 where X1: amount of drug in the central compartment; X2: amount of drug in the peripheral compartment; X3: amount of drug in the first peritoneal exchange; X4: amount of drug in the second peritoneal exchange; CL: non-dialytic clearance from central compartment liters per hour; V: volume of the central compartment liters; k12 and k21: first-order intercompartmental transfer rate constants between central and peripheral compartments inverse hours; k13 and k31: first-order intercompartmental transfer rate constants between central and peritoneal compartments; CONEX1: amount of ertapenem remaining in peritoneal compartment after drainage of first study exchange mg; R1: time-delimited zero-order drug input rate piece-wise input function into central compartment mg per hour; R2: rate constant for first dwell constrained to 0 first dwell turned off or 1 first dwell turned on; R3: rate constant for second dwell constrained to 0 second dwell turned off or 1 second dwell turned on; R4: ertapenem dialysate concentration observed at the end of the first dwell; R5:input rate for residual amount of dialysate volume remaining after drainage of the first dwell. 