Aim: Diclofenac is a non-steroidal anti-inflammatory drug (NSAID), which may cause serious intestinal adverse reactions (enteropathy). In this study we investigated whether co-administration of ciprofloxacin affected the pharmacokinetics of diclofenac and diclofenac-induced enteropathy in rats.
Methods: The pharmacokinetics of diclofenac was assessed in rats after receiving diclofenac (10 mg/kg, ig, or 5 mg/kg, iv), with or without ciprofloxacin (20 mg/kg, ig) co-administered. After receiving 6 oral doses or 15 intravenous doses of diclofenac, the rats were sacrificed, and small intestine was removed to examine diclofenac-induced enteropathy. β-Glucuronidase activity in intestinal content, bovine liver and E coli was evaluated.
Results: Following oral or intravenous administration, the pharmacokinetic profile of diclofenac displayed typical enterohepatic circulation, and co-administration of ciprofloxacin abolished the enterohepatic circulation, resulted in significant reduction in the plasma content of diclofenac. In control rats, β-glucuronidase activity in small intestinal content was region-dependent: proximal intestine<distal intestine<ileal valve. Administration of ciprofloxac caused significant reduction of β-glucuronidase activity in distal small intestine, and particularly in ileal valve. Furthermore, ciprofloxacin (10-2000 μmol/L) dose-dependently inhibited β-glucuronidase activity in distal small intestine content or E coli incubated in vitro, but did not affect that in proximal small intestine content or bovine liver incubated in vitro. After receiving 6 oral doses or 15 intravenous doses of diclofenac, typical enteropathy was developed with severe enteropathy occurred in distal small intestine. Co-administration of ciprofloxacin significantly alleviated diclofenac-induced enteropathy.
Conclusion: Co-administration of ciprofloxacin attenuated enterohepatic circulation of diclofenac and alleviated diclofenac-induced enteropathy in rats, partly via the inhibition of intestinal β-glucuronidase activity.