Influenza medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]

Overview

Antiviral drugs can lessen symptoms and shorten the time of the disease by 1 or 2 days. They also can prevent serious flu complications, such as pneumonia. For people with a high risk medical condition, treatment with an antiviral drug can mean the difference between having milder illness instead of very serious illness that could result in a hospital stay. The two main antivirals used in the treatment and prevention of influenza are oseltamivir and zanamivir. Symptomatic therapy is also important to overcome the symptoms of influenza, this include analgesics, antihistamines, decongestants and cough suppressants.

Medical Therapy

Antiviral Medications

Persons at higher risk for influenza complications recommended for antiviral treatment include:
Children aged younger than 2 years
Adults aged 65 years and older
Persons with the following comorbidities: Chronic pulmonary (including asthma) Cardiovascular (except hypertension alone) Renal, hepatic, hematological (including sickle cell disease) or metabolic disorders (including diabetes mellitus) Neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy, stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury)
Persons with immunosuppression, including that caused by medications or by HIV infection
Women who are pregnant or postpartum (within 2 weeks after delivery)
Persons aged younger than 19 years who are receiving long-term aspirin therapy
American Indians/Alaska Natives
Persons who are morbidly obese (BMI > 40)
Residents of nursing homes and other chronic-care facilities.

• Antiviral medications with activity against influenza viruses are an important adjunct to influenza vaccine in the control of influenza.
• Influenza antiviral prescription drugs can be used to treat influenza or to prevent influenza.
• Four licensed prescription influenza antiviral agents are available in the United States.
• Two FDA-approved influenza antiviral medications are recommended for use in the United States during the 2013-2014 influenza season:

• Oral oseltamivir (Tamiflu®)
• Inhaled zanamivir (Relenza®)

• Oseltamivir and zanamivir are chemically related antiviral medications known as neuraminidase inhibitors that have activity against both influenza A and B viruses.
• Amantadine and rimantadine are antiviral drugs in a class of medications known as adamantanes.
• Adamantanes are active against influenza A viruses, but not influenza B viruses.

Antiviral Therapy Recommendations

Antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who has any of the follwing conditions:

• Is hospitalized.
• Has severe, complicated, or progressive illness.
• Is at higher risk for influenza complications.

Drug Resistance

• Antiviral resistance to oseltamivir and zanamivir among circulating influenza viruses is currently low, but this might change.
• Also, antiviral resistance can emerge during or after treatment in certain patients, such as immunosuppressed individuals.
• As in recent past seasons, there is a high prevalence (>99%) of influenza A(H3N2) and influenza A(H1N1) (2009 H1N1) viruses resistant to adamantanes.
• Therefore, amantadine and rimantadine are not recommended for antiviral treatment or chemoprophylaxis of currently circulating influenza A viruses.

Antiviral Medications Recommended for Treatment and Chemoprophylaxis of Influenza

Antiviral Agent	Activity Against	Use	Recommended For	Not Recommended for Use in	Adverse Reactions
Oseltamivir (Tamiflu®)	Influenza A and B	Treatment	Any age	N/A	Nausea, vomiting. Sporadic, transient neuropsychiatric events (self injury or delirium) mainly reported among Japanese adolescents and adults.
		Prophylaxis	> 3 months of age	N/A
Zanamivir (Relenza®)	Influenza A and B	Treatment	> 7 years old	Patients with underlying respiratory disease, such as asthma or COPD	Allergic reactions such as oropharyngeal or facial edema. Diarrhea, nausea, sinusitis, nasal signs and symptoms, bronchitis, cough, headache, dizziness, and ear, nose and throat infections.
		Prophylaxis	> 5 years old	Patients with underlying respiratory disease, such as asthma or COPD
Table adapted from CDC

Recommended Dosage and Duration of Influenza Antiviral Medications for Treatment or Chemoprophylaxis

Antiviral Agent	Patient	Treatment (5 days)	Prophylaxis (7 days)
Oseltamivir (Tamiflu®)	Children	< 1 yr: 3 mg/kg/dose twice daily >1 yr: dose depends on weight. ≤ 15 kg: 30 mg twice a day >15 to 23 kg: 45 mg twice a day > 23 to 40 kg: 60 mg twice a day >40 kg: 75 mg twice a day	Not recommended for children < 3 months old. 3 months to 1 yr: 3 mg/kg/dose once daily >1 yr: dose depends on weight. ≤ 15 kg: 30 mg once a day >15 to 23 kg: 45 mg once a day > 23 to 40 kg: 60 mg once a day >40 kg: 75 mg once a day
	Adults	75 mg twice a day	75 mg once a day
Zanamivir (Relenza®)	Children	For children > 7 yrs old. 10 mg (2 5-mg inhalations) twice daily	For children > 7 yrs old. 10 mg (2 5-mg inhalations) once daily
	Adults	10 mg (2 5-mg inhalations) twice daily	10 mg (2 5-mg inhalations) once daily
Amantadine	Children	1 - 9 yrs: 5-8 mg/kg/day (max: 150 mg) 9 - 12 yrs: 200 mg daily, divided BID (max: 150 mg)	1 - 9 yrs: 5-8 mg/kg/day 9 - 12 yrs: 200 mg daily, divided BID
	Adults	200 mg daily	200 mg daily
Rimantadine	Children	1 - 9 yrs: 6.6 mg/kg/day, divided BID (max: 150 mg) >10 yrs: 200 mg/day, divided once or twice daily	1 - 9 yrs: 5 mg/kg once daily (max: 150 mg) >10 yrs: 200 mg/day, divided once or twice daily
	Adults	200 mg daily	200 mg daily
Table adapted from CDC and CID 2009:48

Symptomatic Therapy

Over the counter (OTC) medicines may be taken to relieve influenza symptoms, but they do not affect the virus.

Symptom(s)	OTC Medicine
Fever, Aches, Pains, Sinus pressure, Sore throat	Analgesics
Nasal congestion, Sinus pressure	Decongestants
Sinus pressure, Runny nose, Watery eyes, Cough	Antihistamines
Cough	Cough suppressant
Sore throat	Local anesthetics

• Children and teenagers with flu symptoms (particularly fever) should avoid taking aspirin as taking aspirin in the presence of influenza infection (especially Influenzavirus B) can lead to Reye's syndrome, a rare but potentially fatal disease of the liver.

Unconventional treatment

Homeopathic and other cold and flu remedies that fail to meet the regulatory requirements as drugs that treat disease, or the standards of evidence-based medicine, are sold as nutritional supplements.

They may be based on extracts of living things, but may lack documentation of their safety and effectiveness.