Roche, the Swiss pharmaceutical group, is exploring ways to offer its flu treatment Tamiflu over longer periods and at higher doses, a tactic that could further boost sales of the blockbuster antiviral medicine.

David Reddy, the executive responsible for the drug, told the Financial Times that the company was starting clinical trials to test whether Tamiflu (known generically as oseltamivir) is more effective when taken in higher concentrations and for up to twice as long as the current five-day recommendation.