Prolonged bradycardia and hypotension following guanfacine extended release overdose.

Abstract

[Author Affiliation]Jennifer Walton. 1 Department of Pediatrics, Nationwide Children's Hospital, Columbus, Ohio.Michelle Byrum. 2 Department of Clinical Services and Care Coordination, Nationwide Children's Hospital, Columbus, Ohio.Amanda Shumaker. 2 Department of Clinical Services and Care Coordination, Nationwide Children's Hospital, Columbus, Ohio.Daniel L. Coury. 1 Department of Pediatrics, Nationwide Children's Hospital, Columbus, Ohio.Address correspondence to: Jennifer Walton, MD, MPH, Department of Pediatrics, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, E-mail: Jennifer.Walton@nationwidechildrens.orgTo The Editor:Attention deficit hyperactivity disorder (ADHD) is one of the most commonly diagnosed disorders of childhood. Currently, ADHD affects ∼4-9% of the youth population (National Institutes of Health 2000).There are many types of treatments for ADHD, which vary from behavioral therapy to medication. The most commonly prescribed medications for the treatment of ADHD are psychostimulants, derived from either amphetamine or methylphenidate (Wilens and Spencer 2000). However, other treatments include nonstimulant medications such as atomoxetine, clonidine (immediate and extended release), and guanfacine (immediate and extended release).Guanfacine extended release is an α-agonist that is approved to treat ADHD in children and adolescents. Before receiving approval from the United States Food and Drug Administration (FDA) for use in ADHD, guanfacine was approved for use as an antihypertensive medication. In a placebo-controlled trial, guanfacine extended release was shown to be effective at reducing ADHD symptoms, while having mild to moderate adverse effects (somnolence, fatigue, and sedation) that generally subsided after the first 2 weeks of treatment (Sallee et al. 2009). Compared with guanfacine immediate release, guanfacine extended release has a longer duration of action and fewer fluctuations in concentration. As the use of guanfacine extended release in the treatment of ADHD is relatively new, there is not much information regarding intentional or accidental overdose. We present a case report of an accidental overdose of guanfacine extended release in a boy, which resulted in prolonged hypotension, bradycardia, and admission to the intensive care unit.Case ReportThe patient was an 8 years and 11 months old male with ADHD and a history of auditory hallucinations. His home medications include long-acting dexmethylphenidate 20 mg in the morning, short-acting dexmethylphenidate 5 mg at noon, guanfacine extended release 3 mg in the morning, and risperidone 0.25 mg in the evening. He and his parents reported good benefit from this pharmacological regimen.The outpatient clinic staff were notified at 1:26 p.m. by the patient's school that he was accidentally given guanfacine extended release twice, once in the morning (as prescribed) and again at noon. The school stated that at the time of the second administration of guanfacine, the patient did not have any adverse reactions. However, the clinic staff asked the school personnel to contact the local poison control center, monitor the patient's hydration, and monitor for increased fatigue and lowering of blood pressure. School personnel were also advised that if the patient's symptoms worsened, they were to take him to the nearest emergency department (ED). The patient's mother was also notified and made aware of this situation.The patient came home from school at ∼4:30 p.m. and was noted to have significant fatigue; he fell asleep easily but was difficult to arouse. The patient also seemed cold and had been perspiring since he came home. His mother took him to an urgent care center, where his pulse was recorded to be 56 beats per minute and his blood pressure was recorded to be 97/43 mm Hg. …