An open-label,comparative study of rivastigmine,donepezil and galantamine in a real-world setting

SUMMARY

Objective:We analysed the effects of donepezil, rivastigmine and galantamine, prescribed for the treatment of Alzheimer disease in a real-world setting in Italy.

Methods: Outcome measures included the Mini-Mental State Examination (MMSE), the Alzheimer Disease Assessment Scale cognitive subscale (ADAS-cog), Instrumental Activity of Daily Living (IADL) and ADL scales.

Results: Seventy patients were treated with donepezil, 121 with rivastigmine and 51 with galantamine. At 6 months, rivastigmine-treated patients improved by 1.29 points from baseline on the ADAS-cog, while donepezil- and galantamine-treated patients showed 'no change' (changes of < 0.2 points). On the IADL, patients treated with rivastigmine, donepezil and galantamine showed decreases of 0.42,0.58 and 0.75 points, respectively. On the ADL, donepezil- and galantamine-treated patients showed decreases of 0.44 and 0.86 points, respectively, while there was 'no change' with rivastigmine. On the MMSE,

donepezil- and rivastigmine-treated patients showed 'no change' and galantamine-treated patients showed a mean decrease of 1.19 points. A subgroup analysis of 'pseudo-randomised' patients (rivastigmine, n?=?63; donepezil, n?=?55; galantamine, n?=?51) supported the main findings. Side effects were similar (in type and frequency) in the three treatment groups.

Conclusions: This is the first study to compare the effects of the three most commonly-used cholinesterase inhibitors on the MMSE, ADAS-cog, IADL and ADL. Limitations included its small population size, its open-label design, and the fact that patients were randomised only after the introduction of galantamine. There were no statistically significant differences between the three drugs at 3 months. While numerical trends were observed suggesting the effect of rivastigmine > donepezil > galantamine, larger, longer-term prospective studies are needed to confirm whether there are important differences in the long-term efficacy of the three drugs.     

Symptomatic effect of donepezil,rivastigmine, galantamine and memantine on cognitive deficits in the APP23 model

Rationale APP23 mice are a promising model of Alzheimers disease, expressing several histopathological, cognitive and behavioural hallmarks of the human condition. A valid animal model should respond to therapeutic interventions in an equivalent manner as human patients.Objectives To further validate the APP23 model, we examined whether cognitive deficits could be antagonised by donepezil, rivastigmine, galantamine or memantine, which are approved drugs for symptomatic treatment of dementia.Methods Animals were tested at an age at which untreated APP23 mice display severe deficits in visual–spatial learning. Four-month-old APP23 mice and control littermates were administered donepezil (0.3 or 0.6 mg kg^–1), rivastigmine (0.5 or 1.0 mg kg^–1), galantamine (1.25 or 2.5 mg kg^–1), memantine (2 or 10 mg kg^–1) or saline through daily i.p. injections. After 1 week of treatment, acquisition phase commenced, with daily treatment continuing during cognitive testing.Results All cholinesterase inhibitors reduced cognitive deficits with the following optimal daily doses: galantamine 1.25 mg kg^–1, rivastigmine 0.5 mg kg^–1 and donepezil 0.3 mg kg^–1. Higher dosages often did not exert beneficial effects in accordance with inverted U-shaped dose–response curves described for cholinomimetics. Symptomatic efficacy of memantine on cognition was mild, with significant amelioration manifesting during probe trial.Conclusions This is the first study to simultaneously evaluate the efficacy of therapeutically relevant doses of these four compounds in one particular learning and memory paradigm, being the Morris water maze. The fact that symptomatic intervention was able to diminish cognitive impairment, substantially adds to the validity of the APP23 model as a valuable tool to evaluate future therapeutic approaches.     

