Administration of ondansetron is associated with lethal outcome

Benefit-Risk Assessment of Off-Label Drug Use in Children: The Bravo Framework

A drug is granted a license for use after a thorough assessment of risks and benefits based on high-quality scientific proof of its efficacy and safety. Many drugs that are relevant to children are not licensed for use in this population implying that a thorough assessment of risks and benefits in the pediatric population has not been made at all, implying a negative risk-benefit balance in children, or implying insufficient information to establish the risk-benefit balance. Use of drugs without positive assessment of risks and benefits exposes children to potential lack of efficacy, unknown toxicity, and harm. To aid guideline committees and individual prescribers, we here present a tutorial of the Benefit and Risk Assessment for Off-label use (BRAvO) decision framework. This pragmatic framework offers a structured assessment of benefits and risks of off-label drug use, including a clinical pharmacological based approach to age-appropriate dose selection. As proof of concept and to illustrate the practical use, we have applied the framework to assess benefits and risks of off-label use of ondansetron for gastroenteritis-induced nausea and vomiting. The framework could also guide decisions on off-label use in other special populations (e.g., pregnant women, elderly, obese, or critically ill patients) where off-label drug use is frequent, thereby contributing to effective and safe pharmacotherapy.

Effect of intravenous ondansetron on QTc interval in children with gastroenteritis

BACKGROUND

The potential for ondansetron to cause QT prolongation and fatal dysrhythmia is well-reported, including a 2011 FDA report on the topic. Few clinical trials evaluating this phenomenon in the ED setting exist, and only one is pediatric.

OBJECTIVE

We have sought to determine the effect of a standardized dose of intravenous ondansetron on the QTc duration of children under 14years of age treated for gastroenteritis-associated vomiting in a pediatric ED. This study is modeled closely after an FDA "thorough QT study".

METHODS

EGCs were obtained before and 15, 30, 45, and 60min after a 0.15mg/kg IV dose of ondansetron given for gastroenteritis-associated vomiting. QT intervals were measured manually with digital calipers, and the QTc interval calculated both by Bazett's (QTcB) and Fridericia's (QTcF) correction. A paired t-test comparing QTc was conducted, and frequency of categorical outcomes of prolongation>30msec, >60 msec, and absolute prolongation >450 msec, >480 msec, and >500msec were evaluated.

RESULTS

In a 4-month period, 134 patients were included in the study, 46% were male. The average QTc prior to ondansetron administration was: QTcB 415 msec (95% CI 343-565) and QTcF 373 (95% CI 304-499). The mean difference in QTc after ondansetron was 0.4msec for QTcB (95% CI -35-45msec) and 0.1msec for QTcF (95% CI -40-18msec).

CONCLUSION

In these children, 0.15mg/kg of intravenous ondansetron did not cause prolongation of QTcB or QTcF measured 15min after administration, nor at later times.

Fatal Cardiac Arrest in 2 Children: Possible Role of Ondansetron

INTRODUCTION

Ondansetron is commonly used to treat vomiting in gastroenteritis, but has a United States Food and Drug Administration black box warning for risk of Q wave to T wave time interval (QT) prolongation. We report 2 pediatric cases of fatal refractory cardiac arrest after administration of ondansetron.

CASES

A 10-year-old previously healthy boy presented to the emergency room with gastroenteritis symptoms. After intravenous fluids, morphine, antibiotics, and 2 doses of ondansetron, the patient became unresponsive with agonal respirations and a wide complex tachycardia consistent with ventricular tachycardia. In a second case, an 86-day-old infant with previously unidentified congenital cardiomyopathy presented to our emergency department with gastroenteritis symptoms. The patient received ondansetron and subsequently experienced repeated bouts of supraventricular tachycardia which progressed to ventricular fibrillation. Resuscitation efforts failed in each case, and both patients expired.

DISCUSSION

Ondansetron can cause dose-dependent QT prolongation effects, which are more clinically relevant when other proarrhythmic elements are present. There is very limited published experience on use of ondansetron in children younger than 2 years. Our 2 cases join 2 previous case reports of death after ondansetron administration for gastroenteritis. The pharmacology of ondansetron's cardiac effects and drug-induced QT prolongation is discussed.

CONCLUSIONS

Patients may have hidden risk factors that, together with ondansetron, could result in a proarrhythmic state that could lead to adverse effects, such as arrhythmias. Administration of ondansetron should be individualized and used cautiously in patients with risk factors for arrhythmia.

