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Food/Drug Interactions in Coffee
Allopurinol: Coffee and other beverages containing methylxanthine
stimulants (caffeine, theophylline, and theobromine) reduce the
effectiveness of the antigout drug allopurinol, which is designed to
inhibit xanthines.
Analgesics: Caffeine strengthens over-the-counter painkillers
(acetaminophen, aspirin, and other nonsteroidal antiinflammatories [NSAIDS]
such as ibuprofen and naproxen). But it also makes it more likely that
NSAIDS will irritate your stomach lining.
Antibiotics: Coffee increases stomach
acidity, which reduces the rate at which ampicillin, erythromycin,
griseofulvin, penicillin, and tetracyclines are absorbed when they are
taken by mouth. (There is no effect when the drugs are administered by
injection.)
Antiulcer medication: Coffee increases
stomach acidity and reduces the effectiveness of normal doses of
cimetidine and other antiulcer medication.
False-positive test for pheochromocytoma.
Pheochromocytoma, a tumor of the adrenal glands, secretes adrenalin, which
is converted to VMA (vanillylmandelic acid) by the body and excreted in
the urine. Until recently, the test for this tumor measured the levels of
VMA in the patient's urine and coffee, which contains VMA, was eliminated
from patients' diets lest it elevate the level of VMA in the urine,
producing a false-positive test result. Today, more finely drawn tests
make this unnecessary.
Iron supplements: Caffeine binds with iron
to form insoluble compounds your body cannot absorb. Ideally, iron
supplements and coffee should be taken at least two hours apart.
Birth control pills: Using oral
contraceptives appears to double the time it takes to eliminate caffeine
from the body. Instead of five to six hours, the stimulation of one cup of
coffee may last as long as 12 hours.
Monoamine oxidase (MAO) inhibitors:
Monoamine oxidase (MAO) inhibitors are drugs used to treat depression.
They inactivate naturally occurring enzymes in your body that metabolize
tyramine, a substance found in many fermented or aged foods. Tyramine
constricts blood vessels and increases blood pressure. Caffeine is a
substance similar to tyramine. If you consume excessive amounts of a
caffeinated beverage such as coffee while you are taking an MAO inhibitor,
the result may be a hypertensive crisis.
Nonprescription drugs containing caffeine:
The caffeine in coffee may add to the stimulant effects of the caffeine in
over-the-counter cold remedies, diuretics, pain relievers, stimulants, and
weight-control products containing caffeine. Some cold pills contain 30 mg
caffeine, some pain relievers 130 mg, and some weight-control products as
much as 280 mg caffeine. There are 110–150 mg caffeine in a five-ounce cup
of drip-brewed coffee.
Sedatives: The caffeine in coffee may
counteract the drowsiness caused by sedative drugs; this may be a boon to
people who get sleepy when they take antihistamines. Coffee will not,
however, "sober up" people who are experiencing the inebriating effects of
alcoholic beverages.
Theophylline: Caffeine relaxes the smooth
muscle of the bronchi and may intensify the effects (and/or increase the
risk of side effects) of this antiasthmatic drug.
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