It is typically used after other antinausea drugs have failed.There appears to be a low risk of harm to the baby with use during pregnancy, though there may be an increase in heart problems among the babies.Ondansetron is in pregnancy category B in the US. It is not known if ondansetron is excreted in breast milk. Cyclic vomiting syndrome
Ondansetron is one of several antiemetic drugs used during the vomiting phase of cyclic vomiting syndrome. Gastroenteritis
Trials in emergency department settings support the use of ondansetron to reduce vomiting associated with gastroenteritis and dehydration. A retrospective review found it was used commonly for this purpose, being administered in over 58% of cases. Its use reduced hospital admissions, but was also associated with higher rates of return visits to the emergency department. Furthermore, people who had initially received ondansetron were more likely to be admitted on the return visit than people who had not received the drug. However, this effect may simply be due to the agent being used more frequently in people who present with more severe illness. Its use was not found to mask serious diagnoses. Special populations
Children
Ondansetron has rarely been studied in people under 4 years of age. As such, little data is available to guide dosage recommendations. Elderly
It is not necessary to adjust the dosage for people under 75 years of age. The use of ondansetron has not been studied in people older than 75 years of age, and it is not known if dosage should be adjusted for this group.
By this final year of its patent (2006), Zofran had become the 20th highest-selling brand-name drug in the United States, with sales of US$1.3 billion in the first 9 months of 2006 (80% from the US). The first generic versions were approved by the US FDA in December 2006, with marketing approval granted to Teva Pharmaceuticals USA and SICOR Pharmaceuticals. In 2018, University of São Paulo and Biolab were granted a patent for an orodispersible form of the drug. Society and culture
Publication bias
In 1997, ondansetron was the subject of a meta-analysis case study published in the British Medical Journal. Researchers examined 84 trials, with 11,980 people receiving ondansetron, published between 1991 and September 1996. Intravenous ondansetron 4 mg versus placebo was investigated in 16 reports and three further reports which had been duplicated a total of six times. The number needed to treat (NNT) to prevent vomiting within 24 hours was 9.5, with 95% confidence interval 6.9 to 15, in the 16 nonduplicated reports. In the three duplicated reports, the NNT was significantly lower at 3.9 (3.3 to 4.8). When all 25 reports were combined, the apparent NNT improved to 4.9 (4.4 to 5.6). Inclusion of duplicate reports led to a 23% overestimation of ondansetrons antiemetic efficacy.In addition, the authors found the covert duplication of reports on ondansetron was not easy to detect, because of lack of cross-referencing between papers, and reports containing duplicate findings were cited in eight reviews of the drug.