Seizure with ciprofloxacin and theophylline combined therapy.

Ciprofloxacin has been reported to cause theophylline toxicity by inhibiting theophylline metabolism. A 93-year-old woman without a known seizure history, while on ciprofloxacin and theophylline combined therapy, experienced a grand mal seizure. Her serum theophylline concentration at the time was 20 micrograms/mL. On previous occasion of theophylline toxicity, she had a serum theophylline concentration of 27 micrograms/ml but the patient did not experience any seizure. Several reports suggest that the combination of theophylline and ciprofloxacin has an additive inhibitory effect on gamma-aminobutyric acid (GABA) sites. Inhibition of the binding of GABA to its receptor sites has been related to the convulsant effects of other drugs. The seizure in our patient may have been caused by altered pharmacokinetics and pharmacodynamics brought about by combined therapy of theophylline and ciprofloxacin.