Ondansetron for treating nausea and vomiting in the poisoned patient

Antiemetic use in pediatric gastroenteritis: a national survey of emergency physicians, pediatricians, and pediatric emergency physicians

The objective of this study was to review the use of antiemetics for pediatric gastroenteritis and to determine prescribing patterns of physicians. A mailed cross-sectional survey instrument was sent to randomly selected board-certified emergency medicine, pediatric, and pediatric emergency medicine specialists. A total of 1665 surveys were mailed, with 593 completed surveys returned (35.6% response rate). A majority of responders (60.9%) reported using antiemetics for pediatric gastroenteritis at least once in the past year, with a greater than 50% usage for all three specialty groups. Promethazine was the most commonly used antiemetic in all specialties, and per rectum the most common route of administration. Adverse reactions following a single dose of antiemetic were most frequently reported with prochlorperazine. The most common reason for antiemetic use was to prevent further dehydration. The most common concern regarding antiemetic use was potential for side effects. Occasional antiemetic use appears to be a common practice in treating pediatric gastroenteritis, regardless of specialty. Given the absence of literature on efficacy or safety, these drugs should be used only with careful consideration to potential side effects.

Mechanism of action and value of N-acetylcysteine in the treatment of early and late acetaminophen poisoning: a critical review

INTRODUCTION

The mechanism of action of N-acetylcysteine in early acetaminophen poisoning is well understood, but much remains to be learned of the mechanism of its possible benefit in acetaminophen poisoning presenting beyond 15 hours.

METHODS

Selective review of medical literature. N-acetylcysteine should be used in all cases of early acetaminophen poisoning where the plasma acetaminophen concentration lies "above the line;" which line is chosen depends on individual preference and whether enzyme induction is suspected. Particular care should be taken with the use of the nomogram for patients with chronic excess ingestion of acetaminophen or for those who have taken slow-release formulations.

CONCLUSIONS

While there is a trend suggesting a beneficial effect of N-acetylcysteine in some patients presenting beyond 15 hours, further research is necessary to establish just how effective N-acetylcysteine is, particularly in patients presenting with fulminant hepatic failure. Candidate mechanisms for a beneficial effect in-clude improvement of liver blood flow, glutathione replenishment, modification of cytokine production, and free radical or oxygen scavenging. Hemody-namic and oxygen delivery and utilization parameters must be monitored carefully during delayed N-acetylcysteine treatment of patients with fulminant hepatic failure, as unwanted vasodilation may be deleterious to the maintenance of mean arterial blood pressure.

Use of ondansetron and other antiemetics in the management of toxic acetaminophen ingestions

BACKGROUND

Patients presenting with acetaminophen toxicity and vomiting are often treated with antiemetics so that orally administered N-acetylcysteine can be retained. The policy at the West Virginia Poison Center is to reserve ondansetron, an antiemetic with a higher cost than other antiemetics, as a second line agent for patients presenting within 8 hours of an acetaminophen ingestion.

METHODS

A retrospective study of cases between January 1993 and December 1995, in which the primary or secondary drug ingested was an adult-strength, acetaminophen-only formulation and the ingestion resulted in vomiting. Seventy-eight patients with laboratory-verified acetaminophen toxicity and vomiting were evaluated for the type of antiemetics used and the antiemetic's effectiveness.

RESULTS

Of the 78 acetaminophen toxic patients with vomiting, 17/51 patients (33.3%) who received a nonondansetron antiemetic failed therapy and required IV ondansetron. Of the 24 patients who received ondansetron, 4 patients (16.7%) failed therapy. All four patients who failed ondansetron therapy had previously failed other antiemetic therapy.

DISCUSSION

Although ondansetron had a lower failure rate than nonondansetron antiemetics, almost two-thirds of acetaminophen toxic patients with vomiting did not require ondansetron to control their vomiting. Health care costs would have been higher had these patients received ondansetron as their initial therapy. Antiemetics were found to be highly effective as only 3/78 patients (4%) required IV N-acetylcysteine secondary to antiemetic failure.

CONCLUSIONS

Ondansetron should be utilized as a second-line agent in the management of acetaminophen toxic patients with vomiting. Because of its lower failure rate, ondansetron should be administered as a first-line agent in patients with a delay in N-acetylcysteine administration approaching 8 or more hours.

The use of ondansetron in the treatment of nausea and vomiting associated with acetaminophen poisoning

BACKGROUND

Nausea and vomiting associated with poisoning can complicate treatment and in some cases delay potential antidote administration. Side effect such as lowering the seizure threshold may at times discourage the use of traditional phenothiazine and butyrophenone antiemetics.

METHODS

We performed a prospective, single arm, observational study examining the effectiveness of the 5HT3 receptor antagonist ondansetron in the management if nausea and vomiting associated with acetaminophen poisoning. Patients with a history or laboratory evidence of acetaminophen poisoning were eligible for inclusion in the study. Exclusion criteria included age less than 18 or greater than 65, use of other antiemetic therapy within the previous 12 hours, history of preexisting hepatic or hematologic disease, pregnancy, or significant ingestion of other substances. Upon meeting entry criteria, patients were administered 8 mg of intravenous ondansetron. Nausea was graded on a 100 mm scale with number of emetic episodes recorded before and after treatment.

RESULTS

Six patients were entered in the study. All patients had nausea and at least one emetic episode prior to ondansetron and prior to administration of N-acetylcysteine. All patients reported relief of nausea after ondansetron. The degree of nausea decreased by an average of 52% at 30 min and 88% at 60 min following ondansetron administration. No significant vital sign changes were recorded in any patient, and there were no complications related to therapy. Three patients were administered N-acetylcysteine, and all tolerated this therapy without vomiting after ondansetron.

CONCLUSIONS

Ondansetron appears to be a potentially useful adjunct in the management of nausea and vomiting associated with acetaminophen poisoning.

Recent advances in pediatrics

The challenging issues in pediatric pharmacotherapy are both profound and exciting. Microtechnologies for evaluating the impact of genetics in disease (e.g., using polymerase chain reactions) and the possibilities of therapeutic interventions create major clinical and ethical dilemmas that remain to be resolved. Inclusion of pediatric patients in drug development and marketing trials also remains a point of contention. Finally, well-established therapies should not be overlooked in favor of new but unestablished treatment approaches. Future columns will continue to use the current format, in which a few selected topics of high therapeutic importance are discussed. The research technologies, discussion of new drug therapy interventions, and preventive strategies most likely to benefit the health care of infants, children, and adolescents will remain the scope of this column.