OseltamivirOseltamivir Phosphate

About Oseltamivir

Its active form, oseltamivir carboxylate, blocks neuraminidase, an influenza enzyme involved in releasing new virus particles; the label says there is no evidence it helps illness caused by anything other than influenza viruses. Treatment starts within 48 hours of the first flu symptoms and lasts 5 days: 75 mg twice a day for adults and adolescents 13 and older, 30 to 75 mg twice a day by weight for children 1 to 12, and 3 mg/kg twice a day for infants from 2 weeks to under 1 year. Prevention starts within 48 hours of close contact with someone who has flu, using the same dose once a day for at least 10 days in adults and adolescents and 10 days in children, or for up to 6 weeks during a community outbreak; it has not been established for infants under 1 year. Doses are lowered for reduced kidney function, and it is not recommended for end-stage kidney disease without dialysis.

There is no boxed warning. Anyone who has had a serious allergic reaction to oseltamivir or an ingredient must not take it. Anaphylaxis and serious skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, have been reported, and it is stopped if an allergic-like reaction occurs. Delirium and abnormal behavior leading to injury, sometimes fatal, have been reported after marketing in people with flu taking it, mainly children, often starting suddenly and resolving quickly. Influenza itself can cause hallucinations, delirium and abnormal behavior, the drug’s role has not been established, and the label says to watch patients closely for abnormal behavior. Serious bacterial infections can begin with flu-like symptoms or follow flu, and oseltamivir has not been shown to prevent them. Nausea, vomiting and headache are the most common side effects.

The label says it is not a substitute for early yearly flu vaccination, as recommended by the CDC’s Advisory Committee on Immunization Practices, and that because flu viruses change, prescribers weigh current information on resistance. The pharmacist mixes the suspension with water before dispensing, giving 6 mg per mL; a 75 mg dose of it contains 2 g of sorbitol, which matters for hereditary fructose intolerance. Published data suggest no increase in birth defects with use in any trimester of pregnancy, and it passes into breast milk at low levels.

Taking Oseltamivir

How to take it

Twice a day for 5 days to treat flu, or once a day to prevent it, with or without food (food may ease stomach upset). Shake the suspension well and measure each dose with an oral dispenser marked in milliliters. For anyone who cannot swallow capsules the suspension is preferred; if it is unavailable, a prescriber or pharmacist may say to mix a capsule’s contents with a sweetened liquid such as chocolate syrup. Finish the course even if you feel better.

If you miss a dose

Take it as soon as you remember. If the next dose is due in 2 hours or less, skip the missed dose and take the next one at the usual time. Do not take a double dose.

Storage

Capsules at room temperature. Once mixed, the suspension keeps up to 17 days in the refrigerator or up to 10 days at room temperature; do not freeze it. A suspension the pharmacist prepared from capsules keeps 5 weeks refrigerated or 5 days at room temperature.

Interactions to know about

Avoid the live nasal spray flu vaccine from 2 weeks before to 48 hours after oseltamivir unless medically needed; inactivated flu vaccines can be given at any time. Probenecid raises levels of the active drug, but no dose change is needed.

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 Oseltamivir differs from pharmacy to pharmacy

Generic capsules come from many makers and the suspension from several, so quotes for the same course differ by each pharmacy’s fee and markup and by whether oseltamivir is on its flat-price generic list. A prescription that names Tamiflu and blocks substitution is filled with the brand.

Children are dosed by weight, so a 60 mg dose is two 30 mg capsules and a course of suspension can take more than one bottle. A suspension a pharmacist prepares from capsules, allowed by the label only in an emergency when the commercial suspension is unavailable, is a compounded product quoted on its own.

Ways to pay less for Oseltamivir without insurance

• Check that the prescription allows a generic, unless the prescriber has a reason to require Tamiflu.
• Ask whether oseltamivir is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• For a child’s suspension, ask how many bottles the full course needs, so the quote covers all of it.
• Ask whether the pharmacy can fill it the same day, since treatment should start within 48 hours of symptoms.
• 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 Oseltamivir

1. 1.Should I take it with food to settle my stomach?
2. 2.What changes in my child’s behavior should I watch for?
3. 3.When can I have the nasal spray flu vaccine?
4. 4.Is my dose right for my kidney function?

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