Flu Antiviral Medication Comparison Tool
Select Medication to Compare
Quick Take
- Tamiflu (Oseltamivir) is a neuraminidase inhibitor taken orally.
- Relenza (Zanamivir) works the same way but is inhaled.
- Xofluza (Baloxavir marboxil) blocks a different viral enzyme and is a single‑dose pill.
- Peramivir (Rapivab) is given intravenously for severe cases.
- Choose based on symptom onset timing, administration route, side‑effect tolerance, and cost.
How Tamiflu Works
When treating flu, Tamiflu (generic name Oseltamivir) is a neuraminidase inhibitor that blocks the flu virus from spreading in the body. By binding to the neuraminidase enzyme on the surface of influenza A and B viruses, it prevents newly formed viral particles from escaping infected cells. The result is a shorter illness-usually one to two days less-if you start the drug within 48hours of symptoms.
Typical dosing is 75mg twice a day for five days. The pill is easy to swallow, which makes it popular for kids and adults alike. However, it does rely on good kidney function because the drug is cleared renally.
Alternatives Overview
Relenza (generic name Zanamivir) is an inhaled neuraminidase inhibitor. It’s delivered via a small inhaler, so you need a decent amount of lung capacity to use it properly. The advantage is that it works even in people with mild kidney issues.
Xofluza (generic name Baloxavir marboxil) is a cap‑dependent endonuclease inhibitor that stops viral mRNA synthesis. It’s a single 40mg (or 80mg for adults over 80kg) dose taken within 48hours of symptom onset. Because it attacks a different viral protein, it can be useful when resistance to neuraminidase inhibitors emerges.
Peramivir (brand name Rapivab) is an intravenous neuraminidase inhibitor administered as a single infusion. It’s reserved for hospitalized patients or those who can’t take oral or inhaled meds.
All four drugs received FDA approval for treating influenza A and B, but each carries its own set of pros and cons.
Key Comparison Points
| Attribute | Tamiflu (Oseltamivir) | Relenza (Zanamivir) | Xofluza (Baloxavir) | Peramivir (Rapivab) |
|---|---|---|---|---|
| Drug class | Neuraminidase inhibitor | Neuraminidase inhibitor | Cap‑dependent endonuclease inhibitor | Neuraminidase inhibitor |
| Administration | Oral capsule | Inhalation | Single oral dose | IV infusion |
| Typical regimen | 75mg BID ×5days | 5mg inhaled BID ×5days | One dose (40mg or 80mg) | One 600mg infusion |
| Onset window | Within 48h | Within 48h | Within 48h | Within 48h (hospital) |
| Effect on duration | 1‑2days shorter | 1‑2days shorter | ≈2days shorter | 2‑3days shorter (severe cases) |
| Common side effects | Nausea, vomiting, headache | Cough, bronchospasm, nasal irritation | Diarrhea, nausea, elevated liver enzymes | Fever, infusion‑site reactions |
| Renal considerations | Dose adjust if CrCl <30mL/min | No dose change needed | No renal dose change | Generally safe; monitor kidney |
| Cost (US, 2025 avg.) | $30‑$45 for 5‑day course | $65‑$80 for 5‑day course | $150‑$180 single dose | $350‑$400 per infusion |
Who Should Choose Which Antiviral?
Use Tamiflu if: you need an oral option, have normal kidney function, and can start treatment within the first two days of flu symptoms. It's the go‑to for most healthy adults and children over one year.
Pick Relenza when: you have mild renal impairment or prefer not to swallow pills. Asthmatics should be cautious, as the inhaler can trigger bronchospasm.
Consider Xofluza if: you want just one dose and are okay with a higher price tag. It’s also useful when flu strains show resistance to neuraminidase inhibitors-a growing concern in some regions.
Reserve Peramivir for: hospitalized patients, severe cases, or anyone unable to take oral or inhaled medications. Because it’s IV, it’s typically administered in a clinic or emergency department.
Safety, Side‑Effects & Interactions
All flu antivirals share a common safety profile: they’re generally well‑tolerated but can cause gastrointestinal upset. Tamiflu’s most frequent complaint is nausea, which can be mitigated by taking the capsule with food.
Relenza can cause respiratory irritation; patients with chronic lung disease should discuss alternatives with their doctor. Xofluza may raise liver enzymes, so a baseline liver test is recommended for people with hepatitis or heavy alcohol use.
Peramivir’s infusion can lead to fever or chills, a reaction called “infusion‑related syndrome.” Monitoring during the infusion helps keep it under control.
Drug‑drug interactions are rare, but Oseltamivir can slightly increase levels of certain anticoagulants. Always inform your pharmacist about any blood thinners, anti‑epileptics, or chronic steroids you’re taking.
Pricing, Insurance & Access
In 2025, most private insurers cover at least one flu antiviral, but formulary preferences vary. Tamiflu is often listed as a preferred generic, making it the cheapest covered option.
Relenza’s inhaler device adds to its cost, and some plans place it in a higher tier. Xofluza’s single‑dose pricing is steep, but because it avoids a five‑day course, some health plans consider it cost‑effective for high‑risk patients.
Peramivir is usually billed under the hospital outpatient coding, so patients may see a larger bill, though many insurance plans waive it for severe flu hospitalizations.
If you’re uninsured, many pharmacies offer discount cards that bring Tamiflu down to under $20. Local health departments sometimes distribute free courses during flu season, especially for seniors and pregnant women.
Bottom Line
There’s no one‑size‑fits‑all answer. If you need a cheap, easy oral pill and your kidneys are in good shape, Tamiflu comparison points straight to Tamiflu. If you can’t swallow pills or have mild kidney issues, Relenza’s inhaler is a solid backup. For a single‑dose, resistance‑proof option, Xofluza shines-if you’re okay with the price. And for severe or hospital‑bound cases, Peramivir is the IV choice.
Talk to your healthcare provider about symptom timing, any chronic conditions, and insurance coverage to pick the antiviral that fits your situation.
Frequently Asked Questions
Can I take Tamiflu if I’m pregnant?
Yes, Tamiflu is classified as Category C but has been used safely in many pregnant women. Always discuss dosing with your OB‑GYN, especially if you have kidney concerns.
How soon after exposure should I start an antiviral?
The sooner, the better. All four antivirals are most effective when begun within 48 hours of symptom onset. After that window, benefits drop sharply.
Do flu antivirals prevent infection?
No. They treat an already‑started infection. For prophylaxis-preventing flu before you get sick-some doctors prescribe a low‑dose Tamiflu regimen during a known exposure.
What if I miss a dose of Tamiflu?
Take the missed dose as soon as you remember, unless it’s almost time for the next one. Then skip the missed dose-don’t double up.
Are there flu strains resistant to Tamiflu?
Yes, some H1N1 variants have shown reduced susceptibility. In those cases, doctors may opt for Xofluza or a combination approach.
They’re just another pharma plot to keep us dependent