CLINICAL PHARMACOLOGY
Mechanism Of Action
Current theories on the pathogenesis of the cognitive
signs and symptoms of Alzheimer's disease attribute some of them to a
deficiency of cholinergic neurotransmission.
Donepezil hydrochloride is postulated to exert its
therapeutic effect by enhancing cholinergic function. This is accomplished by
increasing the concentration of acetylcholine through reversible inhibition of
its hydrolysis by acetylcholinesterase. There is no evidence that donepezil alters
the course of the underlying dementing process.
Pharmacokinetics
Pharmacokinetics of donepezil are linear over a dose
range of 1-10 mg given once daily. The rate and extent of absorption of ARICEPT
tablets are not influenced by food.
Based on population pharmacokinetic analysis of plasma
donepezil concentrations measured in patients with Alzheimer's disease,
following oral dosing, peak plasma concentration is achieved for ARICEPT 23 mg
tablets in approximately 8 hours, compared with 3 hours for ARICEPT 10 mg
tablets. Peak plasma concentrations were about 2-fold higher for ARICEPT 23 mg
tablets than ARICEPT 10 mg tablets.
ARICEPT ODT 5 mg and 10 mg are bioequivalent to ARICEPT 5
mg and 10 mg tablets, respectively. A food effect study has not been conducted
with ARICEPT ODT; however, the effect of food with ARICEPT ODT is expected to
be minimal. ARICEPT ODT can be taken without regard to meals.
The elimination half life of donepezil is about 70 hours,
and the mean apparent plasma clearance (Cl/F) is 0.13-0.19 L/hr/kg. Following
multiple dose administration, donepezil accumulates in plasma by 4-7 fold, and steady
state is reached within 15 days. The steady state volume of distribution is
12-16 L/kg. Donepezil is approximately 96% bound to human plasma proteins,
mainly to albumins (about 75%) and alpha1 - acid glycoprotein (about 21%) over
the concentration range of 2-1000 ng/mL.
Donepezil is both excreted in the urine intact and
extensively metabolized to four major metabolites, two of which are known to be
active, and a number of minor metabolites, not all of which have been
identified. Donepezil is metabolized by CYP 450 isoenzymes 2D6 and 3A4 and
undergoes glucuronidation. Following administration of 14C-labeled donepezil,
plasma radioactivity, expressed as a percent of the administered dose, was
present primarily as intact donepezil (53%) and as 6-O-desmethyl donepezil
(11%), which has been reported to inhibit AChE to the same extent as donepezil in
vitro and was found in plasma at concentrations equal to about 20% of
donepezil. Approximately 57% and 15% of the total radioactivity was recovered
in urine and feces, respectively, over a period of 10 days, while 28% remained
unrecovered, with about 17% of the donepezil dose recovered in the urine as
unchanged drug. Examination of the effect of CYP2D6 genotype in Alzheimer's
patients showed differences in clearance values among CYP2D6 genotype
subgroups. When compared to the extensive metabolizers, poor metabolizers had a
31.5% slower clearance and ultra-rapid metabolizers had a 24% faster clearance.
Hepatic Disease
In a study of 10 patients with stable alcoholic
cirrhosis, the clearance of ARICEPT was decreased by 20% relative to 10 healthy
age- and sex-matched subjects.
Renal Disease
In a study of 11 patients with moderate to severe renal
impairment (ClC < 18 mL/min/1.73 m²) the clearance of ARICEPT did not differ
from 11 age- and sex-matched healthy subjects.
Age
No formal pharmacokinetic study was conducted to examine
age-related differences in the pharmacokinetics of ARICEPT. Population
pharmacokinetic analysis suggested that the clearance of donepezil in patients
decreases with increasing age. When compared with 65-year old subjects, 90-year
old subjects have a 17% decrease in clearance, while 40-year old subjects have
a 33% increase in clearance. The effect of age on donepezil clearance may not
be clinically significant.
Gender And Race
No specific pharmacokinetic study was conducted to
investigate the effects of gender and race on the disposition of ARICEPT.
However, retrospective pharmacokinetic analysis and population pharmacokinetic analysis
of plasma donepezil concentrations measured in patients with Alzheimer's
disease indicates that gender and race (Japanese and Caucasians) did not affect
the clearance of ARICEPT to an important degree.
Body Weight
There was a relationship noted between body weight and
clearance. Over the range of body weight from 50 kg to 110 kg, clearance
increased from 7.77 L/h to 14.04 L/h, with a value of 10 L/hr for 70 kg
individuals.
