| Pharmacotherapeutic group: anticholinesterases, ATC code: N06DA03Rivastigmine is an acetyl- and butyrylcholinesterase inhibitor of the carbamate type, thought to facilitate cholinergic neurotransmission by slowing the degradation of acetylcholine released by functionally intact cholinergic neurones. Thus, rivastigmine may have an ameliorative effect on cholinergic-mediated cognitive deficits in dementia associated with Alzheimer's disease and Parkinson's disease.Rivastigmine interacts with its target enzymes by forming a covalently bound complex that temporarily inactivates the enzymes. In healthy young men, an oral 3 mg dose decreases acetylcholinesterase (AChE) activity in CSF by approximately 40% within the first 1.5 hours after administration. Activity of the enzyme returns to baseline levels about 9 hours after the maximum inhibitory effect has been achieved. In patients with Alzheimer's disease, inhibition of AChE in CSF by rivastigmine was dose-dependent up to 6 mg given twice daily, the highest dose tested. Inhibition of butyrylcholinesterase activity in CSF of 14 Alzheimer patients treated by rivastigmine was similar to that of AChE. Clinical studies in Alzheimer's dementia The efficacy of rivastigmine has been established through the use of three independent, domain specific, assessment tools which were assessed at periodic intervals during 6 month treatment periods. These include the ADAS-Cog (a performance based measure of cognition), the CIBIC-Plus (a comprehensive global assessment of the patient by the physician incorporating caregiver input), and the PDS (a caregiver-rated assessment of the activities of daily living including personal hygiene, feeding, dressing, household chores such as shopping, retention of ability to orient oneself to surroundings as well as involvement in activities relating to finances, etc.).The patients studied had an MMSE (Mini-Mental State Examination) score of 1024.The results for clinically relevant responders pooled from two flexible dose studies out of the three pivotal 26-week multicentre studies in patients with mild-to-moderately severe Alzheimer's Dementia, are provided in Table 4 below. Clinically relevant improvement in these studies was defined a priori as at least 4-point improvement on the ADAS-Cog, improvement on the CIBIC-Plus, or at least a 10% improvement on the PDS.In addition, a post-hoc definition of response is provided in the same table. The secondary definition of response required a 4-point or greater improvement on the ADAS-Cog, no worsening on the CIBIC-Plus, and no worsening on the PDS. The mean actual daily dose for responders in the 612 mg group, corresponding to this definition, was 9.3 mg. It is important to note that the scales used in this indication vary and direct comparisons of results for different therapeutic agents are not valid.Table 4 | | Patients with Clinically Significant Response (%) | | | Intent to Treat | Last Observation Carried Forward | Response Measure | Rivastigmine 612 mg N=473 | Placebo N=472 | Rivastigmine 612 mg N=379 | Placebo N=444 | ADAS-Cog: improvement of at least 4 points | 21*** | 12 | 25*** | 12 | CIBIC-Plus: improvement | 29*** | 18 | 32*** | 19 | PDS: improvement of at least 10% | 26*** | 17 | 30*** | 18 | At least 4 points improvement on ADAS-Cog with no worsening on CIBIC-Plus and PDS | 10* | 6 | 12** | 6 | *p<0.05, **p<0.01, ***p<0.001Clinical studies in dementia associated with Parkinson's disease The efficacy of rivastigmine in dementia associated with Parkinson's disease has been demonstrated in a 24-week multicentre, double-blind, placebo-controlled core study and its 24-week open-label extension phase. Patients involved in this study had an MMSE (Mini-Mental State Examination) score of 1024. Efficacy has been established by the use of two independent scales which were assessed at regular intervals during a 6-month treatment period as shown in Table 5 below: the ADAS-Cog, a measure of cognition, and the global measure ADCS-CGIC (Alzheimer's Disease Cooperative Study-Clinician's Global Impression of Change).Table 5 Dementia associated with Parkinson's Disease | ADAS-Cog Exelon | ADAS-Cog Placebo | ADCS-CGIC Exelon | ADCS-CGIC Placebo | ITT + RDO population | (n=329) | (n=161) | (n=329) | (n=165) | Mean baseline ± SD Mean change at 24 weeks ± SD | 23.8 ± 10.2 2.1 ± 8.2 | 24.3 ± 10.5 -0.7 ± 7.5 | n/a 3.8 ± 1.4 | n/a 4.3 ± 1.5 | Adjusted treatment difference | 2.881 | n/a | p-value versus placebo | <0.0011 | 0.0072 | | | | | | ITT - LOCF population | (n=287) | (n=154) | (n=289) | (n=158) | | | | | | Mean baseline ± SD Mean change at 24 weeks ± SD | 24.0 ± 10.3 2.5 ± 8.4 | 24.5 ± 10.6 -0.8 ± 7.5 | n/a 3.7 ± 1.4 | n/a 4.3 ± 1.5 | Adjusted treatment difference | 3.541 | n/a | p-value versus placebo | <0.0011 | <0.0012 | | | | | | 1 Based on ANCOVA with treatment and country as factors and baseline ADAS-Cog as a covariate. A positive change indicates improvement.2 Mean data shown for convenience, categorical analysis performed using van Elteren testITT: Intent-To-Treat; RDO: Retrieved Drop Outs; LOCF: Last Observation Carried ForwardAlthough a treatment effect was demonstrated in the overall study population, the data suggested that a larger treatment effect relative to placebo was seen in the subgroup of patients with moderate dementia associated with Parkinson's disease. Similarly a larger treatment effect was observed in those patients with visual hallucinations (see Table 6).Table 6 Dementia associated with Parkinson's Disease | ADAS-Cog Exelon | ADAS-Cog Placebo | ADAS-Cog Exelon | ADAS-Cog Placebo | | Patients with visual hallucinations | Patients without visual hallucinations | | | | | | | ITT + RDO population | (n=107) | (n=60) | (n=220) | (n=101) | | | | | | Mean baseline ± SD Mean change at 24 weeks ± SD | 25.4 ± 9.9 1.0 ± 9.2 | 27.4 ± 10.4 -2.1 ± 8.3 | 23.1 ± 10.4 2.6 ± 7.6 | 22.5 ± 10.1 0.1 ± 6.9 | Adjusted treatment difference | 4.271 | 2.091 | p-value versus placebo | 0.0021 | 0.0151 | | | Patients with moderate dementia (MMSE 10-17) | Patients with mild dementia (MMSE 18-24) | | | | | | | ITT + RDO population | (n=87) | (n=44) | (n=237) | (n=115) | | | | | | Mean baseline ± SD Mean change at 24 weeks ± SD | 32.6 ± 10.4 2.6 ± 9.4 | 33.7 ± 10.3 -1.8 ± 7.2 | 20.6 ± 7.9 1.9 ± 7.7 | 20.7 ± 7.9 -0.2 ± 7.5 | Adjusted treatment difference | 4.731 | 2.141 | p-value versus placebo | 0.0021 | 0.0101 | | | | | | 1 Based on ANCOVA with treatment and country as factors and baseline ADAS-Cog as a covariate. A positive change indicates improvement.ITT: Intent-To-Treat; RDO: Retrieved Drop Outs | |