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Pronunciation | /zəˈnæmɪvɪər/ |
Trade names | Relenza |
AHFS/Drugs.com | Monograph |
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Routes of administration | Inhalation, intravenous |
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Pharmacokinetic data | |
Bioavailability | 2% (oral) |
Protein binding | <10% |
Metabolism | Negligible |
Elimination half-life | 2.5–5.1 hours |
Excretion | Kidney |
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ECHA InfoCard | 100.218.632 |
Chemical and physical data | |
Formula | C12H20N4O7 |
Molar mass | 332.313 g·mol−1 |
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Zanamivir is a medication used to treat and prevent influenza caused by influenza A and influenza B viruses. It is a neuraminidase inhibitor and was developed by the Australian biotech firm Biota Holdings. It was licensed to Glaxo in 1990 and approved in the US in 1999, only for use as a treatment for influenza. In 2006, it was approved for prevention of influenza A and B. [3] Zanamivir was the first neuraminidase inhibitor commercially developed. It is marketed by GlaxoSmithKline under the trade name Relenza as a powder for oral inhalation.
Zanamivir room temperature solubility in water is 36 mg/mL, in DMSO is 66 mg/mL. [4] It's insoluble in ethanol. [4]
Zanamivir is used for the treatment of infections caused by influenza A and influenza B viruses, but in otherwise-healthy individuals, benefits overall appear to be small. It decreases the risk of one's getting symptomatic, but not asymptomatic influenza. The combination of diagnostic uncertainty, the risk for virus strain resistance, possible side effects and financial cost outweigh the small benefits of zanamivir for the prophylaxis and treatment of healthy individuals. [5]
Since then, genes expressing resistance to zanamivir were found in Chinese people infected with avian influenza A H7N9 during treatment with zanamivir. [6]
In otherwise-healthy individuals, benefits overall appear to be small. [5] Zanamivir shortens the duration of symptoms of influenza-like illness (unconfirmed influenza or 'the flu') by less than a day. In children with asthma there was no clear effect on the time to first alleviation of symptoms. [7] Whether it affects the risk of one's need to be hospitalized or the risk of death is not clear. [5] There is no proof that zanamivir reduced hospitalizations or pneumonia and other complications of influenza, such as bronchitis, middle ear infection, and sinusitis. [7] Zanamivir did not reduce the risk of self reported investigator mediated pneumonia or radiologically confirmed pneumonia in adults. The effect on pneumonia in children was also not significant. [8]
Low to moderate evidence indicates it decreases the risk of one's getting influenza by 1 to 12% in those exposed. [5] Prophylaxis trials showed that zanamivir reduced the risk of symptomatic influenza in individuals and households, but there was no evidence of an effect on asymptomatic influenza or on other, influenza-like illnesses. Also there was no evidence of reduction of risk of person-to-person spread of the influenza virus. [7] The evidence for a benefit in preventing influenza is weak in children, with concerns of publication bias in the literature. [9]
As of 2009, no influenza had shown any signs of resistance in the US. [10] A meta-analysis from 2011 found that zanamivir resistance had been rarely reported. [11] Antiviral resistance can emerge during or after treatment with antivirals in certain people (e.g., immunosuppressed). [12] In 2013 genes expressing resistance to zanamivir (and oseltamivir) were found in Chinese patients infected with avian influenza A H7N9. [6]
Dosing is limited to the inhalation route. This restricts its usage, as treating asthmatics could induce bronchospasms. [13] In 2006 the Food and Drug Administration (FDA) found that breathing problems (bronchospasm), including deaths, were reported in some patients after the initial approval of Relenza. Most of these patients had asthma or chronic obstructive pulmonary disease. Relenza therefore was not recommended for treatment or prophylaxis of seasonal influenza in individuals with asthma or chronic obstructive pulmonary disease. [14] In 2009 the zanamivir package insert contains precautionary information regarding risk of bronchospasm in patients with respiratory disease. [15] GlaxoSmithKline (GSK) and FDA notified healthcare professionals of a report of the death of a patient with influenza having received zanamivir inhalation powder, which was solubilized and administered by mechanical ventilation. [16]
In adults there was no increased risk of reported adverse events in trials. There was little evidence of the possible harms associated with the treatment of children with zanamivir. [7] Zanamivir has not been known to cause toxic effects and has low systemic exposure to the human body. [17]
Zanamivir works by binding to the active site of the neuraminidase protein, rendering the influenza virus unable to escape its host cell and infect others. [18] It is also an inhibitor of influenza virus replication in vitro and in vivo. In clinical trials, zanamivir was found to reduce the time-to-symptom resolution by 1.5 days if therapy was started within 48 hours of the onset of symptoms.[ citation needed ]
The bioavailability of zanamivir is 2%. After inhalation, zanamivir is concentrated in the lungs and oropharynx, where up to 15% of the dose is absorbed and excreted in urine. [19]
Zanamivir was first made in 1989 by scientists led by Peter Colman [20] [21] and Joseph Varghese [22] at the Australian CSIRO, in collaboration with the Victorian College of Pharmacy and Monash University. Zanamivir was the first of the neuraminidase inhibitors. The discovery was initially funded by the Australian biotechnology company Biota and was part of Biota's ongoing program to develop antiviral agents through rational drug design. Its strategy relied on the availability of the structure of influenza neuraminidase by X-ray crystallography. It was also known, as far back as 1974, that 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (DANA), a sialic acid analogue, is an inhibitor of neuraminidase. [23]
