indicated that in people genetically predisposed to developing the disease, coffee can increase their risk. Another study found that glaucoma patients who drink two cups of coffee a day show an increase in intraocular pressure, while normal patients who consumed two cups of coffee show no such increase. The greatest increases in intraocular pressure were found to occur in those who drink their coffee very quickly, consuming four cups an hour.

Caffeine also temporarily dilates the eyes, like other stimulants such as cocaine or amphetamine or adrenaline, and can therefore make it difficult to do close work, because dilated eyes cannot focus easily at short range.

Caffeine has been found to alter nutritional homeostasis—that is, the body’s ability to maintain the proper levels of various nutrients, such as calcium, magnesium, and zinc—in experiments on pregnant rats. Theoretically caffeine may have similar effects in humans, although this has not been confirmed.

Caffeine consumed within one hour of eating may interfere with the absorption of dietary iron.
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One study of maternal hemoglobin in non-smoking, teetotaler Costa Rican women found that iron deficiency occurred almost twice as frequently in coffee drinkers and that iron levels were also lower in their breast milk.

Grapefruit juice, which has been implicated in significantly altering the effects of several medicines, is known to raise the blood levels of caffeine.

Studies performed in the first half of the twentieth century in the pharmacology of caffeine and other methylxanthines confirmed traditional beliefs about their moodelevating and analeptic powers and revealed other significant pharmacolgical properties that were subsequently put into therapeutic use. Although more effective treatments have displaced many of these early applications, new uses have more recently come to light. The methylxanthines share many pharmacological properties, but they can be distinguished in terms of the degree of some of their primary effects. The therapeutic uses of each is, obviously, determined in relation to these effects.
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Most of caffeine’s applications depend on its effect as a diuretic, cardiac muscle stimulant, central nervous system stimulant, smooth muscle relaxant, or elevator of plasma levels of FFA (free fatty acids).

As we have repeatedly noted, caffeine and the other methylxanthines have long been used to help alleviate the symptoms of asthma. Less well known are studies demonstrating a protective effect of coffee drinking on the pulmonary complications of cigarette smoking. We have seen that smokers metabolize caffeine more rapidly than non-smokers, so that the caffeine exposure of a smoker who drank a cup of coffee would be lower than the exposure of the non-smoker, a fact that may account for the obviously increased rate of coffee consumption among smokers. Perhaps the occult destiny adduced by Walsh for caffeine is present here as well: For, strange to say, the increase in caffeine metabolism caused by smoking seems to result in an increase in use of caffeine, which in turn protects the smoker from the hazards of lung damage.

Methylxanthines have proved valuable in relieving apnea, or arrested breathing, in premature infants. Traditionally, theophylline has been chosen for this purpose, because a 1921 study demonstrated its greater potency in this respect, but more recently caffeine has been preferred by many physicians because the regimes for dosing (in part resulting from the longer half-life of caffeine in infants) are more easily managed and also because, paradoxically, administering theophylline to infants results in a greater buildup of caffeine in their systems than does the administration of caffeine.

Because of its purported value as an analgesic adjuvant, caffeine has been used for decades in both non-narcotic and narcotic painkillers. Are these benefits genuine? Doctors disagree. One study demonstrated that the potency of analgesics compounded with caffeine was 40 percent greater than the same analgesics without caffeine. This means that, if you add caffeine to aspirin, for example, you will only need about two-thirds as much aspirin to achieve the same result as with aspirin alone. However, this does not mean that caffeine together with aspirin can relieve more intense pain than aspirin alone.
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Caffeine has been especially credited with the relief of headache pain, an effect that has been associated with its action as an adenosine antagonist. Caffeine has demonstrated vasoconstrictor effects on cerebral blood vessels, and it is believed that this action may augment its value in treating headaches, such as migraines, in which vasodilatation is a contributing factor. In addition, caffeine has a specific effect that can help migraine sufferers: It enhances the action of ergotamine, used in the treatment of migraine. This discovery was made by migraine patients who noted that strong coffee provided symptomatic relief, especially when combined with ergot alkaloids. The benefit is believed to result from the fact that caffeine increases ergotamine’s oral and rectal absorption.

In at least one instance, caffeine was the cause of a major headache for one of the leading pharmaceutical companies. Excedrin, an over-the-counter Bristol-Myers Squibb analgesic, contains acetaminophen and caffeine. Recently, however, two 1,000bottle lots of Excedrin caplets were accidentally filled with 200 mg of pure caffeine, as much as in a NoDoz caffeine caplet, another Bristol-Myers Squibb product. Evidently the Excedrin gel tabs were being filled on the same processing line as NoDoz, and, despite all the computerized tracking, someone made a mistake. Bristol-Myers Squibb set up an 800 number to answer consumer questions and recalled the pills in question. Although the company feared an avalanche of bad publicity, the story received little news coverage. A company spokeswoman told us, “One adverse event was documented”: a woman who, after taking the pills, was “treated and released,” although what she was treated for was not specified. The company maintains that “untoward reactions to caffeine are not usually observed” at doses of less than 1,000 milligrams, but acknowledged that sensitivity to caffeine varies widely and that some people might have problems at lower doses.

