Which medication likely contributed to reduced effectiveness of epinephrine in anaphylactic shock?

In cases of anaphylactic shock, epinephrine is a critical medication used to reverse the severe allergic reaction by causing vasoconstriction, increasing heart rate, and relaxing bronchial smooth muscle. When considering medications that could reduce the effectiveness of epinephrine, it is important to note that propranolol is a non-selective beta-adrenergic antagonist.

Propranolol blocks both beta-1 and beta-2 adrenergic receptors. By doing so, it can inhibit the actions of epinephrine, which relies on those receptors to exert its effects, particularly in the bronchial and vascular smooth muscles. If beta-2 receptors are blocked by propranolol, the bronchodilation that epinephrine normally provides may not occur effectively, thereby worsening respiratory distress in anaphylaxis. Additionally, blocking beta-1 receptors can interfere with the cardiovascular effects of epinephrine, such as increased heart rate and contractility.

Other options like doxazosin, metoprolol, and acebutolol either selectively block different receptors or have minimal effects on the critical receptor pathways that epinephrine uses. Doxazosin primarily acts as an alpha-1 blocker, while metoprolol is a selective beta-