A Study of Memantine Hydrochloride (Namenda®) for Cognitive and Behavioral Impairment in Adults With Autism Spectrum Disorders

• Male and female outpatients 18-50 years of age.
• Participants must have DSM-IV-TR diagnosis of PDD and displaying PDD symptoms with at least moderate impairment (SRS score ≥ 85 and CGI-PDD ≥ 4).
• Fulfills diagnosis of autism spectrum disorders by meeting DSM-IV-TR PDD diagnostic criteria of autistic disorder (with the exception of a total lack of spoken language), Asperger's disorder, or PDD-NOS as established by clinical interview and confirmed by DICA-R PDD module.
• Subjects and/or their legal representative must have a level of understanding sufficient to communicate intelligently with the investigator and study coordinator, and to cooperate with all tests and examinations required by the protocol.
• Subjects and/or their legal representative must be considered reliable reporters.
• Each subject and/or their authorized legal representative must understand the nature of the study. The subject and/or their legal representative must sign an informed consent document.
• Subject must be able to participate in mandatory blood draws.
• Subject must be able to swallow pills.
• Subjects with mood, anxiety, or disruptive behavior disorders will be allowed to participate in the study provided they do not meet any exclusionary criteria.

Exclusions

• IQ \< 85.
• Total lack of spoken language.
• DSM-IV-TR PDD diagnoses of Rett's disorder, or childhood disintegrative disorder.
• Clinically unstable psychiatric conditions or judged to be at serious suicidal risk.
• Active symptoms of anorexia or bulimia nervosa
• Current diagnosis of a psychotic disorder or unstable bipolar disorder.
• History of recent or current (past 30 days) clinically significant depressive or anxiety disorder that warrants treatment.
• Current diagnosis of schizophrenia.
• History of substance use (except nicotine or caffeine) within past 3 months
• Serious, stable or unstable systemic illness including hepatic, renal, gastroenterological, respiratory, cardiovascular (including ischemic heart disease), endocrinologic, neurologic, immunologic, or hematologic disease.
• Subjects with severe hepatic impairment (LFTs > 3 times ULN) and those with severely impaired renal function (eGFR \< 30).
• Subjects with genitourinary conditions that raise urine pH (e.g., renal tubular acidosis, severe infection of the urinary tract).
• Uncorrected hypothyroidism or hyperthyroidism.
• Subjects with untreated and/or unstable diabetes.
• Non-febrile seizures without a clear and resolved etiology.
• Pregnant or nursing females.
• Known hypersensitivity to memantine.
• Severe allergies or multiple adverse drug reactions.
• A non-responder or history of intolerance to memantine, after treatment at adequate doses as determined by the clinician.
• Investigator and his/her immediate family defined as the investigator's spouse, parent, child, grandparent, or grandchild.