U.S. regulators have warned Johnson & Johnson unit Janssen Pharmaceutica that a letter sent to doctors about its Risperdal drug to treat schizophrenia and bipolar mania is misleading. In a warning disclosed on Tuesday, the Food and Drug Administration told Janssen that its November letter failed to disclose information added to Risperdal’s labeling about excess blood sugar and diabetes and minimized the risk of serious events including coma and even death. The FDA also said the letter fails to recommend regular testing for diabetes and “misleadingly claims that Risperdal is safer than other atypical antipsychotics.”