Clinical Features

  • A dental series reported an adverse reaction rate as high as 2.5–10% of all patients receiving local anesthetic injections.
  • Majority of adverse reactions are not immunologic
    • Reactions are usually due to anxiety, vasovagal, psychosomatic responses, excessive dosage, inadvertent injection into a blood vessel, and idiosyncratic responses
    • IgE- mediated (type I) allergic reactions are extremely rare and have only been documented in a few case reports


Local Anesthetics

Group 1
Benzoic acid esters--------
Group 2
Amides
  • Benzocaine
  • Chloroprocaine
  • Cocaine
  • Cyclomethycaine
  • Dimethocaine/Larocaine-----
  • Piperocaine
  • Propoxycaine
  • Procaine/Novocaine
  • Proparacaine
  • Tetracaine/Amethocaine
  • Articaine
  • Bupivacaine
  • Cinchocaine/Dibucaine-----
  • Etidocaine
  • Levobupivacaine
  • Lidocaine/Lignocaine
  • Mepivacaine
  • Prilocaine
  • Ropivacaine
  • Trimecaine
  • On the basis of patch testing, group 1 benzoic acid esters cross-react with each other, but they do not cross-react with the group 2 amide drugs. It is not known what relevance this has on immediate-type reactions to local anesthetics.
  • T.R.U.E. test caine mix patch includes benzocaine, tetracaine, and dibucaine


Diagnosis

  • Appropriate workup remains controversial, patients with positive skin tests often have negative challenges (i.e., high false positive rate), and many positive challenges have subjective symptoms, therefore a challenge test is strongly considered even if skin testing is positive.
  • Practice parameter
    • Allergy testing practice parameter (2008) states that skin testing for diagnosis of local anesthetic allergy is limited by false-positive reactions and that the gold standard for establishing a diagnosis of local anesthetic allergy is the provocative challenge.
    • Drug allergy practice parameter (2010) states that to exclude the rare possibility of an IgE-mediated reaction to local anesthetics, skin testing and graded challenge can be performed in patients who present with a reaction history suggestive of possible IgE-mediated allergy to these drugs.
  • Rarely, preservative used in local anesthetic (e.g. methylparaben) may account for positive skin tests; testing and challenge with pure lidocaine should be considered in these situations
  • Testing may be done with the local anesthetic suspected of causing the reaction or with a suitable alternative anesthetic that may be used instead



Published Protocols


Mayo Clinic
  • Vital signs and peak flow obtained at the start of the protocol
  • SPT on the volar surface of the forearm with undiluted preserved local anesthetic without epinephrine
    • SPT sites were examined after 15 min; a positive test is defined as a wheal 3 x 3 mm. Patients with a negative SPT undergo intradermal (ID) testing.
  • ID skin tests on the volar surface of the forearm with 1:100 dilution of the local anesthetic, injected intradermally to produce an initial wheal of 2 x 2 mm.
    • ID sites were examined after 15 min; a positive ID test is defined as a wheal 3 mm greater than the negative control. Patients with negative ID skin testing proceeded to open subcutaneous (SC) challenge.
  • Open supervised challenge performed in the allergy clinic by initially injecting 0.1 mL of undiluted local anesthetic SC into the upper arm.
    • The injection site was examined after 15 min; a positive SC challenge is defined as a wheal 3 mm greater than negative control.
      • If the 0.1-mL challenge was negative, 0.5 mL of undiluted local anesthetic was injected SC into the upper arm at a different location and examined after 15 min.
      • If the 0.5 mL challenge was negative, 1.0 mL of undiluted local anesthetic was injected SC into the upper arm at a different location and examined after 15 min. If negative, the open challenge is negative.
  • Vital signs and peak flow once again obtained before dismissing the patient


Macy
  • Use lidocaine 1% with methylparaben
  • SPT with full strength anesthetic then ID skin test with 0.04 ml of 1:100 dilution
    • A rare individual will be allergic to methylparaben and will be skin test positive
    • If positive skin test, repeat and if still positive, challenge with pure lidocaine (without methylparaben)
  • SC challenge
    • 1 mL saline, then
    • 1 mL lidocaine 1% with methylparaben, then
    • Challenge with other specific local anesthetics if desired (very low chance of true positive)
    • Expect agitation in some individuals with epinephrine containing products


Berkun
  • SPT with undiluted local anesthetic
  • Subcutaneous challenge every 20 min with:
    • 0.1 mL 1:100th (1%)
    • 0.1 mL 1:10 (10%)
    • 0.1, 0.25, 0.5, 1.0 mL (full strength)
  • Recommend testing with preservatives


Practice Parameter (2010)
  • SPT with the undiluted anesthetic. If negative..
  • Successive injections (SC or intradermal) of 0.1 mL of 1:100 dilution, 0.1 mL of 1:10 dilution, and 0.1 mL of full-strength solution are given at 15-minute intervals. If negative...
  • 0.5-1 mL of the anesthetic SC
  • A placebo step may be added after the SPT and before challenging with the local anesthetic

Kahn

  • Protocol
    • SPT with full strength local anesthetic, if negative...
    • ID with 1:100 dilution, if negative...
    • SC injection of saline 1 mL (placebo), then...
    • SC with full strength local anesthetic
  • SC challenge protocol not intended for those rare patients with suspected severe IgE-mediated reactions. A lower starting dose (e.g., 0.1 mL, 1:100) with 10-fold dose increases would be more appropriate.


Local Anesthetic Contact Dermatitis

  • Dentists and other health care professionals may develop contact dermatitis from local anesthetics
  • T.R.U.E. test caine mix patch includes benzocaine, tetracaine, and dibucaine




References