I am a board-certified anesthesiologist in Lake Tahoe, California. I write from the perspective of both a doctor and a patient.
What Is Local Anesthesia?
Lidocaine is an example of a local anesthetic. Local anesthetics can be injected into tissue or around nerves to cause numbing. The numbing will affect the area immediately surrounding the injection site when lidocaine is used for "local anesthesia." Regional anesthesia makes use of the class of drugs called local anesthetics (like lidocaine) to numb a larger area of the body by numbing a nerve or group of nerves that supply that area.
To review and keep the terminology straight:
- Local anesthetics are drugs that cause numbing of tissue.
- Local anesthesia specifically refers to the numbing of an area of skin or tissue at or near the injection site of a local anesthetic.
- Regional anesthesia also utilizes the drugs that are called local anesthetics but in a more indirect manner. The local anesthetic is injected around nerves supplying the body part to be numbed.
How Do Local Anesthetics Work?
Local anesthetics are often discussed in terms of their properties. Their onset time and duration of action, as well as their safety profile, may determine which anesthetic would be useful in certain situations.
The two general classes of local anesthetics are the amides and esters based on their chemical structure. Lidocaine is an amide local anesthetic.
Lidocaine, and local anesthetics in general, work by penetrating tissue and blocking pain signals from being transmitted along nerve endings, preventing the pain signal from reaching the brain. The nerve endings have channels for the electrolyte sodium (Na channels) on them. When tissue is disturbed, the channels open and sodium enters the cell, changing the electrical charge. This electrical change becomes the pain sensation when interpreted by the brain.
The local anesthetics are sodium channel blockers. In other words, they prevent sodium from entering the nerve endings, thus, preventing pain. This is perceived as numbness.
When Is Lidocaine Used?
Lidocaine can be used as a cream, injection, or even as a mist for the nose, mouth, and throat. Lidoderm is a patch containing lidocaine, available by prescription, that is applied to the skin for various painful conditions.
Lidocaine is most commonly used for injection into skin, muscle, and mucous membranes for its local numbing. It is also used in regional anesthesia like spinals, epidurals, and nerve blocks.
Its most common use is as a local anesthetic, but it has also been used for its action on heart cells to help stop or stabilize some abnormal heart rhythms.
Side Effects of Lidocaine?
- Redness at or near injection site
- Itching at or near injection site
- Blistering at or near injection site
- Numbness lasting longer or spreading further than desired
Side effects and complications are more likely if you have certain medical conditions or in combination with some medications. Always tell your doctor about your medical history and medications.
The expected effect of lidocaine is numbness of the target tissue. There are very few side effects of lidocaine used in this way.
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Side effects are those effects that accompany a medicine's use. They are expected in a certain percentage of the population using the medication. They are often bothersome, but not harmful.
Complications, on the other hand, are possible, but not expected effects. Precautions are taken to prevent complications and they are often, but not always, avoidable.
Complications of Use
Complications can occur for a variety of reasons. Overdose of lidocaine, injection or leakage into the wrong space, or allergic reaction can lead to complications.
Allergic reactions are rare. The amide local anesthetics like lidocaine don't have nearly the potential for, or actual incidence of, allergic reaction as local anesthetics of the ester class. It is possible, but unlikely to have a true allergic reaction to lidocaine. Sometimes, the preservative used may cause a reaction, however. Also, lidocaine may be mixed with epinephrine (adrenalin) to prolong its duration of action. The epinephrine will increase heart rate and blood pressure and can cause nausea and hot flushing and feelings of anxiety. This is not an allergic reaction as many patients assume or have been told. It is an exaggerated effect of the normal response to epinephrine.
Injection or leakage into blood vessels and the circulation of lidocaine meant for other tissue can lead to overdose and signs of toxicity. This can also occur when too much lidocaine is injected anywhere in the body. The maximum safe dose of lidocaine is calculated based on body weight and perhaps age and coexisting medical conditions. It is metabolized by the liver and eliminated from the body in the urine, so if you have liver or kidney problems, be sure to tell your doctor before receiving an injection with lidocaine.
