FOREST’s FLUMADINE APPROVED FOR PREVENTION/TREATMENT OF INFLUENZA A

FOREST's FLUMADINE APPROVED FOR PREVENTION/TREATMENT OF INFLUENZA A symptoms on Sept. 17, almost seven years after NDA submission. The NDAs for Flumadine (rimantadine) coated tablet (19-649) and raspberry-flavored syrup (19-650) were filed in November 1986. The antiviral drug is classified "1P" by FDA, designating a new chemical entity with priority review, presumably referring to the period since Forest Labs took over sponsorship of the product a year ago. Flumadine is indicated for "the prophylaxis and treatment of illness caused by various strains of influenza A virus in adults" and "for prophylaxis against influenza A virus in children," labeling states. The recommended dose in adults is 100 mg twice daily for both prophylaxis and treatment. The dose for children less than 10 years old is 5 mg/kg per day not to exceed 150 mg. Flumadine will compete in the influenza market with DuPont Morck's Symmetrel (amantadine), which is approved for prevention of influenza A and treatment of uncomplicated respiratory tract illness caused by the virus. However, a Sept. 17 FDA "Talk Paper" notes that rimantadine appears to have half as many side effects as amantadine when used preventatively. "In a six-week prevention study in 436 healthy adults, 14.7% of those taking amantadine had adverse reactions, compared to 6.9% of those taking rimantadine." The most common side effects of rimantadine therapy were insomnia, nausea and dizziness. Use of rimantadine in the same household has been shown in a study to result in transmission of drug resistant strains of the virus, FDA cautioned. Labeling states that "10% to 30% of patients with initially sensitive virus, upon treatment with rimantadine, shed rimantadine-resistant virus." The Centers for Disease Control and Prevention's Committee on Immunization Practices will meet Oct. 6-7 in Atlanta to discuss, among other topics, viral resistance to rimantadine and amantadine. Rimantadine was recommended for approval in October 1987 by an FDA advisory committee, but the NDA stalled at FDA after rimantadine-resistant influenza was described in a December 1989 New England Journal of Medicine article. At that time, the drug was being developed by Hoffmann-La Roche, which had licensed rimantadine from DuPont. Forest acquired the rights to rimantadine from DuPont Merck in mid-1992. According to FDA's approval letter, all communications from Forest to the agency occurred starting this past June.