The acute toxicity of local anesthetics.
BACKGROUND
Systemic toxicity, usually from overdose or intravascular dose, is feared because it mainly affects the heart and brain, and may be acutely life-threatening.


METHODS
Pharmacological studies of local anesthetic toxicity have largely been reviewed primarily relating to the evaluation of ropivacaine and levobupivacaine during the past decade. This review/opinion focuses more on the principles and concepts underlying the main models used, from chemical pharmacological and pharmacokinetic perspectives.


RESULTS
Research models required to produce pivotal toxicity data are discussed. The potencies for neural blockade and systemic toxicity are associated across virtually all models, with some deviations through molecular stereochemistry. These models show that all local anesthetics can produce direct cardiovascular system toxicity and CNS excitotoxicity that may further affect the cardiovascular system response. Whereas the longer-acting local anesthetics are more likely to cause cardiac death by malignant arrhythmias, the shorter-acting agents are more likely to cause cardiac contraction failure. In most models, equi-anesthetic doses of ropivacaine and levobupivacaine are less likely to produce serious toxicity than bupivacaine.


CONCLUSIONS
Of the various models, this reviewer favors a whole-body large animal preparation because of the comprehensive data collection possible. The conscious sheep preparation has contributed more than any other, and may be regarded as the de facto 'standard' experimental model for concurrent study of local anesthetic toxicity ± pharmacokinetics, using experimental designs that can reproduce the toxicity seen in clinical accidents.
Mather
Laurence E
LE
The University of Sydney, Royal North Shore Hospital, Department of Anaesthesia & Pain Management, St Leonards, Sydney 2065, Australia. lmather@med.usyd.edu.au
D000577:Amides / Q000493:pharmacokinetics / Q000633:toxicity*; D000779:Anesthetics, Local / Q000493:pharmacokinetics / Q000633:toxicity*; D000818:Animals; D002045:Bupivacaine / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000633:toxicity; D002318:Cardiovascular Diseases / Q000139:chemically induced; D002493:Central Nervous System Diseases / Q000139:chemically induced; D004195:Disease Models, Animal; D006801:Humans; D000077554:Levobupivacaine; D000077212:Ropivacaine; D023382:Toxicity Tests, Acute / Q000379:methods
D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D000077554:Levobupivacaine; D002045:Bupivacaine