Basic Product Information
Generic Name (INN) | Oseltamivir phosphate |
| Canadian Brand Names / Trade Names | Tamiflu (Hoffmann-La Roche Limited); generic versions include ACH-Oseltamivir Phosphate, Jamp Oseltamivir, NAT-Oseltamivir, Sandoz Oseltamivir, and others |
| ATC Code | J05AH02 |
| Available Dosage Forms and Strengths | Capsules: 30 mg, 45 mg, and 75 mg oseltamivir (as oseltamivir phosphate). Powder for oral suspension: 6 mg/mL oseltamivir after reconstitution |
| Manufacturers | Hoffmann-La Roche Limited (Tamiflu); Natco Pharma (Canada) Inc. (NAT-Oseltamivir); Jamp Pharma Corporation (Jamp Oseltamivir); Sandoz Canada Incorporated (Sandoz Oseltamivir); Apotex Inc. (ACH-Oseltamivir Phosphate) |
| Prescription Status | Available by prescription only in Canada |
Mechanism of Action
For specialists: Oseltamivir phosphate is an ethyl ester prodrug. It is hydrolyzed by esterases to its active form, oseltamivir carboxylate. This active metabolite is a strong and selective inhibitor of influenza virus neuraminidase enzymes, which are glycoproteins present on the surface of influenza A and B viruses. Neuraminidase is needed for newly formed virus particles to be released from infected cells and for the virus to spread in the respiratory tract. Oseltamivir carboxylate inhibits influenza A and B neuraminidases in vitro. Influenza B viruses are less susceptible to oseltamivir than influenza A viruses (by 10- to 20-fold), so treatment may be less effective against influenza B.
Pharmacokinetics
- Absorption: Oseltamivir is well absorbed from the gastrointestinal tract after oral administration. The active metabolite is not further metabolized and is almost completely eliminated in urine.
- Metabolism: About 90% of oseltamivir is converted in the liver to oseltamivir carboxylate, the active antiviral molecule. This conversion is carried out by esterases found mainly in the liver. There is little potential for drug-drug interactions because oseltamivir does not affect cytochrome P450 enzymes.
- Elimination: The apparent elimination half-life of the active compound (oseltamivir carboxylate) in plasma is 6 to 10 hours in healthy subjects and is similar in older adults. No dose adjustment is needed for age-related changes alone. Oseltamivir carboxylate is eliminated mainly by renal excretion through glomerular filtration and renal tubular secretion (more than 90%).
- Onset of Action: Antiviral activity starts after the prodrug is converted to its active form. For the best chance of benefit, treatment should begin as soon as possible, ideally no later than 48 hours after symptoms start.
- Duration of Action: The therapeutic effect is maintained with continued twice-daily dosing. The standard treatment course is 5 days. Prophylaxis courses are usually 10 days, or up to 14 days during institutional outbreaks.
Uses in Daily Life and Best Practice Advice
In Canada, oseltamivir is prescribed to treat and prevent influenza A and B. Your doctor will decide the right use and dose based on your medical situation.
- Typical Uses: Treatment of uncomplicated acute illness caused by influenza in adults and adolescents (13 years and older) who have had symptoms for no more than 2 days. It is also indicated to treat uncomplicated acute influenza in children 1 year and older who have had symptoms for no more than 2 days. Prevention (prophylaxis) of influenza A and B in adults and children 1 year and older who are close contacts of someone with characteristic influenza symptoms.
- Administration: Capsules are taken by mouth with or without food. Taking oseltamivir with food may help reduce nausea and vomiting. The oral suspension should be shaken well before each dose is measured. Treatment should start as early as possible, ideally within 48 hours of symptom onset.
- Monitoring: If symptoms do not improve or get worse, contact your doctor. Do not use longer than the prescribed duration without medical advice. During outbreaks in long-term care facilities, prophylaxis may continue until the outbreak is declared over.
- Do Not Stop Without Medical Advice: Finish the full course as prescribed, even if you begin to feel better, to make sure the virus is fully cleared.
Morning vs. Evening Dosing
Oseltamivir is usually taken twice daily for treatment. There is no specific clinical recommendation for morning versus evening dosing. Doses are generally taken about 12 hours apart. For prophylaxis, the dose is taken once daily. Always follow the schedule your doctor recommends.
