Lidocaine

Common Uses

Lidocaine is primarily used to block pain signals in specific parts of the body. Its use depends on the form of the medication, such as a cream, patch, or injection.

Medical and Dental Procedures

• Numbing: It is used to numb the skin, eyes, or the lining of the mouth, nose, or throat before minor surgeries, dental work, or medical tests like needle sticks or catheter insertions.
• Anesthesia: Injected forms are used as a local anesthetic for surgical procedures or to provide nerve blocks.

Pain Relief

• Skin Irritation: Topical forms help relieve pain, itching, or soreness caused by minor burns, sunburn, scrapes, and insect bites.
• Nerve Pain: Medicated patches are used to treat the burning pain that can persist after a shingles infection, known as post-herpetic neuralgia.
• Mouth and Throat: Liquid forms can soothe a sore mouth or throat and help prevent gagging during dental or medical exams.

Heart Rhythm Management

When administered by injection in a hospital setting, lidocaine is also used to treat certain types of serious irregular heartbeats, specifically ventricular arrhythmias.

Mechanism of Action

Lidocaine belongs to a class of medications known as local anesthetics. It works by preventing nerves from sending pain signals to the brain. This is achieved by blocking the movement of sodium into the nerve endings at the site of application or injection.

When sodium cannot enter the nerve cells, the electrical signal that normally carries pain information is stopped. This results in a temporary loss of feeling or numbness in the specific area where the medication is used.

Types of Use

Depending on how it is administered, lidocaine works in different ways to manage pain:

• Topical application: When applied to the skin or mucous membranes, it numbs the surface area to relieve itching, burning, or pain from minor irritations.
• Injection: When injected into the skin or surrounding tissues, it provides deeper numbness for medical or dental procedures.
• Ophthalmic use: When used in the eyes, it numbs the surface of the eye for examinations or surgeries.

Common Side Effects

Common side effects of lidocaine are often mild and typically occur at the site of administration. These may include:

• Redness, swelling, itching, or a burning sensation
• Small red or purple spots on the skin
• Skin appearing unusually pale
• Changes in temperature sensation, such as feeling hot or cold
• Dizziness or lightheadedness
• Drowsiness
• Nausea or vomiting

Serious Side Effects

Serious side effects are less common but require immediate medical attention. Seek emergency care for the following symptoms:

• Signs of a severe allergic reaction, such as hives, skin rash, or swelling of the face, lips, tongue, and throat
• Difficulty breathing or swallowing
• Confusion, nervousness, or extreme apprehension
• Blurred or double vision
• Ringing in the ears
• Tremors, muscle twitching, or seizures
• Slow, fast, or irregular heartbeat
• Severe dizziness, fainting, or extreme sleepiness

Teething Pain Warning

The FDA warns against using lidocaine viscous 2% to treat teething pain in infants and young children. Use in this population has been linked to serious adverse events, including seizures, severe brain injury, and heart complications. In some cases, these complications have been fatal.

Systemic Absorption and Toxicity

Lidocaine can be absorbed through the skin into the bloodstream. The risk of life-threatening toxicity increases if the medication is applied to large areas of the body, left on the skin for long periods, or applied to broken, irritated, or scraped skin. Symptoms of excessive absorption include:

• Confusion or drowsiness
• Dizziness
• Blurred vision
• Tremors or seizures
• Slow or irregular heartbeat

Methemoglobinemia Risk

Lidocaine is associated with a rare but serious condition called methemoglobinemia, which reduces the blood's ability to carry oxygen. This risk is higher in children under two years of age and those with certain genetic predispositions. Immediate medical care is necessary if symptoms occur, such as bluish coloring of the skin, lips, or fingernails; shortness of breath; or fatigue.

Medical Precautions

Individuals with certain health conditions may require closer monitoring or should avoid lidocaine:

• Liver Disease: Impaired liver function can lead to higher levels of lidocaine in the blood, increasing the risk of side effects.
• Heart Conditions: People with heart block or severe heart rhythm issues should use lidocaine with caution.
• Allergies: Lidocaine is contraindicated in those with a known hypersensitivity to amide-type local anesthetics.

Application Safety

To minimize risks, lidocaine should not be applied to damaged or infected skin unless directed by a healthcare professional. Avoid covering the application site with airtight dressings or applying external heat, such as a heating pad, as these actions can significantly increase the amount of drug absorbed into the body.

Pregnancy

Lidocaine is often used for local anesthesia during medical procedures in pregnant women. Animal reproduction studies have not shown evidence of harm to the fetus, but there are no adequate and well-controlled studies in humans. It is known that lidocaine crosses the placenta.

Breastfeeding

Lidocaine is excreted into breast milk in small amounts. While it is generally considered compatible with breastfeeding, the potential effects on a nursing infant are not fully established. The amount of medication absorbed by the infant is typically low, particularly when lidocaine is used topically or as a local injection.

Consult Your Doctor

Before using lidocaine, inform your healthcare provider if you:

• Are pregnant or planning to become pregnant.
• Are currently breastfeeding.

Injectable Formulations

Lidocaine is available as an injectable solution used for local or regional anesthesia. It is often supplied in various concentrations and may be combined with other ingredients, such as epinephrine, to help the numbing effect last longer.

Topical Formulations

For application to the skin, lidocaine is available in several preparations, including:

• Creams, gels, and ointments
• Topical solutions and liquids
• Aerosol sprays
• Medicated patches

Oral and Mucosal Preparations

Lidocaine is also formulated as a viscous oral solution for numbing the mouth and throat. Additionally, it is available as a jelly for use on mucous membranes during certain medical procedures.

FDA Approval and Indications

Lidocaine is an FDA-approved medication used as a local anesthetic and for the relief of pain associated with conditions such as post-herpetic neuralgia. It is available in various forms, including injections, topical creams, gels, and patches. While many formulations are available by prescription, some lower-strength topical products are sold over-the-counter (OTC).

Boxed Warning for Pediatric Use

The FDA requires a boxed warning for viscous lidocaine 2% solution, specifically advising against its use for treating teething pain in infants and young children. Regulatory reviews found that using lidocaine for teething can lead to serious health consequences, including:

• Seizures
• Severe brain injury
• Heart problems
• Death

Caregivers are encouraged to follow safer alternatives for teething pain, such as using a chilled teething ring or gently rubbing the child's gums.

Warnings on High-Concentration Topical Products

The FDA has issued warnings regarding the use of certain OTC topical pain relief products that contain high concentrations of lidocaine. These products are often marketed for use before cosmetic procedures like tattooing, piercing, or laser hair removal. When applied to large areas of skin or left on for extended periods, excessive amounts of lidocaine can enter the bloodstream, potentially causing life-threatening issues such as respiratory distress, heart arrhythmias, or seizures.

Common Uses

Lidocaine cream works by blocking nerve signals in the skin. It is frequently used to treat minor pain and itching from conditions such as:

• Sunburn or minor burns
• Insect bites or stings
• Minor cuts and scrapes
• Irritation from poisonous plants like poison ivy

Healthcare providers also use lidocaine cream to numb the skin before procedures like needle sticks, skin grafts, or minor dermatological surgeries.

Application and Safety

When using lidocaine cream, it is important to apply only the amount recommended. Using excessive amounts or applying it to large areas of the body can lead to serious side effects because the medication can be absorbed into the bloodstream. It should generally not be applied to broken, blistered, or irritated skin unless directed by a doctor.

Avoid contact with the eyes. If the cream gets into the eyes, rinse them thoroughly with water. Keep the product out of reach of children and pets, as accidental ingestion can be toxic.