The xanthine derivatives are contraindicated in those with known hypersensitivity, peptic ulcers, seizure disorders (unless well controlled with appropriate anticon-vulsant medication), serious uncontrolled arrhythmias, and hyperthyroidism.
The xanthine derivatives are used cautiously in patients older than 60 years, those with cardiac disease, hypoxemia, hypertension, congestive heart failure, or liver disease. Aminophylline, dyphylline, oxtriphylline, and theophylline are Pregnancy Category C drugs and are used cautiously during pregnancy and lactation.
When xanthine bronchodilators are administered with sympathomimetic drugs (see Chap. 22), additive CNS and cardiovascular effects may occur. If a patient eats large amounts of charcoal-broiled foods while taking the xanthines, a decrease in the therapeutic effect of the xanthines may occur. Certain foods contain xan-thine (eg, coffee, colas, or chocolate) and may increase the risk of cardiac and CNS adverse reactions. Cigarettes, nicotine gum and patches, barbiturates, phenytoin, loop diuretics, isoniazid, and rifampin may decrease the effectiveness of the xanthines. There is an increased risk of xanthine toxicity when the drugs are administered with influenza vaccination, oral contraceptives, glucocorticoids, p-adrenergic blockers, cimeti-dine, macrolides, thyroid hormones, or allopurinol.
The xanthine derivatives, although a different class of drugs, also have bronchodilating activity by means of their direct relaxation of the smooth muscles of the bronchi.
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