Adjunctive galantamine, but not donepezil, enhances the antipsychotic-like effect of raclopride in rats

Acetylcholine (ACh) esterase inhibitors like galantamine and donepezil have been tested as adjunct treatment in schizophrenia. Although ACh esterase inhibition might confer some antipsychotic activity, the role of allosteric potentiation of nicotinic ACh receptors (nAChRs), which is an additional mechanism of galantamine, remains elusive. Therefore, the potential antipsychotic-like effects of galantamine and donepezil, respectively, alone, and in combination with the dopamine D2/3 receptor antagonist, raclopride, were tested in the conditioned avoidance response (CAR) test and extrapyramidal side-effect liability was assessed with the catalepsy test. Neither galantamine nor donepezil alone suppressed CAR selectively. Galantamine, but not donepezil, enhanced the raclopride-induced suppression of CAR, predicting augmentation of antipsychotic activity. In contrast to donepezil, galantamine did not increase catalepsy, alone or combined with raclopride. These data suggest that allosteric potentiation of nAChRs may mediate the antipsychotic-like effect of adjunctive galantamine and provide support for the development of alpha7 nAChR-selective allosteric potentiators for schizophrenia.     

A long-term comparison of galantamine and donepezil in the treatment of Alzheimer's disease

OBJECTIVE: To compare the long-term efficacy and safety of galantamine 24 mg/day and donepezil 10 mg/day in patients with Alzheimer's disease. PATIENTS AND STUDY DESIGN: This was a rater-blinded, randomised, parallel-group multicentre study (18 outpatient clinics) in the UK. 182 patients (69 male, 113 female) with Alzheimer's disease were randomised to galantamine (n = 94) or donepezil (n = 88) for 52 weeks. MAIN OUTCOME MEASURES: The effects of galantamine and donepezil on function using the Bristol Activities of Daily Living Scale (BrADL); cognition using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog/11); behaviour using the Neuropsychiatric Inventory (NPI); caregiver burden using the Screen for Caregiver Burden; and safety were assessed. RESULTS: BrADL total scores showed no significant difference between treatment groups in mean change from baseline to week 52. In the total population, in terms of cognition, galantamine patients' scores on the MMSE at week 52 did not differ significantly from baseline (-0.52 +/- 0.39, p < 0.5 vs baseline), whereas donepezil patients' scores deteriorated significantly from baseline (-1.58 +/- 0.42, p < 0.0005 vs baseline). The between-group difference in MMSE change, which showed a trend for superiority of galantamine, did not reach statistical significance (p < or = 0.1). In the ADAS-cog/11 analysis, between-group differences for the total population were not significant, whereas galantamine-treated patients with MMSE scores of 12-18 demonstrated an increase (worsening) in the ADAS-cog/11 score of 1.61 +/- 0.80 versus baseline, compared with an increase of 4.08 +/- 0.84 for patients treated with donepezil, with a significant between-group difference in favour of galantamine (p < or = 0.05). More caregivers of patients receiving galantamine reported reductions in burden compared with donepezil. Changes from baseline in NPI were similar for both treatments.Both treatments were well tolerated; most adverse events were transient and of mild-to-moderate intensity, and were consistent with the findings of previous clinical trials. CONCLUSIONS: Significant advantages were found in the treatment response to galantamine (versus donepezil) on cognition as measured by response rates on the MMSE and ADAS-cog/11.     

Regional effects of donepezil and rivastigmine on cortical acetylcholinesterase activity in Alzheimer's disease

