Lidocaine - A Comprehensive Review

Overview

Lidocaine belongs to the group of medicines called local anesthetics. This drug prevents pain by blocking the signals at the nerve endings in the skin. Lidocaine does not cause unconsciousness as general anesthetics do when used for surgery. Lidocaine topical jelly or ointment is used on different parts of the body to cause numbness or loss of feeling for patients having certain medical procedures. It is also used to relieve pain and itching caused by conditions such as sunburn or other minor burns, insect bites or stings, poison ivy, poison oak, poison sumac, minor cuts, or scratches. In the late 1940s, Lidocaine became an easily available and exceptionally used medication.

Availability of the Forms of Lidocaine

Lidocaine is available in the following dosage forms:

• Spray.

• Patch, extended release.

• Gel or jelly.

• Cream.

• Ointment.

• Lotion.

• Pad.

• Swab.

• Powder.

• Solution.

What Are the Precautions for Lidocaine Use?

Lidocaine administration is generally safe, but precautions are necessary for some people.

1. Children

It is recommended to limit larger doses than the healthcare provider, or the manufacturer advised while applying Lidocaine topically to large areas of injured skin. Do not let the child scratch or rub the skin while it is numb, and do not let the skin get very hot or very cold.

When using Lidocaine cream, avoid heat sources such as electric blankets or heating pads. Also, do not let the child take long, hot baths or sunbathe because their temperature may rise and cause too much drug to be absorbed into their body.

2. Young Children

For children younger than three years old, Lidocaine should be used only when other treatments are not available. Always inform the healthcare provider first. Health problems like seizures have occurred in children younger than three when it was not used as recommended. Do not use it to treat infants and children with teething pain.

3. Pregnancy

Lidocaine is mostly considered generally safe for pregnant people to use. However, the drug does cross through the placenta and, although the developing fetus is able to metabolize it, caution is warranted.

High doses, in particular, are to be avoided. A 2.5 percent Lidocaine cream is considered safe, but, as is the case when used in other people, it is important to keep it out of the eyes.

It is not known whether Lidocaine applied topically can be passed to an infant through breast milk. Since other drugs are found in nursing mothers’ milk, caution should be exercised when Lidocaine is given to someone who is nursing.

4. Older Adults

Lidocaine comes in different strengths, and it should be used in smaller doses for older adults, depending on their age and physical or medical condition.

This precaution is needed because an individual person's physical makeup, along with the concentration of Lidocaine and formulation of the drug, all have significant effects on the amount of Lidocaine that gets absorbed into the blood. Lidocaine should also be used with caution in people with severe shock or heart block.

Combination Products of Lidocaine

Lidocaine can come in addition to other medications, such as additional pain relievers or steroids.

These products may include drugs like:

• Benzocaine, Lidocaine, and Tetracaine.

• Lidocaine and Prilocaine.

• Lidocaine and a local anesthetic.

• Menthol and Lidocaine.

• Lidocaine and Hydrocortisone.

It is always better to consult with the healthcare provider before using a combination product, especially if a patient is pregnant or has other health-related considerations.

Before using Lidocaine, let the healthcare provider know if a person has any of the following:

• Heart problems.

• Infected, open, or damaged skin wound.

• Allergic reaction to Lidocaine.

Also, inform the doctor if the patient is:

• Pregnant or trying to conceive.

• Breastfeeding.

Administration and Route of Administration

Various routes of administration and different preparations of Lidocaine include the following:

• Subcutaneous Route - Dilute concentrations of Lidocaine, about 0.05 to 0.1 percent, can be infiltrated subcutaneously in large volumes to provide local anesthesia, resulting in swelling and firmness of the site, which helps in certain surgical procedures.

• Intravenous Route - Dilute solutions of 0.25 to 0.5 percent of Lidocaine are administered through intravenous regional anesthesia or infiltration into subcutaneous tissue. One to two percent solutions of Lidocaine are used for regional nerve blocks, including epidural anesthesia, and are also available in intravenous preparations for antiarrhythmic use.

