This study will determine the effectiveness of the antibiotic erythromycin in enhancing gastrointestinal function and decreasing the frequency of binge eating in people with bulimia nervosa.

Bulimia nervosa (BN) is a serious eating disorder that is characterized by frequent uncontrolled eating binges. These binges are often followed by compensatory behavior, including the following: self-induced vomiting; misuse of laxatives, diuretics, enemas, or other medications to induce purging; fasting; or excessive exercise. If left untreated, BN can lead to many serious health issues: tooth decay; irregular menstruation; bowel damage; constipation; heart and kidney disease; intestinal damage; puffiness, especially in the face and fingers; increased hair growth on the face and body; and mineral imbalances in the body. Although there is significant existing knowledge about the characteristics and treatment of BN, more information is needed about gastrointestinal (GI) function and its effect on binge eating behavior. This study will determine the effectiveness of the antibiotic erythromycin in enhancing GI function and decreasing the frequency of binge eating in people with BN.

Participants in this 8-week, double-blind study will first undergo gastric emptying and GI hormone release testing for 1 day. Within 1 week of completing these pre-treatment tests, participants will be randomly assigned to receive either erythromycin or placebo for 6 weeks. Upon medication assignment, participants will meet with a psychiatrist to receive their assigned medication. Participants will receive medication at weekly study visits. Medication dosage will be increased if symptoms do not improve, or decreased if adverse medication side effects are reported. A final day of gastric emptying and GI hormone release testing, as well as routine blood tests, will take place in Week 7, after 6 weeks of medication treatment. Participants' weight will be measured at Weeks 1, 4, and 7. Participants will also receive an EKG 1 week after each upward dosage adjustment. Patients will be informed of their medication assignment at the Week 7 study visit, and will be referred to a non-study clinician for further treatment.

Inclusion Criteria:

• Meets DSM-IV criteria for bulimia nervosa
• Duration of illness is greater than 1 year
• Self-induces vomiting
• Weighs 80%-120 % of ideal weight

Exclusion Criteria:

• Significant medical illness
• Current or lifetime history of schizophrenia, bipolar disorder, or other psychotic disorder, as defined by DSM-IV-TR criteria
• Moderate to severe depression, as defined by a score greater than 18 on the Hamilton Depression Scales
• Current DSM-IV-TR diagnosis of organic mental disorder, factitious disorder, or malingering
• History of a personality disorder (e.g., schizotypal, borderline, or antisocial) that might interfere with assessment or compliance with the study procedures
• At risk for suicide
• Current psychotropic medications and current medications that affect GI function or that inhibit or induce CYP3A gene expression
• Currently pregnant, lactating, or planning to become pregnant
• Drug or alcohol abuse within the 3 months prior to study entry
• Abnormal EKG at baseline or 1 week following each upward dosage adjustment
• Anemia
• Known intolerance to erythromycin, or related antibiotics
• Abnormal results on liver function tests
• Electrolyte abnormalities