*Essam Ezzeldin and Hebatalla Ibrahim Ahmed Simultaneous co-administration of multiple drugs is highly probable to allow effective treatment of a disease or multiple disease symptoms. Ciprofloxacin antibiotic is in use worldwide and it is possible to be used in cardiovascular patient’s treatment. The objective of this study was to investigate the biochemical and pharmacokinetic interactions between ciprofloxacin and captopril in rats. The study was conducted in six groups of rats that received captopril 7.5 mg/kg, ciprofloxacin 50 and 100 mg/kg alone or co-administered with captopril 7.5 mg/kg for 28 days. Captopril and Ciprofloxacin plasma levels were determined by validated HPLC methods. Liver function biomarkers were also assessed. Ciprofloxacin significantly increased the Cmax AUC0-12 and AUC0-inf and prolonged t1/2 and MRT of captopril. Conversely, captopril had no significance effect on the ciprofloxacin.  Ciprofloxacin elevated the liver function biomarkers. Therefore the clinical significant of this work should be taken into consideration when these two agents are concomitantly administered. <br /> International Journal Of Pharmacy 2249-1848 55 2012-04-01 2 244-251 Copyright (c) Pharma Scholars. All rights reserved 2013