Evidence-based On-call

Anaphylaxis

Prevention

Use prophylactic treatments prior to contrast radiography

^a particularly for patients with asthma or on beta-blockers.

Why?

Pre-treatment with hydroxazine reduces adverse effects

Patient	Treatment	Comparison	Outcome	CER	RRR (95% CI)	NNT (95% CI)
adults without history of anaphylaxis undergoing contrast radiography ^a	hydroxyzine 100mg PO prior to examination	placebo	Adverse reaction	15.5%	92% (67% to 98%)	9 (6 to 15)