Eli Lilly is strengthening the warning label to its antipsychotic Zyprexa by adding tougher language concerning weight gain and elevated blood sugar.

The new labeling contradicts earlier public statements by Lilly that weight gain on Zyprexa tends to plateau after a few months of use. The new labeling will also indicate that patients who take Zyprexa may keep gaining weight for as long as two years after starting therapy.

The drugmaker said it decided to take the steps now, after reviewing more data from internal tests and major outside studies and will display the info prominently in the warning section of the label rather than in a lower portion where it could be overlooked.

“Now it will be close to the front of the label and provide a more prominent information point for physicians,” Lilly spokeswoman Marni Lemons told The Indianapolis Star.

Lilly also acknowledged, in a letter to doctors, that Zyprexa is more likely to raise blood-sugar levels than competing drugs.

Zyprexa entered the market in 1996 and is Lilly’s top-selling drug, with 2006 sales of $4.2 billion.

However, Lilly has been fighting legal and health claims, while trying to assure doctors that the Zyprexa is still safe.

Les Funtleyder, a drug analyst at Miller Tabak & Co. in New York, said in The Star report that the move is not a major shift for Lilly, “but is a bit of acknowledgement of reality that it needs to do more to address this.”

“If they change the label, it could actually encourage more claims,” Funtleyder added. “But legal issues are very difficult to handicap.”