Zanamavir, which moderates flu's symptoms, received Health Canada approval in November 1999. It is used to treat patients aged 12 or older who have had the flu for 2 days or less. A 5-day course of the drug costs $45. A spokesperson for the manufacturer, GlaxoSmithKline, told CMAJ that 37 000 prescriptions were written here last year. Submissions have been made to add it to every provincial formulary, but so far none has been granted.

"For a government health plan, the cost of providing zanamavir to the general population would outweigh the benefits," says economist Bruce Brady, coauthor of a 63-page report on the drug. "For it to be cost-effective it would have to substantially reduce the number of hospitalizations for the flu, and the evidence that zanamavir can do this is inconclusive at this time." (The report says that the incremental cost per quality-adjusted life year gained is $195 000 to $235 000; the cost per symptom day avoided is $194 to $234.)

The heavily referenced report says the drug may provide "modest reductions" in length of illness for some patients and lead to reduced antibiotic use, but that it would have no effect on common illnesses that mimic the flu. This means that "routine prescribing would result in a number of patients taking the drug without any benefit." It also says that public coverage of the drug's costs might encourage people who would otherwise not seek treatment to visit their doctors, increasing health care costs.

Dave Clements, spokesperson for the office, says the study was meant to apply only to the general population. "It [zanamavir] may be a useful measure within specific populations," he says. "There may be a cost benefit from using the drug within these populations, but we haven't seen the proof yet."