The Needle: Genetic Resistance to Dental Anesthetics

I had to go to the dentist today, for the first time in 5 years. I always dread doing that since, for some reason, any of the regular anesthetics they use to numb the gums and teeth don't work on me. Anything thats part of the "caine" groups of numbing chemicals (lidocaine, novocaine, etc), well I can't even tell a difference. all my life, I thought it was just normal for those not to work well, and just grin and bore horrible pain to get my teeth cleaned and cavities filled. Hence, why I haven't gone in 5 years.

When I told my doctor about my troubles "getting numb" she said something surprising: There's probably a genetic component. Eureka, of course! She said that blonde haired, blue eyed, fair skinned people of Irish or Scandinavian descent have a much higher likelihood of having resistance to the "caine" family of anesthetics. I was like, check, check, check and check!

Has anyone else ever had this problem, or know what this dentist is talking about?

I really would love to know more about this gene and whether I possess some kind of receptor mutation, etc.

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I have personally had experience, not only with my teeth, but several other parts of my body, where an injected anesthetic was given and the response was either nonexistant or came on 20-30 minutes later. My 8 year old daughter went to the oral surgeon yesterday to have her 4 canines removed and she had laughing gas first, then a million injections, screamed through all of them(she had been given a topical first!) and when the surgeon pulled the first was as though someone had hit her with a bat or something. She screamed and cried and told him it hurt really bad. I don't think he believed her, but I knew the injections hadn't worked and I asked him to stop. We are rescheduled to go to the hospital so she can be sedated instead. I am online today, looking for answers to this problem, which seems to be inherited. Thank you for letting me know we are not alone...

Some people do need more anesthetic than others. There are several reasons for this, one is bone dentisty, the other is accessory nerves going into the tooth.

Irish/Russian/Scandanavian and Xcaine resistant: my husband; his brother and father. Not just dental. Large amounts don't make any difference. He did find some relief when lidocaine was mixed with epinephrine, but that also increase risks.

Now, I wonder about our son...thankfully he hasn't needed an xcaine yet. :-)

I just googled this topic after getting back from the dentist. It took a LOT of shots, and two hours to get my face numb enough for a procedure they were doing. They said "We gave you a block, you will be numb on this entire side of your face for hours." I waited...My lip and chin got numb eventually after several large injections. I flashed back, as I lay on my back, to my vasectomy procedure where the pain was so bad my heart litterally stopped (they made me wear a harness for 24 hours).

I related this, and many other tales (the time I had to get stitches in the nail-bed springs to mind) and my dentist suggested I might be resistant to lidocaine.

Whatever she gave me next, it did the job, but I had a great knot of the fluid at the injection site and was told I had to massage it into the nerve.

Blonde, blue eyed, Norwegian / Scottish ancestry.

I've also had a nerve conduction study that was unusual in that the signals of my nerves are super-clean. The doctor at the time gasped, looking at something like a spectroscope with a clean sine pattern on it. "You have beautiful nerves. Just stunning."

I wonder if these cleanly ocnducting nerves are part of the problems...Anyone else find it makes breathing harder?

My daughter, niece, and now it appears my great niece, are all blond haired fair skinned (and 2 have blue eyes) and have the same issues. My daughter has been diagnosed as a non codeine metaboliser which is a huge issue if the anaesthetist isn't aware of it during an operation. We need to find out more about this, has anyone got any new information/links to help me with this research?

By Lyn Clyne (not verified) on 05 Aug 2011 #permalink

Have had this problem with Novocain for years ...old dentist would usually give me 3 shots & wait about 30 minutes for them to work......went to new dentist last fall for root canal on back molar..nightmare....though he tried the same technique as my old dentist after failing with his usual routine, never did get numb, suffered through 3 visits then went back to old dentist to finish up.
Then TODAY, had an epidural steroid injection in my lower back, they used Lidocaine, did not get numb, felt every injection in back & down leg, agony, afterwards my RN husband commented that he doesn't think doctors give the anesthesia enough time to work......ding ding ding (bell goes off in my head).
Now I read these posts, didn't realize there might be a connection....
I am not blonde hair or blue eyed, but am 1/4 Norwegian

I have the same problem. My tongue goes numb as soon as they give me the first shot but my gums, especially in the back, take shot after shot after shot and even then they never go totally numb. My dad has the same problem. We are dark complected germans though.

the question really is... can't they give you something else?!?!?! that's horrible. When I go numb [I guess I meet the genetic criteria above -glad I didn't get the gene (or lack thereof)] I go numb for a long long time - imagine me drooling all over the place for hours. ;)


Good grief, my mother has this EXACT same problem. She's also blond, pale, and Scandinavian (hazel eyes though)!

