Thank you for your inquiry.
Certainly, there would be no contraindication to premedicating the patient you described with dexamethasone and diphenhydramine. In many instances, if not in the vast majority of instances, reactions to local anesthetics are somatoform in nature, and anything one can do to reassure the patient beforehand that they can take the local anesthetic in question would be of help.
I am not sure there is any physiologic rationale for pretreatment as you described, but there may well be a psychological reason if it enhances the patient’s confidence in the fact that she could tolerate this drug.
However, I do have another suggestion. I would proceed with this patient using the standard incremental challenge regimen (see abstracts copied below). Since these reactions, as noted above, are not, in the vast majority of instances, IgE-mediated, the skin test portion of the incremental challenge procedure could be skipped. Thus, the fact that she is on cetirizine would be of no importance. Or, you could simply test her to histamine. If the histamine test was positive, you could proceed with the skin test portion as well. However, in most instances the skin tests are done as a reassurance to the patient that they are not allergic, and then the incremental challenge is done to confirm this opinion. So, the skin test, when negative, enhances the reassurance.
In summary, certainly a pretreatment regimen could be used, but I would also suggest the incremental dosage regimen mentioned above and discussed in the abstracts copied below.
Thank you again for your inquiry and we hope this response is helpful to you.
J Allergy Clin Immunol. 1984 Oct;74(4 Pt 2):606-16.
Skin testing and incremental challenge in the evaluation of adverse reactions to local anesthetics.
True allergic reactions to local anesthetics (LAs) probably make up no more than 1% of all adverse LA reactions. A diagnosis of true potential allergic reactivity is made difficult because (1) the history of the prior reaction may be vague or equivocal and (2) the lack of identification of the actual specific LA hapten-carrier complex limits the potential usefulness of immunologic tests. Nonetheless, since avoidance of LAs may be associated with substantial increased pain or increased risk and because true allergic reactions are rare, investigators and clinicians have used skin testing, incremental challenge, or both as a means of identifying a safe LA for a patient with a history of a prior adverse reaction. Review of the literature dealing with LA skin testing and incremental challenge suggests the following: (1) Skin testing with LAs may correlate with a history of an adverse reaction but may produce systemic adverse reactions, especially with undiluted drug. (2) Although false positive skin tests have been reported, most skin-tested patients who subsequently tolerate an LA have a negative skin test to that drug, and false negative skin tests have not been clearly documented. (3) Incremental challenge beginning with diluted LA is a safe and effective means of identifying a drug that a patient with a history of a prior adverse reaction can tolerate. (4) Current concepts of non-cross-reacting LA groups may be useful in the choice of a drug for use in skin testing and incremental challenge. (5) Preservatives in LAs may account for some but probably not the majority of adverse reactions to LAs. On the basis of this literature review, a practical protocol including dilutional skin testing and incremental challenge is presented for use in evaluating patients with prior adverse reactions to LAs.
Ann Allergy Asthma Immunol. 2003 Oct;91(4):342-5.
Evaluation of adverse reactions to local anesthetics: experience with 236 patients.
Berkun Y, Ben-Zvi A, Levy Y, Galili D, Shalit M.
Department of Pediatrics, Bikur Cholim Hospital, Jerusalem, Israel.
Background: Adverse reactions to local anesthetics (LAs) are frequently reported. Although most of these reactions are not immune mediated, many patients are referred to allergy clinics and undergo extensive evaluation.
Objective: To determine the prevalence of true LA allergy among the patients referred for suspected hypersensitivity and to evaluate the usefulness of the currently used evaluation protocol.
Methods: A total of 236 patients referred to our allergy clinic for investigation of LA hypersensitivity were included in this study. The evaluation protocol was composed of skin prick and intradermal tests, followed by subcutaneous challenge with unrelated LA preparations that contained preservatives.
Results: Skin prick and intradermal test results were negative for all subjects. No objective adverse reactions were observed during the challenge in all but 1 patient, who developed local erythema at the site of injection and later underwent an uneventful challenge with a different LA.
Phil Lieberman, M.D.