RYR1-related rhabdomyolysis: A common but probably underdiagnosed manifestation of skeletal muscle ryanodine receptor dysfunction

Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are associated with a wide spectrum of inherited myopathies presenting throughout life. Malignant hyperthermia susceptibility (MHS)-related RYR1 mutations have emerged as a common cause of exertional rhabdomyolysis, accounting for up to 30% of rhabdomyolysis episodes in otherwise healthy individuals. Common triggers are exercise and heat and, less frequently, viral infections, alcohol and drugs. Most subjects are normally strong and have no personal or family history of malignant hyperthermia. Heat intolerance and cold-induced muscle stiffness may be a feature. Recognition of this (probably not uncommon) rhabdomyolysis cause is vital for effective counselling, to identify potentially malignant hyperthermia-susceptible individuals and to adapt training regimes. Studies in various animal models provide insights regarding possible pathophysiological mechanisms and offer therapeutic perspectives.

Unexpected MH deaths without exposure to inhalation anesthetics in pediatric patients

Children, later found to have ryanodine receptor type one variants (RYR1), died without exposure to inhalation anesthetics. Family members with the same RYR1 variants had contracture tests consistent with susceptibility to malignant hyperthermia or in vitro testing showed increased sensitivity to RYR1 agonist.

Ondansetron-induced muscular contractures in malignant hyperthermia-susceptible individuals

BACKGROUND

The 5-HT(3)-receptor antagonist ondansetron, commonly used to treat nausea and vomiting, was suspected of triggering malignant hyperthermia (MH) when a 5-year-old boy died after receiving a therapeutic dose of ondansetron. To evaluate a possible influence of ondansetron on the onset of MH, we investigated its effect on muscle specimens of MH-susceptible (MHS) and MH-nonsusceptible (MHN) individuals in vitro.

METHODS

Muscle bundles of 6 MHS and 10 MHN patients were incubated in a tissue bath with ondansetron at increasing concentrations (0.1 to 300 μg/mL). Changes in resting tension and twitch height were monitored continuously. Data are reported as median and interquartile range; Mann-Whitney U test for differences between the groups (P < 0.05).

RESULTS

Weight, length, initial resting tension, and twitch height of the muscle bundles did not significantly differ between the investigated groups. An increasing twitch amplitude after ondansetron application was observed in both groups. However, contractures developed only in MHS but not in MHN muscle at ondansetron concentrations of 50 μg/mL (MHS 2.5 [2.1 to 4.0] vs. MHN 0 [0 to 0] mN) and 100 μg/mL (18.0 [11.8 to 22.8] vs 0 [0 to 0] mN). At 300 μg/mL ondansetron, a muscular response was also observed in MHN (23.3 [20.1 to 40.1] vs 1.8 [0.3 to 4.9] mN).

CONCLUSIONS

Ondansetron induced contractures in skeletal muscle bundles in vitro. The effect was significantly higher in MHS than in MHN muscle. Because the necessary concentration of ondansetron exceeded the therapeutic plasma levels by a minimum of 500 times, a trigger potency in vivo seems unlikely.

Time-series analysis of ondansetron use in pediatric gastroenteritis

OBJECTIVE

Emergency department use of ondansetron in children with gastroenteritis is increasing; however, its effect on clinical outcomes is unknown. We aimed to determine whether increasing ondansetron usage is associated with improved outcomes in children with gastroenteritis.

METHODS

A retrospective cohort study was conducted at The Hospital for Sick Children, Toronto, Canada. Eligible children included those younger than 18 years old with gastroenteritis who presented to an emergency department between 2003 and 2008. There were 22,125 potentially eligible visits; 20% were selected at random for chart review. The primary outcome measure, the intravenous rehydration rate, was evaluated using an interrupted time-series analysis with segmented logistic regression. Secondary outcomes included emergency department revisits, hospitalization, and length of stay.

RESULTS

A total of 3508 patient visits were included in the final analysis. During the study period, there was a significant reduction in intravenous rehydration usage (27%-13%; P < 0.001) and an increase in ondansetron administration (1%-18%; P < 0.001). Time-series analysis demonstrated a level break (P = 0.03) following the introduction of ondansetron. The mean length of stay for children declined from 8.6 ± 3.4 to 5.9 ± 2.8 hours, P = 0.03. During the week following the index visit, there was a reduction in return visits (18%-13%; P = 0.008) and need for intravenous rehydration (7%-4%; P = 0.02).