She will be thrilled to hear it's not just her. I'm her only child and my father was a dark French-Canadian, so I escaped. Novocaine works on me like a charm. Luckily, my mom's dentist found an anaesthetic that does work on her, but I don't know what it is.

I too am blonde/blue with Xcaine resistance. The only thing I found that truly worked was using nitrous oxide. That made going to the dentist much less awful.

By Liz Tracey (not verified) on 10 Jul 2006 #permalink

Yep, it looks like its going to be nitrous for me every time. Even when getting my teeth scraped/cleaned or a cavity.

Sounds like this is a lot less rare than i first imagined. I wonder if there is a whole slew of beautiful blonde people with awful teeth. :)

Wow, thanks for throwing this cagigger at us. I have a bunch of beautiful blond friends with bad teeth who will hear from me very soon. :D

Ginger person here - I've some resistance to injected local anaesthetics, both in my mouth and elsewhere, so I need quite a bit more than the standard dose. I inherit from my dad odd nerve placing at the back of my mouth. That's something to consider if the anaesthetics only seem not to 'take' in your molars - it might be that they're injecting the wrong part of the gum for you.

The drugs don't really numb anything, molars or otherwise, for me. I get a slight tingling in my tongue that lasts about 10 minutes, but thats it.

Coffee: Now that particular "caine" does seem to work for me, not sure why. No worries, it was *not* illicit---I was in a car accident and received a little cocaine injected locally to a cut on my head, worked like a charm. :)

why would cocaine work (for the head wound) and not other -caines? anyone? they all have similar mechanism of action...

Shelley, did thy try other -caine local anesthetics at the hospital first, or did they just go full on with the liquid coke?

I have no idea why that worked as opposed to the others. They did try 2 other ones (i dunno which ones, I just remember two other shots). It still hurt. The third shot was prefaced by the doc saying "Ok, now this BETTER work...." And did it ever.

My dentist once told me redheads with russian background aren't able to open their mouths as wide as others and thats why they always have to pull on my mouth to get it open enough to do their work.

it confused me through the rest of my visit, and when I implored of him further he told me he was just kidding and that its completely random.

so I have a feeling your dentist was pulling your leg using some prior knowledge of your background.

of course, try google!

I think I may have found the answer:
Specific nerve fibres (C-fibres) in the mouth have "TTX (tetrodotoxin) resistant" ion channels, that actually prevent the local anesthetic from reaching inside the neuron. Some people express more of these resistant channels than others, resulting in less or no effective anesthesia from a variey of "caines." Apparently this isn't the case for all caines, as benzocaine has less of an effect that lidocaine. So I guess permutations in structure matter. I found this on a dental FAQ board, but there does seem to be a paper on the topic. (…)

I have this problem as well, an it isn't just my mouth - I've had surgery on other parts of my body as well, and consistently the doctors start to look visibly nervous about the amount of anaesthetic they give me. One doctor said I had the strongest lidocaine resistance he'd seen in 30 years as a surgeon. It seems like simply giving more eventually works, although the amount necessary is unreal.

Dunno if I'm scandinavian - my mom has blond hair and blue eyes, but my dad has dark hair and dark eyes as do I. Jewish immigrant families tend to have family trees which only go back two or three generations.

By Bram Cohen (not verified) on 11 Jul 2006 #permalink

I actually was at the dentist yesterday (he treats most of my family) and claimed that our resistance (Irish descent, very fair) was due to a high bone density. Might explain our apparent inability to get broken bones...
That said, it took three shots to get started and another three given at regular intervals for a one hour surgery. Very frustrating, but I've learned not to be a hero. I let them know when it's worn off right quick. Had a root canal once...

A friend of mine has Ehlers-Danlos Syndrome, a genetic disease that causes faulty collagen. Among many other problems, novocaine does not work well for her. The dentist must wait longer and use more. She is British, mainly Scottish ancestry, by the way.

For more info, see

By Jeff Lanam (not verified) on 27 Jul 2006 #permalink

*shiver* dentists... ugh I had all but 3 baby teeth pulled. And then the braces. Oh, and a million cavities. I swear I brush regularly and correctly! It must be genetic!

On a side note: I'll say hi to all the cute scandinavian girls for ya when I'm in Iceland next week. >:)

It typically takes 6 to 7 shots of local anesthetic before I'm sufficiently numb to have dental work done. I usually don't mind this, but it takes up a lot of my dentist's time.

I'm definitely not blonde, nor am I of Irish or Scandinavian descent. My grandparents arrived on four separate boats from Sicily, Naples, and two different parts of Poland.