Guanfacine overdose resulting in initial hypertension and subsequent delayed, persistent orthostatic hypotension.
BACKGROUND
Guanfacine is an alpha(2)-adrenoreceptor agonist used for the treatment of attention-deficit hyperactivity disorder and tic disorders. Few reports exist regarding overdose with guanfacine.


METHODS
A 16-year-old female with Tourette's syndrome presented with diaphoresis, dry mouth, and hypertension 8 h after ingesting 25 mg of guanfacine. These symptoms improved and her blood pressure (BP) normalized over 2 h. Thirty hours following ingestion, she experienced near syncope and returned to the emergency department. She was noted to have orthostatic hypotension and a prolonged QTc interval of 593 ms on electrocardiogram. With only fluid support, she was asymptomatic by 60 h postingestion and her QTc interval had improved to 511 ms.


CONCLUSIONS
This experience suggests a much delayed onset of symptoms may occur and that the QTc interval may be prolonged, necessitating a longer period of monitoring in a patient presenting with an overdose.
Minns
Alicia B
AB
Division of Medical Toxicology, Department of Emergency Medicine, University of California-San Diego, 200 West Arbor Drive, San Diego, CA 92103-8925, USA. abminns01@yahoo.com
Clark
Richard F
RF
Schneir
Aaron
A
D000293:Adolescent; D000316:Adrenergic alpha-Agonists / Q000506:poisoning* / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D062787:Drug Overdose; D004562:Electrocardiography; D005260:Female; D016316:Guanfacine / Q000506:poisoning* / Q000627:therapeutic use; D006801:Humans; D006973:Hypertension / Q000139:chemically induced*; D007024:Hypotension, Orthostatic / Q000139:chemically induced*; D013997:Time Factors; D005879:Tourette Syndrome / Q000188:drug therapy
D000316:Adrenergic alpha-Agonists; D016316:Guanfacine