THEOPHYLLINE INTERACTS WITH A WIDE VAREITY OF DRUGS. THESE DRUGS DECREASES THEOPHYLLINE CLEARANCE ; ALCOHOL, ALLOPURINOL, CARBAMAZEPINE, CIMETIDINE, CIPROFLOXACIN, ERYTHROMYCIN, AND RIFAMPIN, RITONAVIR, AND AMINOGLUTETHIMIDE INCREASE THEOPHYLLINE CLEARANCE BY INDUCTION OF MICROSOMAL ENZYME ACTIVITY.