OndansetronOndansetron Hydrochloride

About Ondansetron

Ondansetron blocks serotonin 5-HT3 receptors, which are found on nerves from the gut and in the brain area that triggers vomiting; the label says which site matters is not certain. The label approves it to prevent nausea and vomiting from highly emetogenic cancer chemotherapy (including cisplatin at 50 mg/m² or more), from initial and repeat courses of moderately emetogenic chemotherapy, from radiation therapy to the whole body or the abdomen, and after surgery. For highly emetogenic chemotherapy, adults take a single 24 mg dose 30 minutes before; for moderately emetogenic chemotherapy, 8 mg 30 minutes before, again 8 hours later, then every 12 hours for one to two days after. Radiation regimens start with 8 mg one to two hours before treatment, and 16 mg is taken an hour before anesthesia. Oral use in children is established only for moderately emetogenic chemotherapy, from age 4 (4 mg doses under 12). With severe liver impairment the limit is 8 mg a day.

There is no boxed warning. Ondansetron must not be taken by anyone allergic to it, or with apomorphine, because the combination has caused profound low blood pressure and loss of consciousness. Allergic reactions, including anaphylaxis and bronchospasm, have been reported, including in people who have reacted to other 5-HT3 blockers. It can prolong the QT interval, and torsade de pointes has been reported, so it is avoided in congenital long QT syndrome and ECG monitoring is advised with low potassium or magnesium, heart failure, slow heart rhythms or other QT-prolonging drugs. Serotonin syndrome, sometimes fatal, has been reported, mostly with other serotonergic drugs; chest pain from reduced blood flow to the heart (myocardial ischemia) has been reported; and after abdominal surgery or during chemotherapy it can mask a bowel that has stopped moving (ileus) or a swollen stomach. Headache, tiredness, constipation and diarrhea are the most common side effects with chemotherapy, and headache and low blood oxygen (hypoxia) after surgery.

In 2012 a 32 mg single intravenous dose was removed from the label because of QT prolongation; oral doses, including the single 24 mg dose, were unchanged. The orally disintegrating tablets contain aspartame, a source of phenylalanine, which matters for people with phenylketonuria. Use for nausea and vomiting in pregnancy, or from other causes such as gastroenteritis, is not FDA-approved, and the prescriber decides; the label says published studies of birth defects after use in pregnancy have had inconsistent findings and important limitations. Every Zofran form (tablets, orally disintegrating tablets, oral solution and injection) and the Zuplenz oral film are listed by the FDA as discontinued.

Taking Ondansetron

How to take it

Take the first dose before chemotherapy (usually 30 minutes before), radiation (one to two hours before) or surgery (an hour before anesthesia), then as scheduled. Leave an orally disintegrating tablet in its blister until the dose is due, peel back the foil with dry hands rather than pushing the tablet through, and let it dissolve on the tongue, then swallow with saliva.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose. Do not take a double dose.

Storage

Tablets and orally disintegrating tablets at room temperature or in the refrigerator, away from light. Keep the solution upright at room temperature, away from light, heat and moisture. Out of reach of children.

Interactions to know about

Never with apomorphine. Other drugs that prolong the QT interval add to the heart rhythm risk, and SSRIs, SNRIs, MAO inhibitors, mirtazapine, fentanyl, tramadol, lithium and intravenous methylene blue add to the risk of serotonin syndrome.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Ondansetron differs from pharmacy to pharmacy

Ondansetron is filled with generics from several makers, so quotes for the same tablets differ mainly by each pharmacy’s fee and markup and by whether ondansetron is on its flat-price generic list. Plain tablets, orally disintegrating tablets and the solution are separate products, each quoted on its own, and a pharmacist fills the form written.

Its labeled uses are tied to a chemotherapy cycle, a radiation schedule or an operation, so the number of doses written shapes the quote.

Ways to pay less for Ondansetron without insurance

• Ask whether ondansetron is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• If you can swallow tablets, ask the prescriber whether plain tablets would suit you rather than the dissolving tablets or the solution.
• Ask the prescriber how many doses your treatment plan needs, so the quantity written matches it.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Ondansetron

1. 1.Which of my other medicines could affect my heart rhythm with this?
2. 2.Is it safe with my antidepressant, pain medicine or migraine medicine?
3. 3.When should I take each dose around my chemotherapy, radiation or surgery?
4. 4.Is it safe for me during pregnancy or breastfeeding?

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