Ropivacaine plasma concentrations during 120-hour epidural infusion

The pharmacokinetics of ropivacaine were evaluated during long-term continu ous epidural analgesia (CEDA) for about 120 h. The total and free plasma co ncentrations of ropivacaine and the alpha (1)-acid glycoprotein (AAG) conce ntration were measured in 12 patients after total knee arthroplasty. The in fusion rate was adjusted according to patients' analgesic needs or side eff ects. The mean (SD) rate of infusion of ropivacaine (Naropin 2 mg ml(-1)) w as 14.6 (3.2) mg h(-1) on the day of surgery and was increased after surger y to 15.4 (4.4) mg h(-1) on days 1-5. This was equivalent to an absolute do se of 1786 (553) mg of ropivacaine over the entire infusion period. After a n initial increase, the mean free ropivacaine plasma concentration nearly p lateaued and than decreased slightly after approximately 70 h. The individu al peak free plasma concentration was 0.096 (0.034) mug ml(-1). The highest individual free plasma concentration was 0.16 mug ml(-1). The individual p eak total plasma concentration, 4.1 (1.2) mug ml(-1), was achieved after 67 .7 (16.5) h, although the AAG concentration increased throughout the observ ation period. Our data support the safety and efficacy of long-term ropivac aine CEDA.