Donepezil and rivastigmine are acetylcholinesterase (AChE) inhibitors used to improve cholinergic neurotransmission and cognitive function in Alzheimer's disease (AD). This study examined direct effects of these drugs on AChE activity in the frontal, temporal, and parietal cortices in AD. Six AD patients were scanned with positron emission tomography before and after 3 months of treatment with donepezil (10 mg/day), and five AD patients were scanned before and after 3 to 5 months of treatment with rivastigmine (9 mg/day). Healthy unmedicated controls were imaged twice to evaluate the reproducibility of the method. A specific AChE tracer, [methyl-11C]N-methyl-piperidyl-4-acetate, and a 3D positron emission tomography system with MRI coregistration were used for imaging. Treatment with donepezil reduced the AChE activity (k3 values) in the AD brain by 39% in the frontal (p < 0.001, Bonferroni corrected), 29% in the temporal (p = 0.02, corrected) and 28% in the parietal cortex (p = 0.05, corrected). The corresponding levels of inhibition for rivastigmine were 37% (p = 0.003, corrected), 28% (p = 0.03, uncorrected) and 28% (p = 0.05, corrected). When the treatment groups were combined, the level of AChE inhibition was significantly greater in the frontal cortex compared to the temporal cortex (p = 0.03, corrected). The test-retest analysis with healthy subjects indicated good reproducibility for the method, with a nonsignificant 0% to 7% intrasubject variability between scans. The present study provides first evidence for the effect of rivastigmine on cortical AChE activity. Our results indicate that the pooled effects of donepezil and rivastigmine on brain AChE are greater in the frontal cortex compared to the temporal cortex in AD. This regional difference is probably related to the prominent temporoparietal reduction of AChE in AD. We hypothesize that the clinical improvement in behavioral and attentional symptoms of AD due to AChE inhibitors is associated with the frontal AChE inhibition.     

N1phenethyl-norcymserine, a selective butyrylcholinesterase inhibitor, increases acetylcholine release in rat cerebral cortex: a comparison with donepezil and rivastigmine

The effects of (-)-N(1)phenethyl-norcymserine (PEC, 5 mk/kg, i.p.) on acetylcholine release and cholinesterase activity in the rat cerebral cortex were compared with those of donepezil (1 mg/kg, i.p.), a selective acetylcholinesterase inhibitor, and rivastigmine (0.6 mg/kg, i.p.), an inhibitor of acetylcholinesterase and butyrylcholinesterase. Acetylcholine extracellular levels were measured by microdialysis coupled with HPLC; acetylcholinesterase and butyrylcholinesterase activity were measured with colorimetric and radiometric methods. It was found that comparable 2-3 fold increases in cortical extracellular acetylcholine level, calculated as areas under the curve, followed the administration of the three drugs at the doses used. At the peak of acetylcholine increase, a 27% acetylcholinesterase inhibition and no butyrylcholinesterase inhibition was found after donepezil (1 mg/kg, i.p) administration. At the same time point, rivastigmine (0.6 mg/kg, i.p.) inhibited acetylcholinesterase by 40% and butyrylcholinesterase by 25%. After PEC (5 mg/kg, i.p.) administration, there was a 39% butyrylcholinesterase inhibition and no effect on acetylcholinesterase. Since in the present study it was also confirmed that in the brain butyrylcholinesterase activity is only about 10% of acetylcholinesterase activity, it is surprising that its partial inhibition is sufficient to increase extracellular acetylcholine levels. The importance of butyrylcholinesterase as a "co-regulator" of synaptic acetylcholine levels should thus be reconsidered.     

A comparison of donepezil and galantamine in the treatment of cognitive symptoms of Alzheimer's disease: a meta-analysis

This review was conducted in order to determine the efficacy of donepezil and galantamine in the treatment of cognitive symptoms of Alzheimer's disease, and also to determine whether galantamine was a superior pharmacological intervention. Meta-analytic methods were used to analyse the data from eight empirical studies which met the inclusion criteria specified. By finding the mean effect sizes of the treatment on the outcome measures of cognition, it was determined that neither drug was greatly efficacious. However, this result does not necessarily diminish the practical value of the drug. It was also found that galantamine was no better than donepezil at treating cognitive decline in AD.     

