U.S. advisers began considering on Tuesday whether the makers of three blockbuster antipsychotic drugs should be allowed to promote them for children and teens with schizophrenia or bipolar disorder.

Eli Lilly and Co's Zyprexa, AstraZeneca's Seroquel and Pfizer's Geodon are approved for adults and already used to treat children. But the companies need Food and Drug Administration approval before they can advertise them specifically for youths as young as 10 years old.

Winning FDA clearance for wider use may boost sales, which already top a combined $10 billion annually.

Reviewers at the FDA agree the medicines appear effective for treating symptoms, Dr. Thomas Laughren, director of its psychiatry drugs division, told a panel of outside experts. The agency wants the advisers to consider the risks of weight gain, sleepiness and other reactions before deciding whether to recommend approval in younger patients, he said.

Side effects "are of particular concern in pediatric patients primarily because these are lifelong disorders, and these children would face many decades of taking these drugs," Laughren said.

The drugs are members of a family called atypical antipsychotics. Two similar medicines, Johnson & Johnson's Risperdal and Bristol-Myers Squibb Co's Abilify, already are approved to treat youths with bipolar disorder or schizophrenia.

The medicines under review already are widely used. Zyprexa is Lilly's top-selling drug, with sales of $4.7 billion. Seroquel is the second-best-selling product for AstraZeneca, with 2008 sales of $4.5 billion. Sales of Pfizer's Geodon topped $1 billion in 2008.

Laughren said it was "important to acknowledge that both schizophrenia and bipolar disorder are serious illnesses in pediatric patients" and place burdens on families. Schizophrenia causes hallucinations, delusions and disorganized thoughts, while bipolar disorder causes dramatic mood swings from manic episodes to depression.

AstraZeneca data showed children "are susceptible to the same risks seen of (Seroquel) for adults," Liza O'Dowd, a vice president of the company, told the panel. The risks "can be monitored and managed" and are described in the drug's prescribing instructions, she said.

Lilly and Pfizer were scheduled to speak to the panel later on Tuesday. In summaries released before the meeting, both companies said their drugs' risks were acceptable, given their benefits for treating serious mental illnesses.

The FDA advisers were expected to vote Wednesday on whether the medicines were effective and acceptably safe for various age groups. The agency will make the final decision, but usually follows panel recommendations.

AstraZeneca and Lilly are seeking approval for treating acute episodes of both schizophrenia and bipolar mania. Pfizer's application asks for approval only in bipolar disorder.