A company which distributes an anti-flu drug that is a tenth of the price of Relenza is considering legal action against the Department of Health after accusing it of restraint of trade.

Alliance Pharmaceuticals says that the guidance, issued by the DoH in the form of patient group directions - advice on treatment of patients for doctors - creates a possible barrier to trade because it does not include any advice on using its own product, Lysovir (amantadine).

Senior vaccination and immunisation experts have voiced their support of Lysovir, which they say is a cheaper and more effective option than Relenza against influenza A - the main component of influenza forecast for this year.

Director of Alliance Pharmaceuticals Tony Booley said lawyers confirmed that the company could have a case against the DoH for infringing UK and EU competition law by issuing the guidance, in conjunction with the guidance from the National Institute for Clinical Excellence on the use of Relenza among 'at-risk groups'.

'We have expressed our concern to the DoH about the patient group directions leading solely to Relenza and also the decision to allow nurses to administer the drug and pharmacists to distribute it, ' said Mr Booley.

A health service circular on patient group directions issued in August says that black triangle drugs (recently licensed and subject to special reporting arrangements for adverse reactions) may be included in patient group directions 'provided such use is exceptional, justified by current best practice (eg NICE guidance) and that a direction clearly describes the status of the product'.

Mr Booley said that the patient group directions on Relenza did not refer to the product's status as a black triangle drug, and that although amantadine had been licensed for more than 30 years, there had been no patient group direction issued on it. He said that the company still hoped to resolve the issue through discussions with the DoH.