Drug Interactions
Effect Of ARICEPT On The Metabolism Of Other Drugs
No in vivo clinical trials have investigated the effect
of ARICEPT on the clearance of drugs metabolized by CYP 3A4 (e.g., cisapride,
terfenadine) or by CYP 2D6 (e.g., imipramine). However, in vitro studies show a
low rate of binding to these enzymes (mean Ki about 50-130 μM), that,
given the therapeutic plasma concentrations of donepezil (164 nM), indicates
little likelihood of interference. Based on in vitro studies, donepezil shows little
or no evidence of direct inhibition of CYP2B6, CYP2C8, and CYP2C19 at
clinically relevant concentrations.
Whether ARICEPT has any potential for enzyme induction is
not known. Formal pharmacokinetic studies evaluated the potential of ARICEPT
for interaction with theophylline, cimetidine, warfarin, digoxin, and ketoconazole.
No effects of ARICEPT on the pharmacokinetics of these drugs were observed.
Effect Of Other Drugs On The Metabolism Of ARICEPT
Ketoconazole and quinidine, strong inhibitors of CYP450
3A and 2D6, respectively, inhibit donepezil metabolism in vitro. Whether there
is a clinical effect of quinidine is not known. Population pharmacokinetic analysis
showed that in the presence of concomitant CYP2D6 inhibitors donepezil AUC was
increased by approximately 17% to 20% in Alzheimer's disease patients taking
ARICEPT 10 and 23 mg. This represented an average effect of weak, moderate, and
strong CYP2D6 inhibitors. In a 7-day crossover study in 18 healthy volunteers,
ketoconazole (200 mg q.d.) increased mean donepezil (5 mg q.d.) concentrations
(AUC0-24 and Cmax) by 36%. The clinical relevance of this increase in
concentration is unknown.
Inducers of CYP 3A (e.g., phenytoin, carbamazepine,
dexamethasone, rifampin, and phenobarbital) could increase the rate of
elimination of ARICEPT.
Formal pharmacokinetic studies demonstrated that the metabolism
of ARICEPT is not significantly affected by concurrent administration of
digoxin or cimetidine.
An in vitro study showed that donepezil was not a
substrate of P-glycoprotein.
Drugs Highly Bound To Plasma Proteins
Drug displacement studies have been performed in vitro between
this highly bound drug (96%) and other drugs such as furosemide, digoxin, and
warfarin. ARICEPT at concentrations of 0.3-10 micrograms/mL did not affect the
binding of furosemide (5 micrograms/mL), digoxin (2 ng/mL), and warfarin (3
micrograms/mL) to human albumin. Similarly, the binding of ARICEPT to human
albumin was not affected by furosemide, digoxin, and warfarin.
Animal Toxicology And/Or Pharmacology
In an acute dose neurotoxicity study in female rats, oral
administration of donepezil and memantine in combination resulted in increased
incidence, severity, and distribution of neurodegeneration compared with memantine
alone. The no-effect levels of the combination were associated with clinically
relevant plasma donepezil and memantine levels.
The relevance of this finding to humans is unknown.
Clinical Studies
Mild To Moderate Alzheimer’s Disease
The effectiveness of ARICEPT as a treatment for mild to
moderate Alzheimer's disease is demonstrated by the results of two randomized,
double-blind, placebo-controlled clinical investigations in patients with
Alzheimer's disease (diagnosed by NINCDS and DSM III-R criteria, Mini-Mental
State Examination ≥10 and ≤ 26 and Clinical Dementia Rating of 1
or 2). The mean age of patients participating in ARICEPT trials was 73 years with
a range of 50 to 94. Approximately 62% of patients were women and 38% were men.
The racial distribution was white 95%, black 3%, and other races 2%.
The higher dose of 10 mg did not provide a statistically
significantly greater clinical benefit than 5 mg. There is a suggestion,
however, based upon order of group mean scores and dose trend analyses of data
from these clinical trials, that a daily dose of 10 mg of ARICEPT might provide
additional benefit for some patients. Accordingly, whether or not to employ a
dose of 10 mg is a matter of prescriber and patient preference.
Study Outcome Measures
In each study, the effectiveness of treatment with
ARICEPT was evaluated using a dual outcome assessment strategy.
