All About World

08 »

OseltamivirSystematic (IUPAC) nameethyl (3R,4R,5S)-5-amino-4-acetamido-3-(pentan-3-yloxy)cyclohex-1-ene-1-carboxylateIdentifiersCAS number196618-13-0ATC codeJ05AH02PubChem65028Chemical dataFormula ?Mol. mass312.4 g/molSMILESeMolecules & PubChemPharmacokinetic dataBioavailability75%Metabolismhepatic, to GS4071Half life6–10 hoursExcretionrenal (GS4071)Therapeutic considerationsPregnancy cat.B1 (Australia), C (U.S.)Legal statusPrescription Only (S4)(AU) POM(UK) ℞-only(US)RoutesoralOseltamivir (INN) (pronounced /ɒsəlˈtæmɨvɪr/) is an antiviral drug that is used in the treatment and prophylaxis of both Influenzavirus A and Influenzavirus B. Like zanamivir, oseltamivir is a neuraminidase inhibitor. It acts as a transition-state analogue inhibitor of influenza neuraminidase, preventing progeny virions from emerging from infected cells.Oseltamivir was the first orally active neuraminidase inhibitor commercially developed. It is a prodrug, which is hydrolysed hepatically to the active metabolite, the free carboxylate of oseltamivir (GS4071). It was developed by US-based Gilead Sciences and is currently marketed by Hoffmann-La Roche (Roche) under the trade name Tamiflu. In Japan, it is marketed by Chugai Pharmaceutical Co., which is more than 50% owned by Roche. Oseltamivir is generally available by prescription only.Roche estimates that 50 million people have been treated with oseltamivir. The majority of these have been in Japan, where an estimated 35 million have been treated.With increasing fears about the potential for a new influenza pandemic, oseltamivir has received substantial media attention. Governments, corporations, and even some private individuals are stockpiling the drug. Production is currently sufficient to meet the demand for seasonal influenza and for government stockpiling. It is possible that shortages could recur in the event of an actual influenza pandemic.// Clinical use Indications and dosageOseltamivir is indicated for the treatment of infections due to influenza A and B virus in people at least one year of age, and prevention of influenza in people at least one year and older. The usual adult dosage for treatment of influenza is 75 mg twice daily for 5 days, beginning within 2 days of the appearance of symptoms and with decreased doses for children and patients with renal impairment. Oseltamivir may be given as a preventive measure either during a community outbreak or following close contact with an infected individual. Standard prophylactic dosage is 75 mg once daily for patients aged 13 and older, which has been shown to be safe and effective for up to six weeks. The importance of early treatment is that the NA protein inhibition is more effective within the first 48 hours. If the virus has replicated and infected many cells the effectiveness of this medication will be severely diminished, especially over time. Use and dosage for avian influenzaAfter following WHO protocols in treating 41 victims of the H5N1 bird flu virus (19% of the worldwide cases of bird flu reported to date), Nguyen Tuong Van, MD, who runs the intensive care unit of the Center for Tropical Diseases in Hanoi, Vietnam concluded that Tamiflu, the drug most widely stockpiled around the world to combat a potential bird flu pandemic, is "useless". According to this article, the WHO confirmed Van's experience stating that Tamiflu has not been "widely successful in human patients", but speculated the drug has not been administered until late in the disease in many Asian countries.The standard recommended dose incompletely suppresses viral replication in at least some patients with H5N1 avian influenza, increasing the risk of viral resistance and rendering therapy less effective. Accordingly, it has been suggested that higher doses and longer durations of therapy should be used for treatment of patients with the H5N1 virus.Clinical trials for an increased dosage were set to begin by May 2007. All avian influenza cases in Indonesia, Thailand, and Vietnam will be inducted into the trial. The trial will also include 100 cases of severe seasonal influenza from each of those countries, plus the United States. Half of cases will receive the current standard dosage, and half will receive a double dosage, but for the standard length of time.Chokephaibulkit et al. recommend the use of oseltamivir for children with avian influenza, based on experience with one patient. Co-administration with probenecidIt has been suggested that co-administration of oseltamivir with probenecid could extend a limited supply of oseltamivir. Probenecid reduces renal excretion of the active metabolite of oseltamivir. One study showed that 500 mg of probenecid given every six hours doubled both the peak plasma concentration (Cmax) and the half-life of oseltamivir, increasing overall systemic exposure (AUC) by 150 percent. Although the evidence for this interaction comes from a study by Roche, it was publicised only in October 2005 by a doctor who had reviewed the data. Probenecid was used in similar fashion during World War II to extend limited supplies of penicillin. It is still used to increase penicillin concentrations in serious infections. Dosage formsOseltamivir is marketed by Roche under the trade name Tamiflu, as capsules (containing oseltamivir phosphate 98.5 mg equivalent to oseltamivir 75 mg) and as a powder for oral suspension (oseltamivir phosphate equivalent to oseltamivir 12 mg/mL). Adverse effectsCommon adverse drug reactions (ADRs) associated with oseltamivir therapy include: nausea, vomiting, diarrhea, abdominal pain, and headache. Rare ADRs include: hepatitis and elevated liver enzymes, rash, allergic reactions including anaphylaxis, and Stevens-Johnson syndrome.Various other ADRs have been reported in postmarketing surveillance including: toxic epidermal necrolysis, cardiac arrhythmia, seizure, confusion, aggravation of diabetes, and haemorrhagic colitis. Neurological effectsThere are concerns that oseltamivir may cause dangerous psychological, neuropsychiatric side effects including self harm in some users. These dangerous side effects occur more commonly in children than in adults. This stems from cases in Japan, where the drug is most heavily prescribed. Concern has focused on teenagers, but problems have also been reported in children and adults.In March 2007, Japan's Health Ministry warned that oseltamivir should not be given to those aged 10 to 19. The Ministry had previously decided, in May 2004, to change the literature accompanying oseltamivir to include neurological and psychological disorders as possible adverse effects, including: impaired consciousness, abnormal behavior, and hallucinations.According to Japan's Health Ministry, between 2004 and March 2007, fifteen people aged 10 to 19 have been injured or killed by jumps or fallen from buildings after taking oseltamivir, and one 17-year-old died after he jumped in front of a truck. A renewed investigation of the Japanese data was completed in April 2007. It found that 128 patients had been reported to behave abnormally after taking oseltamivir since 2001. Forty-three of them were under 10 years old, 57 patients were aged 10 to 19, and 28 patients were aged 20 or over. Eight people, including five teens and three adults, had died from these actions. (For more on Japan, also see:)In November 2006, the United States Food and Drug Administration (FDA) amended the warning label to include the possible side effects of delirium, hallucinations, or other related behavior. This went further than the FDA's previous pronouncement, from a year before, that there was insufficient evidence to claim a causal link between oseltamivir use and the deaths of 12 Japanese children (only two were from neurological problems, although more have died since then). The change to a more cautionary stance was attributed to 103 new reports that the FDA received of delirium, hallucinations and other unusual psychiatric behavior, mostly involving Japanese patients, received between August 29, 2005 and July 6, 2006. This was an increase from the 126 similar cases logged between the drug's approval in 1999 and August 2005. In October 2006, Shumpei Yokota, a professor of pediatrics at Yokahama City University, released the results of research involving around 2,800 children which found no difference in the behavior between those who took oseltamivir and those who did not. A media source notes that Chugai Pharmaceutical Co. (which produces Tamiflu in Japan) gave Yokota's department 10 million yen ($85,000) over five years.Roche points out that Tamiflu has been used to treat 50 million people since 1999, and states that influenza may itself cause psychological problems.In March 2007, the European Medicines Agency said that the benefits of oseltamivir outweighed the costs, but that it would closely monitor reports from Japan. In April 2007, South Korea issued a safety warning against prescribing tamiflu to teenagers except in special cases. Mode of actionOseltamivir is a neuraminidase inhibitor. By blocking the activity of the neuraminidase, Oseltamivir prevents new viral particles from being released by infected cells. ResistanceAs with other antivirals, resistance to the agent was expected with widespread use of oseltamivir, though the emergence of resistant viruses was expected to be less frequent than with amantadine or rimantadine. The resistance rate reported during clinical trials up to July 2004 was 0.33% in adults, 4.0% in children, and 1.26% overall. Mutations conferring resistance are single amino acid residue substitutions in the neuraminidase enzyme .Mutant H3N2 influenza A virus isolates resistant to oseltamivir were found in 18% of a group of 50 Japanese children treated with oseltamivir . This rate was similar to another study where resistant isolates of H1N1 influenza virus were found in 16.3% of another cohort of Japanese children . Several explanations were proposed by the a

