Xanthine (pronounced /ˈzænθiːn/ or /ˈzænθaɪn/), (3,7-dihydro-purine-2,6-dione), is a purine base found in most human body tissues and fluids and in other organisms. A number of mild stimulants are derived from xanthine, including caffeine and theobromine.
Xanthine is a product on the pathway of purine degradation.
Xanthine is subsequently converted to uric acid by the action of the xanthine oxidase enzyme.
People with the rare genetic disorder xanthinuria lack sufficient xanthine oxidase and cannot convert xanthine to uric acid.
Clinical significance of xanthine derivatives
Derivatives of xanthine, known collectively as xanthines, are a group of alkaloids commonly used for their effects as mild stimulants and as bronchodilators, notably in treating the symptoms of asthma. In contrast to other, more potent stimulants, they only inhibit the actions of sleepiness-inducing adenosine, making them somewhat less effective as stimulants than sympathomimetic amines. Due to widespread effects, the therapeutic range of xanthines is narrow, making them merely a second-line asthma treatment. The therapeutic level is 10-20 micrograms/mL blood; signs of toxicity include tremor, nausea, nervousness, and tachycardia/arrhythmia.
Methylxanthines affect not only the airways but stimulate heart rate, force of contraction, cardiac arrhythmias at high concentrations. In the CNS they increase alertness, stimulate the respiratory centre, and are used for treatment of infantile apnea. In high doses they can lead to convulsions that are resistant to anticonvulsants. Methylxanthines induce acid and pepsin secretions in the GI tract. Methylxanthines are metabolized by Cytochrome P450 in the liver. Methylated xanthines include caffeine, aminophylline, IBMX, paraxanthine, pentoxifylline , theobromine, and theophylline. These drugs act as both
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