When lidocaine enters a space for which it is not meant, it can cause unwanted side effects and complications. For example, epidural medication administration requires many times the dose of medicine injected directly into the spinal fluid. If lidocaine meant for the epidural space enters the spinal fluid instead, the result is an unwanted spinal block with much more medicine than would normally be used for that purpose. In this situation, the spinal can spread and cause a "total spinal" which temporarily paralyzes breathing and affect the heart rate, conduction, and blood pressure in dangerous ways. The same thing can happen with certain peripheral nerve blocks, especially an interscalene block given in the neck before shoulder surgery since the epidural and spinal spaces are close to the injection site. For this reason, these blocks are (or should) only be given by highly-trained professionals who are also certified in advanced life-saving techniques.
Lidocaine toxicity from absorption into the bloodstream is another potential complication.
What Are the Signs of Toxicity?
Overdosage of lidocaine, or lidocaine absorbed into the circulation, can cause toxicity with lidocaine, which is a serious and potentially fatal complication. The severity of the complication depends on the amount that reaches the circulation.
Signs of lidocaine toxicity include:
- Numb tongue or lips
- Ringing in the ears
- Bad taste in the mouth
More severe toxicity is manifested as seizures, respiratory and cardiac arrest, and coma.
Treatment of toxicity includes supportive care—medications to stop seizures and to support the cardiovascular system are used. In addition, a lipid rescue solution is now becoming a front-line treatment to neutralize local anesthetic toxicity and minimize the complications from it.
While the author is a physician anesthesiologist, nothing in this article is intended to represent medical advice. This article is for informational purposes only.
This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
Yve on March 10, 2019:
Went to dentist, while being injected, the room started to spin.
Injected at back of mouth between top and bottom jaw.
To repair last tooth in the back.
I signaled the dentist to stop.
After a while the spinning stopped, started injection without epinephrine.
While waiting for mouth to freeze, a sudden flue symptoms appeared.
Then puki feeling.
Weakness, faint, clammy.
Dentist brought oxygen, could hear them say don't go to sleep, keep your eyes open, she is lathergic.
Then she called the ambulance.
My blood pressure was ok.
Not sure why this happened.
As was not nervous prior to precudere, had been getting treatments all my life never any problems.
I had a treatment 1-2 weeks earlier.
But tooth was not in the back so injection was not at back.
No adverse effects what so ever.
Can't figure out why this happened now.
I should mention, that I felt some liquid trickle down my throat from the numbing agent prior to injection. Bad taste.
Also a year ago, had injection same location but other side.
Was uncomfortable during procedure, crown on last tooth in the back.
Was a rough procedure, felt like I had whiplash for two weeks do to the pressure placed on mouth and at times I thought I could not breath do to mouth being open so wide.
Unpleasant experience, unusual, since had treatments on back teeth before and was fine by different dentist.
Also the previous treatment was to replace crown.
I complained six months earlier that there was odor leaking from the crown. The dentist said it was age related.
Well the crown popped of and indeed the odor was under the crown between tooth and crown. After that odor disappeared completely.
I could not believe how muchmbetter I felt.
I was feeling tired all the times. Once crown popped of, rinsed mouth, felt full of energy.
So there is another possibility.
My family physician said perhaps it was do to laying down and head being tilted sideways.
ken kermack on May 22, 2018:
I am using Lidocaine for Interstitial Cystitis by bladder instillation is there a set rate of absorption into the blood stream. I want to be able to increase amount of 4% lidocaine and keep under the 3mg-5mg per KG of body weight or 5micrograms per ml. I found a small study done in Japan the found lidocaine in the mucous of the damaged gag layer was present up to 3 days. That information would suggest Lidocaine getting in the vascular system could be a lower percentage than I might have thought.
Anyone that has something to help me get a better idea what the upper most level is so I can safely try higher amount to see if a greater degree of relief could be found.
