NEW YORK (AP) — Irish drugmaker Shire PLC said Thursday its net income fell in the first quarter, and it lowered its revenue forecast because sales of several of its drugs are under pressure.

Net income decreased to $64.8 million, or 35 cents per American depository share, for the quarter ended March 31, from $238.4 million, or $1.24 per ADS, a year ago. Excluding one-time items, the company's earnings per share rose to $1.63 from $1.48.

Revenue fell 1 percent to $1.16 billion.

Analysts expected net income of $1.57 per share on $1.21 billion in revenue, according to FactSet.

Shire said sales of its top-selling drug, the attention deficit hyperactivity disorder medication Vyvanse, climbed 15 percent to $298 million in the latest quarter. Sales of its Gaucher disease drug Vpriv increased 14 percent to $82 million.

However, revenue from its Hunter syndrome treatment Elaprase fell 9 percent to $114 million because of a reduction in orders from Latin America, while sales of its Fabry disease drug Replagal shrank to $114 million, down 15 percent, because of greater competition and changes in shipment timing. Sales of the diabetic foot ulcer treatment Dermagraft slid by 62 percent to $19 million because of changes in the company's commercial operations.

Sales of its ADHD drug Adderall XR have been sliding because of growing generic competition. They fell 10 percent to $99.8 million during the quarter.

Shire said it now expects its total product sales to grow in the mid- to high-single digits this year. Previously Shire had expected growth of at least 10 percent. The company reported $4.41 billion in product sales and $4.68 billion in total revenue in 2012.

The company also said it expects to report net income of about $6.67 per share in 2013.

Analysts expect earnings per share of $6.73 and revenue of $5.04 billion, on average.

Shares of Shire lost $5.59, or 6 percent, to $87.77 in afternoon trading.

Separately, Acceleron Pharma said Thursday that Shire decided to end a collaboration between the two companies. Acceleron said the companies suspended clinical research of ACE-031, a drug designed to treat Duchenne muscular dystrophy, in February 2011. It said the companies have decided not to restart clinical development of the drug.