Effects of huperzine A on acetylcholinesterase isoforms in vitro: comparison with tacrine,donepezil, rivastigmine and physostigmine

Five inhibitors of acetylcholinesterase, huperzine A, donepezil, tacrine, rivastigmine and physostigmine, were compared with regard to their effects on different molecular forms of acetylcholinesterase in cerebral cortex, hippocampus, and striatum from the rat brain. In general, huperzine A preferentially inhibited tetrameric acetylcholinesterase (G4 form), while tacrine and rivastigmine preferentially inhibited monomeric acetylcholinesterase (G1 form). Donepezil showed pronounced selectivity for G1 acetylcholinesterase in striatum and hippocampus, but not in cortex. Physostigmine showed no form-selectivity in any brain region. In cortex, the most potent inhibitors of G4 acetylcholinesterase were huperzine A (K(i) 7 x 10(-9) M) and donepezil (K(i) 4 x 10(-9) M). The potent inhibitors of cortical G1 acetylcholinesterase were donepezil (K(i) 3.5 x 10(-9) M) and tacrine (K(i) 2.3 x 10(-8) M). In hippocampus, huperzine A and physostigmine were the most potent inhibitors of G4 acetylcholinesterase, while donepezil and tacrine were most potent against G1 acetylcholinesterase. In striatum, huperzine A and donepezil were the most potent against G4 acetylcholinesterase, while again donepezil was the most potent against G1. Although the inhibition constants (K(i)) of these acetylcholinesterase inhibitors differed significantly from region to region, the nature of the inhibition did not vary. These results suggest that the use of acetylcholinesterase inhibitors in treatment of Alzheimer's disease must consider both form-specific and region-specific characteristics of acetylcholinesterase inhibition.     

Effects of galantamine and donepezil on active and passive avoidance tests in rats with induced hypoxia

The cholinergic system undergoes changes with aging and in Alzheimer's disease. The effects of the anticholinesterase drugs galantamine and donepezil were studied in a model with sodium nitrite-induced hypoxia in rats. The animals were trained in the shuttle-box active avoidance test and in step-through and step-down passive avoidance tests. In the active avoidance test, hypoxic rats showed a decrease in the number of avoidances in the learning session and in retention. The hypoxic rats receiving galantamine showed an increase in the number of avoidances during the learning session. The groups in hypoxia treated with donepezil had an increased number of avoidances in the learning session. In memory retention tests, significant differences were not observed in the hypoxic animals treated with galantamine or donepezil. In the step-through passive avoidance test, rats treated with galantamine had no change in the latency of reactions during the learning session and memory retention tests. In the step-down passive avoidance test, the animals treated with galantamine had increase latency of reactions during the learning and short- or long-memory retention tests. The hypoxic rats receiving donepezil had increased latency of reactions in the step-down short memory retention test. Our results suggest that galantamine and donepezil improve cognitive functions in a model of hypoxia.     

Effect of age on response to rivastigmine or donepezil in patients with Alzheimer's disease

ABSTRACT

Background: Younger Alzheimer's disease (AD) patients appear to differ genetically and neuropathologically from older AD patients, and may experience a more aggressive disease course compared with older patients. A randomised trial investigated the efficacy and tolerability of rivastigmine, an inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and donepezil, an AChE-selective inhibitor, in patients with AD over a 2-year period. This retrospective analysis investigated whether younger and older patients showed differential tolerability and efficacy responses to cholinesterase inhibitor treatment.

Methods: For the current analysis, patients were divided according to age at baseline: those aged < 75 years and those aged ≥ 75 years. Efficacy measures were the Severe Impairment Battery (SIB), Neuropsychiatric Inventory (NPI), Global Deterioration Scale (GDS), Mini-Mental State Examination (MMSE) and the AD Cooperative Study Activities of Daily Living scale (ADCS‐ADL). Changes in efficacy parameters and adverse event frequencies were calculated for rivastigmine and donepezil-treated patients in both age groups. Exploratory analyses were also conducted on SIB, ADCS‐ADL and NPI in patients who consented to pharmacogenetic testing at baseline. Genotyping of the apolipoprotein E (APOE) ε4 allele and the BuChE K-variant was conducted using the TaqMan assay. Main efficacy analyses were based on an intent-to-treat last observation carried forward (ITT‐LOCF) population.