Kelly Mulvaney on September 21, 2017:
I had to get stitches in my thumb. The doctor gave me a lot possibly 10 or more shots of lidocaine. My thumb is still numb from the knuckle to the tip but yet hurts all the time. When you put lidocaine in your thumb there is swelling. That swelling has never went away. I understand there is probably nerve damage, but the swelling seems odd. I have been on two rounds of antibiotics and now I am taking 7.5 mg of meloxicam once a day with no real results. I have seen 2 different doctors who give me stupid remarks likes "it's just you" and carpal tunnel syndrome...lame. does anybody have any idea why this could be. My thumb feels like it will explode. It feels warm at times and when I ice it stays cold longer than my other digits. Help
S. Stanley on September 05, 2017:
QUESTION: As a liver transplant recipient, I am not allowed NSAIDS, because they cause bleeding near liver. I have used Aspercreme (plain) for spot treatment of pains from RA, but recently bought Aspercreme with Lidocaine. Will either one of these cause unwanted internal bleeding from the liver? If so I will use nothing. We are allowed Tylenol, but it hardly works, and, "destroys the liver." Needless to say, that will not do. Can I continue using one or the other Aspercreme OTC safely? I am thankfully still alive, and would rather suffer pain than die. Thank you for your anticipated reply.
Blanca on September 02, 2017:
Hi, the injection site of the ingrown toenail procedure has blistered on one side and is dark purple on the other side. The procedure was on 8/16 and its still numb and can't bend forward. Is this normal?
mickey seigfried on July 12, 2017:
I went to dentist for a longtime the last 2 times lidocaine made me severely vertigo where they had to call ambulance could not move heart rate up and bp was to the 3rd time it was given to me with my esophagus procedure at that time was given more I felt like I was having a stroke vertigo heart raising mouth felling more numb than usally what could cause this scare to go to dentist a year before all this happen never a problem with this drug
Eva Tuersley on June 29, 2017:
Several years ago I had a pre-operative injection into my heel and quite quickly started to experience severe symptoms starting with my tongue feeling numb then progressing to extreme fatigue. The doctor became alarmed because this is apparently quite rare. I now have this included with my list of allergens. Thank you for a great write up.
Gab on June 19, 2017:
Hey there! Awesome article! And since you seem to still check this I'm totally gonna ask you a question! Totally unsure if I have an allergy to lidocaine or not. I have used it a couple of different times BUT there was always something else so I never felt I could single it out and I have just been avoiding lidocaine. I'm kind of tired of being cut open raw,stuff hurts lol. The first time I used it (ten years ) was a patch for pain relief for your back. The patch wasn't on for 20 minutes and I felt burning pain thrust to my ovaries! Like my whole bottom half just whacked out and started burning. The patch didn't have latex, but I'm unsure of any other ingredients. If it helps, it was like a smooth sticky gel but it was very large patch. The second time I used it i had it I injected into the inside of my arm to get Implanon inserted. Seemed fine until a few hours later. Burning itching everywhere sick to my stomach and I almost fainted! I spent an hour outside in the cold to get my breathing right again. It was just the standard 1% that's used. Im curious if you think these are reactions associated either lidocaine, even busy partial. I have a heart murmur so I dont want to try it again if I dont have to. Thank you so much for your time and all the info. :)
Susanne on June 11, 2017:
Had a nipple biopsy and given lidocaine and epinephrine. After the procedure I could not control involuntary shaking of the hands, arms,legs and shivering of the body. Had to spend 40 minutes in the recovery room. Was given liquids and crackers. Still feel out of balance two days later.
Jesus B on October 11, 2016:
They injected lidocaine to numb my teeth for a filling. They had to inject me again when I could feel the pain. After one week, my throat was sore and I couldn't swallow without it hurting, then I had to go the the ER due to unusual heart palpitations, and lastly, I feel dizzy and light headed. Do you think all this could be related to the lidocaine due to the overdose, or am I wrong.
TahoeDoc (author) from Lake Tahoe, California on September 28, 2016:
This cannot figure out how this would happen. The area numbed is usually small and the metabolism so quick that I can't see (or don't know of a mechanism) a relationship. Doesn't mean there isn't something I don't know but nothing I know of would do this unless you have a type of allergic reaction that is just "local" meaning to the surrounding area but not causing overall signs of allergy. That is not a medical conclusion though- just trying to think outside the box. So sorry for your troubles. :(
Marie on September 23, 2016:
I had a small cyst removed by my skin dr and he used xylocaine or lidocane to numb the area. That week I suffered from severe back stiffening for the first time and was bedridden for at least a week. I was curious if the anesthesia may have gone too far into other areas that may have caused my back to stiffen. My doctor assured me it wasn't related. A year later the same Doctor removed a skin growth from my thigh also using the anesthesia to numb the area. A few days later I am in severe throbbing pain in the same thigh that was injected and I cannot stand upright or walk. I tried all pain meds and was hospitalized but they assume it may be a pinched nerve. I am convinced that the anesthesia went too far as it did last time in my back. This can't be a coincidence that the same thing happened again. I am suffering from the pain and wondering how or if I can get the anesthetic out of the area it is affecting.
