Ondansetron typically starts working within about 30 minutes after oral administration, with its effects becoming noticeable between 15 minutes to 2 hours depending on the formulation. The orally disintegrating tablets (ODT) and intravenous injections tend to act faster, with ODTs having peak effects within 15-30 minutes and IV forms working within 10-15 minutes. Regular tablets usually take around 30 minutes to start relieving nausea and vomiting. Factors such as metabolic rate, age, other medications, and dosage form affect how quickly ondansetron works.
Onset times by form:
- Oral disintegrating tablet (ODT): 15–30 minutes
- Oral tablet/liquid: About 30 minutes
- Intravenous (IV) or intramuscular (IM) injection: 10–15 minutes
Ondansetron is used to prevent and treat nausea and vomiting related to chemotherapy, surgery, and radiation therapy. Taking it according to the prescribed method and dose will influence how quickly relief is felt.
In summary, ondansetron typically begins relieving nausea within 30 minutes orally, faster if injected or taken as ODT, with a full effect up to about 2 hours after dosing.