__________________________________________________ DCA02AR Allergic Reactions in Dental Patients
ANTIBIOTICS The oral microflora consists of hundreds of microbial spe- cies, only a few of which cause dental caries and periodontal disease. Antibiotics used in dental treatment are generally chosen in order to treat and/or prevent odontogenic or sys- temic infection. Beta-Lactam Antibiotics Beta-lactam antibiotics are the most frequently used group in dentistry, as they display bactericidal activity against many of the pathogenic bacteria that cause odontogenic infections. The most commonly prescribed in dental practice include penicillin, amoxicillin, and ampicillin. However, generations of bacterial mutations have enabled bacteria to produce the enzyme beta-lactamase, which destroys the structural integrity of these antibiotics and renders them ineffective against some odontogenic infections. Approximately 10% of the U.S. population has a reported allergy to penicillin, but only about 1% of the population has a true IgE-mediated allergic reaction [23; 51]. While most allergic reactions to penicillin and its derivatives result in skin rashes or urticarial lesions, medications in this group are among the most frequent causes of medication-induced anaphylaxis [24]. Type I reactions can progress to anaphylaxis in 0.04% to 0.2% of cases, with a 10% fatality rate [1]. Fortunately, most allergic reactions to penicillin are less severe but can still cause varying degrees of discomfort or morbidity. Cross-reactivity among the beta-lactam antibiotics and the structurally similar cephalosporins (e.g., cephalexin) is a valid concern. The chemical structure of amoxicillin is very similar to penicillin, and patients who have IgE-mediated type I hyper- sensitivity reactions to penicillin have a markedly increased risk of a reaction to amoxicillin as well as cephalosporins and sul- fonamides. There is a 20% chance of a reaction to cephalexin when a patient has had an allergic reaction to penicillin [25]. Clindamycin The two antibiotics most likely to be prescribed when beta- lactams cannot be used are clindamycin and azithromycin. Clindamycin is derived from lincomycin, and its chemical structure varies from that of the beta-lactam antibiotics. At lower doses, it is a bacteriostatic medication that inhibits bacterial protein synthesis; at higher doses, it is bactericidal. It has excellent absorption from the stomach and is capable of penetrating infected tissues and bone. It has a minimum of adverse drug interactions, and type I and type IV hyper- sensitivity reactions are rare but possible [26]. There is no cross-reactivity between clindamycin and any other class of antibiotics [25].
he or she has had an allergic reaction to a local anesthetic, one should have a thorough discussion to determine if it was an adverse, but non-allergic, reaction or if an actual immediate (type I) or delayed-response (type IV) allergic reaction devel- oped. A release of information should be obtained if input from a prior clinician is required to determine the nature of the reaction. If a patient reports a history of adverse or allergic reactions to a local anesthetic, dental treatment should be delayed until the origin of the problem has been identified and addressed. If necessary, consultation with a specialist in allergy and immunology should be sought. Additives Epinephrine is often added to local anesthetics to enhance the clinical dynamics. An allergy strictly to epinephrine does not exist. However, some patients may consider adverse transient reactions to be evidence of an “allergy” to epinephrine. If a patient’s medical history lists an allergy to epinephrine, the clinician should discuss the nature and magnitude of the reac- tion with the patient. The oxidation of epinephrine in local anesthetic solutions diminishes the potency and utility of this vasoconstrictor and will ultimately render it useless. So, preservatives such as sodium metabisulfite or potassium metabisulfite are added to prolong the lifespan of epinephrine by suppressing the oxida- tion process. Patients with allergies to sulfites may exhibit an allergic reaction to these sulfite-based preservatives. Among the general population, patients with asthma are at a greater risk for hypersensitivity to bisulfites, with the potential for a true allergic reaction if a local anesthetic with a vasoconstric- tor is used [22]. Most patients are unaware that bisulfites are used as preservatives in local anesthetics and may not disclose a sulfite allergy in their medical history. As such, clinicians should inquire about allergies beyond obvious medications and materials used in dentistry, including sulfites, latex, and metals. Local anesthetics such as mepivacaine and prilocaine are avail- able in formulations that do not contain epinephrine, and these should be used for patients with sulfite allergy (provided no other allergy or contraindication exists). Without the vaso- constrictive qualities of epinephrine, the duration of anesthesia will be decreased, so clinicians should develop treatment plans that accommodate a shorter working time. The ability to obtain hemostasis during and after procedures such as oral surgery, periodontal surgery, and root planing and curettage will be more challenging in this shorter period. Clinicians should have adjunctive materials that promote hemostasis (e.g., oxidized cellulose) available. Longer procedures, such as full-mouth extractions or multiple quadrants of periodontal surgery or root planing and curettage, may need to be apportioned into smaller segments.
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