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.

 

 

 

 

Additional Information

DRUGS FREQUENTLY IMPLICATED IN ALLERGIC DRUG REACTIONS
Aspirin (other analgesics-antipyretics) Penicillins and cephalosporins Sulfonamides Antituberculous drugs Nitrofurans Antimalarials Griseofulvin	Sedative-hypnotics Anticonvulsants Anesthetics (local and general) Phenolphthalein Antipsychotic tranquilizers Antihypertensive agents (hydralazine) Antiarrhythmia agents (quinidine, procainamide)	Iodinated contrast media Antisera and vaccines Organ extracts (ACTH, insulin) Heavy metals (gold) Allopurinol Penicillamine Antithyroid drugs

 

References

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.