Covidiensaid it expects to see minimal financial impact from the FDA's move to place limits on the amount of acetaminophen in Rx combination products. The company said its fiscal 2011 pharmaceuticals sales, operating income and company operating margin should not be materially affected. The FDA told manufacturers of acetaminophen-containing prescription products to limit the amount of the drug to 325 milligrams per tablet or capsule. Makers of the products have three years to comply. In addition to being the only North American manufacturer of acetaminophen, Covidien also manufactures Rx products that combine the ingredient with the pain medications hydrocodone and oxycodone. Its products are already available in 325 mg formulations, the firm said. The FDA is also requiring warnings on these products, including a black-box warning on the potential risk for severe liver injury. The actions are part of an effort to curb risks from acetaminophen. The agency said 325 milligrams or less per dosage unit are effective for treating pain, and overdoses can result in liver failure.