Tamiflu’s Timely FDA Approval
Tamiflu’s Timely FDA Approval
By William T. Elliott, MD, FACP
With timing that a marketing team could only dream of, Hoffman-Laroche’s oseltamivir (Tamiflu) was approved by the FDA the day before publication of a study in the New England Journal of Medicine that demonstrated the drug’s benefit. The oral anti-influenza drug was approved in October for the treatment of influenza A and B after studies showed it reduces influenza symptoms by an average of one day. It was not approved for prevention of the flu, but that was the subject of the published article. Tested during the 1997-1998 flu season, the drug was shown to effectively prevent influenza by an average of 74% when given once or twice a day. (N Engl J Med 1999:341:1336-1343). Oseltamivir is a neuraminidase inhibitor similar to zanamivir (Relenza-Glaxo Wellcome), but unlike zanamivir, which must be inhaled as a powder through a breath activated device, oseltamivir is taken orally, twice a day, for five days. The magnitude of the effect of oseltamivir is similar to the effect of zanamavir.
Leptin, a protein hormone that appears to modulate appetite, may show promise in promoting weight loss. A recent, randomized, placebo-controlled trial tested subcutaneous injections of recombinant leptin in 54 lean and 73 obese patients. All patients were initially treated for four weeks; obese patients were then treated for an additional 20 weeks (JAMA 1999;282:1568-1575). Weight loss was demonstrated in both lean and obese individuals. The average weight loss in the obese patients was a modest 15 lbs, but it was almost entirely due to fat loss. Weight loss was greater in the highest dose ranges of the drug. Leptin was well tolerated and did not exacerbate insulin resistance. Leptin is manufactured by Amgen of Thousand Oaks, Calif.
RotaShield, Wyeth Lederle’s rotavirus vaccine, is being withdrawn from the market because of safety concerns. The vaccine has been linked to an increased incidence of intussusception in vaccinated infants. More than 100 cases have been reported, with two deaths. The vaccine was temporarily suspended by the FDA in July in order to further study the problem. Then in October, the Center for Disease Control’s Advisory Committee on Immunization Practices withdrew its recommendation that infants be vaccinated against rotavirus vaccine since there was overwhelming evidence of an increased risk of intussusception in the first two weeks after vaccination. The drug was approved in August 1998.
Sildenafil (Viagra) is readily available on the Internet without a prescription or a doctor visit, and, often, even without a medical history. Reasearchers from Penn State found more than 85 sites offering the drug, with only half asking patients about a history of coronary disease. The authors concluded that 40% of the sites would be unable to determine if the drug was inappropriate for their customers (N Engl J Med 1999;341:1389-1392). The drug is ideal for the Internet entrepraneuer because of the discomfort many men feel talking about erectile dysfunction and the embarrassment of getting the drug at a local pharmacy. This study points out the importance of obtaining a detailed medical history when starting nitrates or other drugs that may have an interaction with sildenafil.
The opiate receptor antagonist naltrexone is finding new uses as a result of two German studies. Psychiatrists evaluated the effects of the drug in 13 patients with personality disorders. After two weeks of therapy, naltrexone was effective in reducing dissociative phenomena, tonic immobility, and flashbacks. This lends credence to the theory that dissociative phenomena are mediated by the endogenous opioid system (J Clin Psychiatry 1999;60:598-603). Naltrexone also appears to be effective in treating severe, antihistamine-resistant pruritus. In a non controlled study of 50 patients with pruritus from a variety of causes including internal diseases, the drug provided significant benefit in 70% after one week of therapy (J Am Acad Dermatol 1999;41:533-539). Both studies required titration of the drug in patients who developed tachyphylaxis.
Recent FDA actions:
Pharmacia & Upjohn has received approval to market exemestane (Aromasin) for the treatment of advanced breast cancer in postmenopausal women. The drug is an aromatase inactivator that is approved for breast cancer that is unresponsive to tamoxifen.
Approval was also given for moxifloxacin (Avelox- Bayer), a new oral quinolone antibiotic that can be given once a day. The drug was approved for outpatient treatment of pneumonia, sinusitis, exacerbation of chronic bronchitis, and uncomplicated skin and skin structure infections. The drug carries a warning about QT prolongation and has been associated with the development of atrial fibrillation. It may be effective against penicillin-resistant pneumococcus, but it did not receive approval for that indication. However, an FDA advisory panel has found a different quinolone that it feels may fill that role. The panel has given its recommendation for expanding the indication of levofloxacin (Levaquin J&J) for the treatment of penicillin-resistant Streptococcus pneumoniae. Full FDA approval is needed before the indication is granted.
Entacapone (Comtan-Novartis), a new catechol-O-methyltransferase (COMT) inhibitor for the treatment of Parkinson’s disease was granted approval in October. The drug is approved as an adjunct to levodopa/carbadopa. Entacapone works to inhibit the metabolism of levodopa, thereby potentiating the benefit of the drug. When used together, the two drug combination increases "on" time without significant side effects.
Ivax Corporation has been granted tentative approval for its generic form of fluoxetine (Prozac-Lilly). Barr Laboratories also has a generic form of fluoxetine ready to go pending court room maneuvering. Generic Prozac represents the first generic in the lucrative SSRI antidepressant market.
Pfizer is planning an early 2000 launch for its new anti-arrythmic dofetilide (Tikosyn) following FDA approval. The drug was approved for the conversion of highly symptomatic atrial fibrillation or atrial flutter patients to sinus rhythm and for maintenance of sinus rhythm. Because of the drug’s propensity to cause torsade de pointes, a boxed warning accompanies the package insert stating that patients should be hospitalized on continuous telemetry for at least three days when initiating or reinitiating the drug.
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