Critical
Ciprofloxacin × Theophylline
Fluoroquinolone antibacterials×Methylxanthine
Mechanism
Ciprofloxacin is a strong CYP1A2 inhibitor. Theophylline (NTI, target 10-20 mcg/mL) rises 2-fold. Fatal cases reported – seizures, arrhythmias, cardiac arrest.
Symptoms
Tachycardia, tremor, nausea, vomiting, seizures, arrhythmias when theophylline above 20 mcg/mL.
Management
Combination contraindicated. Alternative – levofloxacin (minimal CYP1A2 effect) or amoxicillin-clavulanate for pneumonia.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.