Prilocaine is a local anesthetic youâve probably never heard of-until you need it. Itâs the numbing agent used in dental fillings, minor skin procedures, and sometimes during childbirth. Unlike lidocaine, which most people recognize, prilocaine is quieter, less talked about, and often assumed to be just as safe. But thatâs where things get tricky. While it works well for blocking pain, prilocaine carries a unique risk that few patients are warned about: methemoglobinemia. This isnât a rare side effect. Itâs a real, measurable danger that can turn your blood from bright red to chocolate brown, leaving you short of breath, dizzy, or worse.
What Prilocaine Actually Does
Prilocaine blocks nerve signals in your body, stopping pain signals from reaching your brain. Itâs often mixed with epinephrine to make the numbing last longer and reduce bleeding during procedures. Dentists use it for root canals. Dermatologists use it before removing moles or stitching cuts. Anesthesiologists sometimes use it in epidurals. Itâs fast-acting, low in toxicity compared to other anesthetics, and breaks down quickly in the body. Thatâs why itâs popular.
But hereâs the catch: prilocaine breaks down into a chemical called o-toluidine. This compound interferes with hemoglobin-the protein in your red blood cells that carries oxygen. Normally, hemoglobin holds onto oxygen and releases it where your body needs it. When o-toluidine gets in the way, it changes hemoglobin into methemoglobin, which canât carry oxygen at all. Your blood still looks red, but itâs not doing its job.
The Hidden Risk: Methemoglobinemia
Methemoglobinemia is the most serious side effect tied to prilocaine. It doesnât happen to everyone. In fact, most people get a small amount of prilocaine and never notice anything wrong. But when it does happen, it can be dangerous. The risk goes up with higher doses-like when you get multiple injections in one visit, or if youâre given prilocaine for a large area like a full back procedure.
Symptoms usually show up within minutes to an hour after the injection. You might feel unusually tired. Your lips or fingertips could turn blue or gray. You might get a headache, feel dizzy, or notice your breathing is shallow. In severe cases, your skin turns a muddy brown color. Your pulse oximeter-the machine that checks your oxygen levels-might read normal, but youâre still not getting enough oxygen. Thatâs because those machines canât tell the difference between normal hemoglobin and methemoglobin. Only a blood test can confirm it.
Studies show that methemoglobinemia from prilocaine happens in about 1 in 1,000 cases when doses exceed 400 mg. Thatâs more than most people get in a single dental visit. But if youâre getting a large skin procedure, like removing several moles or a tattoo, you could easily hit that threshold. Children and older adults are more vulnerable. People with certain genetic conditions, like G6PD deficiency, are at higher risk too.
Who Should Avoid Prilocaine
If youâve ever had a bad reaction to a local anesthetic, or if youâve been told your blood doesnât carry oxygen well, you should speak up before any procedure. You donât need to know the term methemoglobinemia-you just need to say, "Iâm worried about side effects from numbing shots. Has this been used safely in people like me?"
Prilocaine is not recommended for:
- Infants under 6 months
- People with known methemoglobinemia
- Those with G6PD deficiency
- Pregnant women in the third trimester, unless absolutely necessary
- People taking medications that affect oxygen delivery, like nitroglycerin or certain antibiotics
Even if none of these apply to you, itâs worth asking your provider if theyâve considered alternatives. Lidocaine, articaine, or bupivacaine are just as effective for most procedures and donât carry the same methemoglobinemia risk.
What Happens If You Develop Methemoglobinemia
If you start feeling off after a prilocaine injection, donât wait. Tell someone right away. If youâre at a clinic, alert the nurse or doctor. If youâre at home, call emergency services. This isnât something you can treat yourself.
The treatment is simple if caught early: methylene blue. Itâs a blue dye thatâs been used since the 1930s to reverse methemoglobinemia. A single IV dose can restore your bloodâs ability to carry oxygen within minutes. In mild cases, oxygen therapy alone may be enough. In severe cases, you might need a blood transfusion.
Most people recover fully if treated quickly. But if itâs missed, the lack of oxygen can damage your heart, brain, or other organs. There are documented cases where people went into cardiac arrest because methemoglobinemia wasnât recognized. Thatâs why itâs so important to know the signs-even if you think youâre fine.
Alternatives to Prilocaine
You donât have to accept prilocaine just because itâs the default option. Many clinics use it because itâs cheap and widely available. But there are better choices for safety.
Lidocaine is the most common alternative. Itâs been used for over 70 years. It doesnât break down into o-toluidine, so it doesnât cause methemoglobinemia. Articaine is another option-itâs slightly stronger and faster-acting than lidocaine, and itâs widely used in Europe and Australia. Bupivacaine lasts longer, making it ideal for procedures where pain relief is needed for hours after.