The ability of ARICEPT to improve cognitive performance
was assessed with the cognitive subscale of the Alzheimer's Disease Assessment Scale
(ADAS-cog), a multi-item instrument that has been extensively validated in
longitudinal cohorts of Alzheimer's disease patients. The ADAS-cog examines
selected aspects of cognitive performance including elements of memory,
orientation, attention, reasoning, language, and praxis. The ADAS-cog scoring
range is from 0 to 70, with higher scores indicating greater cognitive
impairment. Elderly normal adults may score as low as 0 or 1, but it is not
unusual for non-demented adults to score slightly higher.
The patients recruited as participants in each study had
mean scores on the ADAS-cog of approximately 26 points, with a range from 4 to
61. Experience based on longitudinal studies of ambulatory patients with mild to
moderate Alzheimer's disease suggest that scores on the ADAS-cog increase
(worsen) by 6-12 points per year. However, smaller changes may be seen in
patients with very mild or very advanced disease since the ADAS-cog is not
uniformly sensitive to change over the course of the disease. The annualized
rate of decline in the placebo patients participating in ARICEPT trials was
approximately 2 to 4 points per year.
The ability of ARICEPT to produce an overall clinical
effect was assessed using a Clinician's Interview-Based Impression of Change
that required the use of caregiver information, the CIBIC-plus. The CIBIC-plus
is not a single instrument and is not a standardized instrument like the
ADAS-cog. Clinical trials for investigational drugs have used a variety of
CIBIC formats, each different in terms of depth and structure.
As such, results from a CIBIC-plus reflect clinical
experience from the trial or trials in which it was used and cannot be compared
directly with the results of CIBIC-plus evaluations from other clinical trials.
The CIBICplus used in ARICEPT trials was a semi-structured instrument that was
intended to examine four major areas of patient function: General, Cognitive,
Behavioral, and Activities of Daily Living. It represents the assessment of a
skilled clinician based upon his/her observations at an interview with the
patient, in combination with information supplied by a caregiver familiar with
the behavior of the patient over the interval rated. The CIBICplus is scored as
a seven-point categorical rating, ranging from a score of 1, indicating
“markedly improved,” to a score of 4, indicating “no change” to a score of 7,
indicating “markedly worse.” The CIBIC-plus has not been systematically
compared directly to assessments not using information from caregivers (CIBIC)
or other global methods.
Thirty-Week Study
In a study of 30 weeks duration, 473 patients were
randomized to receive single daily doses of placebo, 5 mg/day or 10 mg/day of
ARICEPT. The 30-week study was divided into a 24-week double-blind active treatment
phase followed by a 6-week single-blind placebo washout period. The study was
designed to compare 5 mg/day or 10 mg/day fixed doses of ARICEPT to placebo.
However, to reduce the likelihood of cholinergic effects, the 10 mg/day
treatment was started following an initial 7-day treatment with 5 mg/day doses.
Effects On The ADAS-cog
Figure 1 illustrates the time course for the change from
baseline in ADAS-cog scores for all three dose groups over the 30 weeks of the
study. After 24 weeks of treatment, the mean differences in the ADAS-cog change
scores for ARICEPT treated patients compared to the patients on placebo were
2.8 and 3.1 points for the 5 mg/day and 10 mg/day treatments, respectively.
These differences were statistically significant. While the treatment effect
size may appear to be slightly greater for the 10 mg/day treatment, there was
no statistically significant difference between the two active treatments.
Following 6 weeks of placebo washout, scores on the
ADAS-cog for both the ARICEPT treatment groups were indistinguishable from
those patients who had received only placebo for 30 weeks. This suggests that
the beneficial effects of ARICEPT abate over 6 weeks following discontinuation
of treatment and do not represent a change in the underlying disease. There was
no evidence of a rebound effect 6 weeks after abrupt discontinuation of
therapy.
Figure 1: Time-course of the Change from Baseline in
ADAS-cog Score for Patients Completing 24 Weeks of Treatment.
Figure 2 illustrates the cumulative percentages of
patients from each of the three treatment groups who had attained the measure
of improvement in ADAS-cog score shown on the X axis. Three change scores
(7-point and 4-point reductions from baseline or no change in score) have been
identified for illustrative purposes, and the percent of patients in each group
achieving that result is shown in the inset table.
The curves demonstrate that both patients assigned to
placebo and ARICEPT have a wide range of responses, but that the active
treatment groups are more likely to show greater improvements. A curve for an
effective treatment would be shifted to the left of the curve for placebo,
while an ineffective or deleterious treatment would be superimposed upon or
shifted to the right of the curve for placebo.
