We presented a case of a guanfacine poisoning patient who experienced transient ST-segment elevation during hospitalization. Guanfacine, an alpha-2 agonist, not only causes hypotension and bradycardia due to the interruption of sympathetic outflow, but it has also been revealed to occasionally cause a transient decrease in ventricular wall motion. Therefore, patients with guanfacine poisoning should be carefully monitored for changes in their ECG after admission.

Guanfacine received FDA approval for the treatment of ADHD in 2009, leading to its significant increase in availability and exposure to the public [2]. It has a half-life of 10 to 30 h, which varies based on kidney and liver functions [1]. Guanfacine is affected by drug interactions with CYP3A4 inhibitors or inducers [4]. Guanfacine poisoning is frequently associated with cardiac events. Common cardiovascular symptoms of guanfacine poisoning include hypotension, bradycardia, and prolonged QTc [5]. In addition, previous reports have shown that hypotension and bradycardia requiring vasopressors or atropine were rare, but there have been cases of cardiogenic pulmonary edema requiring intubation [5, 6].

The novelty of this case lies in the occurrence of transient ST-segment elevation in the anterior precordial lead on the ECG. Previous literature has demonstrated that alpha-2 adrenoceptor stimulation can lead to a transient decrease in anterior wall motion related to an epinephrine surge in rats exposed to psychological stress [7]. Although the patient’s blood concentration of guanfacine decreased over time, it remained significantly higher compared to that in adults taking the normal dose of guanfacine [8, 9]. When the patient’s blood guanfacine concentration approached the range of normal guanfacine dosage, the ECG changes resolved. This case is a rare instance of guanfacine poisoning where the transient ST-segment elevation, indicative of a decrease in anterior wall motion, was also observed in humans.

In conclusion, guanfacine poisoning patients should be carefully monitored after admission for its potential of causing a variety of cardiovascular events.