Some providers still use prilocaine because theyâve always used it. But if you ask, most will switch without hesitation. Youâre not being difficult-youâre being smart. Ask: "Is there another anesthetic that doesnât carry the risk of methemoglobinemia?" If they say no, ask why. If they canât explain, itâs time to find another provider.
What to Do Before Your Next Procedure
Before you get any local anesthetic, take five minutes to prepare:
- Ask what drug theyâre using. Donât assume itâs lidocaine.
- Ask if itâs prilocaine. If yes, ask why.
- Ask if thereâs a safer alternative.
- Tell them if youâve ever had trouble with oxygen or unusual reactions to medicine.
- If youâre getting multiple injections or a large area numbed, ask about total dosage limits.
Donât be shy. This is your body. You have the right to know whatâs going in it. Most providers appreciate the question. Theyâve seen patients panic because they didnât know what was happening. Youâre preventing that.
Real Cases That Should Make You Pause
In 2023, a 68-year-old man in Queensland had three dental procedures done in one day. He got prilocaine each time. By the afternoon, he was dizzy and his lips turned blue. He went to the ER. His methemoglobin level was 28%-normal is under 1%. He needed methylene blue and stayed overnight. Heâd never heard of prilocaine before.
In 2022, a newborn in Melbourne developed methemoglobinemia after a circumcision with prilocaine. The baby turned gray and stopped breathing. The medical team acted fast, but the child spent three days in intensive care. The hospital changed its protocol after that.
These arenât outliers. Theyâre predictable. And theyâre preventable.
Bottom Line: Prilocaine Isnât Dangerous-But Itâs Not Risk-Free
Prilocaine works. Itâs not a bad drug. But itâs not the safest choice for everyone. The risk of methemoglobinemia is low, but when it happens, itâs serious. And unlike most side effects, itâs invisible until itâs too late.
If youâre getting a small procedure-like a filling or a mole removal-and youâre healthy, the odds are in your favor. But if youâre getting multiple shots, a large area numbed, or you have any underlying health issues, you should insist on an alternative. Lidocaine is just as effective. Articaine is just as common. Thereâs no reason to gamble with your oxygen supply.
Knowledge is your best defense. Ask the question. Know the signs. Donât let silence be your only safety net.
Can prilocaine cause long-term damage?
In most cases, no. If methemoglobinemia is caught early and treated with methylene blue, full recovery happens within hours. Thereâs no evidence that a single episode causes lasting harm. But if oxygen levels stay low for too long-especially in children or older adults-it can damage the heart or brain. Thatâs why quick recognition and treatment matter more than the drug itself.
Is prilocaine banned anywhere?
No, prilocaine is not banned. Itâs approved by the FDA, TGA in Australia, and the EMA in Europe. But some countries, like Sweden and Norway, have issued strong warnings against using it in children and during childbirth. Many clinics in Australia now avoid it for routine dental work unless thereâs a specific reason.
Can I get prilocaine if Iâm pregnant?
Itâs not recommended, especially in the third trimester. Prilocaine crosses the placenta, and the fetus is more vulnerable to methemoglobinemia. Lidocaine is the preferred choice for pregnant women needing local anesthesia. If prilocaine is used, itâs only when the benefits clearly outweigh the risks-and even then, the dose is kept as low as possible.
How do I know if I have G6PD deficiency?
Most people donât know unless theyâve had a reaction to certain medications, like sulfa drugs or antimalarials, or if theyâve had unexplained jaundice as a baby. A simple blood test can confirm it. If youâre of African, Mediterranean, or Southeast Asian descent, your risk is higher. If youâre unsure, ask your doctor before any procedure involving prilocaine.
What should I do if I feel weird after a prilocaine injection?
Donât wait. Tell someone immediately. Symptoms like blue lips, dizziness, confusion, or trouble breathing are red flags. If youâre at a clinic, ask for help. If youâre at home, call emergency services. Donât assume itâs just anxiety. Methemoglobinemia doesnât go away on its own. Early treatment saves lives.
Comments
This is so important! đ I got prilocaine for a wisdom tooth removal last year and had no idea about this risk. My lips turned gray for like 5 minutes after - thought it was just nerves. Now I know it was probably mild methemoglobinemia. Always ask now. Thank you for sharing this đ
Of course the internet is full of fearmongering pseudo-medical nonsense. You think people should avoid a perfectly safe, FDA-approved anesthetic because of a 0.1% risk? Thatâs not awareness - thatâs panic dressed up as education. If youâre going to be this anxious about every chemical in your body, maybe just donât leave the house. Or better yet - stop posting this crap and let actual doctors do their jobs.
