Drug-induced urticaria

Drug-induced urticaria occurs by immunologic and nonimmunologic mechanisms. The primary mechanism for drug-induced urticaria involves a type-I hypersensitivity reaction mediated by IgE antibodies, commonly observed with ß-lactam use. This immune-mediated reaction necessitates a sensitization period, leading to more severe systemic reactions, including angioedema and anaphylaxis. Additionally, drug-induced urticaria can result from the activation of the complement cascade, a type-III hypersensitivity mediated by immune complexes. Complement cascade activation generates anaphylatoxins, releasing chemical mediators from basophils and mast cells, subsequently causing urticaria. This mechanism is seen in serum sickness and is associated with systemic symptoms such as fever, joint pain, and neurological symptoms. Topical medications, typically cause contact dermatitis, though can also induce urticaria through immune-mediated or non-immunological mechanisms. Antibiotics, often present in topical creams, are a common source of contact urticaria. == Treatment and prevention ==

Patients experiencing drug-induced urticaria should avoid the causative drug if possible. When avoidance is not feasible, alternatives, such as using selective COX-2 inhibitors in place of typical NSAIDs, may be considered. Evidence suggests that individuals with NSAID-induced urticaria, particularly with angioedema, may develop tolerance over time. Pre-treatment with anti-histamines or leukotriene antagonists can potentially prevent reactions in cases where avoidance or substitution is challenging. For post-exposure urticaria, discontinuation of the offending medication is crucial. Symptoms typically resolve upon removal of the causal agent, and management may involve anti-histamines or corticosteroids based on the severity of the reaction. == List of medications known to cause urticaria ==

• Nonsteroidal anti-inflammatory agents • Antibiotics: cephalosporins, penicillins, tetracyclines, aminoglycosides, sulfonamides, sorbitol complexes, • Angiotensin-converting enzyme (ACE) inhibitors • Hydralazine • Narcotic analgesics • Contrast media • Enzymes: streptokinase, trypsin, chymopapain • Vaccines • Antifungal agents: ketoconazole, fluconazole • Steroids • Polypeptide hormones: insulin, corticotrophin • Vasopressin • Anesthetic agents (local and general) • Quinidine • Anticancer drugs • Muscle myorelaxants (curare) • Mannitol • Dextrans • Protamine • Vitamins == See also ==