<prompt> Drugs which increase level of theophylline include:chloramphenicolCimetidineAllopurinolAll of the above  <response>: Drugs which inhibit theophylline metabolism and increase its plasma level are-erythromycin, ciprofloxacin, cimetidine, oral contraceptives,allopurinol, chloramphenicol- all enzyme inhibitors dose should be reduced to 23rds of the usual dose KD TRIPATHI Page No:227 