Efficacy of memantine in PDD and DLB: an extension study including washout and open-label treatment

This 30-week extension trial was a continuation of the first double-blind randomized controlled trial (RCT) to study memantine in dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). The objective was to evaluate the presence of recurrence of symptoms upon drug withdrawal. Furthermore, the aim was to explore washout dynamics in order to inform clinical practice.

Patients were enrolled from psychiatric, memory and neurological outpatient clinics in Norway, Sweden and the UK. The trial comprised a 4-week washout period and a 26-week open-label treatment period. Outcome measures were presence of recurrence of symptom upon drug withdrawal, Clinical Global Impression of Change (CGIC) and modified motor Unified Parkinson's Disease Rating Scale (UPDRS).

recurrence of symptoms occurred more frequently (p=0.04) in patients receiving memantine (58%) than in patients receiving placebo (25%). There was a significant global deterioration (p=0.0003) during washout within the memantine group as measured by CGIC. The patients seemed to recover during the open-label treatment, however these findings were non-significant.

The findings inform clinical practice that any possible memantine-associated benefits might be rapidly lost after drug withdrawal. The magnitude of deterioration suggests a symptomatic rather than a disease-modifying effect of the drug. Open-label results should merely be considered inspiration for future trials.