A case of prolonged hypotension due to intoxication with an angiotensin II receptor blocker and a selective β₁ antagonist

Abstract

We report a case of prolonged hypotension due to overdose of antihypertensive medication: a 50-year-old man presented to the emergency department with impaired consciousness, bradycardia, and hypotension. The patient had a history of taking beta-blockers, alpha-blockers, and angiotensin receptor blockers (ARBs). Attempts were made to raise pressure with catecholamines, but the patient had difficulty maintaining mean arterial pressure (MAP) of 60 mmHg, and MAP remained below 60 mmHg until the sixth day. The prolonged hypotension was attributed to beta-blockers and ARBs, but subsequent blood analysis revealed that blood levels of azilsartan and bisoprolol had improved to the therapeutic range by day 4. Azilsartan dissociates slowly from its receptor, and its metabolite also acts as an angiotensin Ⅱ receptor type 1 inhibitor. Similarly, metabolites of bisoprolol retain β₁ receptor inhibitory activity. Although no specific treatment for ARB overdose has been established, catecholamines were found to be ineffective in controlling blood pressure, and vasopressin boosting was effective. In cases of acute drug intoxication due to overdose, not only the blood concentration of the drug but also the activity of metabolites and the potency of receptor binding inhibition must be considered.