Health officials are trying to figure out why the dominant flu strain in the U..Thousands of Tamiflu doses, the WHO recommended drug to combat avian influenza, have reached their expiry dates, a high-ranking official says.The problem is not yet a public health crisis because this has been a below-average flu season so far and the chief strain circulating is still susceptible to other drugs. plans to use the antiviral Tamiflu in the event of widespread avian flu infection in humans,scientists say. !Flu Viruses Growing Resistant to TamifluThe main drug used to treat the most-common form of flu in the United States this season is resistant to the popular antiviral drug Tamiflu, but government health officials said Thursday there is no reason to panic.S.Influenza's ability to resist the effects of cheap and popular antiviral agents in Asia and Russia should serve as a cautionary tale about U. In recent years, doctors have relied on the drug Tamiflu to treat serious flu cases.S. health officials say almost 100% of the type A H1N1 strain showed resistance to the leading antiviral drug..S..TOKYO, Feb 22 (Reuters) - Japan's Daiichi Sankyo Co (4568. � is ineffective against most cases tested so far this flu

tamiflu

Oseltamivir phosphate. information on cold and influenza symptoms, local flu reports and FAQs.

Read more...

Flu Treatment and Flu Prevention | TAMIFLU

Learn about prescription TAMIFLU for flu treatment and flu prevention in adults and children 1 year and older.

Read more...

TAMIFLU for Flu Treatment and Flu Prevention | TAMIFLU

Исследования показали, каким образом «Tamiflu» влияет на мозг

Read more...

Исследования показали, каким образом ...

Препарат Tamiflu – против гриппа и его осложнений. Недавно проведенные исследования показали, что ...

Read more...

Препарат Tamiflu – против гриппа и его ...

БобрДобр — это сервис «социальных закладок». Он позволяет пользователям хранить и ...

Read more...