Flu Treatment and Prevention: What Pharmacists Need to Know

Top Takeaways

• Start antivirals ASAP for high-risk patients, even if it’s after 48 hours.
• Stick with oseltamivir for most high-risk patients. Baloxavir is a one-dose option for eligible outpatients.
• Save prophylaxis for select exposed patients...and start it within 48 hours.

Patients will look to you to sort out if they need a flu antiviral...with an early surge in influenza in some parts of Canada.

Treat high-risk patients ASAP. Recommend an antiviral for suspected or confirmed flu in patients at high risk of complications...such as kids under age 5, adults 65 and up, patients who are immunocompromised or pregnant, and those with chronic conditions (diabetes, lung disease, etc).

Don’t wait for a positive test when flu is circulating...and ensure these patients still get treatment if symptoms started MORE than 48 hours ago.

But treatment is optional for otherwise healthy patients. It can shorten symptoms by about a day if started within 48 hours.

Stick with oseltamivir for most high-risk patients. It has the most data and is preferred in pregnancy, severe illness, and young kids. It costs about $11 for 5 days. Advise taking it with food...to limit nausea.

Verify adolescent and adult doses...usually 75 mg twice daily for 5 days. Keep in mind to reduce the dose if eGFR is 60 mL/min or less.

Stay tuned. There’s a preprint study that shows oseltamivir isn’t effective and may worsen outcomes in patients who are critically ill with influenza...versus placebo. We’re awaiting peer review and publication.

Consider baloxavir as a one-dose option. It seems to work as well as oseltamivir for uncomplicated flu...with less nausea. But it’s only for patients 12 and up...and it costs about $175 per 40 mg dose.

Keep in mind, it’s not recommended in pregnancy, breastfeeding, or patients who are severely ill or immunocompromised. Data are lacking.

Tell patients not to take it with dairy, antacids, or supplements with calcium, iron, magnesium, or zinc...these can lower absorption.

Reserve inhaled zanamivir (Relenza) for patients age 7 and up when oral options aren’t feasible...and avoid it in asthma or COPD.

Save post-exposure prophylaxis for select patients. Advise it for exposed residents during institutional outbreaks...unvaccinated household contacts of a high-risk person...and patients who are immunocompromised.

Recommend oseltamivir 75 mg ONCE daily for adults. Point out that duration is usually 7 to 10 days in most cases.

Encourage flu vaccines as long as flu is circulating...along with fluids, rest, handwashing, staying home when sick, etc.

Get our chart, Antivirals for Influenza, for med considerations and dosing...and use our Flu Vaccines for 2026-2027 chart for guidance.

• Chart: Antivirals for Influenza
• Chart: Flu Vaccines for 2026-27 (Canada)