title: Plasma lidocaine, monoethylglycinexylidide, and glycinexylidide concentrations after epidural administration in geriatric patients.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of age on the pharmacokinetics of lidocaine after epidural administration.
  
  
  METHODS
  Two percent lidocaine with epinephrine (5 microg/mL) was administered in two different age groups: an adult group (age 42 +/- 6 years, n = 10) and an elderly group (age 77 +/- 4 years, n = 10). Concentrations of lidocaine and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were measured in plasma samples obtained after 15, 30, 45, 60, 90, 120, 150, and 180 minutes of administration using high-performance liquid chromatography with ultraviolet detection.
  
  
  RESULTS
  No significant differences in plasma concentrations of lidocaine and its metabolites were observed between the two groups during the 3 hours of study. However, the elderly group showed significantly longer mean residence times (MRTs) and lower plasma clearance of lidocaine during the period compared with the adult group (P < .05). Plasma concentration ratios of MEGX/lidocaine were significantly lower in the elderly group after 2 hours of lidocaine administration (P < .05).
  
  
  CONCLUSIONS
  The increase in plasma lidocaine concentration after epidural anesthesia in elderly patients was not as high as anticipated. However, the elderly patients showed longer MRTs, lower clearance, and lower ratios of MEGX/lidocaine than did the adult (middle-age) patients.
authors.affiliation: Department of Anesthesiology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan. taekof@md.tsukuba.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Fukuda
authors.forename: Y
authors.initials: Y
authors.lastname: Kakiuchi
authors.forename: M
authors.initials: M
authors.lastname: Miyabe
authors.forename: N
authors.initials: N
authors.lastname: Okubo
authors.forename: Y
authors.initials: Y
authors.lastname: Yaguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Kohda
authors.forename: H
authors.initials: H
authors.lastname: Toyooka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D008875:Middle Aged
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine; C001306:glycinexylidide; C001173:monoethylglycinexylidide