Beta blockers (often styled β-blockers) are medications used primarily for their impact on blood pressure and heart rhythm. Given their low cost and relative safety, beta blockers are very commonly prescribed for a number of other conditions as well, including anxiety. They work by blocking beta adrenergic receptors found throughout the body and specifically interfere with the action of norepinephrine and epinephrine.
The use of beta blockers in patients with risk of anaphylaxis requires some special consideration. This is because beta blockers directly block many of the places where epinephrine works to mitigate anaphylaxis. This means that using epinephrine to treat the anaphylaxis may be ineffective. This particular topic has been heavily researched and has not always yielded uniform findings.
The largest and most robust study included over 5000 patients with a history of systemic allergic reactions. This study found that patient use of beta blockers increased the risk of severe anaphylaxis. Use of ACE inhibitors, another drug class that impacts blood pressure, also increased the risk of severe anaphylaxis but to a smaller extent.
However, the risk of severe anaphylaxis was most increased in patients who took both beta blockers and ACE inhibitors together. Both beta blockers and ACE inhibitors were found to both decrease the threshold for mast cell activation and to prime mast cells (make them more easily activated).
Ongoing treatment with beta blockers has been found to be a risk factor for fatal anaphylaxis in some studies. It has also been found to be a risk factor for biphasic anaphylaxis, a type of anaphylaxis in which you have a second anaphylactic episode in the hours that follow successfully treated anaphylaxis.
Patients who must take beta blockers may be given a glucagon autoinjector for use prior to using injectable epinephrine. The reason for this is glucagon is the antidote to beta blocker overdose. When epinephrine binds to the beta receptor, it results in the cells making a molecule called cAMP. cAMP is a very important molecule for cells and it sends signals within the cell to regulate bodily processes. When a patient takes beta blockers, epinephrine can’t tell the cell to make cAMP. Glucagon is able to tell the cell to make cAMP even if the beta receptor is blocked. This action effectively counteracts the beta blocker.
Mast cell patients are usually recommended to use other medications to manage blood pressure and arrhythmias, including calcium channel blockers or renin inhibitors.
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