- Twice Daily (Treatment): The treatment dose is taken twice daily for 5 days.
- Once Daily (Prophylaxis): The prophylactic dose is taken once daily.
- Consistency: Take oseltamivir at the same times each day to keep effects consistent.
- Missed Dose: If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take two doses at the same time.
Administration With or Without Food
Oseltamivir can be taken with or without food. Taking it with food may help reduce stomach upset, especially nausea and vomiting, which are the most common side effects.
- Take the capsule with a full glass of water.
- Oseltamivir can be taken with or without food.
- Taking it with food may reduce nausea and vomiting.
- For the oral suspension, shake the bottle well before measuring each dose with the provided measuring device.
- If you have hereditary fructose intolerance, note that the oral suspension contains sorbitol and should not be used.
Interaction Warnings
| Interaction | Advice |
|---|---|
| Probenecid | Taking probenecid with oseltamivir increases exposure to oseltamivir carboxylate about twofold because of increased active anionic tubular secretion in the kidney. The dosage may need to be adjusted. |
| Clopidogrel (Plavix) | A laboratory study suggested that clopidogrel prevents the conversion of oseltamivir to its active metabolite, oseltamivir carboxylate. If given with clopidogrel, oseltamivir may lose its therapeutic effect. |
| Warfarin | Increased INR has been reported in patients taking oseltamivir and warfarin together. Monitor INR closely if both are used. |
| Amantadine, Triamterene, Hydrochlorothiazide, Trimethoprim-Sulfamethoxazole | Drug interactions have been observed when these medicines are taken with oseltamivir. |
| Alcohol | No direct interaction has been established, but alcohol may worsen dehydration and gastrointestinal symptoms. Avoid drinking too much alcohol. |
Indications for Oseltamivir
| Condition | Status |
|---|---|
| Treatment of uncomplicated influenza A and B in adults and adolescents (≥13 years) who have had symptoms for no more than 2 days | Approved (Health Canada) |
| Treatment of uncomplicated influenza in children 1 year and older who have had symptoms for no more than 2 days | Approved (Health Canada) |
| Prevention (prophylaxis) of influenza A and B in adults and children 1 year and older who are close contacts of someone with characteristic influenza symptoms | Approved (Health Canada) |
| Treatment of avian influenza (AI) | Off-label / Recommended for AI because of wide availability and efficacy |
"Off-label" means use outside the officially approved indication, usually based on current medical guidelines and scientific evidence.
Guidelines for Correct Use
- Take oseltamivir exactly as your doctor prescribes. Do not change your dose without medical advice.
- Take the capsule with a full glass of water, with or without food. Taking it with food may reduce nausea and vomiting.
- For the oral suspension, shake the bottle well before measuring each dose with the provided measuring device.
- Complete the full course of treatment as prescribed, even if you start to feel better.
- Treatment should begin as early as possible, ideally within 48 hours of symptom onset.
- Do not use longer than the prescribed duration without medical advice.
- Tell every healthcare provider (including dentists, surgeons, and pharmacists) that you are taking oseltamivir.
- If you are pregnant, planning to become pregnant, or breastfeeding, talk to your doctor before use.
- If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not double the dose.
- Store at room temperature (15–30°C) in a dry place. Keep out of reach of children.
Alternative Treatment Options
- Zanamivir (Relenza): An inhaled neuraminidase inhibitor approved in Canada for treatment and prophylaxis of influenza A and B. It is taken by oral inhalation using a diskhaler device. It is not recommended for patients with underlying respiratory disease such as asthma or COPD because of the risk of bronchospasm.
- Peramivir (Rapivab): An intravenous neuraminidase inhibitor approved in some jurisdictions for treatment of acute uncomplicated influenza. It is given as a single intravenous dose by a healthcare professional. Availability in Canada may be limited.
- Baloxavir marboxil (Xofluza): A cap-dependent endonuclease inhibitor approved in some jurisdictions for treatment of acute uncomplicated influenza. It is given as a single oral dose. Availability in Canada may be limited.
- Amantadine: An older antiviral active against influenza A only. It is no longer routinely recommended because of widespread viral resistance. It is avoided in treatment to prevent resistance.
- Rimantadine: An older antiviral with a similar profile to amantadine. It is also limited by viral resistance and is not recommended for routine use.
