Three products are currently available in the US for treatment of high-risk,1 nonhospitalized adults with mild to moderate COVID-19: oral ritonavir-boosted nirmatrelvir (Paxlovid), IV remdesivir (Veklury), and oral molnupiravir (Lagevrio). Remdesivir is FDA-approved for such use; nirmatrelvir/ritonavir and molnupiravir are available under an FDA Emergency Use Authorization. Because the pivotal clinical trials of these products for outpatient use were conducted in patients who were not vaccinated against COVID-19, some clinicians have questioned whether they can benefit vaccinated outpatients.

Influenza is generally a self-limited illness, but complications such as pneumonia, respiratory failure, and death can occur, especially in patients at increased risk for influenza complications (see Table 1). Antiviral drugs recommended for treatment and chemoprophylaxis of influenza this season are listed in Table 2. Updated information on influenza activity and antiviral resistance is available from the CDC at www.cdc.gov/flu. None of the drugs that are FDA-approved for treatment of influenza have clinically relevant antiviral activity against SARS-CoV-2.

View the Comparison Chart: Antiviral Drugs for Influenza for 2022-2023

Maribavir (Livtencity – Takeda), an oral cytomegalovirus (CMV) pUL97 kinase inhibitor, has been approved by the FDA for treatment of post-transplant CMV infection refractory to standard antiviral therapy in patients ≥12 years old who weigh at least 35 kg.

On December 22, 2021, the FDA issued an Emergency Use Authorization (EUA) for the investigational antiviral drug nirmatrelvir copackaged with the HIV-1 protease inhibitor ritonavir (Paxlovid – Pfizer) for oral treatment of mild to moderate COVID-19 in outpatients ≥12 years old who weigh at least 40 kg and are at high risk of progressing to severe disease, including hospitalization or death. Paxlovid was the first oral antiviral drug to be authorized in the US for treatment of COVID-19; Merck's oral antiviral drug molnupiravir was granted an EUA for treatment of COVID-19 on December 23, 2021. The IV antiviral drug remdesivir (Veklury) was approved by the FDA in 2020 for treatment of COVID-19 in hospitalized patients.

The investigational oral antiviral drug molnupiravir (Merck/Ridgeback Biotherapeutics) was granted an FDA Emergency Use Authorization (EUA) on December 23, 2021 for treatment of mild to moderate COVID-19 in outpatients ≥18 years old who are at high risk of progressing to severe disease, including hospitalization or death (see Table 1), and for whom alternative treatment options are not available or clinically appropriate. Paxlovid (Pfizer), nirmatrelvir copackaged with ritonavir, was granted an EUA on December 22, 2021. The IV antiviral drug remdesivir (Veklury) was approved by the FDA in 2020 for treatment of COVID-19 in hospitalized patients.

Influenza is generally a self-limited illness, but complications such as pneumonia, respiratory failure, and death can occur, especially in patients at higher risk for complications (see Table 1). Antiviral drugs recommended for treatment and chemoprophylaxis of influenza this season are listed in Table 2. Updated information on influenza activity and antiviral resistance is available from the CDC at www.cdc.gov/flu.

View the Comparison Chart: Antiviral Drugs for Influenza for 2021-2022

Influenza is generally a self-limited illness, but complications such as pneumonia, respiratory failure, and death can occur, especially in patients at increased risk for influenza complications (see Table 1). Antiviral drugs recommended for treatment and chemoprophylaxis of influenza this season are listed in Table 2. Updated information on influenza activity and antiviral resistance is available from the CDC at www.cdc.gov/flu.

View the Comparison Chart: Antiviral Drugs for Influenza

Remdesivir (Veklury – Gilead), an investigational antiviral drug administered by IV infusion, is now available through an FDA Emergency Use Authorization (EUA) for treatment of COVID-19 in all hospitalized patients. An earlier EUA limited use of the drug to patients hospitalized with severe disease.

Healthcare providers are often asked if drugs can be used past their expiration date. Because of legal restrictions and liability concerns, manufacturers do not sanction such use and usually do not comment on the safety or effectiveness of their products beyond the date on the label. Since our last article on this subject, more data have become available.

Influenza is generally a self-limited illness, but pneumonia, respiratory failure, and death can occur. FDA-approved antiviral drugs for influenza are listed in Table 2. The neuraminidase inhibitors oseltamivir (Tamiflu, and generics), which is taken orally, and zanamivir (Relenza), which is inhaled, are approved for prophylaxis and treatment of acute uncomplicated influenza. The IV neuraminidase inhibitor peramivir (Rapivab) and the oral polymerase acidic (PA) endonuclease inhibitor baloxavir marboxil (Xofluza) are approved only for treatment. All of these drugs are active against both influenza A and influenza B viruses. Updated information on influenza activity and antiviral resistance is available from the CDC at www.cdc.gov/flu.

The drugs of choice for treatment of viral infections (other than HIV) and their dosages are listed in Tables 1-6 on the pages that follow. Some of the indications and dosages recommended here have not been approved by the FDA. Vaccines used for the prevention of viral infections are discussed elsewhere.

Antiviral drugs can be used for treatment and prophylaxis of influenza. In recent years, the susceptibility of circulating influenza strains has evolved rapidly and treatment recommendations have changed during the influenza season. The CDC influenza website provides frequently updated information on antiviral resistance (www.cdc.gov/flu).

Antiviral drugs can be used for treatment of patients with influenza and for prophylaxis when exposure to the disease occurs before or less than 2 weeks after vaccination. They can also be used to control institutional outbreaks of influenza. In recent years, the susceptibility of circulating influenza strains has evolved rapidly and treatment recommendations have changed during the influenza season. The CDC influenza web site provides frequently updated information on antiviral resistance (www.cdc.gov/flu)

Since publication of our recent article on antiviral drugs for influenza, increased levels of resistance to oseltamivir (Tamiflu) have been detected in influenza A H1N1 strains.

Antiviral drugs are an important adjunct to influenza vaccination and can be used for treatment of patients with influenza within 2 days of the onset of illness and for chemoprophylaxis of influenza exposures that occur before or less than 2 weeks after vaccination. Patients who are immunocompromised or immunosuppressed, have pulmonary disease, are elderly or are healthcare workers may also be appropriate candidates for chemoprophylaxis.

Antiviral prophylaxis is indicated for influenza exposures that occur before (or less than 2 weeks after) vaccination with inactivated vaccine, or in years when circulating strains differ from those included in the vaccine. Antiviral drugs can also be used for treatment of patients who develop symptoms of influenza, regardless of vaccination status.
Please see Update: Influenza Resistance to Amantadine and Rimantadine

The drugs of choice for non-HIV viral infections are listed in the table that on page 30. The treatment of HIV infections was discussed in the Medical Letter issue of Spetember 3, 1993 (volume 35, page 79).