Ciprofloxacin should not be given to an asthmatic using theophylline because:: (A) Ciprofloxacin inhibits theophylline metabolism, (B) Theophylline inhibits ciprofloxacin metabolism, (C) Ciprofloxacin decreases effect of theophylline, (D) Theophylline induces metabolism of ciprofloxacin
Answer is A. 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.