Comparison: Oseltamivir is the most widely used and available antiviral for influenza in Canada. It differs from zanamivir by being oral and by being approved for children 1 year and older. Zanamivir is inhaled and may be preferred for patients who cannot tolerate oral medicine, but it is not recommended for those with underlying respiratory disease. Baloxavir and peramivir are newer agents that offer the convenience of single-dose regimens, but their availability in Canada may be limited and they are generally more expensive. Oseltamivir remains the preferred antiviral for avian influenza because of its wide availability, efficacy, and safety profile. Your doctor will choose the best option for your condition.
Legal Status, Registration, and Coverage in Canada
- Registration: Oseltamivir phosphate is authorized for sale in Canada by Health Canada as a prescription drug. Tamiflu (Hoffmann-La Roche Limited) has DIN 02381842 for the 6 mg/mL oral suspension and DIN 02304848 for the 30 mg capsule. Generic formulations include ACH-Oseltamivir Phosphate (DIN 02536900), Jamp Oseltamivir (DIN 02497409 for 30 mg, DIN 02497425 for 75 mg), NAT-Oseltamivir (DIN 02472635 for 30 mg, DIN 02472643 for 45 mg, DIN 02499894 for 6 mg/mL suspension), and Sandoz Oseltamivir (DIN 02504006).
- Prescription Status: Prescription only in Canada.
- Coverage: Coverage varies by province and territory. In Ontario, oseltamivir is listed on the Ontario Drug Benefit (ODB) formulary as a Limited Use benefit, with a drug benefit price of $2.1150 per 30 mg capsule and $3.2540 per 45 mg capsule. In Quebec, oseltamivir capsules for influenza treatment are provided free of charge to eligible Quebec residents under a government program; the guaranteed selling price for 30 mg, 45 mg, and 75 mg capsules is $1.55, $2.39, and $3.23 respectively, and a 5-day treatment course for adults costs $31. In British Columbia, oseltamivir is covered under PharmaCare for treatment and prophylaxis of influenza A and B during outbreaks among permanent residents of licensed long-term care facilities. Generic formulations are generally more affordable than the brand-name product.
- Pharmacovigilance: Adverse reactions should be reported to Health Canada's MedEffect Canada program.
Recent Research and Clinical Guidelines (2022–2026)
- A critical shortage of oseltamivir powder for oral suspension occurred in Canada in early 2026 because of higher-than-expected demand during the influenza season. Health Canada allowed exceptional importation of US-labelled oseltamivir phosphate for oral suspension (6 mg/mL) to help reduce the shortage. Supply constraints were expected to continue for the rest of the flu season.
- A shortage of Tamiflu 75 mg capsules was reported in January 2026 due to increased demand related to influenza spread in Canada. The shortage was resolved in February 2026.
- Current evidence shows that resistance to neuraminidase inhibitors such as oseltamivir remains rare and has not been consistently linked to clinically meaningful adverse patient outcomes. During the 2021–2022 influenza season, 100% of tested influenza viruses were sensitive to oseltamivir. In the 2019–2020 season, 99.6% of tested influenza A (H1N1) viruses were sensitive to oseltamivir.
- Oseltamivir is the preferred antiviral for avian influenza (AI) because of its wide availability, efficacy, and safety profile.
- Guidelines from AMMI Canada and public health authorities continue to recommend early oseltamivir for influenza treatment, especially in high-risk groups such as people 65 years and older, residents of long-term care facilities, and those with underlying medical conditions. Treatment is recommended for at-risk individuals even if more than 48 hours have passed between illness onset and antiviral administration.
- In long-term care facilities during confirmed influenza outbreaks, oseltamivir prophylaxis is recommended for all residents, regardless of vaccination status, and should continue until the outbreak is declared over (usually 7 days after symptom onset in the last case). Reimbursement for prophylaxis and treatment in residents is available only during public health-confirmed influenza outbreaks, with supply limited to a maximum of 6 weeks for prophylaxis and 5 days for treatment.
