Elan Corp ended 2011 by posting an increased loss for the fourth quarter, due to charges, but sales of its multiple sclerosis blockbuster Tysabri continue to grow.

The Irish drugmaker’s net loss came in at $134.7 million, versus a loss of $52.2 million in the like, year-earlier period. Sales declined to $271.0 million from $308.9 million, although the company said they actually rose 18% excluding revenue from its divested Elan Drug Technologies unit, which was sold to Alkermes.

Global turnover of Tysabri (natalizumab) climbed 14% to $379.6 million, while Elan’s share of sales from the drug, which is marketed with Biogen Idec, reached $270.6 million, up from $229.4 million. At the end of December, some 64,400 patients were on Tysabri, up 13% on the same period a year earlier.

Last month, Elan and Biogen were given a green light from the US Food and Drug Administration to update the product labelling for Tysabri to help identify those at most risk of developing the rare but potentially fatal viral brain infection PML (progressive multifocal leukoencephalopathy).

Nigel Clerkin, chief financial officer, said 2011 was "a year of tremendous financial progress for Elan" and "we were pleased to have met or exceeded all of our financial guidance for the year". He added that the sale of EDT "transformed our balance sheet, and enabled us to pay down more than half our debt, reducing our annual interest payments by close to $60 million".

For 2012, he said the firm expects to generate $1.20-$1.25 billion in revenues, with adjusted earnings before interest, taxes, depreciation and amortisation of greater than $200 million. This would represent "a greater than 35% increase over the $146.7 million we achieved in 2011, excluding EDT".