Penicillin allergy labels are common and have a tremendous impact upon the selection of an antibiotic. Unfortunately many of these penicillin allergy labels are inappropriate. The topic is discussed here.
Authored By: Timothy Gauthier, Pharm.D., BCPS-AQ ID
Penicillin allergy is something that significantly effects the lives of both patients and caregivers. Many times patients have a penicillin allergy label for life. Because of its importance to the fields of infectious diseases and antimicrobial stewardship, I wrote a post on the topic for Pharmacy Times. The following takes that text and expands upon it, providing a fresh perspective on the subject.
One of the first steps towards learning your way around a community pharmacy is to gain an understanding of the tools used for counting and measuring various drug products. It is during these early of days in the profession that most will encounter a tool with a readily apparent purpose: a counting tray and spatula labeled “penicillin.”
As indicated by the label, penicillin (and only penicillin) is counted out with this tray and spatula, which ensures that patients with a true penicillin allergy are not exposed to penicillin via contamination of other drug products with penicillin powder. In turn, awareness and special attention is given to penicillin allergy.
It is estimated that the prevalence of penicillin allergy in the United States is between 8% and 10% [1], making it one of the most important drug allergies in health care today. Pharmacists in hospital, community, and other practice settings are encountering patients labeled with a penicillin allergy on a daily basis.
Given the importance of this allergy to our profession, here is a list of 5 things to know about patients who are labeled with a penicillin allergy.
1. Penicillin allergy should be taken seriously, but there is a fair chance it is NOT A TRUE ALLERGY.
Allergic reaction to penicillin can be significant and lead to mortality. In turn, proper precautions should be observed when caring for those labeled with a penicillin allergy.
That said, it is important to recognize that things like inaccurate medical histories and loss of antipenicillin immunoglobulin E (IgE) antibodies over time can lead to patients being inappropriately labeled with a penicillin allergy. In fact, literature suggests that only 10% of patients labeled with a penicillin allergy have a true IgE-mediated allergic reaction [2].
2. Penicillin skin testing may verify the allergy.
Type I hypersensitivity reactions (eg, immediate reactions) are mediated by penicillin-specific IgE antibodies and occur within 1 hour of exposure [3]. For patients with a vague history, penicillin skin testing can be employed to rule out IgE-mediated penicillin allergy [2].
Penicillin skin testing is typically done in 3 steps: preparation, skin prick, and intradermal test, though there is also the option to follow with an oral penicillin challenge as a fourth step. When done correctly, penicillin skin testing can have a negative predictive value of 97% or more, with a positive predictive value of 50%.
3. Penicillin allergy does not always mean beta-lactam allergy.
The odds that a patient with a penicillin allergy will also be allergic to a cephalosporin or a carbapenem remain a point of debate. However, a 2014 review of IgE-mediated penicillin allergy found that recent literature shows a rate of cross reactivity for cephalosporins at less than 3% and carbapenems at less than 1% [4].
Therefore, many patients labeled with a penicillin allergy may safely receive a cephalosporin or carbapenem.
4. Penicillin allergy can result in patients receiving less-preferred drugs.
The use of penicillins, cephalosporins, or carbapenems is not recommended as surgical prophylaxis for patients with documented or presumed IgE-mediated penicillin allergy [5]. In fact, beta-lactam allergy has such a profound impact on the selection of therapy for surgical prophylaxis that guidelines have a column of recommended agents followed by a column of alternatives (eg, non-preferred drugs) for patients with a beta-lactam allergy.
Unfortunately, the impact of removing beta-lactams as a therapeutic option extends well beyond surgical prophylaxis and can force clinicians to use therapies with less than ideal characteristics (eg, drugs only available in an intravenous formulation and drugs with more concerning side effect profiles) Combine this fact with an infection due to an antimicrobial-resistant pathogen, and a penicillin-allergic patient can be left with very few therapeutic alternatives.
5. Antimicrobial stewardship programs are interested in penicillin allergies.
As antimicrobial stewardship activities aim to improve the appropriate and safe use of antimicrobial drugs, the widespread impact that penicillin allergies have on clinical practice has become a point of interest [2,6]. In turn, antimicrobial stewardship pharmacists, allergists, infectious diseases physicians, and other stakeholders are collaborating to implement penicillin skin testing programs.
Although there is still much work to be done in this area, it is clear that more accurately labeling patients with penicillin allergy and using penicillin skin testing to de-label patients with a penicillin allergy has the potential to make an impact.
References
1. Management of persons who have a history of penicillin allergy, 2015 sexually transmitted diseases treatment guidelines. US Centers for Disease Control and Prevention. Available at: http://www.cdc.gov/std/tg2015/pen-allergy.htm. Accessed 16 November 2015.
2. Unger NR, et al. Penicillin skin testing: potential implications for antimicrobial stewardship. Pharmacother. 2013;33(8):856-67.
3. Salkind AR, et al. Is this patient allergic to penicillin? An evidence-based analysis of the likelihood of penicillin allergy. JAMA. 2001;285(19):2498-2505.
4. Terico AC, Gallagher JC. Beta-lactam hypersensitivity and cross-reactivity. J Pharm Pract. 2014;27(6):530-544.
5. Bratzler DW, et al. Clinical practice guidelines for antimicrobial prophylaxis in surgery. Am J Health-Syst Pharm. 2013;70:195-283.
6. Trubiano J, Phillips E. Antimicrobial stewardship’s new weapon? A review of antibiotic allergy and pathways to ‘de-labeling’. Curr Opin Infect Dis. 2013; 26(6).
