Treatment of Overweight Induced by Antipsychotic Medication in Young People With Autism Spectrum Disorders (ASD) (MET)

Inclusion Criteria:

1. Diagnosis of Autism Spectrum Disorder (autistic disorder, pervasive developmental disorder not otherwise specified), Asperger's disorder) based upon an Autism Diagnostic Observation Scale (ADOS) and Diagnostic and Statistical Manual (DSM-IV) interview.
2. Minimum of 1 month on a stable atypical antipsychotic dose with no plans to change the dose for the next 4 months.
3. A documented greater than/equal to 7% increase in BMI since starting atypical antipsychotic therapy(going back as far as prior 12 months); or, if BMI is greater or equal to 85th percentile corrected for age and sex, then a greater than 5% body weight increase per year (prorated at greater than 5% body weight increase if medicated for longer than a year).
4. Age 6 years to 17 years, 4 months.
5. Subjects and their parents (guardians) must be judged reliable for medication compliance and must agree to keep appointments for study visits and tests as outlined in the protocol.
6. Prior to the conduct of any study-specific procedures, the subject must provide assent to participate in the study (if developmentally appropriate), and their parents (guardians) must provide written informed consent.

Exclusion Criteria:

1. History of intolerable adverse effects with metformin.
2. Prior history of an exposure to metformin of sufficient dose or duration to determine response status.
3. History of liver disease, renal impairment, congestive heart failure, pernicious anemia, any other condition increasing the risk for lactic acidosis, or any serious medical illness requiring treatment.
4. Use of cationic drugs excreted by the kidneys.
5. Planned surgery or procedure requiring contrast.
6. Pregnant at screening contact.
7. On other psychotropic concomitant medications for less than 2 months.
8. Treatment or planned treatment with concomitant medications with unacceptable interactions with metformin, including topiramate, levetiracetam, beta blockers, angiotensin-converting-enzyme (ACE) inhibitors, diuretics, or histamine H2 receptor antagonists.
9. Unable to tolerate blood work.
10. Current use of medication for target symptoms of appetite or weight loss.
11. Planned change of medication, medication dose, or behavioral treatment targeting weight loss during the study period.