Resolution of Inappropriate Sexual Behavior in an Elderly Male with Intellectual Disability with Memantine: Case Report, and Review of the Literature

Abstract

BackgroundMemantine is a non-competitive N-methyl-d-aspartate receptor antagonist approved for the treatment of moderate to severe Alzheimer's disease (AD). However, given its involvement of glutamate pathways, monotherapy as well as combination with other medications has been found to be effective in a number of psychiatric conditions (1). Resolution of new onset inappropriate sexual behavior (ISB) with memantine in a 67 year old male with intellectual disability (ID) is presented.Case presentationA 67 year old, white male with ID with a full scale IQ of 68, was treated in psychiatry long term for intermittent agitation and anxiety. At age 65, he manifested ISB which was not controlled with non pharmacologic measures and various medications. ISB resolved when memantine was added to his concurrent psychotropics and gradually increased to 10 mg BID. There was a recurrence of ISB after two years which remitted when memantine was increased to 25 mg. Based on clinical follow ups and serial MOCAs over three years, it was determined that this patient did not have a major neurocognitve disorder.ConclusionISB and its treatment is an understudied subject in individuals with intellectual disability. Resolution of new onset ISB in a 67 year old male with intellectual disability and comorbid mood disorder, is a previously unreported therapeutic effect of memantine. His ISB resolved with the addition of memantine 20 mg daily after multiple failed trials of various classes of psychotropics. Two years later, reemergence of ISB subsided with memantine 25 mg which is a higher than the recommended dose of this medication. Additional studies would be helpful in determining the maximum dose of this medication given its therapeutic efficacy at 25 mg daily which was well tolerated with stable medical tests.