Ondansetron is a highly specific and selective serotonin 5-HT3 receptor antagonist, with low affinity for dopamine receptors.
The 5-HT3 receptors are present both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone of the area postrema.
(Oral dosing recommendations remain intact, including the recommendation of a single 24-mg oral dose when indicated.) Electrolyte imbalances should be corrected before the use of injectable ondansetron.
Patients are cautioned to seek immediate medical care if symptoms such as irregular heartbeat/palpitations, shortness of breath, dizziness, or fainting occur while taking ondansetron.
It is broken down by the hepatic cytochrome P450 system and it has little effect on the metabolism of other drugs broken down by this system.
Anecdotally, ototoxicity has also been reported if injected too quickly.
A 2006 double-blind, randomized controlled trial indicated ondansetron may have value in the treatment of schizophrenia, as an adjunct to haloperidol.
The study found the combination to significantly improve negative schizophrenia symptoms, and people taking both drugs experienced fewer of the adverse effects commonly associated with haloperidol.
receptor antagonists are the primary drugs used to treat and prevent chemotherapy-induced nausea and vomiting and radiotherapy-induced nausea and vomiting.
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 patients receiving ondansetron, published between 1991 and September 1996.
The use of ondansetron has not been studied in patients older than 75 years of age, and it is not known if dosage should be adjusted for these patients.
The maximum recommended dose for patients with severe liver function impairment is 8 mg/day.