Intravenous lidocaine is generally well-tolerated by most patients, but occasional side effects do occur within the central nervous system, cardiovascular system, and gastrointestinal tract. In most cases, these reactions are dose dependent, meaning that lowered dosages or discontinuation of the medication will alleviate side effects. Side effects are usually more prevalent in the elderly, or in those with certain underlying health conditions.
One of the most common side effects of intravenous lidocaine is central nervous system toxicity. This side effect is most common in elderly patients, those with heart failure, or those with severely damaged liver function which inhibits the metabolism of certain drugs. The most frequently noted symptom of nervous system toxicity is tremor. Other symptoms include dizziness, insomnia, slurred speech, ataxia, depression, agitation, change in personality, hallucinations, and memory impairment. When this occurs, the dosage is usually lowered or use of lidocaine is discontinued in lieu of another drug.
Cardiovascular toxicity is another potential side effect of lidocaine. Symptoms of this condition may include shock, hypotension, or asystole. This complication is generally rare and is mostly well-tolerated, even in those with underlying heart disease, although cardiovascular toxicity is most common in those with a heart condition. In the majority of cases, this side effect is the result of overdose.
Gastrointestinal side effects of intravenous lidocaine are usually well-tolerated and may vary from patient to patient. Symptoms can include nausea and vomiting. Other more rare side effects of lidocaine may include temporary psychosis, allergic reactions such as skin eruptions, dizziness, or tongue tingling, and respiratory distress. These effects are generally very rare and only occur in a very small number of patients who are particularly sensitive to lidocaine.
Less severe and temporary side effects of intravenous lidocaine can include pain or redness at the injection site, numbness, shortness of breath, and swelling. These are generally mild and may be caused by an allergic reaction. They do not typically lead to a discontinuation of the drug, but should be closely monitored to prevent a more severe reaction. In very rare instances patients may experience seizures when taking lidocaine. Another drug may be given in substitution of lidocaine in patients who are found to be especially sensitive to side effects.
Any unusual symptoms should be reported to a doctor right away. These are not limited to the symptoms listed above, although these are the most commonly reported. Most patients are able to tolerate and use intravenous lidocaine without incident, and even those with reported side effects are able to continue taking the drug when the benefits outweigh any discomfort.