Figure 2: Cumulative Percentage of Patients Completing
24 Weeks of Double-blind Treatment with Specified Changes from Baseline
ADAS-cog Scores. The Percentages of Randomized Patients who Completed the Study
were: Placebo 80%, 5 mg/day 85%, and 10 mg/day 68%.
Effects On The CIBIC-plus
Figure 3 is a histogram of the frequency distribution of
CIBIC-plus scores attained by patients assigned to each of the three treatment
groups who completed 24 weeks of treatment. The mean drug-placebo differences
for these groups of patients were 0.35 points and 0.39 points for 5 mg/day and
10 mg/day of ARICEPT, respectively. These differences were statistically
significant. There was no statistically significant difference between the two
active treatments.
Figure 3: Frequency Distribution of CIBIC-plus Scores
at Week 24.
Fifteen-Week Study
In a study of 15 weeks duration, patients were randomized
to receive single daily doses of placebo or either 5 mg/day or 10 mg/day of
ARICEPT for 12 weeks, followed by a 3-week placebo washout period. As in the 30-week
study, to avoid acute cholinergic effects, the 10 mg/day treatment followed an
initial 7-day treatment with 5 mg/day doses.
Effects On The ADAS-cog
Figure 4 illustrates the time course of the change from
baseline in ADAS-cog scores for all three dose groups over the 15 weeks of the
study. After 12 weeks of treatment, the differences in mean ADAS-cog change
scores for the ARICEPT treated patients compared to the patients on placebo
were 2.7 and 3.0 points each, for the 5 and 10 mg/day ARICEPT treatment groups,
respectively. These differences were statistically significant. The effect size
for the 10 mg/day group may appear to be slightly larger than that for 5
mg/day. However, the differences between active treatments were not statistically
significant.
Figure 4: Time-course of the Change from Baseline in
ADAS-cog Score for Patients Completing the 15-week Study.
Following 3 weeks of placebo washout, scores on the
ADAS-cog for both the ARICEPT treatment groups increased, indicating that
discontinuation of ARICEPT resulted in a loss of its treatment effect. The
duration of this placebo washout period was not sufficient to characterize the
rate of loss of the treatment effect, but the 30- week study (see above)
demonstrated that treatment effects associated with the use of ARICEPT abate
within 6 weeks of treatment discontinuation.
Figure 5 illustrates the cumulative percentages of
patients from each of the three treatment groups who attained the measure of
improvement in ADAS-cog score shown on the X axis. The same three change scores
(7-point and 4-point reductions from baseline or no change in score) as
selected for the 30-week study have been used for this illustration. The
percentages of patients achieving those results are shown in the inset table. As
observed in the 30-week study, the curves demonstrate that patients assigned to
either placebo or to ARICEPT have a wide range of responses, but that the
ARICEPT treated patients are more likely to show greater improvements in
cognitive performance.
Figure 5: Cumulative Percentage of Patients with
Specified Changes from Baseline ADAS-cog Scores. The Percentages of Randomized
Patients Within Each Treatment Group Who Completed the Study Were: Placebo 93%,
5 mg/day 90%, and 10 mg/day 82%.
Effects On The CIBIC-plus
Figure 6 is a histogram of the frequency distribution of
CIBIC-plus scores attained by patients assigned to each of the three treatment
groups who completed 12 weeks of treatment. The differences in mean scores for ARICEPT
treated patients compared to the patients on placebo at Week 12 were 0.36 and
0.38 points for the 5 mg/day and 10 mg/day treatment groups, respectively.
These differences were statistically significant.
Figure 6: Frequency Distribution of CIBIC-plus Scores
at Week 12.
In both studies, patient age,
sex, and race were not found to predict the clinical outcome of ARICEPT
treatment.
Moderate To Severe Alzheimer’s
Disease
The effectiveness of ARICEPT in
the treatment of patients with moderate to severe Alzheimer’s disease was established
in studies employing doses of 10 mg/day and 23 mg/day. Results of a controlled
clinical trial in moderate to severe Alzheimer’s Disease that compared ARICEPT
23 mg once daily to 10 mg once daily suggest that a 23 mg dose of ARICEPT provided
additional benefit.
