Memantine for dementia.

BACKGROUND: Alzheimer's disease, vascular and mixed dementia are the commonest forms of dementia in older people. There is evidence that the excitatory activity of L-glutamate plays a role in the pathogenesis of Alzheimer's disease and in the damage from an ischaemic stroke. A low affinity antagonist to N-Methyl-D-aspartate (NMDA) type receptors, such as memantine, may prevent excitatory amino acid neurotoxicity without interfering with the physiological actions of glutamate required for memory and learning.

OBJECTIVES: To determine the clinical efficacy and safety of memantine for people with Alzheimer's disease, vascular, or mixed dementia.

SEARCH STRATEGY: Trials were identified from a search of the Trial-based Specialized Register of the Cochrane Dementia and Cognitive Improvement Group on 9 October 2002 using the terms: memantin*, D-145, DMAA, DRG-0267. All major health care databases and trial databases within the scope of the group are searched regularly to keep this Register up to date.

SELECTION CRITERIA: Double-blind, parallel group, placebo-controlled, randomized and unconfounded trials in which memantine was administered to people with dementia.

DATA COLLECTION AND ANALYSIS: Data were extracted, pooled where possible, and weighted mean differences, standardized mean differences or odds ratios were estimated. Intention-to-treat (ITT) and observed cases (OC) analyses are reported, where data were available.

MAIN RESULTS: There were a total of seven trials that met inclusion criteria, of which five had sufficient data for analysis. The analysis of change from baseline for cognition gave statistically significant results in favour of memantine (20 mg/day) (MD: -2,83 95% CI -4.37 to -1.29, P=0.0003) at 28 weeks and for memantine (30mg/day) at 6 weeks (MD: -3.04. 95% CI -5.68 to -0.40, P=0.02). Effects on Activities of Daily living (ADL) were difficult to interpret. One study provided data using a non-validated scale for measuring five simple instrumental tasks under the guidance of an investigator. When pooled with another study the analysis gave statistically significant results in favour of memantine for 30 mg/day at 6 weeks (SMD: -1.36 95% CI -1.77 to -0.96, P=0.0003). Mood and behaviour: One trial provided data on memantine 30 mg/day at 6 weeks using the NOSIE scale. The OC analysis found statistically significant differences in favour of treatment (MD: 23.30 95% CI 17.83 to 28.77, P<0.00001). Global scales: The analysis revealed a statistically significant difference in favour of memantine (20mg/day ) at 6 weeks (MD: -12.30 95% CI -16.90 to -7.70, P<0.00001). Similar results were found for larger doses (memantine 30 mg/day) at 6 weeks in a pooled meta-analysis of two other studies (WMD: -10.77 95% CI -13.46 to -8.09, P<0.00001). With regard to the Global Impression of Change three studies found statistically significant results in favour of 10, 20 and 30 mg/day of memantine compared with placebo at 6 or 12 weeks. There was a benefit in favour of memantine (20 mg/day) compared with placebo at 6 weeks, for the numbers improved ( 24/41 compared with 11/41)(OR, 3.85, 95% CI 1.52 to 9.75, P=0.004), in favour of memantine (30 mg/day) compared with placebo at 6 weeks, for the numbers improved ( 20/30 compared with 8/29)(OR, 5.25, 95% CI 1.72 to 15.98, P=0.004) and in favour of memantine (10 mg/day) compared with placebo at 12 weeks, for the numbers improved ( 60/82 compared with 38/84)(OR, 3.30, 95% CI 1.72 to 6.33, P=0.0003). In general memantine seemed to be well tolerated. There was no statistically significant difference between memantine and placebo for the three studies that reported adverse events. There were some data on specific adverse events. In one study the incidence of restlessness by the end of the treatment at 6 weeks was statistically significantly lower in the placebo group than in the group taking memantine 30 mg/day (15/30 compared with 2/29) (OR 13.50, 95% CI 2.71 to 67.19, P=0.001). The number of dropouts was similar in treatment and placebo groups at 6 or 28 weeks time for memantine 20 mg/day and at 6 weeks for memantine 30 mg/day.

REVIEWER'S CONCLUSIONS: Memantine is a safe drug and may be useful for treating Alzheimer's, vascular,and mixed dementia of all severities. Most of the trials so far reported have been small and not long enough to detect clinically important benefits. However there is a possible benefit on cognition and global measures, and an early improvement in behaviour in people with dementia. More studies are needed.