UMEM Educational Pearls

Category: Toxicology

Title: My patient really has all these drug allergies?

Keywords: Drug Allergy, ADR, ADE (PubMed Search)

Posted: 12/1/2016 by Kathy Prybys, DO (Emailed: 12/2/2016) (Updated: 12/2/2016)
Click here to contact Kathy Prybys, DO


Misclassification of adverse drug effects as allergy is commonly encountered in clinical practice and can lead to use of suboptimal alternate medications which are often less effective.

  • Nomenclature surrounding drug safety needs to be clear and unambiguous to avoid confusion. 
  • Adverse Drug Effect (ADE) = All drug induced disease. Majority are predictable based on drug's known pharmacology. Include harm related to medication errors and drug/food interactions. 
  • Adverse Drug Reaction (ADR) = Noxious or unintended reaction to a drug that is administered at therapeutic doses during normal use. Divided into predictable (majority 75-80%), related to pharmacologic actions of the drug in otherwise normal individuals) and unpredictable reactions (related to individual’s immunological response). 
  • "Drug allergies"  are relatively uncommon with cited incidence of 10%. Immunologically mediated reactions (type I to IV) to a pharmaceutical and/or formulation (excipient) in a sensitized person. They are dose independent and unrelated to pharmacological action of the drug. Most commonly, IgE-mediated type I (immediate) reactions caused by rapid release of vasoactive mediators from mast cells and peripheral basophils causing generalized reaction including urticaria, angioedema, stridor, wheezing, and cardiovascular collapse.
  • The skin is the most frequently and notably affected by drug induced allergic reactions.
  • Antibiotics, particuarly Beta-Lactams, are the most important cause of immediate hypersensitivity reactions. Approximately 10% of patients report a history of penicillin allergy, however after complete evaluation, up to 90% of these individuals are able to tolerate penicillin and are designated as having “penicillin allergy” unnecessarily.
  •  Pseudoallergy can occur with opioids due to histamine release. Codeine and morphine are most commonly associated with pseudoallergy. Coadministration of an antihistamine or use of a semi or synthethic opioid (Fentanyl, hydromorphone) can prevent this reaction.







Aspirin (other analgesics-antipyretics)
Penicillins and cephalosporins
Antituberculous drugs

Anesthetics (local and general)
Antipsychotic tranquilizers
Antihypertensive agents (hydralazine)
Antiarrhythmia agents (quinidine, procainamide)

Iodinated contrast media
Antisera and vaccines
Organ extracts (ACTH, insulin)
Heavy metals (gold)
Antithyroid drugs



Understanding adverse drug reactions and drug allergies: principles, diagnosis and treatment aspects. Pourpak Z, et al. Recent Pat Inflamm Allergy Drug Discov. 2008 Jan;2(1):24-46.

Drug Allergy: An Updated Practice Parameter. Joint Task Force. Annals of Allergy, Asthma, & Immunology. Vol 105 ctober , 2010.

Antibiotic allergies in the medical record: effect on drug selection and assessment of validity. Lutomski,DM. Pharmacotherapy. 2008 Nov;28(11) 1348-53.