Lidocaine: 7 things you should know
Medically reviewed by Carmen Fookes, BPharm. Last updated on Feb 20, 2019.
1. How it works
- Lidocaine may be used as a local anesthetic or in the treatment of arrhythmias.
- Lidocaine works by blocking the influx of sodium ions into the membrane surrounding nerves. This prevents the initiation and conduction of impulses along the nerve, which results in an anesthetic effect.
- Lidocaine belongs to the class of medicines known as class-1b antiarrhythmic drugs. It may also be called an anesthetic.
- Lidocaine prevents the transmission of pain impulses and is used as a local anesthetic to numb specific areas of the body before minor surgical, dental, or other procedures. The effect of lidocaine is almost immediate.
- May be combined with epinephrine which increases the intensity and duration of the anesthetic effect and constricts the blood vessels, reducing bleeding.
- Lidocaine may also be used to produce regional anesthesia (a loss of sensation in a specific region of the body; for example, an arm or a leg or the entire pelvic region).
- Lidocaine antiarrhythmic may be used in the emergency treatment of cardiac arrest, ventricular arrhythmias or other severe heart conditions.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Skin redness, itching, a rash, or a feeling of warmth may occur in the region where lidocaine has been administered subcutaneously when used for local anesthesia. Bruising, bleeding, swelling and pain at the injection site are less common.
- Side effects may be more severe with lidocaine antiarrhythmic and include lightheadedness, drowsiness, nausea or vomiting, slow heartbeat, and low blood pressure. Drowsiness is usually a reflection of high blood levels of lidocaine.
- Local anesthetics injected into the head or neck area may produce side effects similar to systemic toxicity including confusion, convulsions, and respiratory depression.
- IM lidocaine may increase creatine phosphokinase levels which may compromise tests for this enzyme following an acute myocardial infarction.
- May not be suitable for some people including those with respiratory disease, cardiovascular disease, liver or kidney disease, low blood pressure, epilepsy, myasthenia gravis or congestive heart failure.
- May interact with some medications including beta-blockers, cimetidine, antiarrhythmics, and HIV agents.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Lidocaine will be administered to you by a health professional. Talk to them if you have any concerns.
- Tell all your healthcare providers about all your medical conditions, allergies, and all the medicines you use. Also let them know if you have had recent surgery.
- When used for local or regional anesthesia, a temporary loss of sensation and a restriction in the ability to move the affected body area may occur.
6. Response and Effectiveness
- When administered as a local or regional anesthetic, lidocaine is effective almost immediately. Duration of effect is approximately 60 to 90 minutes.
- Higher dosages or volumes of lidocaine will result in a shorter time to the onset of anesthesia, a longer duration of effect, a greater degree of muscle relaxation, and an increase in the spread of the anesthesia.
- The duration of action of lidocaine may be prolonged in people with liver disease.
Medicines that interact with lidocaine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with lidocaine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed. Common medications that may interact with lidocaine include:
- antiarrhythmics, such as dofetilide
- anticonvulsants, such as phenytoin
- antidepressants, such as fluvoxamine
- antipsychotics, such as pimozide
- cancer treatments, such as pomalidomide
- cystic fibrosis medications, such as ivacaftor
- Gaucher's disease treatments, such as eliglustat
- HIV medications, such as fosamprenavir
- lipid-lowering agents, such as lomitapide
- antimalaria medications, such as mefloquine
- other anesthetics (eg, bupivacaine)
- tyrosine kinase inhibitors, such as axitinib or bosutinib
- vasopressor drugs (such as ephedrine or phenylephrine) or ergot-type oxytocic drugs (such as ergometrine) (the combination may cause severe and persistent high blood pressure (hypertension) which may increase the risk of stroke).
Lidocaine may also interact with grapefruit juice.
Note that this list is not all-inclusive and includes only common medications that may interact with lidocaine. You should refer to the prescribing information for lidocaine for a complete list of interactions.
- Lidocaine injections [Package Insert]. Revised 04/2018. B. Braun Medical Inc. https://www.drugs.com/pro/lidocaine.html
- Lidocaine antiarrhythmic [Package Insert]. Drugs.com https://www.drugs.com/monograph/lidocaine-hydrochloride.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use lidocaine only for the indication prescribed.
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