Computational chemistry techniques were used to probe the active site of the enzyme, in an attempt to design derivatives of DANA that would bind tightly to the amino acid residues of the catalytic site, so would be potent and specific inhibitors of the enzyme. The GRID software by Molecular Discovery was used to determine energetically favourable interactions between various functional groups and residues in the catalytic site canyon. This investigation showed a negatively charged zone occurs in the neuraminidase active site that aligns with the C4 hydroxyl group of DANA. This hydroxyl is, therefore, replaced with a positively charged amino group; the 4-amino DANA was shown to be 100 times better as an inhibitor than DANA, owing to the formation of a salt bridge with a conserved glutamic acid (119) in the active site. Glu 119 was also noticed to be at the bottom of a conserved pocket in the active site that is just big enough to accommodate the larger, but more basic guanidine functional group. [24] Zanamivir, a transition-state analogue inhibitor of neuraminidase, was the result. [25]
In 1999, the product was approved for marketing in the US and Europe for treatment of influenza A and B. The FDA advisory committee had recommended by a vote 13 to 4 that it should not be approved, because it lacked efficacy and was no more effective than placebo when the patients were on other drugs such as paracetamol. But the FDA leadership overruled the committee and criticised its reviewer, biostatistician Michael Elashoff. The review of oseltamivir, which was also in approval process at that time, was taken away from him, and reassigned to someone else. [26] In 2006 zanamivir was approved in the US and Europe for prevention of influenza A and B. [3]
Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Antiviral drugs are a class of antimicrobials, a larger group which also includes antibiotic, antifungal and antiparasitic drugs, or antiviral drugs based on monoclonal antibodies. Most antivirals are considered relatively harmless to the host, and therefore can be used to treat infections. They should be distinguished from virucides, which are not medication but deactivate or destroy virus particles, either inside or outside the body. Natural virucides are produced by some plants such as eucalyptus and Australian tea trees.
Avian influenza, also known as avian flu or bird flu, is a disease caused by the influenza A virus, which primarily affects birds but can sometimes affect mammals including humans. Wild aquatic birds are the primary host of the influenza A virus, which is endemic in many bird populations.
Oseltamivir, sold under the brand name Tamiflu, is an antiviral medication used to treat and prevent influenza A and influenza B, viruses that cause the flu. Many medical organizations recommend it in people who have complications or are at high risk of complications within 48 hours of first symptoms of infection. They recommend it to prevent infection in those at high risk, but not the general population. The Centers for Disease Control and Prevention (CDC) recommends that clinicians use their discretion to treat those at lower risk who present within 48 hours of first symptoms of infection. It is taken by mouth, either as a pill or liquid.
Rimantadine is an orally administered antiviral drug used to treat, and in rare cases prevent, influenzavirus A infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Rimantadine can mitigate symptoms, including fever. Both rimantadine and the similar drug amantadine are derivates of adamantane. Rimantadine is found to be more effective than amantadine because when used the patient displays fewer symptoms. Rimantadine was approved by the Food and Drug Administration (FDA) in 1994.
Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes influenza (flu), predominantly in birds. It is enzootic in many bird populations, and also panzootic. A/H5N1 virus can also infect mammals that have been exposed to infected birds; in these cases, symptoms are frequently severe or fatal.
Amantadine, sold under the brand name Gocovri among others, is a medication used to treat dyskinesia associated with parkinsonism and influenza caused by type A influenzavirus, though its use for the latter is no longer recommended because of widespread drug resistance. It acts as a nicotinic antagonist, dopamine agonist, and noncompetitive NMDA antagonist. The antiviral mechanism of action is antagonism of the influenzavirus A M2 proton channel, which prevents endosomal escape.
Exo-α-sialidase is a glycoside hydrolase that cleaves the glycosidic linkages of neuraminic acids:
Neuraminidase inhibitors (NAIs) are a class of drugs which block the neuraminidase enzyme. They are a commonly used antiviral drug type against influenza. Viral neuraminidases are essential for influenza reproduction, facilitating viral budding from the host cell. Oseltamivir (Tamiflu), zanamivir (Relenza), laninamivir (Inavir), and peramivir belong to this class. Unlike the M2 inhibitors, which work only against the influenza A virus, NAIs act against both influenza A and influenza B.
Peramivir is an antiviral drug developed by BioCryst Pharmaceuticals for the treatment of influenza. Peramivir is a neuraminidase inhibitor, acting as a transition-state analogue inhibitor of influenza neuraminidase and thereby preventing new viruses from emerging from infected cells. It is approved for intravenous administration.
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Influenza, commonly known as "the flu" or just "flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
Viral neuraminidase is a type of neuraminidase found on the surface of influenza viruses that enables the virus to be released from the host cell. Neuraminidases are enzymes that cleave sialic acid groups from glycoproteins. Viral neuraminidase was discovered by Alfred Gottschalk at the Walter and Eliza Hall Institute in 1957. Neuraminidase inhibitors are antiviral agents that inhibit influenza viral neuraminidase activity and are of major importance in the control of influenza.
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