<prompt> Theophylline levels are increased in all, exceptErythromycinSmokingCimetidineCHF  <response>: Ans. is b i.e., Smoking Smoking induces theophylline metabolism and decreases its plasma level.In certain conditions theophylline concentration is increased, so its dose has to be reduced.These conditions are - Age 60 years CHFPneumonia Liver failureDrugs causing increased concentration of theophyllineErythromycinCiprofloxacinCimetidineOral contraceptivesAllopurinol 