Drugs which increase level of theophylline include:
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 2/3rds of the usual dose KD TRIPATHI Page No:227
chloramphenicol
Cimetidine
Allopurinol
All of the above
Respiratory system