Pharmacokinetics of prilocaine in intravenous regional anaesthesia

To determine the acute pharma-cokinetics of prilocaine in intravenous regional anaesthesia (IVRA), plasma prilocaine levels before and after tourniquet release were measured for sixteen patients (including six children) with forearm fractures. A dose of 2.5mg/kg was used with a minimum cuff occlusion time of 20 minutes. No patients had detectable drug levels prior to tourniquet release. Peak drug concentrations were reached within 10 minutes of tourniquet release in all patients. Average peak drug concentration was 1.23mcg/ml. By 30 minutes, drug levels had reached an average of 0.34mcg/ml (range <0.3–0.6mcg/ml). The pharmacokinetic curves of the children were similar in profile to the adults, with analysis of variance failing to demonstrate a significant difference between curves. In no patients did prilocaine reach toxic levels. These results show that prilocaine used at a dose of 2.5 mg/kg is safe and that an observation period of 30 minutes following IVRA is adequate. IVRA does not appear to be contraindicated in children.