JANE WARDELL AP Business Writer LONDON (AP) — Drug maker AstraZeneca posted a 42 percent rise in first quarter net profit on Thursday, boosted by sales of its heart drug Toprol-XL in the United States where the company ramped up production to meet demand after competitors withdrew generic versions. The first quarter earns were also lifted by one-off gains including the sale of U.S. marketing rights for breast cancer treatment Abraxane and lower tax rates, leading AstraZeneca to maintain its full-year guidance. "There were a number of specific factors that supplemented what I think was a good general execution," Chief Financial Officer Simon Lowth told reporters on a conference call. Net profit came in at $2.15 billion, up from $1.51 billion a year ago, and far higher than analyst expectations of closer to $1.8 billion. Revenue, meanwhile, was barely changed at $7.70 billion, compared to $7.67 billion a year ago, due to the negative impact of exchange rate movements. Despite the strong first-quarter result, the company maintained its full-year earnings per share guidance of $5.15 to $5.45 based on constant exchange rates to reflect continued caution about the 2009 economic outlook. "We are certainly recession resistant, but we are not recession proof," Lowth said. The report was well-received by the market with AstraZeneca's share price rising 3.7 percent to 2,535 pence ($37.66) on the London Stock Exchange. Total sales rose 7 percent in the United States, compared with the first quarter of 2008, after two generic competitors withdrew their products from the market. However, Lowth said that those strong sales could not be guaranteed in the months to come. "We really don't have any visibility about whether they might come back to the market," he said. Among the company's leading drugs, total sales of cholesterol drug Crestor rose 35 percent to $969 million. Around half the value of those sales were in the United States, where the drug's market share increased to 10.3 percent from 8.3 percent in March last year. Sales of heartburn drug Nexium rose 2 percent to $1.19 billion, sales of anti-psychotic drug Seroquel rose 11 percent to $1.12 billion and asthma treatment Symbicort sales jumped 24 percent to $515 million. Lowth said the company also continued to make progress on its cost-cutting program, under which it aims to reduce the cost structure by $2.5 billion by 2013. Asked about potential takeovers, Lowth said that AstraZeneca was not looking to join other pharmaceutical companies in large-scale mergers and acquisition. "We don't believe we are lacking scale in any of our activities," Lowth said, adding that the company continued to keep an eye out for any smaller-sized potential acquisitions.