CONCLUSIONS

Ondansetron use has increased significantly and is associated with reductions in the use of intravenous rehydration, emergency department revisits, and length of stay. The selective use of ondansetron is associated with improved clinical outcomes.

Identical de novo mutation in the type 1 ryanodine receptor gene associated with fatal, stress-induced malignant hyperthermia in two unrelated families

BACKGROUND

Mutations in the type 1 ryanodine receptor gene (RYR1) result in malignant hyperthermia, a pharmacogenetic disorder typically triggered by administration of anesthetics. However, cases of sudden death during exertion, heat challenge, and febrile illness in the absence of triggering drugs have been reported. The underlying causes of such drug-free fatal "awake" episodes are unknown.

METHODS

De novo R3983C variant in RYR1 was identified in two unrelated children who experienced fatal, nonanesthetic awake episodes associated with febrile illness and heat stress. One of the children also had a second novel, maternally inherited D4505H variant located on a separate haplotype. Effects of all possible heterotypic expression conditions on RYR1 sensitivity to caffeine-induced Ca release were determined in expressing RYR1-null myotubes.

RESULTS

Compared with wild-type RYR1 alone (EC50 = 2.85 ± 0.49 mM), average (± SEM) caffeine sensitivity of Ca release was modestly increased after coexpression with either R3983C (EC50 = 2.00 ± 0.39 mM) or D4505H (EC50 = 1.64 ± 0.24 mM). Remarkably, coexpression of wild-type RYR1 with the double mutant in cis (R3983C-D4505H) produced a significantly stronger sensitization of caffeine-induced Ca release (EC50 = 0.64 ± 0.17 mM) compared with that observed after coexpression of the two variants on separate subunits (EC50 = 1.53 ± 0.18 mM).

CONCLUSIONS

The R3983C mutation potentiates D4505H-mediated sensitization of caffeine-induced RYR1 Ca release when the mutations are in cis (on the same subunit) but not when present on separate subunits. Nevertheless, coexpression of the two variants on separate subunits still resulted in a ∼2-fold increase in caffeine sensitivity, consistent with the observed awake episodes and heat sensitivity.

Oral ondansetron administration in emergency departments to children with gastroenteritis: an economic analysis

BACKGROUND

The use of antiemetics for children with vomiting is one of the most controversial decisions in the treatment of gastroenteritis in developed countries. Ondansetron, a selective serotonin receptor antagonist, has been found to be effective in improving the success of oral rehydration therapy. However, North American and European clinical practice guidelines continue to recommend against its use, stating that evidence of cost savings would be required to support ondansetron administration. Thus, an economic analysis of the emergency department administration of ondansetron was conducted. The primary objective was to conduct a cost analysis of the routine administration of ondansetron in both the United States and Canada.

METHODS AND FINDINGS

A cost analysis evaluated oral ondansetron administration to children presenting to emergency departments with vomiting and dehydration secondary to gastroenteritis from a societal and health care payer's perspective in both the US and Canada. A decision tree was developed that incorporated the frequency of vomiting, intravenous insertion, hospitalization, and emergency department revisits. Estimates of the monetary costs associated with ondansetron use, intravenous rehydration, and hospitalization were derived from administrative databases or emergency department use. The economic burden in children administered ondansetron plus oral rehydration therapy was compared to those not administered ondansetron employing deterministic and probabilistic simulations. We estimated the costs or savings to society and health care payers associated with the routine administration of ondansetron. Sensitivity analyses considered variations in costs, treatment effects, and exchange rates. In the US the administration of ondansetron to eligible children would prevent approximately 29,246 intravenous insertions and 7,220 hospitalizations annually. At the current average wholesale price, its routine administration to eligible children would annually save society US$65.6 million (US$49.1-US$81.1) and health care payers US$61.1 million (US$46.2-US$76.3). In Canada the administration of ondansetron to eligible children would prevent 4,065 intravenous insertions and 1,003 hospitalizations annually. Its routine administration would annually save society CDN$1.72 million (CDN$1.15-CDN$1.89) and the health care system CDN$1.18 million (CDN$0.88-CDN$1.41).

CONCLUSIONS

In countries where intravenous rehydration is often employed, the emergency department administration of oral ondansetron to children with dehydration and vomiting secondary to gastroenteritis results in significant monetary savings compared to a no-ondansetron policy. Please see later in the article for the Editors' Summary.