Why are you allergic to topical anesthetics?

Article written by Pharmacist Nguyen Van Thang - Faculty of Pharmacy - Vinmec Times City International Hospital

Anesthesia is the name of a group of drugs that temporarily desensitize an area of ​​the body, thereby reducing pain caused by stimuli or minor skin or surgical procedures. mucosa. Local anesthetics can be given as an injection, topical, or spray. Topical formulations are often used to relieve the burning sensation of sunburn, burns, insect stings, pain during injections, or certain other skin procedures. Like all drugs, the use of local anesthetics can cause unwanted effects, including allergies.

In general, the manifestations of an allergy to local anesthetics are similar to allergies to other drugs, with varying degrees of severity, ranging from itchy rashes to difficulty breathing, low blood pressure... Allergic reactions can be It begins with urticaria with raised papules on the skin with a feeling of heat, itching, fast can be from 5 to 10 minutes, slow is a few days. May be accompanied by difficulty breathing, swollen lips, eyes, abdominal pain, headache, fatigue, heart palpitations, low blood pressure...
However, according to the world's medical literature, allergy to anesthetics is extremely rare. Specifically, according to a study in Denmark, when examining cases of suspected allergy due to anesthetics for 10 years (from 2004 to 2013), there were no cases of true allergy. In another study in France, only 6 out of 1816 patients, or less than 1% of patients with allergic reactions around surgery, were allergic to local anesthetics. Therefore, in fact, anesthetic allergy is extremely rare, many cases of suspected anesthetic allergy are actually anesthetic poisoning.

Anesthesia poisoning can occur soon, right after taking the drug (especially with the injection route) but there are also cases more than 60 minutes after taking the drug. The extent and rate of manifestation may vary, depending on the drug used, route of administration and mode of administration. With the topical form, the risk of poisoning is lower than with the injectable form and is almost non-existent if used correctly. Factors that increase the risk of anesthetic toxicity include: low weight, cardiovascular disease, impaired liver and kidney function, the elderly and young children, repeated use too many times or doses that are too high for comparison. with recommendations.
Manifestations of anesthetic poisoning may include: dizziness, dizziness, double vision, metallic taste in the mouth (bitter, acrid), tachycardia, increased blood pressure, more severe can cause muscle convulsions, generalized rigidity, arrhythmia, coma, cardiac arrest and respiratory arrest.

It is often difficult to distinguish a local anesthetic allergy from local anesthetic toxicity. To definitively confirm an allergy to local anesthetics, an examination and confirmation by tests by an allergist-clinical immunologist is required.

To reduce the risk of anesthetic poisoning, you need to:
Buy drugs from trusted, quality-assured establishments. Use exactly as directed by your doctor and pharmacist, if you are not sure about the dose or number of times a day, ask your doctor or pharmacist. Do not take the medicine more often than recommended. Do not use the medicine on open wounds or freshly shaved skin, unless advised by your doctor or pharmacist. In case of drug use for children, it is necessary to supervise the child after taking the drug, to keep the medicine out of the reach of children. Stop taking the medicine and see your doctor if you see no improvement after a week, the site becomes infected, a rash develops, or it starts to feel hot or sore. If you have unusual symptoms such as decreased vision, dizziness, feeling too hot, too cold or numb, headache, sweating, ringing in your ears, unusually fast or slow heartbeat, trouble breathing, If you feel sluggish, see your doctor or call 911 right away.

Vinmec International General Hospital is one of the hospitals that not only ensures professional quality with a team of leading medical doctors, modern equipment and technology, but also stands out for its examination and consultation services. comprehensive and professional medical consultation and treatment; civilized, polite, safe and sterile medical examination and treatment space.

References: Update