Pharmacokinetics of 1R-cis 1'R-cis atracurium besylate (51W89) and plasma laudanosine concentrations in health and chronic renal failure.

To ascertain the effects of chronic renal failure on the pharmacokinetics of 1R-cis 1'R-cis atracurium besylate (a stereoisomer, designated 51W89), we gave a bolus dose of 0.1 mg kg-1 (2 x ED95) to 17 patients with end-stage renal failure and to 15 patients with normal renal function undergoing elective surgery. All patients received thiopentone, fentanyl and midazolam i.v. and 70% nitrous oxide in oxygen. Blood samples were obtained over 8 h and plasma analysed for 51W89 and laudanosine concentration, using high pressure liquid chromatography. A two-compartment model was fitted to the 51W89 plasma concentration data using the NONMEM program, to estimate pharmacokinetic variables and to determine the influence of renal failure, age, weight and sex. Clearance of 51W89 was found to be reduced by 13% in renal failure. The typical value of T1/2 beta was 4.2 min longer in renal failure than in the healthy patients (34.2 vs 30.0 min, P < 0.005). In the healthy patients, clearance of 51W89 was greater in males, but it decreased with increasing age by approximately 1.5 ml min-1 yr-1. Mean plasma laudanosine concentrations were significantly higher in the renal failure group; nevertheless, they were approximately one-tenth of those reported after atracurium.