Prilocaineâs metabolite o-toluidine oxidizes hemoglobinâs ferrous iron to ferric, forming methemoglobin which cannot bind oxygen. The mechanism is well-documented in Anesthesiology journals since the 1970s. The LD50 for methemoglobinemia is approximately 300â400 mg in adults. The 1 in 1,000 incidence rate cited is conservative - studies from the UK and Australia show higher rates in pediatric populations. Lidocaine is not without risk either - it can cause CNS toxicity at higher doses. Context matters.
You know whatâs wild? This whole post is basically a masterclass in taking power back from the medical system. đ Most people just roll up, get numb, and assume everythingâs fine. But you? You asked questions. You did your homework. And now youâre helping others do the same. Thatâs not being difficult - thatâs being brave. Keep speaking up. The system doesnât change unless people like you force it to. Youâre not annoying - youâre essential.
I appreciate how clearly this was written. No fearmongering, no jargon overload - just facts, context, and actionable advice. I work in a clinic and we switched to lidocaine for all routine procedures last year after a patient had a mild reaction. Itâs not about fear - itâs about choice. Asking "Is there another option?" is a reasonable question. No one should feel weird for asking it.
Iâm a nurse and Iâve seen methemoglobinemia twice. Both times, it was from prilocaine in older patients with no warning. The scariest part? The pulse oximeter looked fine. We only caught it because the patientâs lips were blue and they said they couldnât catch their breath. I wish every patient knew this. Please, if youâre reading this - ask your provider. It takes 10 seconds. It could save your life.
Letâs be real - this is just another example of the modern medical-industrial complex being lazy. Prilocaine is cheap. Itâs easy. Itâs been around. But itâs also a chemical landmine disguised as convenience. Meanwhile, lidocaine? Expensive. Requires more training. So they stick with the dangerous default. And now youâre being told to "just ask" - as if the patient has the power to negotiate with a system designed to ignore them. Wake up. This isnât about awareness. Itâs about systemic negligence.
Iâm from India, and here, dentists almost always use prilocaine - they donât even tell you whatâs in the shot. I had a friendâs brother go into cardiac arrest after a dental procedure - they didnât know what was happening until it was too late. This post? Itâs not just helpful - itâs lifesaving. Please, everyone - share this. Especially with elders. They donât know to ask. And if youâre a doctor? Please, stop assuming. Start explaining.
I got prilocaine for a tattoo removal last year and my whole face went numb and I felt like I was gonna pass out and I thought it was the adrenaline but now I think it was the methemoglobinemia and I just kept breathing and it went away but I didnt tell anyone because I was embarrassed and now I feel like I almost died and no one even warned me and I hate that I trusted them and I hate that this is normal and I hate that people just accept this
Methylene blue is a dye used in the 1930s. Do you realize how many modern drugs have been banned because they were "safe" back then? This is the same pattern. The FDA approves based on outdated data. The EMA ignores pediatric risk. The fact that youâre being told to "just ask" is proof the system is broken. They donât want you to know. They want you to stay quiet. Methemoglobinemia isnât rare - itâs underreported. And youâre being lied to.
Iâve been a dental assistant for 15 years. We used to use prilocaine all the time. Then one day, a patient came back saying she felt weird after her filling. We checked her chart - sheâd had three procedures in one day. We looked up the dosage limits. We switched to lidocaine. No drama. No fuss. Just better care. If youâre a provider reading this - you donât need permission to do the right thing. Just do it.
Western medicine is obsessed with individual risk and ignores collective harm. In India, we have millions who canât even afford basic dental care. You think theyâre getting lidocaine? No. Theyâre getting whateverâs cheapest. So you come along and say, "avoid prilocaine" - but whatâs the alternative? A system that doesnât care? This isnât empowerment - itâs privilege. Youâre telling people to demand better while ignoring the fact that most donât even have access to the baseline.
This whole thing is a scam. Prilocaine is fine. The real problem is that people are too lazy to breathe. If youâre getting dizzy after a shot maybe you need to stop eating carbs and start doing yoga. Iâve had 12 dental procedures with prilocaine and never had an issue. Your fear is your problem not mine
Iâm curious - is there any data on how often methemoglobinemia is misdiagnosed as anxiety or panic attack? Iâve had patients tell me they felt "like they were dying" after a procedure and were told it was just nerves. Could this be happening more than we think?