UPDATE 1-Lilly adds new warnings to antipsychotic Zyprexa

(Adds BOSTON dateline, detail throughout)

By Toni Clarke

BOSTON, Oct 5 (Reuters) - Eli Lilly & Co (LLY.N) said on Friday its antipsychotic Zyprexa was more likely than rival treatments to raise blood glucose levels, a condition that can lead to diabetes, and has added the warning to the drug's label.

The warning follows discussions with the U.S. Food and Drug Administration, and marks the first time Lilly has officially conceded that Zyprexa, known chemically as olanzapine, carries a greater risk of causing elevated blood sugars than almost all drugs in the same class.

Zyprexa is one of a group of drugs known as atypical antipsychotics that include AstraZeneca Plc's (AZN.L) Seroquel, Bristol-Myers Squibb Co's (BMY.N) Abilify and Pfizer Inc's (PFE.N) Geodon, most of which carry a degree of risk for causing metabolic side effects.

Until now, however, Zyprexa has not been singled out by regulators as having greater risk, even though many psychiatrists have long considered it one of the worst offenders in causing elevated blood sugar, alongside a relatively little-used drug called clozapine.

"The evidence has been clear for a long time that Zyprexa and clozapine are at the far end of the spectrum in terms of causing adverse metabolic side effects," said Dr. Herbert Meltzer, professor of psychiatry and pharmacology at Vanderbilt University School of Medicine. "This is the first time it has been clearly stated."

Elevated blood glucose is associated with Type II diabetes, the most common form of the disease, and Lilly has paid more than $1.2 billion to settle lawsuits from plaintiffs claiming the company did not provide them with sufficient warning of the risk of blood sugar abnormalities.

The new label, which also applies to Lilly's drug Symbyax -- a pill combining the active ingredients of Zyprexa and Prozac that is approved to treat bipolar depression -- warns, in addition, of significantly greater risk of elevated cholesterol and triglycerides. And it formally warns of weight gain.

In addition, the label includes data on the metabolic impact of Zyprexa on adolescents, for which the drug is not approved. The company said it included the data because doctors prescribe the drug "off-label" to teenagers. Physicians are allowed to prescribe drugs for any condition, but companies are not allowed to market it for any condition for which it has not been approved by the FDA.

Lilly has submitted an application with the FDA to be allowed to market the drug for adolescents. In April the agency issued a so-called "approvable" letter, which means it declined to approve the application until the company provides further information.

Dr. Sara Corya, global medical director at Lilly, said the company was conducting additional analysis of the data to clarify the relative risk of metabolic disturbances.

Lilly is also seeking approval to market Symbyax as a treatment for treatment-resistant depression. The updated warnings apply similarly to Symbyax, but Symbyax causes a statistically significant rise in cholesterol compared to Zyprexa.

The company received an "approvable" letter in this indication in March.