HOLLYWOOD, FLA. – Treatment with memantine appears to delay progressive driving impairment in patients with mild Alzheimer’s disease, according to a year-long, double-blind, albeit small, randomized controlled trial.
"For many patients with Alzheimer’s disease, driving cessation is a major life-changing event that negatively impacts them and their caregivers. Until highly effective disease-altering treatments are available, there is a need to develop therapies that can prolong independent functioning," Dr. Peter J. Holland said in explaining the rationale for the driving skills study he presented at a meeting of the New Clinical Drug Evaluation Unit sponsored by the National Institute of Mental Health.
Dr. Peter J. Holland
He chose memantine for the study for a couple of reasons. Preclinical evidence suggests the drug might have neuroprotective properties. And, in his experience, it’s a very well-tolerated drug.
There are a number of large controlled studies in which the dropout rate from adverse events was higher in the placebo group than with memantine, observed Dr. Holland, a psychiatrist and research professor of biomedical science at Florida Atlantic University, Boca Raton.
He reported on 60 otherwise healthy subjects with mild Alzheimer’s disease who were randomized to 12 months of double-blind memantine titrated to a target of 20 mg/day or placebo. All participants were still driving. The primary study endpoint was their score on the DriveABLE On Road Evaluation at 12 months. This structured, behind-the-wheel road test measures driving-related neurocognitive performance.
All 13 subjects on memantine either improved or maintained their baseline driving ability at 12 months, as did only 9 of 12 on placebo, a statistically significant difference (P = .05).
Asked about the high dropout rate, Dr. Holland noted that it’s a real challenge to keep older patients with Alzheimer’s disease in a study lasting a full year.
"The P value is there. I’d like to see the study replicated. If this holds true, it’s such a benign medication – it’s so well tolerated – that if it has a chance of being helpful, I think it’s worth further study," Dr. Holland added.
Memantine’s approved indication is in treating patients with moderate to-severe Alzheimer’s disease, so this application of the drug to delay driving impairment in patients with mild Alzheimer’s disease is off-label use.
In addition to the DriveABLE On Road test, study participants completed a battery of neurocognitive assessments at baseline, 6, and 12 months. These assessments were chosen because they test skills necessary for safe driving, including executive function, selective attention, and visuospatial abilities.
Thus far, Dr. Holland has determined that the memantine-treated group performed significantly better than controls at 12 months on the Rey-Osterrieth Complex Figure Test. In contrast, no significant difference between the two groups was noted on the Trail Making Part B test. As the study was only recently completed, the investigator is still analyzing the results on the Useful Field of View, Motor Free Visual Perception Test, and Alzheimer's Disease Assessment Scale-Cognitive test.
An estimated 5.2 million Americans aged 65 years or older have Alzheimer’s disease. And according to the American Automobile Association, in another dozen years, fully one-quarter of all U.S. drivers will be 65 years or older. A medication that slows driving impairment would have a large clinical impact, Dr. Holland noted.
His investigator-initiated study was funded by a research grant from Forest Pharmaceuticals.