According to researchers at New York’s Columbia University College of Physicians and Surgeons, an anti-obesity drug that turns off the same brain circuits which trigger the marijuana-induced hunger pangs, appears to produce sustained weight loss among patients.

After a two-year study period, the researchers say the drug Acomplia, or rimonabant needs more research into its long-term effects as the study was limited by a high dropout rate.

The drug company Sanofi-Aventis funded the study and is now waiting for approval by the U.S. Food and Drug Administration (FDA) .

However despite speculation that the drug could become the world’s first blockbuster anti-obesity medicine, given the continued concern voiced by respected doctors and researchers not directly involved with the clinical trials of Acomplia (rimonabant), FDA approval could well be delayed.

Many critics consider that the FDA should only approve the weight-loss drug with input from an independent FDA advisory panel.

While many experts are voicing concern regarding the side effects of Accomplia, Sanofi-Aventis, has consistently downplayed concern about possible side effects, and has repeatedly said it expects approval soon, and plans to the market the drug in the United States before the end of June.

The new report is based on a study involving more than 3,000 patients that began in 2001 and also involved diet and exercise changes, the initial findings of which were released at an American Heart Association meeting in 2004.

The report says that the drug plus diet and exercise promotes modest but sustained reductions in weight and waist circumference and favorable changes in risk factors such as cholesterol and triglycerides.

It appears that almost 50 percent of the patients in the study saw a weight loss of 5 percent or more after one year, depending on the dose of the drug, while the favorable changes in cholesterol and triglycerides were twice that expected from weight loss alone.

The researchers say this suggests the drug has some direct impact on fat metabolism beyond that caused by slimming down.

Rimonabant is the first of a new class of drugs that works by blocking cannabinoid receptors found in the brain and other body tissues which stimulate eating.

Experts from the U.S. National Heart, Lung, and Blood Institute say the researchers should have done more follow-up work, and point out that a higher rate of psychiatric disorders was among those who received the drug compared to those who received a placebo.

Concern has also been expressed that the trials showed when people discontinued taking Acomplia after one year, they regained virtually all of the weight they had lost and only participants who continued taking Acomplia through the second year maintained their first-year weight loss.

If Acomplia must be used indefinitely, experts worry that new adverse effects may emerge once the drug is taken by a far greater number of people for longer periods of time.