Ciprofloxacin should not be given to an asthmatic using theophylline because:

Ans. (A) Ciprofloxacin inhibits theophylline metabolism(Ref: KDT 8/e p761)Theophylline has a narrow margin of safety (low therapeutic index) Ciprofloxacin inhibits theophylline metabolism and increases its plasma level leading to toxicity. Thus, ciprofloxacin should not be given to an asthmatic using theophylline.