What Is Lidocaine Toxicity?

Lidocaine toxicity is a reaction to the effects or dosage amounts of lidocaine, a common topical anesthetic. Reactions of lidocaine range from mild to severe. Mild side effects of lidocaine might include dizziness, increased heart rate and respiratory rate, elevated blood pressure, involuntary eye movement, and unconsciousness. Severe reactions include drowsiness, brain seizures, dropped blood pressure and heart rate, decreased respiratory rate, and unconsciousness.

Lidocaine toxicity is a serious medical emergency as symptoms may occur without warning and spur life-threatening complications, such as brain seizures, cardiac arrest and oxygen depletion. The toxicity risks of lidocaine vary somewhat among individuals. Lidocaine is metabolized by the liver, and patients with impaired livers or liver disease may experience more severe complications with lower doses than healthy patients. Doses of 10 mcg/mL or more induce severe toxic reactions, but for some patients a dosage of 6 mcg/mL may cause a reaction.

Toxicity is also dependent on many other factors. Lidocaine is a synthetic amino amide anesthetic and may cause reactions in patients with low protein counts. Excessive acid in the body fluids from kidney dysfunction, called acidosis, may cause lidocaine toxicity. Patients on beta-blockers or certain antibiotics may experience severe lidocaine drug interactions.

Generally, most cases of lidocaine toxicity occur from unintended overdose of the drug. Used as a spray, lidocaine dosage is difficult to control especially when applied to a highly vascular surface of the body, such as the mucous membranes of the mouth and throat. Rate of injection can also affect toxicity, as the faster the rate of injection the less capable the body is of processing the drug.

While lidocaine toxicity is a serious medical condition, severe reactions, long-term complications and fatalities are extremely rare. Medical professionals are aware of the dangers of this anesthetic and monitor its uses as well as the patient during the medical procedure. Most patients suffering from lidocaine toxicity may experience only slight dizziness or discomfort. Lidocaine reactions quickly decrease as the body absorbs, metabolizes and inoculates the effects of the drug.

Uses of lidocaine vary in medical procedures, but it is commonly applied as a topical anesthetic for dental procedures, injected as a local anesthetic for dental nerve block or surgical procedures, and applied to the skin as a topical solution for the relief of mild to moderate pain. Lidocaine is uncommonly used as a treatment for postherpetic neuralgia, as an antiarrhythmic as well as for relieving jellyfish stings. When used as an inhalant, lidocaine acts as a cough suppressant.