Earnings after tax slumped to $1.53 billion in the three months to the end of September, compared with $3.48 billion in the same period of 2011, AstraZeneca said in a results statement.
Sales tumbled 19 percent to $6.68 billion.
“As expected, the revenue decline in the third quarter reflected the ongoing effect from the loss of exclusivity on several brands,” AstraZeneca said in the statement.
The company added that its financial targets for the full year remained unchanged.
The company is facing crucial patent expires up until 2015 on drugs such as schizophrenia treatment Seroquel and heartburn and ulcer drug Nexium.
It will also suffer the loss of patent protection in the United States for its best-selling anti-cholesterol drug, Crestor, in 2016.
The latest earnings update was meanwhile the first under the group’s new chief executive Pascal Soriot.
The Frenchman who was previously a senior executive at Swiss drugs group Roche took up his role at the start of October following the resignation of American David Brennan, who stepped down as AstraZeneca boss in April.
“As I take up my new role as chief executive, my priority is to restore the company to growth and scientific leadership,” Soriot said in Thursday’s statement.
Earlier this year, Brennan announced plans to cut 7,300 jobs by 2014 to improve profitability at AstraZeneca, which has come under heavy pressure in recent times from generic drugs competition.