Patients taking an obesity pill in clinical trials were more likely to report suicidal thoughts or actions, US drug reviewers have said. A Food and Drug Administration advisory panel will consider on Wednesday whether regulators should approve US sales.

The FDA said the 20-milligram dose of the drug, Zimulti, produced clinically significant weight loss over one year.

With a low-calorie diet, the drug "was shown to reduce body weight by approximately 5% relative to diet alone during trials of more than 6000 moderately overweight and obese subjects", the FDA reviewers said.

Known generically as rimonabant, the drug is already sold in 18 countries under the name Acomplia.

Adverse events

The agency has delayed a final decision on rimonabant several times amid concerns about depression and a high drop-out rate in clinical trials. "We remain concerned about rimonabant's adverse event profile, specifically adverse psychiatric reactions," an FDA staff summary said.

Psychiatric problems "represent the most common and worrisome rimonabant-induced adverse events", the reviewers said. Depression was roughly twice as high for rimonabant patients compared with others who received a placebo, they said.

Sanofi-Aventis, which makes the drug, agreed that more rimonabant patients reported suicidal thoughts, but added that the drug's benefits "clearly outweigh the defined risks that are manageable in clinical practice".

Food craving

Rimonabant works by blocking food craving signals in the brain. Sanofi developed the drug to target the brain receptors that trigger intense hunger after marijuana use.

The French drug maker has predicted that the drug could eventually generate sales of $3 billion a year or more. Sales for the first quarter of 2007 were about $20 million but approval for the US market would take that figure significantly higher.

The FDA will ask outside advisers to assess the risks of suicidal behaviour, other psychiatric problems, neurological problems and seizures, and whether the drug should be approved. The agency usually follows panel recommendations.

Industry experts said it was hard to predict what the panel would decide. Karl Heinz Koch, an analyst from investment bank Vontobel, noted that other weight-loss drugs - Roche AG's Xenical and Abbott Laboratories' Meridia - were approved even though higher rates of depression are noted on their labels.