Pharmacokinetics of indomethacin ester prodrugs: gastrointestinal and hepatic toxicity and the hydrolytic capacity of various tissues in rats.
In order to develop a potential prodrug of indomethacin (IM) which causes less irritation to the gastrointestinal mucosa, the ester prodrugs [butyl ester (IM-BE) and octyl ester (IM-OE)] of IM were synthesized and evaluated for their ulcerogenic activity and hepatic injury after oral administration in rats. Additionally, the kinetics of hydrolysis of the prodrugs were examined to characterize the tissues or organs capable of hydrolyzing the ester bonds. The plasma levels of IM after the oral administration of IM-OE and IM-BE were comparatively low compared with those after IM, with a small bioavailability (2.1 and 15.0%, respectively). Ulcerogenic activity and hepatic injury, expressed by decreased hepatic microsomal enzyme activities, were hardly seen after repeated oral administration of the prodrugs, in contrast with the severely irritating effects of IM alone. Hydrolysis of the prodrugs was adequately described by first-order kinetics. IM-BE was relatively rapidly hydrolyzed in plasma, skin and whole blood, but the hydrolysis in the intestinal mucosa and liver was very slow. The hydrolytic rates for IM-OE were exceedingly small or negligible. These results indicate that the main part of IM-BE and IM-OE administered orally might not be hydrolyzed to IM in the gastrointestinal tract, and that the ester prodrugs themselves were absorbed through the mucosa; also, that the hydrolysis of ester bonds would be carried out mainly in the circulatory system. Consequently, IM-BE seems to be an ideal prodrug of IM.
Ogiso
T
T
Faculty of Pharmaceutical Sciences, Kinki University, Osaka, Japan.
Iwaki
M
M
Tanino
T
T
Nagai
T
T
Ueda
Y
Y
Muraoka
O
O
Tanabe
G
G
D000284:Administration, Oral; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D056486:Chemical and Drug Induced Liver Injury / Q000473:pathology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004952:Esters / Q000378:metabolism / Q000493:pharmacokinetics; D005767:Gastrointestinal Diseases / Q000139:chemically induced* / Q000473:pathology; D006868:Hydrolysis; D007213:Indomethacin / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D007275:Injections, Intravenous; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D011355:Prodrugs / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D013276:Stomach Ulcer / Q000139:chemically induced / Q000473:pathology
D000894:Anti-Inflammatory Agents, Non-Steroidal; D004952:Esters; D011355:Prodrugs; D003577:Cytochrome P-450 Enzyme System; D007213:Indomethacin