CLINICAL PHARMACOLOGY
Mechanism of Action
Solifenacin is a competitive
muscarinic receptor antagonist. Muscarinic receptors play an important role in
several major cholinergically mediated functions, including contractions of
urinary bladder smooth muscle and stimulation of salivary secretion.
Pharmacodynamics
Cardiac Electrophysiology
The effect of 10 mg and 30 mg solifenacin succinate on
the QT interval was evaluated at the time of peak plasma concentration of
solifenacin in a multi-dose, randomized, double-blind, placebo and
positive-controlled (moxifloxacin 400 mg) trial. Subjects were randomized to
one of two treatment groups after receiving placebo and moxifloxacin
sequentially. One group (n=51) went on to complete 3 additional sequential
periods of dosing with solifenacin 10, 20, and 30 mg while the second group
(n=25) in parallel completed a sequence of placebo and moxifloxacin. Study
subjects were female volunteers aged 19 to 79 years. The 30 mg dose of
solifenacin succinate (three times the highest recommended dose) was chosen for
use in this study because this dose results in a solifenacin exposure that
covers those observed upon co-administration of 10 mg VESIcare with potent
CYP3A4 inhibitors (e.g. ketoconazole, 400 mg). Due to the sequential dose
escalating nature of the study, baseline EKG measurements were separated from
the final QT assessment (of the 30 mg dose level) by 33 days.
The median difference from baseline in heart rate
associated with the 10 and 30 mg doses of solifenacin succinate compared to
placebo was -2 and 0 beats/minute, respectively. Because a significant period
effect on QTc was observed, the QTc effects were analyzed utilizing the
parallel placebo control arm rather than the pre-specified intra-patient
analysis. Representative results are shown in Table 2.
Table 2: QTc changes in msec (90%CI) from baseline at
Tmax (relative to placebo)*
Drug/Dose |
Fridericia method (using mean difference) |
Solifenacin 10 mg |
2 (-3,6) |
Solifenacin 30 mg |
8 (4,13) |
*Results displayed are those
derived from the parallel design portion of the study and represent the comparison
of Group 1 to time-matched placebo effects in Group 2 |
Moxifloxacin was included as a
positive control in this study and, given the length of the study, its effect
on the QT interval was evaluated in 3 different sessions. The placebo
subtracted mean changes (90% CI) in QTcF for moxifloxacin in the three sessions
were 11 (7, 14), 12 (8, 17), and 16 (12, 21), respectively.
The QT interval prolonging
effect appeared greater for the 30 mg compared to the 10 mg dose of
solifenacin. Although the effect of the highest solifenacin dose (three times
the maximum therapeutic dose) studied did not appear as large as that of the
positive control moxifloxacin at its therapeutic dose, the confidence intervals
overlapped. This study was not designed to draw direct statistical conclusions
between the drugs or the dose levels.
Pharmacokinetics
Absorption
After oral administration of
VESIcare to healthy volunteers, peak plasma levels (Cmax) of solifenacin are reached
within 3 to 8 hours after administration, and at steady state ranged from 32.3
to 62.9 ng/mL for the 5 and 10 mg VESIcare tablets, respectively. The absolute
bioavailability of solifenacin is approximately 90%, and plasma concentrations
of solifenacin are proportional to the dose administered.
Effect of food
VESIcare may be administered
without regard to meals. A single 10 mg dose administration of VESIcare with
food increased Cmax and AUC by 4% and 3%, respectively.
Distribution
Solifenacin is approximately
98% (in vivo) bound to human plasma proteins, principally to ∞1-acid glycoprotein. Solifenacin is highly distributed to
non-CNS tissues, having a mean steady-state volume of distribution of 600L.
Metabolism
Solifenacin is extensively
metabolized in the liver. The primary pathway for elimination is by way of
CYP3A4; however, alternate metabolic pathways exist. The primary metabolic
routes of solifenacin are through N-oxidation of the quinuclidin ring and
4R-hydroxylation of tetrahydroisoquinoline ring. One pharmacologically active
metabolite (4R-hydroxy solifenacin), occurring at low concentrations and
unlikely to contribute significantly to clinical activity, and three
pharmacologically inactive metabolites (N-glucuronide and the N-oxide and 4R-hydroxy-N-oxide
of solifenacin) have been found in human plasma after oral dosing.
