His concern follows advice by the Japanese authorities in March 2007 against prescribing oseltamivir to adolescents after the separate suicides of two 14-year-olds who jumped to their deaths while taking the drug.
So far, oseltamivir has been thought to be well tolerated and safe, but the recent events in Japan have prompted a reappraisal, writes Simon Maxwell from the University of Edinburgh.
Before 2007, there had already been more than 100 reports of neuropsychiatric events (including delirium, convulsions, and encephalitis) with oseltamivir in children, almost entirely from Japan, which has the highest usage of oseltamivir worldwide. But a Food and Drug Administration (FDA) review concluded that these events were not clearly drug related.
Since last November, the FDA has required that doctors be warned that patients should be closely monitored for signs of abnormal behaviour throughout the treatment period and the European Medicine Evaluation Agency (EMEA) took similar steps in February.
In the UK, oseltamivir is a 'black triangle' drug so it remains under more intensive surveillance and healthcare professionals are asked to report all minor as well as serious adverse events.
Dr Maxwell highlights that prelicensing trials pick up common adverse events, but the detection of rarer and potentially more serious events has to await exposure of large numbers of patients.
He recognises that oseltamivir reduces the number of flu episodes when used as treatment or prophyaxis. However, since the episodes in healthy people are usually modest and short duration he recommends conservative strategies such as rest, fluid intake and taking simple analgesics.
In people at higher risk of serious complications the potential benefit of treatment seems greater, although convincing evidence about reductions in hospital admission or mortality is still awaited, he writes. In these groups, Dr Maxwell suggests that vaccination still offers a cost effective first line of defence.
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