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Giving Tamiflu to patients who may have been exposed to swine flu—such as family members of confirmed cases—as a preventive measure, may result in their developing drug-resistant strains of the virus, according to an account published in this week’s issue of the New England Journal of Medicine. In a letter to the editor, a team of physicians from Quebec write about the case of a 59-year-old man prescribed Tamiflu (oseltamivir) preventively after his 13-year-old son was diagnosed with a case of H1N1 flu. (The boy’s two older sisters were also given Tamiflu as a preventive measure.) Eight days after beginning the treatment, the father developed a serious cough, and when he went to the doctor to be examined, they discovered he had developed a resistant strain of the disease (H275Y, the same mutation that causes Tamiflu resistance in seasonal flu strains). (The boy’s sisters never developed swine flu symptoms.) These findings add to a group of similar cases reported to the World Health Organization in which Tamiflu-resistant strains of the virus developed in people who were given the drug preventively but had already been exposed to H1N1. “These observations support the need for limiting postexposure prophylaxis,” the authors write. In other words, if you live with someone or have regular exposure to someone who already has swine flu, it may possibly do more harm than good to preemptively put you on Tamiflu.
Additionally, the Canadian medical team writes, for patients who are taking precautionary doses of Tamiflu, it’s important to recognize if and when H1N1 symptoms set in and promptly change from low dose prophylactic treatment to higher dose therapeutic treatment, as delaying the higher dosage could increase the risk for developing a drug-resistant strain. As the battle against H1N1 continues, it is important to continue close monitoring of any drug-resistant strains, the authors argue, in order to prevent a larger scale spread of Tamiflu-resistant swine flu.