Swedish 6 Month Study (10
mg/day)
The effectiveness of ARICEPT as
a treatment for severe Alzheimer’s disease is demonstrated by the results of a randomized,
double-blind, placebo-controlled clinical study conducted in Sweden (6 month
study) in patients with probable or possible Alzheimer’s disease diagnosed by
NINCDS-ADRDA and DSM-IV criteria, MMSE: range of 1-10. Two hundred and forty
eight (248) patients with severe Alzheimer’s disease were randomized to ARICEPT
or placebo. For patients randomized to ARICEPT, treatment was initiated at 5 mg
once daily for 28 days and then increased to 10 mg once daily. At the end of
the 6 month treatment period, 90.5% of the ARICEPT treated patients were
receiving the 10 mg/day dose. The mean age of patients was 84.9 years, with a range
of 59 to 99. Approximately 77% of patients were women, and 23% were men. Almost
all patients were Caucasian. Probable Alzheimer’s disease was diagnosed in the
majority of the patients (83.6% of ARICEPT treated patients and 84.2% of
placebo treated patients).
Study Outcome Measures
The effectiveness of treatment
with ARICEPT was determined using a dual outcome assessment strategy that evaluated
cognitive function using an instrument designed for more impaired patients and
overall function through caregiver-rated assessment. This study showed that
patients on ARICEPT experienced significant improvement on both measures
compared to placebo.
The ability of ARICEPT to
improve cognitive performance was assessed with the Severe Impairment Battery (SIB).
The SIB, a multi-item instrument, has been validated for the evaluation of
cognitive function in patients with moderate to severe dementia. The SIB
evaluates selective aspects of cognitive performance, including elements of memory,
language, orientation, attention, praxis, visuospatial ability, construction,
and social interaction. The SIB scoring range is from 0 to 100, with lower
scores indicating greater cognitive impairment.
Daily function was assessed
using the Modified Alzheimer’s Disease Cooperative Study Activities of Daily Living
Inventory for Severe Alzheimer’s Disease (ADCS-ADL-severe). The ADCS-ADL-severe
is derived from the Alzheimer’s Disease Cooperative Study Activities of Daily
Living Inventory, which is a comprehensive battery of ADL questions used to
measure the functional capabilities of patients. Each ADL item is rated from
the highest level of independent performance to complete loss. The
ADCS-ADL-severe is a subset of 19 items, including ratings of the patient’s
ability to eat, dress, bathe, use the telephone, get around (or travel), and
perform other activities of daily living; it has been validated for the
assessment of patients with moderate to severe dementia. The ADCS-ADL-severe
has a scoring range of 0 to 54, with the lower scores indicating greater
functional impairment. The investigator performs the inventory by interviewing
a caregiver, in this study a nurse staff member, familiar with the functioning
of the patient.
Effects On The SIB
Figure 7 shows the time course
for the change from baseline in SIB score for the two treatment groups over the
6 months of the study. At 6 months of treatment, the mean difference in the SIB
change scores for ARICEPT treated patients compared to patients on placebo was
5.9 points. ARICEPT treatment was statistically significantly superior to
placebo.
Figure 7: Time Course of the
Change from Baseline in SIB Score for Patients Completing 6 Months of Treatment.
Figure 8 illustrates the
cumulative percentages of patients from each of the two treatment groups who
attained the measure of improvement in SIB score shown on the X-axis. While
patients assigned both to ARICEPT and to placebo have a wide range of
responses, the curves show that the ARICEPT group is more likely to show a greater
improvement in cognitive performance.
Figure 8: Cumulative
Percentage of Patients Completing 6 Months of Double-blind Treatment with
Particular Changes from Baseline in SIB Scores.
Figure 9: Time Course of the Change from Baseline in
ADCS-ADL-Severe Score for Patients Completing 6 Months of Treatment.
Effects On The ADCS-ADL-severe
Figure 9 illustrates the time
course for the change from baseline in ADCS-ADL-severe scores for patients in
the two treatment groups over the 6 months of the study. After 6 months of
treatment, the mean difference in the ADCS-ADL-severe change scores for ARICEPT
treated patients compared to patients on placebo was 1.8 points. ARICEPT treatment was statistically significantly
superior to placebo.
Figure 10 shows the cumulative
percentages of patients from each treatment group with specified changes from baseline
ADCS-ADL-severe scores. While both patients assigned to ARICEPT and placebo
have a wide range of responses, the curves demonstrate that the ARICEPT group
is more likely to show a smaller decline or an improvement.
Figure 10: Cumulative
Percentage of Patients Completing 6 Months of Double-blind Treatment with
Particular Changes from Baseline in ADCS-ADL-Severe Scores.
