title: The half-life of 2-chloroprocaine.
abstract: The purpose of this study was to examine the discrepancy between the reported in vitro half-life of chloroprocaine and the slower observed disappearance of the drug in maternal plasma. The study had two aims. The first was to redetermine the in vitro half-life of 2-chloroprocaine in maternal and fetal plasma. The second was to determine the apparent half-life of 2-chloroprocaine in vivo after intrapartum epidural anesthesia in obstetric patients. Gas chromatography or gas chromatography/mass spectrometry techniques were used to measure 2-chloroprocaine in maternal or fetal plasma. Mean in vitro half-lives of 11.2 +/- 2.8 and 15.4 +/- 5.2 sec were found for maternal and fetal plasma from nine patients, respectively. The maternal half-life was significantly shorter than the fetal half-life (P less than 0.05). The mean apparent in vivo half-life in maternal plasma was found to be 3.1 +/- 1.6 min. The results of this study show that the half-life in vitro is correctly measured in seconds. However, the apparent half-life in vivo after epidural anesthesia is 3.1 +/- 1.6 min and ranges from 1.5 to 6.4 min. The differences in the magnitude of the two findings is probably due to continuous uptake of the drug from the epidural space.
mesh_terms: D000328:Adult; D000767:Anesthesia, Epidural; D000773:Anesthesia, Obstetrical; D000779:Anesthetics, Local / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D066298:In Vitro Techniques; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D011343:Procaine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000779:Anesthetics, Local; D011343:Procaine; C004616:chloroprocaine