Results: Of the 994 patients who received the study drug, 362 (36.4%) were younger than 75 years and 632 (63.6%) were aged 75 years or over. Rivastigmine provided significant benefits in younger patients compared with donepezil on the NPI‐10, NPI‐12, NPI‐D, GDS and ADCS‐ADL (all p < 0.05, ITT‐LOCF). With the exception of the NPI‐D in favour of donepezil (?p < 0.05, ITT‐LOCF), no significant treatment differences were observed in older patients. Younger patients with two wild-type BuChE alleles had a significantly greater response to rivastigmine than donepezil on the ADCS‐ADL (?p < 0.01, ITT‐LOCF) and SIB (?p < 0.05, ITT‐LOCF). The most common adverse events were nausea and vomiting and these were more frequent in rivastigmine-treated patients.

Conclusion: In this sub group analysis, patients younger than 75 years of age showed greater treatment responses to rivastigmine than donepezil. Analysis of response by BuChE genotype suggests that this differential effect may be due to the inhibition of BuChE, in addition to AChE, by rivastigmine.     

Effect of age on response to rivastigmine or donepezil in patients with Alzheimer's disease

BACKGROUND: Younger Alzheimer's disease (AD) patients appear to differ genetically and neuropathologically from older AD patients, and may experience a more aggressive disease course compared with older patients. A randomised trial investigated the efficacy and tolerability of rivastigmine, an inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and donepezil, an AChE-selective inhibitor, in patients with AD over a 2-year period. This retrospective analysis investigated whether younger and older patients showed differential tolerability and efficacy responses to cholinesterase inhibitor treatment. METHODS: For the current analysis, patients were divided according to age at baseline: those aged < 75 years and those aged >or= 75 years. Efficacy measures were the Severe Impairment Battery (SIB), Neuropsychiatric Inventory (NPI), Global Deterioration Scale (GDS), Mini-Mental State Examination (MMSE) and the AD Cooperative Study Activities of Daily Living scale (ADCS-ADL). Changes in efficacy parameters and adverse event frequencies were calculated for rivastigmine and donepezil-treated patients in both age groups. Exploratory analyses were also conducted on SIB, ADCS-ADL and NPI in patients who consented to pharmacogenetic testing at baseline. Genotyping of the apolipoprotein E (APOE) epsilon4 allele and the BuChE K-variant was conducted using the TaqMan assay. Main efficacy analyses were based on an intent-to-treat last observation carried forward (ITT-LOCF) population. RESULTS: Of the 994 patients who received the study drug, 362 (36.4%) were younger than 75 years and 632 (63.6%) were aged 75 years or over. Rivastigmine provided significant benefits in younger patients compared with donepezil on the NPI-10, NPI-12, NPI-D, GDS and ADCS-ADL (all p < 0.05, ITT-LOCF). With the exception of the NPI-D in favour of donepezil (p < 0.05, ITT-LOCF), no significant treatment differences were observed in older patients. Younger patients with two wild-type BuChE alleles had a significantly greater response to rivastigmine than donepezil on the ADCS-ADL (p < 0.01, ITT-LOCF) and SIB (p < 0.05, ITT-LOCF). The most common adverse events were nausea and vomiting and these were more frequent in rivastigmine-treated patients. CONCLUSION: In this sub group analysis, patients younger than 75 years of age showed greater treatment responses to rivastigmine than donepezil. Analysis of response by BuChE genotype suggests that this differential effect may be due to the inhibition of BuChE, in addition to AChE, by rivastigmine.     

Reversible and persistent decreases in cocaine self-administration after cholinesterase inhibition: different effects of donepezil and rivastigmine

