Ondansetron
A 5-HT3 receptor antagonist antiemetic that blocks serotonin in the GI tract and chemoreceptor trigger zone to prevent nausea and vomiting.
Ondansetron (Zofran) is first-line for chemotherapy-induced, post-operative, and pregnancy-related nausea. It is well tolerated but can cause headache and constipation.
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