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As a clinician skilled in Advanced Cardiac Life Support (ACLS), it is important to have a deep understanding of the drugs used in the algorithms, how they work, and why they are a good choice for treating certain conditions.

Lidocaine is one such drug, and has uses both as a local anesthetic and as an antiarrhythmic. The drug was discovered in 1943 by Swedish chemist Nils Lofgren and was approved and available for use in 1949. It is sold under the trade names Xylocaine, Ztildo, and others.

Lidocaine Uses

Lidocaine is a drug with many uses that comes in several different preparations and routes of administration.

It is a commonly used local anesthetic, and as such can be injected into the tissue or applied topically via a cream or spray. These types of anesthetic preparations are used by physicians for numbing during procedures and in more diluted over-the-counter medications for sore throats and sunburns. Dosage for anesthetic administration varies widely, depending on the route and type of procedure. Dosages featuring a 1-2% Lidocaine solution are the most commonly distributed.

Lidocaine is also used as a cardiac antiarrhythmic, which is the primary focus of this article. It works by blocking sodium channels and thus decreasing the rate of heart contractions.

Specific situations where Lidocaine is indicated for cardiac use include:

Note that the first two situations typically accompany a sudden cardiac arrest, while the second two situations would require background knowledge of the patient’s condition(s) and a hospital environment. These second two scenarios of Lidocaine usage are cardiac in nature, but not quite as emergent (allowing more time for targeted treatment plans).


Lidocaine Hydrochloride Injection, USP is a sterile, nonpyrogenic, isotonic sodium chloride solution. It is classified as a tertiary amine, and is a class Ib antiarrhythmic agent on the Vaughan-Williams classification. As an antiarrhythmic, it is used as an intravenous (IV) drip to maintain a regular heart rhythm, or as an IV or intraosseous (IO) injection to reestablish normal heart rhythm when a cardiac emergency occurs.

Lidocaine is metabolized by the liver with some metabolites, and a small amount of the drug excreted by the kidneys. In an otherwise healthy human, the drug is metabolized rapidly with a half-life of 1.5 to 2.0 hours after intravenous injection. For patients with liver dysfunction, the half-life may be twice as long or more. Renal dysfunction does not affect Lidocaine HCl pharmacokinetics. However, it may cause the accumulation of metabolites in the blood.

As previously mentioned, Lidocaine works on the central nervous system (CNS) by inhibiting the movement of sodium ions required to conduct neural impulses. This accounts for both its anesthetic action and cardiac antiarrhythmic action. Because of this action toward the CNS, Lidocaine readily crosses the blood-brain barrier and placental barriers via passive diffusion.

Treatment Options and the ACLS Algorithm

Lidocaine has been around longer than some of the newer antiarrhythmics on the market. However, it is still included in the ACLS protocol. Prior to the addition of the newer antiarrhythmic amiodarone to the ACLS protocol in 2020, lidocaine was more frequently used in practice. In the current American Heart Association (AHA) ACLS manual, lidocaine can be used during and immediately after a ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) cardiac arrest. It has been widely considered as a functional equivalent to amiodarone. If maximum doses of amiodarone are given to the patient first with no return of spontaneous circulation (ROSC), lidocaine may be used at the beginning of the next full cycle of CPR in order to ensure good distribution of the drug.

The ACLS manual emphasizes the use of high-quality CPR and early defibrillation as first-line treatments prior to the use of medications.

A 2018 focused update by the AHA summarizes some of the most recent published evidence and recommendations for the use of antiarrhythmic drugs during VF/VT cardiac arrests. Several peer-reviewed studies have been conducted comparing patient outcomes after administration of amiodarone versus lidocaine in various situations. A meta-analysis published in the American Journal of Emergency Medicine (2020) found that, out of nine studies analyzed, lidocaine had the best effect on survival to hospital discharge, while amiodarone had the most favorable neurological outcomes. Because of these findings, the 2018 focused update states:

“Lidocaine is now recommended as an alternative to amiodarone and has now been added to the ACLS Cardiac Arrest Algorithm for treatment of shock-refractory VT/pVT.”


The following IV lidocaine dosage guidelines are given for ACLS:

It is important to note that lidocaine may be given endotracheally in situations where IV/IO access is unavailable. In these cases, it should be given at a dose of 2 to 2.5 times the IV dose in 5 to 10 mL of distilled water.

