Alteration of Hepatic microsomal enzyme systems and the lethal action of non-steroidal anti-arthritic drugs in acute and chronic models of inflammation.

Depression of the hepatic microsomal enzyme system(s) in adjuvant-induced polyarthritis (AIP), a chronic inflammation model, has been confirmed indirectly by the enhancement of hexobarbital Na-induced sleeping time and extended for the first time to zoxazolamine-induced paralysis. In addition, barbital Na-induced anesthesia was increased during the course of AIP development, indicating that the CNS of these rats appears to be more sensitive to drug effects, since this barbiturate is excreted virtually unmetabolized. Most likely because of these effects, LD50 values for acetylsalicylic acid, phenylbutazone and indomethacin in AIP rats decreased in terms of mg/kg (increased toxicity) as the disease became more severe (Day 21) since they are known ultimately to be metabolized by the liver. On the other hand, the toxicity of a new non-steroidal anti-inflammatory agent, meseclazone, was not altered significantly in AIP. This is most likely due to the fact that its near total conversion to 5-chlorosalicylic acid has been shown to occur by hydrolytic cleavage as it pases through the intestinal wall with litter hepatic involvement. Finally, carrageenan edema, a model of acute inflammation, did not affect barbiturate sleeping times of zoxazolamine paralysis, nor were any of these drugs studied more lethal in this disease state.