I love when complex medication questions come across my desk from folks like Drs. Amal Mattu, Rob Orman, Mike Winters, and Haney Mallemat (just to name a few). This week I received one from Dr. Scott Weingart that someone had sent to him. This paramedic was reviewing his anaphylaxis protocol with some new medics and providers. They asked a challenging question regarding a “pearl” they learned in which half-dose epinephrine should be administered in anaphylactic patients on beta-blockers. Patients on beta-blockers do have an increased risk for anaphylaxis, so there is a chance you’ll see a case just like this at some point.
You might be asking why this ‘pearl’ has gained any ground considering it makes intuitive sense to actually need an INCREASED dose of epinephrine to overcome any preexisting beta-blockade. Before I even started my search, I will admit my bias was to actually give more epinephrine to overcome the beta blockade. The justification behind the ‘pearl’ is that giving epinephrine in the setting of beta-blockade may cause unopposed alpha-1 mediated vasoconstriction leading to hypertensive crisis and reflex bradycardia. This may be more pronounced in non-selective beta-blockers such as propranolol. So, what’s the answer? Is this really a concern? Should we be decreasing the epinephrine dose for anaphylactic patients on beta-blockers? Let’s take a closer look.
World Allergy Organization Guidelines
The World Allergy Organization Guidelines on Anaphylaxis make no mention of adjusting epinephrine dose in various situations . The dose is 0.3 to 0.5 mg. In fact, they point out that you may not see a response with epinephrine and suggest the possibility of needing a higher dose in patients on beta-blockers.
- In one case report, the patient was on propranolol (non-selective) and had a blood pressure of 73/58 before epi . Afterward she had “normalization of BP” and then developed chest pain and a troponin leak. The cardiac cath was negative. Coronary vasospasm is a potential side effect when adding an agent with beta/alpha adrenergic properties (see cocaine literature), but it didn’t cause hypertensive crisis with reflex bradycardia. There are also cases of vasospasm in patients not on beta blockers. 
- In another case report, a patient on metoprolol (selective) developed anaphylaxis during elective laparoscopic cholecystectomy. She was administered epi and BP slowly normalized. Again, no hypertensive crisis. 
- A third case reported resistance to epinephrine in a patient on propranolol with anaphylaxis. This suggests the need to use higher epi doses. 
- In a fourth case, a patient had anaphylaxis to radio-contrast media during elective coronary angiography. After epinephrine administration his blood pressure transiently rose to 280/110 mm Hg with subsequent anterolateral ST depressions. No beta-blocker was mentioned in this case. 
What’s the bottom line?
- Simons FE, et al. World allergy organization guidelines for the assessment and management of anaphylaxis. World Allergy Organ J 2011;4(2):13-37. [PMID 23268454]
- Cunnington C, et al. Epinephrine-induced myocardial infarction in severe anaphylaxis: is non-selective beta-blockade a contributory factor? Am J Emerg Med 2013;31(4):759.e1-2. [PMID 23380109]
- Shaver KJ, et al. Acute myocardial infarction after administration of low-dose intravenous epinephrine for anaphylaxis. CJEM 2006;8(4):289-94. [PMID 17324313]
- Gandhi R, et al. Severe anaphylaxis during general anaesthesia in a beta-blocked cardiac patient: considerations. Acta Anaesthesiol Scand 2008;52(4):574. [PMID 18339170]
- Newman BR, et al. Epinephrine-resistant anaphylaxis in a patient taking propranolol hydrochloride. Ann Allergy 1981;47(1):35-7. [PMID 6114688]
- Madowitz JS, et al. Severe anaphylactoid reaction to radiographic contrast media. JAMA 1979;241(26):2813-5. [PMID 448843]