title: 2-Chloroprocaine antagonism of epidural morphine analgesia.
abstract: BACKGROUND
  2-Chloroprocaine (2-CP) used for lumbar epidural anesthesia (LEA) reportedly decreases the efficacy of epidural morphine (EM) administered for post-cesarean section (CS) analgesia. The amount of supplemental i.v. morphine self-administered by the patient via the patient-controlled analgesia device (PCA) is used to study the interaction between EM and 2-CP.
  
  
  METHODS
  Forty-two patients scheduled for elective CS were randomly divided into 3 equal groups, and received 2-CP, 2-CP + epinephrine (Epi, 5 micrograms.ml-1) or 2% lidocaine (Lido) with Epi for LEA. All patients received 5 mg EM and i.v. PCA morphine for postoperative pain. Cumulative amount of i.v. morphine used in the first 24 hours as well as the amount of the drug used during each 2-h period were noted. Nonparametric analysis of variance and Chi-squared analysis were used for statistical comparisons.
  
  
  RESULTS
  The mean cumulative 24-h i.v. PCA morphine requirement in the 2-CP, 2-CP+Epi and Lido+Epi groups respectively was 20.5 +/- 24, 33.1.5 +/- 27 and 4.07 +/- (mean +/- SD). The Lido + Epi group used significantly less morphine (P = 0.01) compared to either of the 2-CP groups with no significant difference between the 2-CP groups. The maximum i.v. PCA morphine use occurred in the first 4 hours following surgery in all three groups.
  
  
  CONCLUSIONS
  Analgesic efficacy of EM is decreased when 2-CP is used for LEA compared to when Lido + Epi is used.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Magee-Womens Hospital, University of Pittsburgh School of Medicine, Pennsylvania, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Karambelkar
authors.forename: S
authors.initials: S
authors.lastname: Ramanathan
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural; D016362:Analgesia, Obstetrical; D016058:Analgesia, Patient-Controlled; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009020:Morphine / Q000037:antagonists & inhibitors*; D011247:Pregnancy; D011343:Procaine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D011343:Procaine; C004616:chloroprocaine; D009020:Morphine