The Effect of Administration Routes on the Absorption, Metabolism and Excretion of Sulpyrin in Rats

After intravenous, intramuscular, or oral administration of sulpyrin (10, 100μmole/head) to rats, sulpyfrin, 4-monomethylaminoantipyrine, 4-aminoantipyrine and 4-acetylaminoantipyrine excreted in urine were determined successively. Based on these data, the absorption rate was estimated and the change of sulpyrin metabolism with the administration route was investigated. Between intravenous and intramuscular injection, the average value of the urinary excretion of sulpyrin+4-monomethylaminoantipyrine was smaller, in the latter but there was no significant difference between them. In contrast, a remarkable decrease was recogdized both in the amount and rate of excretion in the case of oral administration, and it was considered that the absorption of sulpyrin in the digestive tract was slow and sulpyrin was decomposed during its absorption. The excretion of 4-aminoantipyrine was significitly delayed in the case of intramuscular injection compared with initravenous injection. The excretion of 4-acetylaminoantipyrine increased in the order of intravenous, intramuscular, and oral administration. It was found that the metabolism of sulpyrin changed with administration route. The estimation of absorption rate of sulpyrin by convolution method using the excretion data of sulpyrin+4-monomethylaminoantipyrine showed that the absorption ended in 1 hr after the intramuscular injection, but it continued more than 5 hr atter the oral administration. It was found that sulpyrin was partly decomposed when it was absorbed both in intramuscular and oral administration. The decompose substance was considered to be also absorbed and to be excreted in urine as 4-aminoantipyrine and 4-acetylaminoantipyrine by metabolism.