Metabolism and measurement of chloroprocaine, an ester-type local anesthetic

Blood levels of intact chloroprocaine were determined using a GLC procedure capable of detecting as little as 10 ng of chloroprocaine/ml of blood. It was necessary to detective plasma cholinesterases in collected samples by adding echothiophate iodide to blood sampling tubes. An extraction procedure, followed by a TLC separation and spectrodensitometric assay, was developed for measurement of the metabolite 2-chloro-4-aminobenzoic acid in plasma and urine. With these procedures, data were obtained showing that chloroprocaine is hydrolyzed rapidly by plasma cholinesterases. No unchanged drug could be detected in any blood samples obtained from volunteers who received chloroprocaine by intravenous infusion or from obstetric patients who had epidural anesthesia during labor and delivery. Blood levels of 2-chloro-4-amino-benzoic acid rose promptly with the administration of chloroprocaine and declined rapidly after drug administration. Most of the metabolite was recovered in urine.