A study by Dr. Margaret Moline of the New York Hospital-Cornell Medical Center, presented to the Boston Sleep Research Society in 1994, suggested that jet lag can be averted with judicious use of caffeine.
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Moline isolated five middle-aged men from clocks, televisions, windows, or any other external indicia of the passage of time. All the men followed their natural sleep schedules and received only a placebo for the first five days. After this, they were allowed to go to sleep at their normal time, but were awakened six hours earlier than usual and given either a pill containing 200 mg of caffeine or a placebo. This sleep displacement simulated the displacement experienced by travelers from New York to London. The results strongly suggested that a subject who took caffeine helped to reset his body’s clock with less intense disturbances and of a shorter duration than a subject who was given the placebo.

Books on jet lag often advise abstaining from caffeine for a week or two before a flight and then drinking several strong cups of coffee or tea at the correct hour to reset your biological clock to daytime after arriving at your destination. We have tried this and found that it works remarkably well.

We do not know enough to say if, or under what conditions, or for which subjects, or in what doses, caffeine can contribute to efforts to lose weight. Because it is evident that it can do so sometimes, for some people, anyone with a weight problem may be well advised to give caffeine a careful try, if he has no problems using caffeine to begin with.

Caffeine’s therapeutic effects on low blood pressure caused by failure of the autonomic regulatory system, a condition afflicting about fifty thousand Americans, was investigated by researchers at Vanderbilt University Medical School in 1985. They administered two and one-half cups of coffee a day to patients with low blood pressure caused by autonomic failure, a disorder of the blood pressure regulatory mechanism that results in pressure so low that victims often faint when they stand up, especially after eating a meal. The autonomic nervous system controls the motor functions of the heart, lungs, intestines, and other internal organs. When experiencing autonomic failure, the body does not respond properly to conditions in which it needs to raise the blood pressure, such as while standing up or eating.

Caffeine has been shown to raise blood pressure in normal subjects, but only if they have not had any coffee in several days. Usually this effect wears off when coffee is consumed regularly. Nevertheless, as a result of his study, David
Robertson, in a report in the
New England Journal of Medicine,
concluded, “We now advise our patients with autonomic failure to drink two cups of coffee with breakfast and to abstain for the rest of the day.”
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The International Olympic Committee, convinced that caffeine has positive ergogenic effects—that is, that an athlete can increase output or endurance by using caffeine—has restricted the urine levels of caffeine that competing athletes may exhibit after a competition. Laboratory studies, however, are not so clear if or when or to what degree these beneficial effects occur, whether they are more or less likely to be observed in trained athletes than in people in average condition, whether they are observed more in relation to certain muscle groups, whether they are observed only when the activity in question is sustained at a very high level for a very long time, and other similar questions.

Atopic dermatitis may be treatable with topical use of caffeine. Topical treatment with 30 percent caffeine in a hydrophilic base or in a hydrocortisone cream produces improvement in various forms of this skin condition, including pruritus, erythema, scaling, lichenification, oozing, and dermatitis. The improvement may be related to caffeine’s ability to liberate water from epidermal and subcutaneous tissues.
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A high intake of caffeine may be associated with a lower incidence and slower pro-gression of Parkinson’s disease. A study reported in the
Journal of the American Medical Association
(May 24, 2000), led by G.Webster Ross, M.D., staff neurologist at the Department of Veterans Affairs in Honolulu, analyzed thirty years of data from the Honolulu Heart Program, which has followed more than 8,000 Japanese-American men since 1965. Age-adjusted incidence of Parkinson disease dropped dramatically, from
10.4 per 10,000
man-years in men who drank no coffee to
1.9 per 10,000
manyears in men who drank over 28 ounces, or about five 6-ounce cups, a day. A similar decline was observed for caffeine intake from sources other than coffee. Ross concluded that “caffeine has a medicinal effect. It could be treating motor symptoms.”

As reported in an interview in
HealthScout
(May 23, 2000), Abraham Lieberman, M.D., professor of neurology at the University of Miami and medical director of the National Parkinson Foundation, attributes the possible role of caffeine in preventing Parkinson’s Disease to its ability to block adenosine receptors and increase the levels of dopamine, which are low in people suffering from the disease. However, Lieberman maintains, further long-term studies of the progression of the disease are needed to establish the treatment potential of caffeine in Parkinson’s disease more definitively.

Clinical Actions of the Methylxanthines