ONDANSETRON Antiemetic, 5HT3 antagonist Availability11 Brand name Quick guide Oral liquid 4 mg/5 mL Zofran Tablet, film-coated 4 mg, 8 mg Onsetron, Zilfojim, Zofran, Zondan Multiple generics are available Orally-disintegrating tablet and wafer Onsetron ODT, Zilfojim ODT, 4 mg, 8 mg Zofran Zydis Multiple generics are available Effect of food Can be given without regard to food.1 Absorption Absorbed in the upper small intestine, colon and rectum.2 Other May reduce lower bowel motility and cause constipation. Review need in people with ileus or intestinal obstruction.1 What to do for people with enteral feeding tubes Option 1 Use the oral liquid. Stop the feed and flush the tube with 30 mL of water. Draw the required dose into an enteral syringe and dilute with at least an equal volume of water. Mix well and give into the enteral feeding tube. Flush the tube with 30 mL of water and restart the feed. Each 5 mL contains 2.1 g of sorbitol.3 May not be suitable for jejunal administration, consider using the injection. Option 2 Disperse the wafer or orally-disintegrating tablet in 10–20 mL of water in an enteral syringe. The wafer will disperse within 1 minute. Zofran wafers disperse almost instantly in 5 mL of water if required.4 See Method A for instructions. Option 3 Disperse the plain (film-coated) tablet in 10–20 mL of water in an enteral syringe. The tablet will disperse within 5 minutes. The dispersion settles rapidly, shake well and often to avoid tube blockage.4 See Method A for instructions. Option 4 Ondansetron injection can be given into the enteral feeding tube.2 Consult the prescriber 424 Don’t Rush to Crush 3rd Edition Update September 2020 . What to do for people with swallowing difficulties Option 1 Use the orally-disintegrating tablet or wafer. Place the tablet or wafer on top of the tongue and allow it to dissolve.1 Option 2 Use the oral liquid. Measure the dose using an oral dispenser or a medicine measure. Check the thickness of the liquid as it may not be suitable for some people with swallowing difficulties. Option 3 Disperse the plain (film-coated) tablet in water. The tablet will disperse within 5 minutes.4 See Method D for instructions. Option 4 Ondansetron injection may be a suitable option for some people. The injection can be mixed with orange juice and given orally.5 Consult the prescriber. REFERENCES: 1. Product information. Available from www.tga.gov.au. Accessed 28/07/20. 2. Hsyu PH, Pritchard JF, Bozigian HP, Lloyd TL, Griffin RH, Shamburek R, et al. Comparison of the pharmacokinetics of an ondansetron solution (8mg) when administered intravenously, orally, to the colon and to the rectum. Pharm Res 1994; 11: 156-9. 3. Shams S. Zofran oral liquid [email]. St Leonards, NSW: Aspen Australia; 18/02/15. 4. SHPA. Drug dispersion database; 2015, 2017. 5. Graham CL, Dukes GE, Fox JL, Kao CF, Hak LJ. Stability of ondansetron hydrochloride injection in extemporaneously prepared oral solutions. Am J Health-Syst Pharm 1993; 50: 106-8. Don’t Rush to Crush 3rd Edition Update September 2020 425.