Availability and Supply in Canada
| Packaging Format | Typical Price (CAD, per unit) | Availability |
|---|---|---|
| Tamiflu 30 mg capsule (brand) | About $2.12 per capsule (ODB unit price) | Available at pharmacies across Canada; prescription required |
| Tamiflu 45 mg capsule (brand) | About $3.25 per capsule (ODB unit price) | Available at pharmacies; prescription required |
| Tamiflu 75 mg capsule (brand) | About $4.57 per capsule (NLPDP list price); $4.20 per capsule (historical list price) | Available at pharmacies; prescription required. Shortage reported in January 2026, resolved February 2026. |
| Generic oseltamivir 30 mg, 45 mg, 75 mg capsules | Price varies; check with pharmacy | Available at pharmacies; multiple generic manufacturers. Interchangeable with Tamiflu. |
| Tamiflu oral suspension 6 mg/mL | Price varies; check with pharmacy | Critical shortage in Canada as of February 2026; exceptional importation of US-labelled product authorized. Very short supply expected for the rest of the flu season. |
Prices and availability may vary by province, territory, and pharmacy. Generic oseltamivir capsules are widely available in Canada and are generally more affordable than the brand-name product. The oral suspension is in critical shortage as of early 2026, and Health Canada has permitted exceptional importation of US-labelled product. In Quebec, oseltamivir capsules for influenza treatment are provided free of charge to eligible residents. Check with your local pharmacy for current pricing and availability. https://thebigsource.blogspot.com/2026/10/tamiflu-oseltamivir-my-experience.html
Frequently Asked Questions (FAQ)
- What is Tamiflu used for?
Tamiflu (oseltamivir) is used to treat influenza (flu) in adults and children 1 year and older who have had symptoms for no more than 2 days. It is also used to prevent influenza in people who have been in close contact with someone who has the flu. - How long does Tamiflu take to work?
Tamiflu starts working after it is converted to its active form in the body. For best results, it should be started within 48 hours of the first symptoms. It helps shorten the illness by about 1 to 1.5 days and reduces symptom severity. - What is the correct dose of Tamiflu?
For adults and adolescents 13 years and older, the treatment dose is 75 mg twice daily for 5 days. The prophylaxis dose is 75 mg once daily for 10 days (or longer during outbreaks). For children, the dose is based on body weight. Your doctor will determine the right dose for your condition. - Can I take Tamiflu with food?
Yes. Tamiflu can be taken with or without food. Taking it with food may help reduce nausea and vomiting, which are the most common side effects. - What should I do if I miss a dose?
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take two doses at the same time. - Can I drink alcohol while taking Tamiflu?
No direct interaction has been established, but alcohol may worsen dehydration and gastrointestinal symptoms. Avoid excessive alcohol while recovering from influenza. - What are the serious side effects of Tamiflu?
Serious side effects include lower gastrointestinal bleeding, severe skin reactions (such as Stevens-Johnson syndrome), neuropsychiatric events (confusion, hallucinations, seizures), and severe allergic reactions. Seek immediate medical attention if you experience these symptoms. - Is Tamiflu safe during pregnancy?
Oseltamivir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Insufficient data are available about possible toxic effects on the fetus. Pregnant women are at higher risk of complications from influenza, so treatment may be recommended. Consult your doctor if you are pregnant or planning to become pregnant. - Is Tamiflu safe during breastfeeding?
Oseltamivir may be considered for nursing women when the potential benefit to the mother justifies the potential risk to the nursing infant. Limited data show that oseltamivir and the active metabolite are detected in breast milk at low levels. Consult your doctor before use. - Are there generic versions of Tamiflu available in Canada?
Yes. Generic oseltamivir capsules are widely available in Canada from multiple manufacturers, including Natco Pharma (NAT-Oseltamivir), Jamp Pharma (Jamp Oseltamivir), Sandoz Canada (Sandoz Oseltamivir), and Apotex (ACH-Oseltamivir Phosphate). Generic versions are generally more affordable than the brand-name product. - What is the difference between Tamiflu and the flu vaccine?
Tamiflu is an antiviral medicine used to treat or prevent influenza after exposure. The flu vaccine is given to prevent influenza by stimulating your immune system before you are exposed. Tamiflu is not a substitute for annual influenza vaccination. - Is Tamiflu covered by Canadian health insurance?
Coverage varies by province and territory. In Ontario, oseltamivir is listed on the ODB formulary as a Limited Use benefit. In Quebec, oseltamivir capsules for influenza treatment are provided free of charge to eligible residents. In British Columbia, coverage is available for residents of long-term care facilities during confirmed outbreaks. Check with your provincial drug plan and private insurance provider for coverage details.