We recently observed that pretreatment with the cholinesterase inhibitor, tacrine can produce long-lasting reductions in cocaine-reinforced behavior, described as persistent attenuation. In addition to inhibiting both acetylcholinesterase (AChE) and butyrylcholinesterase, tacrine can potentiate actions of dopamine. This study was carried out to evaluate the effects of donepezil (which selectively inhibits AChE) and rivastigmine (which inhibits both AChE and butyrylcholinesterase) on cocaine self-administration. High self-administration rats self-administered different doses of cocaine under a fixed ratio-5 schedule. Over a 4-day period, vehicle, donepezil, or rivastigmine was infused as animals were maintained in home cages (21 h per day), with signs of cholinergic stimulation (fasciculation, vacuous jaw movements, yawning, and diarrhea) scored by a blinded observer. Both compounds dose-dependently decreased cocaine self-administration, but differed in the potency and temporal pattern of their effects. Self-administration of low-dose cocaine was decreased to a greater degree by rivastigmine than donepezil (50% effective doses of 2.33 and 6.21 mg/kg/day, respectively), but this early effect did not continue beyond sessions immediately after treatment with rivastigmine. Group means for cocaine self-administration were decreased at some time points occurring between 1 and 3 days after the treatment with 10 mg/kg/day of donepezil (late effects), with decreases of more than 80% observed in some individual rats that persisted for 1 week or longer. Early, but not late, effects were correlated with signs of cholinergic stimulation. In summary, pretreatment with donepezil, but not rivastigmine produced persistent reductions in cocaine-reinforced behavior, which were not associated with signs of cholinergic stimulation.     

An open-label study of tiagabine in panic disorder

gamma-aminobutyric acid (GABA) has been implicated in the pathophysiology of anxiety disorders, including panic. Tiagabine, a selective GABA reuptake inhibitor (SGRI), has been shown to reduce symptoms of anxiety. This pilot study evaluated the efficacy and safety of tiagabine in patients with panic disorder. Male and female outpatients aged 18-64 years with a DSM-IV diagnosis of severe to moderately severe panic disorder (with or without agoraphobia) received open-label tiagabine 2-20 mg/day for 10 weeks. Outcome assessments included the Sheehan Panic Disorder Scale (SPS), Panic Disorder Severity Scale (PDSS), Bandelow Panic and Agoraphobia Scale (PAS), Hamilton Rating Scale for Anxiety (HAM-A), 21-point Clinician Global Improvement Scale (CGI-21), 21-point Patient Global Improvement (PGI-21) and the Sheehan Disability Scale (SDS). Scores were recorded at baseline and weekly intervals thereafter. Adverse events were monitored throughout the study. Of the 28 patients who enrolled in the study, 23 had one post-baseline visit and were available for LOCF outcome analysis. Although statistically significant reductions from baseline were observed for all of the outcome measures, the percentage improvements on individual scales were only in the 25-32% range which is not clinically significant. Tiagabine was generally well tolerated; the most common adverse events were nausea, dizziness and headaches. Only one patient discontinued tiagabine due to adverse events. These findings suggest that administration of tiagabine may be of little benefit in patients with panic disorder.     

Long-term efficacy and safety of donepezil in the treatment of Alzheimer's disease: final analysis of a US multicentre open-label study.

This multicentre, open-label study evaluated the long-term efficacy and safety of donepezil in the treatment of patients with mild to moderately severe Alzheimer's disease (AD). The 133 patients who entered the study had previously completed a 14-week randomized, double-blind, placebo-controlled study with donepezil. In this open-label study, patients were treated initially with 3 mg per day donepezil, which could be increased to 5, 7 and 10 mg per day in a step-wise fashion. Patients attended the clinic for assessments at 3-week intervals for the first 12 weeks, then subsequently at 12-week intervals for up to 240 weeks (254 cumulative weeks). Efficacy was assessed using the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) and the Clinical Dementia Rating-Sum of the Boxes scale (CDR-SB), and data were compared with those predicted for historical untreated AD patients. During the first 6-9 months of the study, mean ADAS-cog and CDR-SB scores showed evidence of clinical improvement from baseline. After this time scores gradually deteriorated. Overall the decline was less than that estimated if this cohort of patients had not been treated. The most common adverse events were related to the nervous and digestive systems, and were generally mild and transient, resolving without the need for dose modifications. There was no evidence of hepatotoxicity. In conclusion, these data demonstrate that donepezil is a well-tolerated, realistic symptomatic treatment for AD over a period of up to 4.9 years. An interim report of the first 98 weeks of the study has been published previously.