Shire Plc CEO Angus Russell

Shire Plc, the Dublin-based maker of Adderall XR, said first quarter earnings rose 20 percent as group sales passed the $1bn mark.

Earnings per share were reported at $1.48, around $0.02 ahead of analysts' forecast. Group revenues rose 24 percent to $1.172bn, the company said in a statement Thursday, adding it expects full-years sales to grow by around 13 percent for the full year.

Vyvanse, its top-performing attention-deficit and hyperactivity drug, had sales of $260m in the first quarter, up 17 percent from the same period last year. Adderall, the group's attention-deficit-disorder drug, saw a 7 percent increase in sales to $111.4m

"Shire continues to perform strongly with first quarter results in-line with our expectations," said group CEO Angus Russell in a statement. "Our focus on demonstrating value to the healthcare system through meeting the needs of our patients is continuing to deliver"

Shire also said research and development costs would grow by between 12 percent and 14 percent for the year and that it expects the "marginal" dilution of gross margins to continue throughout the year, reflecting the impact of the group's $750m purchase of Advanced BioHealing last month.

Shares in the group were 33 pence, or 1.65 percent, higher following the earnings release, changing hands at 2,035.67 pence per share in London trading. Shire stock has fallen 10.8 percent so far this year.