One of the nation’s largest processors of pharmacy prescriptions said Thursday that extortionists are threatening to disclose personal and medical information on millions of Americans if the company fails to meet payment demands. St. Louis-based Express Scripts said that in early October it received a letter that included the names, birth dates, Social Security numbers and in some cases prescription data on 75 of its customers. The authors threatened to expose millions of consumer records if the company declined to pay up, Express Scripts said in a statement. The company’s chief executive George Paz said Express Scripts has no intentions of paying the extortion demand and said his company is working with the FBI to track down the person or persons responsible for the scam. Express Scripts is among the largest pharmacy benefit management firms, companies that process and pay prescription drug claims. It handles roughly 500 million prescriptions a