Excretion
Following the administration of
10 mg of 14C-solifenacin succinate to healthy volunteers, 69.2% of
the radioactivity was recovered in the urine and 22.5% in the feces over 26
days. Less than 15% (as mean value) of the dose was recovered in the urine as
intact solifenacin. The major metabolites identified in urine were N-oxide of
solifenacin, 4R-hydroxy solifenacin and 4R-hydroxy-N-oxide of solifenacin and
in feces 4R-hydroxy solifenacin. The elimination half-life of solifenacin
following chronic dosing is approximately 45-68 hours.
Drug Interactions
Potent CYP3A4 Inhibitors
In a crossover study, following
blockade of CYP3A4 by coadministration of the potent CYP3A4 inhibitor,
ketoconazole 400 mg, once daily for 21 days, the mean Cmax and AUC of
solifenacin increased by 1.5 and 2.7-fold, respectively [see DOSAGE AND
ADMINISTRATION and DRUG INTERACTIONS].
Warfarin
In a crossover study, subjects
received a single oral dose of warfarin 25 mg on the 10th day of
dosing with either solifenacin 10 mg or matching placebo once daily for 16
days. For R-warfarin when it was coadministered with solifenacin, the mean Cmax
increased by 3% and AUC decreased by 2%. For S-warfarin when it was
coadministered with solifenacin, the mean Cmax and AUC increased by 5% and 1%,
respectively [see DRUG INTERACTIONS].
Oral Contraceptives
In a crossover study, subjects
received 2 cycles of 21 days of oral contraceptives containing 30 ug ethinyl
estradiol and 150 ug levonorgestrel. During the second cycle, subjects received
additional solifenacin 10 mg or matching placebo once daily for 10 days
starting from 12th day of receipt of oral contraceptives. For
ethinyl estradiol when it was administered with solifenacin, the mean Cmax and
AUC increased by 2% and 3%, respectively. For levonorgestrel when it was
administered with solifenacin, the mean Cmax and AUC decreased by 1% [see DRUG
INTERACTIONS].
Digoxin
In a crossover study, subjects
received digoxin (loading dose of 0.25 mg on day 1, followed by 0.125 mg from
days 2 to 8) for 8 days. Consecutively, they received solifenacin 10 mg or
matching placebo with digoxin 0.125 mg for additional 10 days. When
digoxin was coadministered with solifenacin, the mean Cmax and AUC increased by
13% and 4%, respectively [see DRUG INTERACTIONS].
Clinical Studies
VESIcare was evaluated in four twelve-week, double-blind,
randomized, placebo-controlled, parallel group, multicenter clinical trials for
the treatment of overactive bladder in patients having symptoms of urinary
frequency, urgency, and/or urge or mixed incontinence (with a predominance of
urge). Entry criteria required that patients have symptoms of overactive
bladder for ≥ 3 months duration. These studies involved 3027 patients (1811
on VESIcare and 1216 on placebo), and approximately 90% of these patients
completed the 12-week studies. Two of the four studies evaluated the 5 and 10
mg VESIcare doses and the other two evaluated only the 10 mg dose. All patients
completing the 12-week studies were eligible to enter an open label, long term
extension study and 81% of patients enrolling completed the additional 40-week
treatment period. The majority of patients were Caucasian (93%) and female
(80%) with a mean age of 58 years.
The primary endpoint in all four trials was the mean
change from baseline to 12 weeks in number of micturitions/24 hours. Secondary
endpoints included mean change from baseline to 12 weeks in number of
incontinence episodes/24 hours, and mean volume voided per micturition. The
efficacy of VESIcare was similar across patient age and gender. The mean
reduction in the number of micturitions per 24 hours was significantly greater
with VESIcare 5 mg (2.3; p < 0.001) and VESIcare 10 mg (2.7; p < 0.001)
compared to placebo, (1.4).
The mean reduction in the number of incontinence episodes
per 24 hours was significantly greater with VESIcare 5 mg (1.5; p < 0.001) and
VESIcare 10 mg (1.8; p < 0.001) treatment groups compared to placebo (1.1).
The mean increase in the volume voided per micturition was significantly
greater with VESIcare 5 mg (32.3 mL; p < 0.001) and VESIcare 10 mg (42.5 mL;
p < 0.001) compared with placebo (8.5 mL).
The results for the primary and secondary endpoints in
the four individual 12-week clinical studies of VESIcare are reported in Tables
3 through 6.
