[thee-uh-fil-een, -in]
noun Pharmacology.
a white, crystalline, poisonous alkaloid, C 7 H 8 N 4 O 2 , an isomer of theobromine, extracted from tea leaves or produced synthetically: used to relieve bronchial spasms, in the treatment of certain heart conditions, and as a diuretic.

1890–95; theo-, irregular combining form representing Neo-Latin thea tea + -phyll + -ine2 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
theophylline (ˌθɪəˈfɪliːn, -ɪn, θɪˈɒfɪlɪn)
See also xanthine a white crystalline slightly water-soluble alkaloid that is an isomer of theobromine: it occurs in plants, such as tea, and is used to treat asthma. Formula: C7H8N4O2
[C19: from theo(bromine) + phyllo- + -ine²]

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

theophylline the·oph·yl·line (thē-ŏf'ə-lĭn, thē'ō-fĭl'ēn')
A colorless crystalline alkaloid derived from tea leaves or made synthetically, used as a cardiac stimulant and diuretic.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
theophylline   (thē-ŏf'ə-lĭn)  Pronunciation Key 
A colorless, crystalline alkaloid derived from tea leaves or made synthetically. It is used in medicine especially as a bronchial dilator. Theophylline is a xanthine that is similar in structure to caffeine and is a structural isomer of theobromine. Chemical formula: C7H8N4O2.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


alkaloidal drug used in medicine as an antiasthmatic, coronary vasodilator, and diuretic. Theophylline is a xanthine alkaloid, a methylxanthine chemically related to caffeine and theobromine. Along with caffeine, it is an active constituent of tea (Camellia sinensis), but it is commercially produced in pharmaceutical manufacture by chemical synthesis.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Over-the-counter drugs should be taken with caution, especially those that contain stimulants or a medicine called theophylline.
In patients who do not respond to bronchodilators, slow-release theophylline may be used.
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