Adverse drug reactions (ADRs) are rare when lidocaine is used as a local anesthetic and is administered correctly. Most ADRs associated with lidocaine for anesthesia relate to administration technique (resulting in systemic exposure) or pharmacological effects of anesthesia, and
allergic reactions only rarely occur. Systemic exposure to excessive quantities of lidocaine mainly results in
central nervous system (CNS) and
cardiovascular effects – CNS effects usually occur at lower
blood plasma concentrations and additional cardiovascular effects present at higher concentrations, though cardiovascular collapse may also occur with low concentrations. ADRs by individual organ systems are: • CNS excitation: nervousness, agitation, anxiety, apprehension, tingling around the mouth (circumoral paraesthesia), headache,
hyperesthesia, tremor, dizziness, pupillary changes, psychosis, euphoria, hallucinations, and seizures • CNS depression with heavier exposure: drowsiness, lethargy, slurred speech,
hypoesthesia, confusion, disorientation, loss of consciousness,
respiratory depression, and
apnoea. • Cardiovascular:
hypotension,
bradycardia,
arrhythmias, flushing, venous insufficiency, increased defibrillator threshold,
edema, and/or
cardiac arrest – some of which may be due to
hypoxemia secondary to respiratory depression. • Respiratory: bronchospasm, dyspnea, respiratory depression or arrest • Gastrointestinal: metallic taste, nausea, vomiting, agita, and diarrhea • Ears:
tinnitus • Eyes: local burning, conjunctival hyperemia, corneal epithelial changes/ulceration, diplopia, visual changes (opacification) • Skin: itching, depigmentation, rash,
urticaria, edema, angioedema, bruising,
inflammation of the vein at the injection site, irritation of the skin when applied topically • Blood:
methemoglobinemia • Allergy ADRs associated with the use of intravenous lidocaine are similar to the toxic effects of systemic exposure above. These are dose-related and more frequent at high infusion rates (≥3 mg/min). Common ADRs include headache, dizziness, drowsiness, confusion, visual disturbances, tinnitus, tremor, and/or
paraesthesia. Infrequent ADRs associated with the use of lidocaine include:
hypotension,
bradycardia,
arrhythmias,
cardiac arrest, muscle twitching,
seizures,
coma, and/or respiratory depression. While concerns of tissue death, if used in these areas, have been raised, the evidence does not support these concerns. There is some weak evidence to suggest that the use of alternative anesthetic medications such as
prilocaine,
procaine,
bupivacaine,
ropivacaine, or
levobupivacaine may decrease the risk of a person developing transient neurological symptoms.
Contraindications Absolute contraindications for the use of lidocaine include: •
Heart block, second or third degree (without pacemaker) • Severe
sinoatrial block (without pacemaker) • Serious
adverse drug reaction to lidocaine or amide local anesthetics • Hypersensitivity to corn and corn-related products (corn-derived dextrose is used in the mixed injections) • Concurrent treatment with
quinidine,
flecainide,
disopyramide,
procainamide (class I antiarrhythmic agents) • Prior use of
amiodarone hydrochloride •
Adams–Stokes syndrome •
Wolff–Parkinson–White syndrome Exercise caution in people with any of these: •
Hypotension not due to
arrhythmia •
Bradycardia •
Accelerated idioventricular rhythm • Elderly •
Ehlers–Danlos syndromes; efficiency of local anesthetics can be reduced •
Pseudocholinesterase deficiency • Intra-articular infusion (this is not an approved indication and can cause
chondrolysis) •
Porphyria, especially
acute intermittent porphyria; lidocaine has been classified as porphyrogenic because of the hepatic enzymes it induces, although clinical evidence suggests it is not.
Bupivacaine is a safe alternative in this case. • Impaired liver function – people with lowered hepatic function may have an adverse reaction with repeated administration of lidocaine because the drug is metabolized by the liver. Adverse reactions may include neurological symptoms (e.g. dizziness, nausea, muscle twitches, vomiting, or seizures).
Overdosage Overdoses of lidocaine may result from excessive administration by topical or
parenteral routes, accidental oral ingestion of topical preparations by children (who are more susceptible to overdose), accidental intravenous (rather than subcutaneous,
intrathecal, or paracervical) injection, or from prolonged use of subcutaneous infiltration anesthesia during cosmetic surgery. The maximum safe dose is 3 mg per kg. Symptoms include central nervous system manifestations such as numbness of the tongue, dizziness, tinnitus, visual disturbances, convulsions, reduced consciousness progressing to coma, as well as respiratory arrest and cardiovascular disturbances. Lidocaine and its two major metabolites may be quantified in blood, plasma, or serum to confirm the diagnosis in potential poisoning victims or to assist forensic investigation in a case of fatal overdose. Lidocaine is often given intravenously as an antiarrhythmic agent in critical cardiac-care situations. Treatment with intravenous lipid emulsions (used for
parenteral feeding) to reverse the effects of local anaesthetic toxicity is becoming more common. Lidocaine has been used by veterinarians for
euthanasia of
horses,
livestock, and more recently of
dogs and
cats. Due to its side effects,
intravenous lidocaine can be given only to anesthetized patients, making it less attractive perhaps than
pentobarbital, which can be given intravenously to awake patients. In 2025
Russian Army nurses have reported the use of 1-2 %
intravenous lidocaine in 60 mL dosage for
mercy killing of mortally wounded servicemen.
Postarthroscopic glenohumeral chondrolysis Lidocaine in large amounts may be toxic to
cartilage and intra-articular infusions can lead to
postarthroscopic glenohumeral chondrolysis. ==Pharmacology==