The American Heart Association also notes that maintenance doses should be reduced when there are signs of left ventricular dysfunction or impaired liver function. If signs of toxicity begin, immediately cease lidocaine infusion.

Patients should always be under constant ECG monitoring during administration of IV/IO lidocaine.


With any mode of administration (but especially with IV/IO), lidocaine can reach toxic levels in the body. Compared to some other anesthetics and antiarrhythmics, however, lidocaine has a good safety margin before reaching toxic blood levels. This makes toxicity relatively rare. To prevent toxicity and minimize systemic negative effects, it is important to keep track of the cumulative dosage given in all forms to a patient.

The total dose threshold for lidocaine toxicity is considered 4.5mg/kg of body weight. If the rate of absorption is impaired by liver insufficiency, this dosage may be less.

Lidocaine toxicity to muscles and peripheral nerves can occur locally at the site of injection, or systemically in the case of intravenous/intraosseous infusion. Local signs and symptoms of toxicity include circumoral numbness, facial tingling, restlessness, vertigo, tinnitus, slurred speech, and tonic-clonic seizures. Systemic toxicity results in seizures, loss of consciousness, and rarely cardiac collapse.


The first standard contraindication for any form of lidocaine would be a prior allergic reaction to any medication or product containing lidocaine. If allergy information is accessible during an ACLS situation, then it should be checked as CPR is being initiated and administered.

To understand the following contraindications and side effects, it is helpful to remember how lidocaine works — by blocking the sodium channel signal in neurons. When the drug is given intravenously, it not only blocks heart nerve impulses but others as well.

Another contraindication for lidocaine is any type of heart block in the absence of an implanted pacemaker. This includes SA, AV, and intraventricular heart blocks as well as 2nd and 3rd degree heart blocks. Also included is the uncommon disorder Adams-Stokes syndrome, which causes a sudden decrease in cardiac output (often with complete heart block) that results in syncopal episodes. Another uncommon condition that presents a contraindication is Wolff-Parkinson-White Syndrome, which is an electrical conduction disorder in the heart causing life-threatening periods of rapid, irregular heartbeat.

Patients with congestive heart failure (CHF) and cardiogenic shock are also contraindicated for lidocaine. Caution should be used in the presence of beta blockers and cimetidine, as the lidocaine effects will be increased and the heart rate may become bradycardic. Caution should also be used in patients with a history of baseline bradycardia.

Caution should also be taken if the patient has liver disease, since the drug is metabolized by the liver. Respiratory depression, marked hypoxia, and hypovolemia should be treated with caution as well. Lidocaine may be acceptable to use during pregnancy in emergency situations, due to its short half-life. However, human studies are not available. It does cross into breast milk, and caution should be taken if breastfeeding.

Side Effects

Common side effects of IV Lidocaine include:

Serious side effects of IV Lidocaine include:

The following drugs can present a severe interaction with lidocaine: Bupivacaine liposome, dofetilide, eliglustat, flibanserin, and lomitapide.

These drugs can present a serious interaction with lidocaine: axitinib, bosutinib, cobimetinib, fentanyl (any route, including transdermal), fluvoxamine, fosamprenavir, ivabradine, ivacaftor, mefloquine, naloxegol, olaparib, Pefloxacin, phenytoin, pimozide, and pomalidomide.


As part of the study of Advanced Cardiac Life Support, the complete picture of lidocaine usage should be known in order to make the best possible clinical decisions. It is important to note that this guide is for adult administration of lidocaine, and other resources should be used to study pediatric usage. Please consult the package insert to find out more about the chemical makeup of lidocaine and specific prescribing information.

To learn more about drugs, ECG rhythms, and clinical scenarios associated with ACLS, BLS, and PALS, or for help with your certification exams, study materials based on the most recent AHA guidelines are available through AMRI. We have helped more than one million medical professionals to get certified or recertified since 1983. AMRI is also accredited by the National Board of Emergency Care Certifications (NBECC). As such, your certification through AMRI comes with a one-year 100% money back guarantee. If your employer doesn’t accept the certification card we give you, we'll refund the price of your certification.

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