Key takeaways:
Tamiflu (oseltamivir) backorders may affect specific capsule strengths, the oral suspension, or even certain manufacturers. But other formulations or generic products may still be available.
When the commercial oral suspension is unavailable, pharmacies can often compound a suspension from capsules using FDA-approved instructions with prescriber authorization.
Alternative therapies, including Xofluza (baloxavir marboxil), Relenza (zanamivir), and Rapivab (peramivir) may be appropriate for some patients.
Regularly monitoring drug shortage resources can help healthcare professionals stay ahead of Tamiflu backorders.
Seasonal influenza continues to place a substantial burden on the U.S. healthcare system each year. Prompt antiviral treatment can shorten symptom duration and reduce the risk of influenza-related complications. Because antiviral therapy is most effective when started within 48 hours of symptom onset, timely access to treatment is essential.
Tamiflu (oseltamivir) is the most prescribed antiviral medication for influenza treatment. However, during periods of high influenza activity, increased demand can cause strain on medication suppliers. This can lead to Tamiflu shortages and temporary backorders of one or more formulations. Understanding why Tamiflu shortages occur, how these shortages affect patient care, and what alternatives are available can help healthcare professionals minimize treatment delays.
Backorder causes
Drug shortages rarely have a single cause. Instead, they often result from a combination of factors. Several factors may contribute to a Tamiflu shortage, including:
Increased influenza activity that rapidly increases demand
Regional spikes in influenza activity that exceed local inventory
Prolonged flu seasons or flu seasons that begin earlier than anticipated
Supply chain interruptions
Manufacturing quality issues
Influenza activity can increase rapidly during peak season, and even temporary disruptions in manufacturing or distribution can lead to local and national Tamiflu shortages. Because antiviral therapy is most effective within 48 hours of symptom onset, minimizing treatment delays is essential. Knowing how to respond to a Tamiflu backorder can help healthcare professionals ensure timely treatment for their patients.
What to do
Before changing therapy, consider whether another formulation or manufacturer is available. Because shortages can sometimes affect only certain products, patients may still be able to receive Tamiflu without switching to a different antiviral medication. Depending on local inventory, options may include:
Checking nearby pharmacies for available inventory.
Using a different Tamiflu capsule strength. Capsules are available in 30 mg, 45 mg, and 75 mg strengths.
Switching from oral suspension to capsules in patients who can swallow capsules.
Prescribing generic Tamiflu (oseltamivir), if available.
Authorizing pharmacists to compound an oral suspension from capsules when the commercial suspension is unavailable.
Compounding instructions
When the commercially available Tamiflu suspension is unavailable, pharmacies can often prepare an oral suspension from Tamiflu capsules using FDA-approved compounding instructions.
Most pharmacies require the prescriber’s authorization before compounding a Tamiflu suspension. Including substitution authorization on the original prescription may eliminate the need for clarification.
For example, prescribers may consider adding language such as, “may substitute with compounded Tamiflu suspension if the commercial suspension is unavailable.” This should allow pharmacies to proceed with filling the prescription without needing to obtain verbal authorization. However, requirements may vary based on individual pharmacy policies and state regulations.
Tamiflu alternatives
There are currently four FDA-approved antiviral treatments for influenza, including Tamiflu. If Tamiflu is unavailable, other influenza antiviral medications may be appropriate, depending on the patient’s illness severity, age, pregnancy status, and comorbidities.
Xofluza (baloxavir marboxil)
Xofluza is administered as a single oral dose, available as tablets or suspension.
Indications:
Xofluza is approved to treat influenza in patients 5 years and older who have been symptomatic for no more than 48 hours, and who are otherwise in good health or at high risk of developing influenza-related complications. Xofluza is not currently recommended in pregnant or postpartum women due to a lack of safety and efficacy data.
Xofluza is also approved for post-exposure prophylaxis of influenza in people 5 years and older.
In June 2026, the FDA approved the first generic version (oral only) of Xofluza (baloxavir marboxil), providing healthcare professionals with access to an additional treatment option during periods of high demand or Tamiflu shortages.
Relenza (zanamivir)
Relenza is a brand-name-only inhaled powder approved to treat acute, uncomplicated illness due to influenza A and B infections.
Indications:
Relenza is approved to treat influenza in patients 7 years or older who have been symptomatic for no more than 2 days.
It’s also approved for post-exposure prophylaxis of influenza in people 5 years and older without underlying airway disease.
Relenza carries a risk of serious bronchospasm in patients with underlying airway disease, such as asthma or chronic obstructive pulmonary disease (COPD), and is generally not recommended in these patients.
Resources
Healthcare professionals can proactively monitor Tamiflu availability using the following sources:
American Society of Health-System Pharmacists (ASHP) drug shortages resource: Provides real-time updates on drug shortages, available products, estimated resupply dates, and management strategies for healthcare professionals.
FDA drug shortages database: Provides easy access to information about drugs currently in shortage. The database also includes information on resolved shortages, discontinued drug products, and resources. Patients, organizations, and healthcare professionals can notify the FDA of a suspected drug shortage by emailing drugshortages@fda.hhs.gov or by using the public reporting portal.
The bottom line
Tamiflu (oseltamivir) backorders can affect capsules, oral suspension, or even specific manufacturers. Fortunately, backorders don’t always mean that all formulations are unavailable. Alternative manufacturers, compounded suspension, or alternative antiviral medications may still be appropriate to prevent treatment delays.
When the Tamiflu commercial suspension is unavailable, pharmacists can often compound a suspension using FDA-approved instructions. Prescribers can include authorization to substitute with a compounded suspension on the original prescription. This may help avoid clarification calls and allow treatment to begin sooner.
Healthcare professionals should also be familiar with alternative treatment options, including Xofluza (also available as generic baloxavir marboxil) and Relenza (zanamivir). Additionally, monitoring trusted drug shortage resources throughout flu season can help healthcare professionals anticipate supply issues before they affect patient care.
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References
Centers for Disease Control and Prevention. (2026). About estimated flu burden.
CDC Yellow Book. (2025). Influenza. Centers for Disease Control and Prevention.
Chow, E. J., et al. (2021). Clinical effectiveness and safety of antivirals for influenza in pregnancy. Open Forum Infectious Diseases.
Genentech. (2025). Tamiflu- oseltamivir phosphate capsule; Tamiflu- oseltamivir phosphate powder, for suspension [package insert]. DailyMed.
Genentech. (2025). Xofluza- baloxavir marboxil tablet, film coated; baloxavir marboxil granule, for solution; baloxavir marboxil granule, for suspension [package insert]. DailyMed.
GlaxoSmithKline. (2023). Relenza- zanamivir powder [package insert]. DailyMed.
Rothberg, M. B., et al. (2008). Complications of viral influenza. The American Journal of Medicine.
U.S. Food and Drug Administration. (n.a.). Current and resolved drug shortages and discontinuations reported to FDA.
U.S. Food and Drug Administration. (2024). Frequently asked questions about drug shortages.
U.S. Food and Drug Administration. (2026). FDA approves first single-dose generic treatment for influenza.