TahoeDoc (author) from Lake Tahoe, California on August 04, 2014:
That sounds some of numbing medicine (lidocaine or bupivicaine or ropivicaine are most commonly used, I think) was absorbed into your blood stream. There may have also been some epinephrine in the mixture. Epinephrine is added to the numbing medicine to make it last longer and could contribute to the heart racing if it got into the blood stream. During difficult epidurals, blood vessels may be poked and some medicine can get in.
So, it seems as if some of the medicine probably went into the blood stream and not just around the nerves. Of course, I have to give the disclaimer that I can't make a diagnosis without having been there in case there is more to it than I can tell here.
KJ on July 31, 2014:
Very interesting article! Question for you - as a chronic back pain sufferer, I get facet injections, epidural injections and SI Joint injections. Recently I was supposed to have another epidural and the doc was unable to get to the correct spot because I had some calcification in the area he was trying to get to. He tried many spots and couldn't get through but after the unsuccessful injection I was extremely dizzy, tongue was numb, slight confusion and my heart was racing. Do you think it was lidocaine toxicity?
TahoeDoc (author) from Lake Tahoe, California on November 13, 2013:
What is the source of the 9.6% spray? Where on the body is it being used?
pogana on November 03, 2013:
This article was very informative. I have a question may be someone answer can a person having normal liver enzymes used lidocaine spray 9.6 % w/w ( 7.7 mg per metered spray) 12 g occasionally ? Is it safe ?
Mmargie1966 from Gainesville, GA on July 13, 2012:
Very informative, especially since I know someone who will be getting an epidural in the next 6 months.
My Mother has lidocaine patches for arthritis in her lower back. It really is helpful for her.
Thanks for sharing, Doc! Voted up and useful!
TahoeDoc (author) from Lake Tahoe, California on July 05, 2012:
Me too Nettlemere!
Nettlemere from Burnley, Lancashire, UK on July 04, 2012:
I completely agree - if it's chemistry it needs to be very straight forward for me to have 1/2 a chance of even vaguely understanding it!
TahoeDoc (author) from Lake Tahoe, California on July 04, 2012:
Austin- Glad that patch is helping, it can be really good for that kind of pain/irritation. And nah, the body does such a good job of regulating and maintaining the sodium and potassium concentrations that would reach the site of action with flux into and out of cells, through the kidneys, etc. An alteration that would significantly affect that concentration would be physiologically dangerous.
Thanks for reading :)
@Marcy- thank you as always for your comments and insights. You are a star!
@Nettle- the video is simplistic (and NOT mine), but sometimes that is the best way to illustrate these processes at first. It gets pretty complex. Thanks for stopping by.
@Dolphan- Thank you for following along and being such a great supporter of my hubs!
Dolphan5 from Warwick R.I on July 03, 2012:
Thanks again Doc! Informative and well written.
Thumbs Up and interesting, useful.
Nettlemere from Burnley, Lancashire, UK on July 03, 2012:
very useful to know understand the difference between local and regional anesthesia. And vaguely remembering esters from poorly understood chemistry lessons I'm pleased to know they have a use!
Also thought the song was a perfect match for the schematic video.
Marcy Goodfleisch from Planet Earth on July 03, 2012:
What a valuable article! Lidocaine can seem harmless to some people because it can be used topically, but it is so important to understand there are still risks. I've heard about sone of the major side effects you mention here. Excellent information!
Lela from Somewhere near the heart of Texas on July 03, 2012:
Thanks for this information. I use the Lidoderm patch for neuropathy in my feet. It feels like I am being tasered on the bottom of my foot sometimes. I have a damaged sciatic nerve. The patch is the only thing I have tried that actually works to stop the pain.
Would lowering the Na+ help? Or increasing the K+?