Widely prescribed drugs fail in mild cognitive impairment and found to cause harm
Cognitive enhancers including cholinesterase inhibitors and memantine, used to treat dementia are unclear regarding their effectiveness for mild cognitive impairment.
Mild cognitive impairment (MCI) is defined by deficits in memory that do not significantly impact daily functioning. However, some individuals with MCI develop cognitive deficits and functional impairment consistent with Alzheimer’s disease. Physicians sometimes will prescribe cholinesterase inhibitors for those with mild cognitive impairment with the main symptom of memory loss.
Dr. Andrea C. Tricco, PhD, MSc, of St. Michael's Hospital in Toronto, Ontario, and colleagues conducted a systematic review to examine the efficacy and safety of cognitive enhancers for mild cognitive impairment.
Researchers conducted a systematic review of existing evidence by examining eight randomized trails that included that looked at the effects of four cognitive enhancers; donepezil (Aricept), galantamine (Razadyne), rivastigmine (Exelon), or memantine (Namenda) to a placebo among patients diagnosed with mild cognitive impairment. The studies reported on cognition, function, behaviour, global status, and mortality or harms.
The researchers found no significant improvements in cognition were seen with the cognitive enhancing drug however; they did find short –term benefits to using these drugs on one cognition scale, but after a year and half there were no benefits.
The team also concluded that there was "very little evidence" for memantine (Namenda). Over a three year follow-up patients who had taken donepezil (Aricept), galantamine (Razadyne) or rivastigmine (Exelon), experienced significantly more side effects including nausea and vomiting, diarrhea, leg cramps and abnormal dreams. One study also found a higher risk of a heart condition known as bradycardia (slow heartbeat) among patients who received galantamine (Aricept).
The researchers write in their conclusion “Cognitive enhancers did not improve cognition or function among patients with mild cognitive impairment and were associated with a greater risk of gastrointestinal harms. Our findings do not support the use of cognitive enhancers for mild cognitive impairment.”
Dr. Sharon E. Straus, MD, FRCPC, co-author of the study noted in a statement These agents were not associated with any benefit and led to an increase in harms. Patients and their families should consider this information when requesting these medications. Similarly, health care decision-makers may not wish to approve the use of these medications for mild cognitive impairment, because these drugs might not be effective and are likely associated with harm."
This study is published in in the Canadian Medical Association Journal.