Updated: September 11, 2009

 

Even though few strains of novel Influenza A (H1N1) 2009 have shown resistance to antivirals, most of them remain susceptible to neuraminidase inhibitors, ie, Oseltamivir (Tamiflu) and Zanamivir (Relenza).

 

Remember that to be most effective antivirals must be started early (within 48 hours of initiation of symptoms) and even then the effect is modest (36 hours shortening of duration of symptoms). Hence, since most patients with mild symptoms will recover uneventfully, antivirals either for treatment or prophylaxis are best reserved for those with severe symptoms or those who belong to any group that put them at high-risk for severe influenza illness, if infected.

These high-risk groups are:

·         Children younger than 5 years old.

·         Chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematologic (including sickle cell disease), neurologic, neuromuscular, or metabolic disorders (including diabetes mellitus).

·         Immunosuppression, including that caused by medications or by HIV.

·         Pregnant women.

·         Persons younger than 19 years of age who are receiving long-term aspirin therapy.

·         Residents of nursing homes and other chronic-care facilities.

·         Adults 65 years of age and older.

 

In these situations, the doses of antivirals to use are:

Oseltamivir (Tamiflu):

Presentation: oral suspension 12 mg/ml (25 ml); caps 75 mg.
For treatment, use below dose twice daily for 5 days.
For prophylaxis, use below dose once daily for 10 days.

            Age or weight              Dose
            < 3 months                    12 mg
            3-5 months                     20 mg
            6-11 months                   25 mg
            < 15 Kg                          30 mg
            15-23 Kg                        45 mg
            23-40 Kg                        60 mg
            > 40 Kg                         75 mg

Zanamivir (Relenza):

Presentation:     powder, 5 mg/inhalation
Dose:                10 mg (2 inhalations), same dose for all age groups
Treatment:         twice daily for 5 days; start at 7 years and older
Prophylaxis:      once daily for 10 days; start at 5 years and older

 

Sources of Information:

We will keep this site updated as new information becomes available, so visit us frequently. You can also e-mail Dr Rodolfo E Bégué (rbegue@lsuhsc.edu) with any question (we will post your question and the answer) or call Dr Bégué at (504) 896-9820. You can also find all sorts of information at CDC’s website (www.flu.gov). Dr. Begue is Professor of Pediatrics, Division Head, Infectious Diseases at LSUHSC & Director, Infection Control, Children’s Hospital, New Orleans.