Table 3: Mean Change from Baseline to Endpoint for
VESIcare (5 mg and 10 mg daily) and Placebo: Study 1
Parameter |
Placebo
(N=253)
Mean (SE) |
VESIcare 5 mg
(N=266)
Mean (SE) |
VESIcare 10 mg
(N=264)
Mean (SE) |
Urinary Frequency (Number of Micturitions/24 hours) * |
Baseline |
12.2 (0.26) |
12.1 (0.24) |
12.3 (0.24) |
Reduction |
1.2 (0.21) |
2.2 (0.18) |
2.6 (0.20) |
P value vs. placebo |
|
< 0.001 |
< 0. 001 |
Number of Incontinence Episodes/24 hours† |
Baseline |
2.7 (0.23) |
2.6 (0.22) |
2.6 (0.23) |
Reduction |
0.8 (0.18) |
1.4 (0.15) |
1.5 (0.18) |
P value vs. placebo |
|
< 0.01 |
< 0.01 |
Volume Voided per micturition [mL]† |
Baseline |
143.8 (3.37) |
149.6 (3.35) |
147.2 (3.15) |
Increase |
7.4 (2.28) |
32.9 (2.92) |
39.2 (3.11) |
P value vs. placebo |
|
< 0.001 |
< 0.001 |
* Primary endpoint
† Secondary endpoint |
Table 4: Mean Change from
Baseline to Endpoint for VESIcare (5 mg and 10 mg daily) and Placebo: Study 2
Parameter |
Placebo
(N=281)
Mean (SE) |
VESIcare 5 mg
(N=286)
Mean (SE) |
VESIcare 10 mg
(N=290)
Mean (SE) |
Urinary Frequency (Number of Micturitions/24 hours) * |
Baseline |
12.3 (0.23) |
12.1 (0.23) |
12.1 (0.21) |
Reduction |
1.7 (0.19) |
2.4 (0.17) |
2.9 (0.18) |
P value vs. placebo |
|
< 0.001 |
< 0. 001 |
Number of Incontinence Episodes/24 hours† |
Baseline |
3.2 (0.24) |
2.6 (0.18) |
2.8 (0.20) |
Reduction |
1.3 (0.19) |
1.6 (0.16) |
1.6 (0.18) |
P value vs. placebo |
|
< 0.01 |
0.016 |
Volume Voided per micturition [mL]† |
Baseline |
147.2 (3.18) |
148.5 (3.16) |
145.9 (3.42) |
Increase |
11.3 (2.52) |
31.8 (2.94) |
36.6 (3.04) |
P value vs. placebo |
|
< 0.001 |
< 0.001 |
* Primary endpoint
† Secondary endpoint |
Table 5: Mean Change from
Baseline to Endpoint for VESIcare (10 mg daily) and Placebo: Study 3
Parameter |
Placebo
(N=309)
Mean (SE) |
VESIcare 10 mg
(N=306)
Mean (SE) |
Urinary Frequency (Number of Micturitions/24 hours) * |
Baseline |
11.5 (0.18) |
11.7 (0.18) |
Reduction |
1.5 (0.15) |
3.0 (0.15) |
P value vs. placebo |
|
< 0. 001 |
Number of Incontinence Episodes/24 hours† |
Baseline |
3.0 (0.20) |
3.1 (0.22) |
Reduction |
1.1 (0.16) |
2.0 (0.19) |
P value vs. placebo |
|
< 0.001 |
Volume Voided per micturition [mL]† |
Baseline |
190.3 (5.48) |
183.5 (4.97) |
Increase |
2.7 (3.15) |
47.2 (3.79) |
P value vs. placebo |
|
< 0.001 |
*Primary endpoint
† Secondary endpoint |
Table 6: Mean Change from
Baseline to Endpoint for VESIcare (10 mg daily) and Placebo: Study 4
Parameter |
Placebo
(N=295)
Mean (SE) |
VESIcare 10 mg
(N=298)
Mean (SE) |
Urinary Frequency (Number of Micturitions/24 hours) * |
Baseline |
11.8 (0.18) |
11.5 (0.18) |
Reduction |
1.3 (0.16) |
2.4 (0.15) |
P value vs. placebo |
|
< 0. 001 |
Number of Incontinence Episodes/24 hours† |
Baseline |
2.9 (0.18) |
2.9 (0.17) |
Reduction |
1.2 (0.15) |
2.0 (0.15) |
P value vs. placebo |
|
< 0.001 |
Volume Voided per micturition [mL]† |
Baseline |
175.7 (4.44) |
174.1 (4.15) |
Increase |
13.0 (3.45) |
46.4 (3.73) |
P value vs. placebo |
|
< 0.001 |
* Primary endpoint
† Secondary endpoint |