Background: Clinical studies reported that treatments for Alzheimer’s disease may have an impact on behavioral and psychiatric disorders. We tested the hypothesis that memantine treatment initiation modifies psychotropic medication in real-life practice patients. Methods: A 2-year follow-up cohort study was performed. A sample of patients treated in the general population, extracted from the database of the French national healthcare system (CNAM-TS), was examined. The sample included 4,600 memantine-treated patients (mean age 79.8 years, 69% women) randomly selected from the database of the CNAM-TS covering 69% of the French population aged 65 years and over. The follow-up rate was 95.0%. This database includes exhaustive data on drug consumption. We used interrupted time series analysis of the proportion of psychotropics users (all psychotropic drugs and specific categories) before and after onset of memantine. Results: There was a 39–50% regular increase in patients treated with psychotropic drugs before memantine initiation This increasing trend stopped after memantine initiation, the proportion of psychotropic users remaining stable around 53% up to the end. The trends before and after memantine onset were significantly different (p < 0.001). Conclusions: Our results suggest a temporal relationship between the onset of memantine and the stabilization of psychotropic drugs use in this large sample of elderly patients.