Japanese 24-Week Study (10
mg/day)
In a study of 24 weeks duration
conducted in Japan, 325 patients with severe Alzheimer’s disease were randomized
to doses of 5 mg/day or 10 mg/day of donepezil, administered once daily, or
placebo. Patients randomized to treatment with donepezil were to achieve their
assigned doses by titration, beginning at 3 mg/day, and extending over a
maximum of 6 weeks. Two hundred and forty eight (248) patients completed the
study, with similar proportions of patients completing the study in each
treatment group. The primary efficacy measures for this study were the SIB and
CIBIC-plus.
At 24 weeks of treatment,
statistically significant treatment differences were observed between the 10
mg/day dose of donepezil and placebo on both the SIB and CIBIC-plus. The 5
mg/day dose of donepezil showed a statistically significant superiority to
placebo on the SIB, but not on the CIBIC-plus.
Study Of 23 mg/day
The effectiveness of ARICEPT 23
mg/day as a treatment for moderate to severe Alzheimer’s disease has been demonstrated
by the results of a randomized, double-blind, controlled clinical investigation
in patients with moderate to severe Alzheimer’s disease. The controlled
clinical study was conducted globally in patients with probable Alzheimer’s
disease diagnosed by NINCDS-ADRDA and DSM-IV criteria, MMSE: range of 0-20. Patients
were required to have been on a stable dose of ARICEPT 10 mg/day for at least 3
months prior to screening. One thousand four hundred and thirty four (1434)
patients with moderate to severe Alzheimer’s disease were randomized to 23
mg/day or 10 mg/day. The mean age of patients was 73.8 years, with a range of 47
to 90. Approximately 63% of patients were women, and 37% were men.
Approximately 36% of the patients were taking memantine throughout the study.
Study Outcome Measures
The effectiveness of treatment
with 23 mg/day was determined using a dual outcome assessment strategy that evaluated
cognitive function using an instrument designed for more impaired patients and
overall function through caregiver-rated assessment.
The ability of 23 mg/day to
improve cognitive performance was assessed with the Severe Impairment Battery (SIB).
The SIB, a multi-item instrument, has been validated for the evaluation of
cognitive function in patients with moderate to severe dementia. The SIB
evaluates selective aspects of cognitive performance, including elements of
memory, language, orientation, attention, praxis, visuospatial ability,
construction, and social interaction. The SIB scoring range is from 0 to 100,
with lower scores indicating greater cognitive impairment.
The ability of 23 mg/day to
produce an overall clinical effect was assessed using a Clinician’s
Interview-Based Impression of Change that incorporated the use of caregiver
information, the CIBIC-plus. The CIBIC-plus used in this trial was a
semi-structured instrument that examines four major areas of patient function:
General, Cognitive, Behavioral, and Activities of Daily Living. It represents
the assessment of a skilled clinician based upon his/her observations at an
interview with the patient, in combination with information supplied by a caregiver
familiar with the behavior of the patient over the interval rated. The
CIBIC-plus is scored as a sevenpoint categorical rating, ranging from a score
of 1, indicating “markedly improved,” to a score of 4, indicating “no change”
to a score of 7, indicating “markedly worse.”
Effects On The SIB
Figure 11 shows the time course
for the change from baseline in SIB score for the two treatment groups over the
24 weeks of the study. At 24 weeks of treatment, the LS mean difference in the
SIB change scores for 23 mg/day-treated patients compared to patients treated
with 10 mg was 2.2 units (p = 0.0001). The dose of 23 mg/day was statistically
significantly superior to the dose of 10 mg/day.
Figure 11: Time-course of
the Change from Baseline in SIB Score for Patients Completing 24 Weeks of Treatment.
Figure 12 illustrates the cumulative percentages of
patients from each of the two treatment groups who attained the measure of
improvement in SIB score shown on the X-axis. While patients assigned both to
23 mg/day and to 10 mg/day have a wide range of responses, the curves show that
the 23 mg-group is more likely to show a greater improvement in cognitive
performance. When such curves are shifted to the left, this indicates a greater
percentage of patients responding to treatment on the SIB.
Figure 12: Cumulative Percentage of Patients
Completing 24 Weeks of Double-blind Treatment with Specified Changes from
Baseline SIB Scores.
Effects On The CIBIC-plus
Figure 13 is a histogram of the frequency distribution of
CIBIC-plus scores attained by patients at the end of 24 weeks of treatment. The
mean difference between the 23 mg/day and 10 mg/day treatment groups was 0.06
units. This difference was not statistically significant.
Figure 13: Frequency Distribution of CIBIC-plus Scores
at Week 24.