A patient of bronchial asthma is on theophylline. Which of the following drugs should not be indicated to treat the upper respiratory tract infection in the same patient?: (A) Ciprofloxacin, (B) Amoxicillin, (C) Ampicillin, (D) All of the above
Answer is A. Drugs like ciprofloxacin, erythromycin and cimetidine are powerful microsomal enzyme inhibitors, predisposing to toxicity of theophylline.