Pharmacokinetics of theophylline and phenobarbital during peritoneal dialysis compared with intestinal dialysis in rats.

The transfer rates of theophylline and phenobarbital from blood into the peritoneal cavity were investigated after their intravenous administrations at a dose of 10 mg/kg each in rats. Appreciable amounts of both drugs were transported into the dialysate with their transfer rates decreasing as the serum concentrations declined. The average amount of theophylline transferred into the dialysate was 17% and 24% of dose in 2 and 4 h, respectively, while that of phenobarbital was 13% and 45% of dose in 2 and 8 h, respectively. The amounts appeared to be greater than those transported into the intestinal lumen which was previously reported by the authors. Peritoneal dialysis decreased the serum half-life and the area under the serum concentration-time curve (AUC) value of theophylline from 2.1 to 1.5 h and from 38 to 26 micrograms.h/ml, respectively and increased the total body clearance by 47% as compared with the control. The dialysis also decreased the serum half-life and the AUC value of phenobarbital from 8.3 to 5.3 h and from 116 to 83 micrograms.h/ml, respectively and increased the total body clearance by 112% as compared with the control. Overall, the effectiveness of peritoneal dialysis in removing theophylline and phenobarbital appears to be not very different from that of intestinal dialysis with oral activated charcoal which has been previously reported by the authors in spite of the difference in transport into the intestinal lumen and peritoneum.