Influenza is generally a self-limited illness, but 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 for the 2023-2024 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 2023-2024

Annual vaccination in the US against influenza A and B viruses is recommended for everyone ≥6 months old without a contraindication. Influenza vaccines that are available in the US for the 2023-2024 season are listed in Table 2.

Annual vaccination against influenza A and B viruses is recommended for everyone ≥6 months old without a contraindication.1 Available influenza vaccines for the 2021-2022 season are listed in Table 2.

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.

The drugs of choice for treatment of non-HIV viral infections with their dosages and cost are listed in Tables 1-6. Some of the indications and dosages recommended here have not been approved by the FDA. Vaccines used in the prevention of viral infections are discussed in the "Adult Immunization" issue of Treatment Guidelines.

Antiviral drugs can be used to control institutional influenza outbreaks and for prophylaxis of 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. They can also be used for early treatment of patients with influenza.

The FDA has approved over-the-counter (OTC) sales of Plan B (Duramed), an emergency contraceptive package that contains two 0.75-mg tablets of levonorgestrel, to women ≥18 years old. Younger women still require a prescription. In one trial, two levonorgestrel 0.75-mg tablets taken 12 hours apart, the first within 72 hours after unprotected intercourse, decreased the pregnancy rate to 1%, compared to an expected rate of 8% (Task Force on Postovulatory Methods of Fertility Regulation, Lancet 1998; 352:428). How high doses of a progestin taken after coitus prevent pregnancy is unclear; they may interfere with ovulation, fertilization or implantation.

Nausea and vomiting can occur. The drug will not terminate an established pregnancy. No fetal malformations have been reported after unsuccessful use.

Plan B will not be available OTC until the end of the year, according to the manufacturer, and the OTC price is not yet available. The retail price for the prescription product varies from about $25 to $40. In order to enforce the age restriction, the drug will be kept behind the pharmacist’s counter, and a valid photo ID will be required.

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Our article on Antiviral Drugs for Prophylaxis and Treatment of Influenza (Med Lett Drugs Ther 2005;47:93) mentioned possible use of amantadine (Symmetrel, and others) and rimantadine (Flumadine, and others), but warned that the incidence of resistance has increased substantially. The CDC recently issued a Health Alert (www.cdc.gov) saying that current evidence indicates that a high proportion of circulating influenza A viruses in the US are now resistant to amantadine and rimantadine and they should not be used for this indication, at least this year. Click here to go to this update article.

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

Entecavir (Baraclude - Bristol-Myers Squibb), a nucleoside analog, has been approved by the FDA for treatment of adults with active chronic hepatitis B virus (HBV) infection.

The drugs of choice for non-HIV viral infections with their dosages and cost are listed in the tables that begin on page 24. Some of the indications and dosages recommended here have not been approved by the FDA.

The first commercially available virucidal tissue, KLEENEX Anti-Viral Tissue (Kimberly-Clark), was recently introduced and is being heavily promoted to the general public. Patients may ask healthcare providers about the usefulness of these products. Theoretically, virucidal tissues could interrupt transmission of viral infections by blocking hand contamination and/or small particle aerosols from nose-blowing, sneezing and coughing.

Due to the unanticipated shortage in the US supply of inactivated influenza vaccine, many persons who normally would have received the vaccine will be unable to get it this year. Antiviral drugs can be used for prophylaxis of unvaccinated persons who are exposed to influenza, and for treatment of both vaccinated and unvaccinated patients who develop symptoms of the disease.