Influenza medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Influenza, commonly known as flu, is an infectious disease of birds and mammals caused by RNA viruses of the biological family Orthomyxoviridae (the influenza viruses). In humans, common symptoms of influenza infection are fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort

Further information: [[:Influenza treatment]]

Medical therapy

People with the flu are advised to get plenty of rest, drink a lot of liquids, avoid using alcohol and tobacco and, if necessary, take medications such as paracetamol (acetaminophen) to relieve the fever and muscle aches associated with the flu. Children and teenagers with flu symptoms (particularly fever) should avoid taking aspirin during an influenza infection (especially influenza type B) because doing so can lead to Reye's syndrome, a rare but potentially fatal disease of the liver. Since influenza is caused by a virus, antibiotics have no effect on the infection; unless prescribed for secondary infections such as bacterial pneumonia, they may lead to resistant bacteria. Antiviral medication is sometimes effective, but viruses can develop resistance to the standard antiviral drugs.

The two classes of anti-virals are neuraminidase inhibitors and M2 inhibitors (adamantane derivatives). Neuraminidase inhibitors are currently preferred for flu virus infections. The CDC recommended against using M2 inhibitors during the 2005–06 influenza season.

Neuraminidase inhibitors

Antiviral drugs such as oseltamivir (trade name Tamiflu) and zanamivir (trade name Relenza) are neuraminidase inhibitors that are designed to halt the spread of the virus in the body. These drugs are often effective against both influenza A and B. The Cochrane Collaboration reviewed these drugs and concluded that they reduce symptoms and complications. Different strains of influenza virus have differing degrees of resistance against these antivirals and it is impossible to predict what degree of resistance a future pandemic strain might have.

M2 inhibitors (adamantanes)

The antiviral drugs amantadine and rimantadine are designed to block a viral ion channel and prevent the virus from infecting cells. These drugs are sometimes effective against influenza A if given early in the infection, but are always ineffective against influenza B. Measured resistance to amantadine and rimantadine in American isolates of H3N2 has increased to 91% in 2005.

Antiviral Drugs

These treatments are antiviral drugs that affect the virus itself and may be used as either a prophylactic (that is, before infection) or as treatment. In general, antiviral drugs for treatment of influenza must be taken within a few days of the onset of symptoms.

Due to increasing incidence of drug resistance to amantadine and rimantadine in H3N2 during the 2005-2006 flu season in the United States, the CDC recommended the use of oseltamivir for flu prevention and the use of oseltamivir or zanamivir for flu treatment.

Approved

These prescription drugs have been approved by the US Food and Drug Administration as safe and effective.

Antiviral drugs to treat influenza

Class	Effective Against	Brand Name	Drug Name (INN)	Year Approved	Manufacturer
M2 inhibitors (adamantane derivatives)	Influenza A	Symmetrel®	Amantadine	1976	Endo Pharmaceuticals
		Flumadine®	Rimantadine	1994	Forest Laboratories
Neuraminidase inhibitors	Influenza A & B	Relenza®	Zanamivir	1999	GlaxoSmithKline
		Tamiflu®	Oseltamivir	1999	Hoffmann-La Roche
Note: Neuraminidase inhibitors are approved for prophylaxis use in children and adults.

Experimental

Peramivir is being developed by BioCryst Pharmaceuticals, but has not yet been approved for sale in the United States.

Conventional symptomatic relief

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

OTC medicines provide relief for 'flu symptoms

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.