This has nothing to do with pharmacy technology, but I thought it would be worth posting. Questions about cross reactivity of one local anesthetic to another don’t come along often, but when they do it’s never easy to formulate a quick answer. Lucky for me I’m an electronic pack-rat and saved a small drug information consult I did a few years ago regarding the issue. Remember, this is for entertainment purposes only. ;-)
Local anesthetics are grouped into either the “ester” group – cocaine, procaine, cholroprocaine, tetracaine - or the “amide” group – lidocaine, bupivacaine, etidocaine, mepivacaine, ropivacaine. Fortunately, true allergic reactions to local anesthetics are rare, but possible. There does not appear to be cross-allergenicity with amide local anesthetics – meaning that someone may be allergic to lidocaine and mepivacaine, but not to bupivacaine, for example. Lots of times multi-dose vials of amides (e.g. lidocaine, bupivacaine) may contain the preservative methylparaben, causing allergic reactions. The other source of antigens is metabisulfite which is present in epinephrine containing local anesthetic solutions. Cross-sensitive reactions are possible because many other drugs, foods and beverages contain preservatives such as metabisulfites and hydroxybenzoates.
Fisher et al(1) conducted a study to determine the incidence of true local anesthetic allergy in patients with an alleged history of local anesthetic allergy and whether subsequent exposure to local anesthetics was safe. Two hundred and eight patients with a history of allergy to local anesthetics were referred over a twenty-year period to their Anesthetic Allergy Clinic at the Royal North Shore Hospital, Sydney, Australia. In this open study, intradermal testing was performed in three patients and progressive challenge in 202 patients. Four patients had immediate allergy and four patients delayed allergic reactions. One hundred and ninety-seven patients were not allergic to local anesthetics. In 39 patients an adverse response to additives in local anesthetic solutions could not be excluded. In all but one patient local anesthesia had been given without event subsequently. They contend, “a history of allergy to local anesthesia is unlikely to be genuine and local anesthetic allergy is rare. In most instances it can be excluded from the history and the safety of local anesthetic verified by progressive challenge.”
Following a Medline search of articles published (over the period 1985-1996) on allergy to local anesthetics, Egglestone et al(2) suggested the following recommendations concerning the appropriate use of local anesthetics and alternative therapies in patients with documented local anesthetic reactions. “A true immunologic reaction to a local anesthetic is rare. Patients who are allergic to ester local anesthetics should be treated with a preservative-free amide local anesthetic. If the patient is not allergic to ester local anesthetics, these agents may be used in amide-sensitive patients. In the rare instance that hypersensitivity to both ester and amide local anesthetic occurs, or if skin testing cannot be performed, then alternative therapies including diphenhydramine, opiods, general analgesia, or hypnosis can be used.”
References:
1. Alleged Allergy to Local Anaesthetics Fisher MM, Bowie CJ Anaesth Intensive
care 1997 Dec;25(6):611-4
2. Understanding Allergic reactions to Local Anaesthetics Eggleston ST, Lush LW
Ann Pharmacotherapy 1996 Jul-Aug;30(7-8)851-7
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