Effect of butyrylcholinesterase genotype on the response to rivastigmine or donepezil in younger patients with Alzheimer's disease.

A randomized double-blind trial evaluated the efficacy and tolerability of rivastigmine, an inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and donepezil, an AChE-selective inhibitor, in patients with Alzheimer's disease over a 2-year period. A retrospective analysis showed differential responses to cholinesterase inhibitors (ChE-Is) in patients younger than 75 years. This analysis investigated the effect of BuChE genotype on response to ChE-I therapy in these patients. In a retrospective analysis, patients younger than 75 who had consented to pharmacogenetic analysis were divided into groups according to BuChE genotype. Efficacy measures were the Severe Impairment Battery (SIB), Neuropsychiatric Inventory (NPI), Global Deterioration Scale (GDS), Mini-Mental State Examination (MMSE) and the Alzheimer's Disease Cooperative Study-Activities of Daily Living Scale (ADCS-ADL). Changes on efficacy parameters were calculated for rivastigmine-treated and donepezil-treated patients in both groups. Of 114 (34.1%) patients younger than 75 who were successfully assessed for BuChE genotype, 76 (66.7%) were homozygous for wild-type BuChE, and 38 (33.3%) carried at least one BuChE K-variant allele. Wild-type BuChE carriers showed significantly greater responses to rivastigmine than to donepezil on the SIB, ADCS-ADL, GDS and NPI. No significant between-treatment differences in efficacy were observed in BuChE K-variant carriers, although adverse events were more frequent in rivastigmine-treated patients. In this retrospective analysis, Alzheimer's disease patients younger than 75 with wild-type BuChE exhibited differential efficacy to rivastigmine, while BuChE K-variant carriers experienced similar long-term treatment effects with both agents. These differences may reflect rivastigmine's ability to inhibit BuChE and AChE.

Response to rivastigmine or donepezil in Alzheimer's patients with symptoms suggestive of concomitant Lewy body pathology.

BACKGROUND: A double-blind randomized trial evaluated the efficacy and tolerability of rivastigmine and donepezil in patients with Alzheimer's disease (AD) over 2 years. Baseline data indicated that some patients had symptoms suggestive of concomitant Lewy body disease. This retrospective analysis investigated whether AD patients with and without symptoms suggesting concomitant Lewy body pathology demonstrated different responses to therapy. METHODS: AD patients were divided by the presence/absence of symptoms suggestive of concomitant Lewy body disease. These were identified by a concomitant diagnosis of dementia with Lewy bodies and/or use of anti-parkinsonian medication at baseline. Baseline characteristics, demographics, changes on efficacy parameters and adverse event (AE) frequencies were calculated for rivastigmine- and donepezil-treated patients. Efficacy parameters were the Severe Impairment Battery (SIB), Mini-Mental State Examination (MMSE), Global Deterioration Scale (GDS), Neuropsychiatric Inventory (NPI) and AD Cooperative Study Activities of Daily Living scale (ADCS-ADL). Main efficacy analyses were based on an intent-to-treat last observation carried forward (ITT-LOCF) population. RESULTS: Both populations reached mean doses of rivastigmine and donepezil that were within therapeutic ranges. Nine hundred and ninety-four AD patients received study drug, of whom 49 (4.9%) had symptoms suggestive of concomitant Lewy body disease (25 rivastigmine, 24 donepezil). In this subpopulation, changes from baseline after 2 years of treatment with rivastigmine were significantly better than those seen with donepezil on the SIB, MMSE and ADCS-ADL (ANCOVA or Wilcoxon analyses, p < 0.05, ITT-LOCF). Statistical significance was not maintained in non-ITT-LOCF analyses, except for EP analyses on the SIB and ADCS-ADL (both p < 0.05). Rivastigmine also provided significantly better functioning than donepezil in patients without Lewy body pathology, as shown by a significant treatment difference at endpoint on the ADCS-ADL (p < 0.05, ITT-LOCF; not maintained in non-ITT-LOCF analyses). NPI changes from baseline did not differ significantly between treatment groups. AD patients with symptoms suggestive of concomitant Lewy body disease receiving rivastigmine or donepezil experienced fewer gastrointestinal side effects, leading to fewer discontinuations due to AEs, compared with patients without Lewy body pathology. CONCLUSION: In this retrospective analysis, AD patients who had symptoms suggestive of concomitant Lewy body disease appeared to show greater treatment responses to rivastigmine than to donepezil, and experienced fewer adverse events under either drug, compared with patients without Lewy body pathology.

Rivastigmine and donepezil treatment in moderate to moderately-severe Alzheimer's disease over a 2-year period.

OBJECTIVES: Randomised controlled trials that directly compare cholinesterase inhibitors for the treatment of Alzheimer's disease have been characterised by significant methodological limitations. As a consequence, they have failed to establish whether there are differences between agents in this class. To help address this question, a double-blind, randomised, controlled, multicentre trial was designed to evaluate the efficacy and tolerability of cholinesterase inhibitor treatment in patients with moderate to moderately-severe Alzheimer's disease over a 2-year period. METHODS: Patients were randomly assigned to rivastigmine 3-12 mg/day or donepezil 5-10 mg/day. Efficacy measures comprised assessments of cognition, activities of daily living, global functioning and behavioural symptoms. Safety and tolerability assessments included adverse events and measurement of vital signs. RESULTS: In total, 994 patients received cholinesterase inhibitor treatment (rivastigmine, n = 495; donepezil, n = 499), and 57.9% of patients completed the study. The most frequent reason for premature discontinuation in both treatment groups was adverse events, primarily gastrointestinal. Adverse events were more frequent in the rivastigmine group during the titration phase, but similar in the maintenance phase. Serious adverse events were reported by 31.7% of rivastigmine- and 32.5% of donepezil-treated patients, respectively. Rivastigmine and donepezil had similar effects on measures of cognition and behaviour, but rivastigmine showed a statistically significant advantage on measures of activities of daily living and global functioning in the ITT-LOCF population. However, this was not maintained in the non-ITT-LOCF populations. In secondary subgroup analyses, AD patients who had genotypes that encoded for full expression of the butyrylcholinesterase enzyme (BuChE wt/wt; n = 226/340), who were < 75 years of age (n = 362/994) or who had symptoms suggestive of concomitant Lewy body disease (n = 49/994) showed significantly greater benefits from rivastigmine treatment. CONCLUSIONS: Cholinesterase inhibitor treatment may offer continued therapeutic benefit for up to 2 years in patients with moderate AD. Although both drugs performed similarly on cognition and behaviour, rivastigmine may provide greater benefit in activities of daily living and global functioning.