Features of an injection site reaction: swelling, erythema, pruritis and pain at the injection site
Risk factors for injection site reactions:
(1) frequent injections
(2) allergic reaction, immediate or delayed
(3) recall reaction (? nonallergic immune response)
Risk factors for drug discontinuation:
(1) limited clinical response (no perceived benefit, lack of efficacy)
(2) cosmetic appearance
(3) severe symptoms (pain, flu-like symptoms, etc)
(4) failure to respond to interventions to reduce reactions (antihistamine, corticosteroid)
Differential diagnosis:
(1) cellulitis at the injection site