Lidocaine Toxicity

Criticisms of Current Recommenations

The current recommendations regarding maximum doses of local anesthetics presented in textbooks, or by the responsible pharmaceutical companies, are not evidence based (ie, determined by randomized and controlled studies). Rather, decisions on recommending certain maximum local anesthetic doses have been made in part by extrapolations from animal experiments, clinical experiences from the use of various doses and measurement of blood concentrations, case reports of local anesthetic toxicity, and pharmacokinetic results” {Rosenberg PH. Reg Anesth Pain Med 29: 564, 2004}

Signs and Symptoms

Lidocaine toxicity (and all local anesthetic toxicity) can cause circumoral numbness, facial tingling, restlessness, vertigo, tinnitus, slurred speech, and tonic-clonic seizures. Local anesthetics are actually CNS depressants, thus tonic-clonic seizures are thought to be caused by depression of inhibitory pathways.

Lidocaine Toxicity in Various Clinical Scenarios

Spinal Anesthesia

There is evidence that lidocaine, when used for spinal anesthesia, can be neurotoxic [Drasner Reg Anesth Pain Med 27: 576, 2002], even in single-injection doses [Drasner Anesthesiology 87: 469, 1997]

Local Injection

The maximum recommended single dose of lidocaine is 300 mg (or 500 mg when combined with epinephrine)


The American Academy of Dermatology has published guidelines for liposuction {J Am Acad Dermatol 45: 438, 2001} which indicate a maximum safe of lidocaine of 55 mg/kg; however, this remains an area of significant controversary. Some experts note that 35 mg/kg is a more reasonable limit noting that the hepatic metabolism of lidocaine by means of CYP3A4 is saturable and once saturation occurs, absorption exceeds elimination, and plasma lidocaine concentrations increase precipitously {NEJM 340: 1471, 1999}

Further Reading

An excellent review of the issues surrounding determination of a maximal dose of local anesthetics can be found at {Rosenberg PH. Reg Anesth Pain Med 29: 564, 2004, PMID 15635516}