Produce a bumper set of results at the top end of market forecasts, sit on £1 billion (€1.27 billion) in cash in the balance sheet and announce that a key new product would get regulatory approval in the next few months, and one would normally expect a share to get a bit of a boost - even in these turbulent markets.

But for the Irish market's biggest stock, Elan, the exact opposite has happened, with the share down 10 per cent in the past week.

That sort of downgrade is difficult to justify.

Elan has been hugely successful in transforming itself from a company that developed ways of delivering other companys' products into a fully integrated pharmaceutical group, which in the past quarter increased the proportion of revenues it derives from drugs it delivers to 79 per cent of the total.

Elan has not tried to take on the "big pharma" companies in developing blockbuster drugs, but has instead specialised on niche products to treat cancer, neurological problems such as multiple sclerosis and Alzheimer's and now pain treatment, following the $50 million (€55 million) acquisition of a suite of opiate products from Roxane. Add its war chest to make big acquisitions and its virtually unblemished track record, and the share deserves earnings multiples at least comparable to those of its peers.

But from a situation last week where Elan was being given "buy" recommendations on historic p/e's of 25 and prospective p/e's of 21, Elan shares have fallen from $50 to $45 and are on historic and forward multiples of 22 and 19 respectively.

Most speciality pharma stocks in the US and comparable stocks in Britain, like Galen and Shire, are all trading on significant premiums to Elan, premiums that are difficult to justify.