Shire met analyst expectations with a 5% increase in fourth quarter revenues $1.2 billion driven by a strong performance by attention deficit hyperactivity drug Vyvanse in the USA.

Overall there was a mixed picture for Shire's flagship ADHD franchise, however. While Vyvanse (lisdexamfetamine dimesylate) grew 18% to $257 million in the quarter, thanks also to a price increase and increasing use in adults, older product Adderall XR (mixed amphetamine salts) fell 35% to $82 million on generic competition.

For the full year sales of Vyvanse grew 29% to $1 billion, while Adderall XR fell 19% to $429 million, although Shire managed to boost overall revenues by 10% to $4.7 billion across its portfolio, with another ADHD drug - Intuniv (guanfacine) - rising 29% to $289 million.

Outgoing chief executive Angus Russell - who will step down from his post in April to be replaced by Flemming Ornskov - noted that the UK and Ireland have ratified the EU approval of lisdexamfetamine granted late last year, setting up launches under the Elvanse brand name in the second quarter which will drive growth in 2013.

He also noted that Shire now has Phase III clinical trials of lisdexamfetamine in binge eating disorder and for the negative symptoms in schizophrenia such as social withdrawal and apathy which could expand the market for the drug further.

Shire's 2012 net profit fell from $865 million in 2011 to $745 million, as a result of $171 million in impairment charges relating to constipation treatment Resolor (prucalopride), and specifically from "the challenging market and reimbursement environment for this product in Europe," said Shire's chief financial officer Graham Hetherington.

The firm's rare disease business was another growth driver with sales up 20%, helped by the launch of Firazyr (icatibant) which made $116 million in its first full year on the market as a treatment for hereditary angioedema (HAE).

Replagal (agalsidase) for Fabry disease rose 10% to $498 million in 2012 - despite greater competition as rival drug Fabrazyme (agalsidase beta) from Genzyme has moved clear of supply constraints - while Vpriv (velaglucerase alfa) for Gaucher disease advanced 23% to $307 million.  

On the downside skin substitute Dermagraft was down 21% to $154 million on a full-year basis, with Shire in the midst of a restructuring of its commercial team for the product.

Meanwhile, Shire also announced that Sylvie Gregoire, head of its rare genetic diseases unit, will leave the company at the end of March after five years at the firm.

For 2013, the company said it expects sales and earnings growth in the low double digits -  roughly in line with market expectations of 10% - although royalties and other revenue are expected to be 30%-40% lower.