Effect of pregnenolone carbonitrile, promethazine and antipyrine pretreatment on antipyrine metabolite formation in rats

Effects of salbutamol on the absorption and disposition of sulphamethoxazole in adult volunteers

On the basis of the reports that beta-adrenergic stimulation affects gastrointestinal motility in man as well as induces N-acetyltransferase in rat pineal gland, we decided to assess the effects of salbutamol pretreatment on the absorption as well as disposition of sulphamethoxazole (SMZ). After a control pharmacokinetic study of SMZ, each of six healthy volunteers took salbutamol at a dose of 4 mg four times daily for two weeks, and the kinetic study of SMZ was repeated after the morning dose on the fifteenth day. None of SMZ half-life, volume of distribution, renal and hepatic clearance rates was significantly altered. However, salbutamol pretreatment resulted in significant reduction in the absorption rate constant of SMZ from 1.168 +/- 0.509 h-1 (mean +/- S.D.) to 0.688 +/- 0.348 h-1 (P less than 0.025), and this was associated with prolongation of tmax from 3.00 +/- 1.69 h to 4.33 +/- 1.51 h (P less than 0.025). Cmax, however, was not correspondingly reduced probably as a result of significant increase in the extent of SMZ absorption from 611 +/- 108 mg to 749 +/- 78 mg (P less than 0.025). Our findings suggest that beta-adrenergic stimulation does not significantly induce human hepatic N-acetyltransferase enzyme. However, it does reduce the absorption rate as well as increase the extent of absorption of SMZ.