• Topical Application - One to two percent aqueous gels, mostly including an antiseptic such as Chlorhexidine, are used to topicalize and lubricate the urethra prior to procedures like Foley catheterization. Four percent solution is used for topical anesthesia of the mucous membranes of the airway, which may include the mouth, pharynx, and respiratory tract, using methods like gargling, spraying, or using an atomizer. Five percent ointment, typically mixed with Hydrocortisone, is employed topically on other mucous membranes such as the skin or in the rectum. Ten percent solution is also used topically for airway anesthesia, typically by spraying from a metered-dose atomizer.

For Patients

What Is Local Anesthesia?

Local anesthesia is a type of drug that may also be called an anesthetic to numb a small area of the body temporarily. The healthcare professional might use a local anesthetic before doing a minor procedure, such as a biopsy (testing tissue samples) or aesthetic procedure. A patient might receive local anesthesia before a dental procedure, such as a tooth extraction. Unlike general anesthesia, local anesthesia does not make the patient fall asleep; it just numbs the particular area.

Mostly, the local anesthetics work by preventing the nerves in the affected area from communicating sensations of pain to the brain. It is sometimes used as a sedative.

What Are the Different Types of Local Anesthesia?

There are two main types of local anesthetics, depending on the route of administration.

1. Topical Anesthetics

Topical anesthetics are applied directly over the skin or mucous membranes, such as the inside of the mouth, nose, or throat. They can also be applied to the surface of the eye. There are different forms of topical anesthetics:

• Liquids.

• Creams.

• Gels.

• Sprays.

• Patches.

In some conditions, the doctor might use a combination of local anesthetics for a more long-lasting effect.

Examples of procedures that might involve topical anesthesia include:

• Applying or removing stitches.

• IV (Intravenous) insertions.

• Catheter insertion.

• Laser treatments.

• Cataract (eye disorder) surgery.

• Endoscopy (procedure to see inside a person's body inserting a long optical tube).

Some over-the-counter (OTC) topical anesthetics, such as Benzocaine, can also help manage pain from:

• Mouth sores.

• Open wounds.

• Sore throat.

• Minor burns.

• Bug bites.

• Hemorrhoids (swelling of veins present near rectum or anus).

2. Injection

Local anesthetics can also be administered as an injection. Injectable anesthetics are typically used for numbing during procedures rather than pain management.

Procedures that might include an injection of a local anesthetic include.

• Dental procedures.

• Biopsy.

• Removal of growth under the skin.

• Mole or deep wart removal.

• Pacemaker (device to enhance the heart’s electrical activity) insertion.

• Diagnostic tests, such as a lumbar puncture (inserting needle inside the lumbar vertebral spaces) or bone marrow biopsy.

What Are the Risk Factors of Local Anesthesia?

The risk of side effects is mostly less while using local anesthesia as compared to general anesthesia. Local anesthesia is a safer option, but it is possible for a patient to be unusually sensitive to a drug and to develop severe side effects. Due to this, there must always be emergency medical care available when local anesthetics are used.

The most common side effects following local anesthesia are soreness and bruising at the injection site. These side effects are temporary and nothing to be concerned about. However, inform the healthcare provider if a bruise expands or does not get better within a week or two.

Serious side effects that may occur during use include:

• Allergic reaction to the anesthetic drug.

• Abnormal heart rhythm (arrhythmia).

• Seizure.

• Dizziness.

• Headache.

• Blurred vision.

• Twitching muscles or shivering.

Some serious but uncommon side effects that can arise in the days to weeks following a procedure involving local anesthesia include:

• Infection at the injection site.

• Nerve or tissue damage at the injection site is usually temporary but can persist for a few months or permanently.

How to Store Lidocaine?

It is highly recommended to keep Lidocaine out of reach of children. Store at room temperature between 15 and 30 degrees Celsius (59 and 86 degrees Fahrenheit). Throw away any medicine which is not within the usage period after checking the expiration date.

What if a Patient Misses a Dose?

If a patient misses a dose, use it as soon as they can if it is a topical drug. If it is almost time for the next dose, use only that dose. It is always recommended to avoid double or extra doses.

How Should a Patient Use This Lidocaine?

Lidocaine is for use on the skin. This drug may be used in the mouth, nose, or throat and may be administered by a healthcare professional. Strictly follow the directions on the prescription label. Apply the medicine at regular intervals. Do not use it more often than directed.

