Withdrawal Study of Memantine in Pediatric Patients With Autism, Asperger's Disorder, or Pervasive Developmental Disorder Not Otherwise Specified Previously Treated With Memantine

Inclusion Criteria:

1. Completed at least 12 weeks of exposure to study drug in lead-in study MEM-MD-91
2. Met responder criterion at two consecutive visits separated by at least two weeks in lead-in study MEM-MD-91
3. Provide written informed assent, when developmentally appropriate, to participate in the study before conduct of any study-specific procedures. The parent/guardian/LAR must provide written informed consent before the patient's participation in the study. A separate written informed consent for the caregiver must also be obtained before the conduct of any study specific procedures
4. Have a knowledgeable caregiver who is capable of providing reliable information about the patient's condition, attending all clinic visits with the patient, and overseeing the administration of study drug. Every effort should be made to maintain the same caregiver as used in the lead-in study throughout this study
5. Have normal results from the physical examination, laboratory tests, ECG, and vital signs at Visit 1 of this study (last visit of Study MEM-MD-91). Any abnormal findings must be deemed not clinically significant by the Investigator and documented
6. Be able to speak and understand English sufficiently (or their native language if this can be accommodated by the site), as well as have a caregiver and parent/guardian/LAR who is able to speak and understand English sufficiently (or their native language if this can be accommodated by the site), to comprehend the nature of the study and to allow for the completion of all study assessments
7. Have a family that is sufficiently organized and stable to guarantee adequate safety monitoring and continuous attendance to clinic visits for the duration of the study
8. Females who are 9 years and older or who have had onset of menses must have a negative urine pregnancy test at Visit 1

Exclusion Criteria:

1. Patients with a concurrent medical condition that might interfere with the conduct of the study, confound interpretation of the study results, or endanger the patient's well being
2. Significant risk of suicidality
3. Patients with evidence or history of malignancy (other than excised basal cell carcinoma) or any significant hematologic, endocrine, cardiovascular (including any rhythm disorder), neurologic, respiratory, renal, hepatic, or gastrointestinal disease
4. Female patients of child-bearing potential who are not using or not willing to use a conventional method of contraception approved by the PI. Abstinence is an acceptable method of contraception
5. Patients requiring treatment with prohibited concomitant medications
6. Patients who, in the opinion of the Investigator, might not be suitable for the study
7. Employee or immediate relative of an employee of Forest Laboratories, Inc., any of its affiliates or partners, or the study center