Anorexia nervosa patients who get to a normal body weight are more likely to hang on to those needed pounds if they take Prozac, a new study has found.
Led by Dr. Walter Kaye, an eating disorder expert from the University of Pittsburgh School of Medicine, the study showed that Prozac, or fluoxetine, substantially lowered the relapse rate among anorexic patients. The findings are in this month's issue of Biological Psychiatry.
After hospitalization and treatment get them to a healthy body weight, as many as two-thirds to three-quarters of people with anorexia resume avoiding food and engaging in other behaviors that can make them dangerously thin.
Previous studies have shown there is no benefit to giving psychiatric medications to patients when they are underweight and very ill, Kaye said.
"We think that malnutrition actually compromises the effectiveness of these drugs," he said. "So we asked the question: Would these medications be more effective if we gave them to people after they got to healthy body weight?"
The researchers randomly assigned 35 people hospitalized with anorexia nervosa to receive a year of outpatient treatment with either fluoxetine or a placebo. Drug dosage varied from one pill every other day to three pills daily, depending on response. All the patients had psychotherapy and regular follow-up visits.
Two-thirds of the patients taking fluoxetine maintained their weight, and were less depressed, anxious and obsessive as measured by standard tests. The remaining third of the group lost weight. In contrast, 85 percent of the placebo group began shedding pounds and most relapsed within four months of leaving the hospital.
The results "really need to be confirmed in a larger study," Kaye said. "Several universities are now engaged in larger studies to see whether they can show this response in other people."
Experts suspect that anorexia nervosa, once thought to be caused by unhealthy family and social dynamics, is the result of overactivity of serotonin, a chemical messenger in the brain. Too much serotonin can make someone feel full and cause them to stop eating. Drugs like Prozac may work by reducing that activity.
It may be that people with anorexia stop eating as a way to decrease serotonin production. Kaye is writing a paper that examines this possibility.
"Serotonin comes from tryptophan, an essential amino acid you can only get in your diet," he said. "Extreme dieting (might be) one way of driving down brain serotonin activity."
Kaye is also leading an international project to look for genes that put people at higher risk for eating disorders. Anorexia nervosa and bulimia nervosa, which is characterized by episodic food binges and purging, tend to run in families.
"There's lots of data to suggest that these may be highly biologic, highly genetic disorders," he noted.