Pharmacokinetic Study of Intravenous Lidocaine in Young and Elderly Patients

Aging is accompanied by a gradual alteration in the functional reserve of several organs and a change in body composition that can affect the pharmacokinetics, response, and safety profile of medications. Lidocaine is a local anesthetic used daily in perineural or intravenous administration to reduce the need for opioids. Although its analgesic efficacy is well-established, there is currently only one older study regarding the pharmacokinetics and pharmacokinetic-pharmacodynamic (PK-PD) relationship of lidocaine in healthy elderly patients. In this study, conducted with a small sample size (13 subjects over 64 years old and 24 young subjects under 38 years old) and using a low bolus of 25 mg, the half-life of lidocaine was increased by 59% and clearance was decreased by 35% in elderly male subjects without significant differences in females. However, the recommendations for intravenous administration of lidocaine for analgesic purposes are the same for all: a bolus of 1 to 2 mg/kg followed by continuous administration of 1.5 to 2 mg/kg/h. Morphine sparing is particularly important in elderly patients due to their increased sensitivity to adverse effects. With this study, the investigators aim to define the optimal dose to administer in elderly subjects, in order to optimize analgesia while remaining within the therapeutic range to limit the adverse effects of lidocaine.