Pediatric guanfacine exposures reported to the National Poison Data System, 2000–2016

Synergistic interaction of guanfacine or dexmedetomidine coadministered with lidocaine for cutaneous analgesia in rats

BACKGROUND

This study examined the cutaneous analgesic effects of lidocaine co-injected with guanfacine and its comparison with dexmedetomidine.

METHODS

Cutaneous analgesic effects are quantified through the blocking effects of the cutaneous trunci muscle reflex against skin pinpricks in rats. The dose-response curves of guanfacine, dexmedetomidine, and lidocaine were constructed and drug-drug interactions were analyzed by the ED50 isobologram.

RESULTS

Subcutaneous injections of guanfacine, dexmedetomidine, and lidocaine produced dose-dependently nociceptive/sensory blockade. On the ED50 (50% effective dose) basis, the potency rankings of the drug are dexmedetomidine (0.09 [0.08-0.11] μmol/kg) > guanfacine (3.98 [2.96-5.34] μmol/kg) > lidocaine (25.40 [23.51-27.44] μmol/kg) (p < 0.01). On their equipotent doses (ED25, ED50, and ED75), the duration of sensory blockade induced by guanfacine or dexmedetomidine was longer than lidocaine's (p < 0.01). Both guanfacine and dexmedetomidine showed synergistic effects with lidocaine.

CONCLUSIONS

We showed that guanfacine elicits dose-dependent cutaneous analgesia when administered subcutaneously. Lidocaine is less potent than guanfacine or dexmedetomidine. Both guanfacine and dexmedetomidine enhance the potency and duration of lidocaine. Better synergistic responses we are getting with guanfacine plus lidocaine.

Guanfacine poisoning resulting in transient ST-segment elevation: a case report

BACKGROUND

Guanfacine is an alpha-2 adrenergic agonist that decreases norepinephrine release and sympathetic outflow. With the increased use of guanfacine for attention-deficit hyperactivity disorder (ADHD), reports of guanfacine poisoning have also risen.

CASE PRESENTATION

A 15-year-old male (height: 170 cm, weight: 48 kg), who was taking 2 mg/day of guanfacine for ADHD, was brought to our emergency department after ingesting 40 tablets of guanfacine due to poor exam results. He presented with impaired consciousness and sinus bradycardia on an electrocardiogram (ECG), leading to diagnosis of guanfacine poisoning. Gastric lavage (5 L) was performed, and activated charcoal was administered. Although his consciousness gradually recovered, he developed ST-segment elevation on the ECG. Despite the absence of chest pain and elevated myocardial enzymes, coronary artery stenosis was not observed on coronary artery computed tomography. As his blood guanfacine level decreased, his ECG returned to normal.

CONCLUSIONS

This case highlights the need for careful monitoring of guanfacine poisoning patients due to the potential for various cardiovascular events.

QT-Interval Prolongation Associated with Supratherapeutic Guanfacine Concentration: A Case Report

INTRODUCTION

Guanfacine, an alpha-2 adrenergic agonist, is used to treat attention deficit hyperactivity disorder (ADHD). Although cardiovascular effects including hypotension and bradycardia are common adverse effects of guanfacine, the effect of guanfacine on QT intervals remains unclear. The association between the serum concentration of guanfacine and its toxicity has also not been fully investigated.

CASE REPORT

This is a case of a 21-year-old woman with ADHD who developed repeated presyncope 1 day before admission. She was taking 3 mg of extended-release guanfacine and 50 mg of sertraline. On admission, she had bradycardia and hypotension. An electrocardiogram (ECG) showed a QT interval of 0.68 s and a QTcF interval of 0.648 s. The QT intervals were manually measured and corrected by the Fridericia formula (QTcF = QT/RR1/3). Although she denied taking an overdose of guanfacine and other drugs, we suspected guanfacine toxicity. The serum guanfacine concentration was 13.0 ng/mL on admission and decreased to 3.2 ng/mL on day 1 and 0.4 ng/mL on day 2. Changes in QTcF intervals and her vital signs correlated with serum guanfacine concentrations.

CONCLUSION

Supratherapeutic serum guanfacine concentrations may induce QT prolongation.

Pediatric ADHD Medication Errors Reported to United States Poison Centers, 2000 to 2021

OBJECTIVES

To investigate the characteristics and trends of out-of-hospital attention-deficit/hyperactivity disorder (ADHD) medication-related therapeutic errors among youth <20 years old reported to US poison centers.

METHODS

National Poison Data System data from 2000 through 2021 were analyzed. Population-based rates were calculated using US census data.

RESULTS

There were 124 383 ADHD medication-related therapeutic errors reported to US poison centers from 2000 through 2021, with the annual frequency increasing by 299.0% during that period. Two-thirds (66.6%) of the 87 691 first-ranked exposures involved children 6 to 12 years old, three-fourths (76.4%) were among males, and half (50.5%) involved amphetamines and related compounds. Most (79.7%) therapeutic errors were single-substance exposures. Although most (82.7%) individuals did not receive treatment in a health care facility (HCF), 2.3% were admitted to a HCF and 4.2% had a serious medical outcome. Children <6 years old were more likely to experience a serious medical outcome (odds ratio = 2.1; 95% confidence interval: 1.9-2.3) or be admitted to a HCF (odds ratio = 3.4; 95% confidence interval: 3.0-3.7) than 6 to 19-year-olds. The most common scenarios were "inadvertently taken or given medication twice" (53.9%), followed by "inadvertently taken or given someone else's medication" (13.4%), and "wrong medication taken or given" (12.9%).

CONCLUSIONS

The frequency of cases reported to poison centers of pediatric out-of-hospital therapeutic errors related to ADHD medications increased by almost 300% during the 22-year study period and is likely attributable to increased prescribing of these medications. Because therapeutic errors are preventable, more attention should be given to patient and caregiver education and development of improved child-resistant medication dispensing and tracking systems.

Delayed Signs and Symptoms of Extended Release Guanfacine Overdose in Two Adolescent Patients: Implications of Monitoring on the Psychiatry Unit

Guanfacine is a selective alpha-2a adrenoreceptor agonist that with overdose can cause symptoms ranging from mild sedation to coma, respiratory depression, hyporeflexia, hypotonia, bradycardia, and hypotension. Despite a well-defined and predictable toxidrome, variations can be seen based on multiple factors including age, quantity ingested, organ functions, coingestions, time since ingestion, and specific dosage form. Here, we describe two cases of delayed presentation of extended release guanfacine toxicity and highlight the variations encountered in the toxidrome presentation. These cases bring to attention the importance of maintaining a high suspicion for such atypical presentations, keeping in mind the limitations of managing these complications on an inpatient psychiatric unit.