UPDATE 2-US panel cautiously OKs antipsychotic drugs for kids

* FDA advisers back AstraZeneca, Lilly and Pfizer drugs

* Panelists concerned about long-term use

* FDA to weigh panel votes, gives no timeline for decision (Adds panelist, FDA and companies' comments)

By Susan Heavey

ADELPHI, Md., June 10 (Reuters) - Three widely used antipsychotic medications appear safe and effective overall in treating children and teenagers with schizophrenia or bipolar disorder, a U.S. advisory panel said on Wednesday.

The Food and Drug Administration's panel of outside experts backed wider use of the pills -- Eli Lilly and Co's (LLY.N) Zyprexa, AstraZeneca's (AZN.L) Seroquel and Pfizer's (PFE.N) Geodon -- but expressed concern over long-term effects the medications may have in younger patients.

The drugs are already approved for adults and are given to youngsters at a doctor's discretion, reaching $10 billion in combined annual sales. FDA approval would allow the drugmakers to market them specifically for children and teenagers.

Panelists overall said the companies' data showed the drugs, known as atypical antipsychotics, are effective and reasonably safe for children as young as 10 years old. But some members said the short-term studies do not show how youngsters would fare when treated over time for the chronic conditions.

"I'm concerned about the lack of true long-term studies" especially in younger patients "who will have a long lifetime, hopefully," said Ruth Day, a researcher at Duke University.