AstraZeneca has completed a deal to pay $520 million to settle federal investigations into marketing practices for its blockbuster schizophrenia drug, Seroquel. AstraZeneca becomes the fourth pharmaceutical giant in the last three years to admit to federal charges of illegal marketing of antipsychotic drugs, a lucrative category of medications that have quickly risen to the top of United States sales charts. Aggressive sales and promotional practices have helped expand the use of powerful new antipsychotic drugs for children and the elderly. The company, based in London, has been accused of misleading doctors and patients by playing up favorable research and not adequately disclosing studies that show Seroquel increases the risk of diabetes. AstraZeneca still faces more than 25,000 civil lawsuits filed on behalf of patients contending that the company did not disclose the drugs risks. As a result of aggressive marketing, Seroquel has been increasingly used for children and elderly people for indications not approved by the Food and Drug Administration. The drugs have caused rapid weight gain in children, and side effects including deaths have prompted warnings against giving the drugs to elderly patients for dementia.