Zofran works by antagonizing, i.e., blocking, 5-HT3 (serotonin) receptors (http://theoncologist.alphamedpress.org/content/7/5/424.full) in both the central nervous system and the gastrointestinal tract.
|Signals involved in chemotherapy-induced nausea and vomiting. Image is from "Nausea and vomiting with high-dose chemotherapy and stem cell rescue therapy: a review of antiemetic regimens." M E Trigg and D M Inverso. Bone Marrow Transplant (2008) 42:501-506. (http://www.nature.com/bmt/journal/v42/n8/full/bmt2008257a.html)|
It seems to me that the less risky way to address sulfite irritation is to help the body break down sulfite into sulfate (via support of the enzyme sulfite oxidase) and pass sulfite out of the gastrointestinal tract more quickly (via measures to speed gastric emptying) rather than working to block sulfite's effects on the 5-HT3 receptors, for the 5-HT3 receptors have other jobs to do in the body (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4417587/, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4263148/, https://www.ncbi.nlm.nih.gov/pubmed/27401036, https://www.ncbi.nlm.nih.gov/pubmed/25986676, https://www.ncbi.nlm.nih.gov/pubmed/25196083) besides mediate vomiting. Also, there will still be sulfite in the stomach and intestine which could continue to damage the mucosal lining. Unless my theory is disproven, I cannot get behind widespread use of Zofran for NVP.