Consult the pediatrician regarding the use of this medicine in children. While this drug may be prescribed for selected conditions, precautions do apply.

For Doctors

Indication

Lidocaine is a commonly used anesthetic that belongs to the amide group indicated for the production of local or regional anesthesia by infiltration techniques such as percutaneous injection and intravenous regional anesthesia by peripheral nerve block techniques or by topical application.

Pharmacology

Mechanism of Action

Lidocaine is a local anesthetic belonging to the amide type. It is used to achieve local anesthesia by nerve blockade at various sites in the body. Lidocaine works by stabilizing the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby affecting local anesthetic action. In addition, the Lidocaine agent acts on sodium ion channels located on the internal surface of nerve cell membranes. At these channels, neutral, uncharged Lidocaine molecules diffuse through neural sheaths into the axoplasm, where they are subsequently ionized by joining with hydrogen ions. The resultant Lidocaine cations are then capable of reversibly binding the sodium channels from the inside, keeping them locked in an open state that prevents nerve depolarization. As a result, with sufficient blockage, the membrane of the postsynaptic neuron will ultimately not depolarize and will thus fail to transmit an action potential. This facilitates an anesthetic effect by not merely preventing pain signals from propagating to the brain but by aborting their generation in the first place.

In addition to blocking conduction in nerve axons in the peripheral nervous system, Lidocaine has important effects on the central nervous system and cardiovascular system. After absorption, Lidocaine may cause stimulation of the CNS (central nervous system) followed by depression, and in the cardiovascular system, it acts primarily on the myocardium, where it may produce decreases in electrical excitability, conduction rate, and force of contraction.

Absorption

Lidocaine is mostly absorbed across mucous membranes and damages the skin. The agent is quickly absorbed from the upper airway, tracheobronchial tree, and alveoli into the bloodstream. Although Lidocaine is also well absorbed across the gastrointestinal tract, oral bioavailability is only about 35 percent as a result of a high degree of first-pass metabolism.

Onset

Intravenous: 45 to 90 seconds.

Duration

Ten to 20 minutes.

Volume of Distribution

The volume of distribution determined for Lidocaine is 0.7 to 1.5 L/kg (liter per kilogram).

Protein Binding

The protein binding for Lidocaine is about 60 to 80 percent and is mainly dependent upon the plasma concentration of alpha-1-acid glycoprotein.

Metabolism

Lidocaine is metabolized rapidly by the liver, and metabolites and unchanged drugs are excreted by the kidneys. Biotransformation includes oxidative N-dealkylation, ring hydroxylation, cleavage of the amide linkage, and conjugation.

Route of Elimination

The excretion of unchanged Lidocaine and its metabolites occurs predominantly through the kidney, with less than five percent from the urine.

Half-life

The elimination half-life of Lidocaine is 1.5 to two hours.

Clearance

The mean systemic clearance for intravenously administered Lidocaine is 0.64 +/- 0.18 L/min (liter per minute).

Toxicity

The toxicity caused by Lidocaine is mostly because of overdosing on the drug. The following are symptoms seen in cases of overdose.

• Circumoral paraesthesia.

• Numbness of the tongue.

• Light-headedness.

• Hyperacusis.

• Tinnitus.

• Visual disturbance.

• Muscular tremors or muscle twitching.

• Generalized convulsions.

Contraindications

The use of Lidocaine is contraindicated in cases of known hypersensitivity to the drug or its components and previous history of developing allergic response or anaphylactic reactions.

What Are the Drug Interactions of Lidocaine?

The following are the drugs that should be avoided, along with the indication of Lidocaine. It is observed that they interact with each other, and may result in some serious conditions.

• Bupivacaine liposome.

• Dofetilide.

• Eliglustat.

• Flibanserin.

• Lomitapide.

• Abametapir.

• Axitinib.

• Bosutinib.

• Cobimetinib.

• Eliglustat.

• Fentanyl.

• Fluvoxamine.

• Fosamprenavir.

• Givosiran.

• Ivabradine.

• Ivosidenib.

• Lonafarnib.

• Mefloquine.

• Naloxegol.

• Olaparib.

• Pefloxacin.

• Phenytoin.

• Pimozide.

• Pomalidomide.