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.
Pharmacodynamics
Cardiac Electrophysiology
The effect of 10 mg and 30 mg solifenacin succinate (three times the maximum recommended dose) on the QT interval was evaluated in adults at the time of peak plasma concentration of solifenacin in a multi-dose, randomized, double-blind, placebo and positive-controlled (moxifloxacin 400 mg) trial [see WARNINGS AND PRECAUTIONS]. After receiving placebo and moxifloxacin sequentially, adult subjects were randomized to one of two treatment groups. One group (n=51) completed 3 additional sequential periods of dosing with solifenacin succinate 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 coadministration of 10 mg solifenacin succinate with strong CYP3A4 inhibitors (e.g., ketoconazole, 400 mg). Due to the sequential dose escalating nature of the study, baseline ECG 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 3.
Table 3: QTc changes in msec (90% CI) from baseline at Tmax (relative to placebo) in adults1
Drug/Dose | Fridericia Method (using mean difference) |
Solifenacin succinate 10 mg | 2 (-3,6) |
Solifenacin succinate 30 mg | 8 (4,13) |
1. 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 of the highest solifenacin succinate dose (three times the maximum therapeutic dose) studied was not as large as that of the positive control moxifloxacin at its recommended dose. However, the confidence intervals overlapped, and this study was not designed to draw direct statistical conclusions between the drugs or the dose levels.
Pharmacokinetics
Absorption
After oral administration of VESIcare LS in pediatric patients with neurogenic detrusor overactivity (NDO) aged 2 to 17 years, peak plasma concentrations (Cmax) of solifenacin were reached within 2 to 6 hours after administration (tmax) and, at steady-state, the dose-normalized Cmax ranged from 2.5 - 29 ng/mL/mg. The absolute bioavailability of solifenacin in adults is approximately 90%, with plasma concentrations of solifenacin proportional to the dose administered.
Effect Of Food
Food intake did not significantly affect the Cmax and AUC of solifenacin following oral administration of VESIcare LS.
Distribution
Solifenacin is approximately 98% (in vivo) bound to human plasma proteins, principally to α1-acid glycoprotein. Solifenacin is highly distributed to non-CNS tissues, having a median steady-state volume of distribution of 211 L in pediatric neurogenic detrusor overactivity (NDO) patients from 2 to 17 years old.
Elimination
The median elimination half-life of solifenacin is approximately 26 hours in pediatric neurogenic detrusor overactivity (NDO) patients 2 years of age and older.
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 the 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-hydroxyÂN-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 adult volunteers, 69% of the radioactivity was recovered in the urine and 23% 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.
Specific Populations
Patients With Renal Impairment
In studies with solifenacin succinate 10 mg in adults, there was a 2.1-fold increase in AUC and a 1.6-fold increase in t½ of solifenacin in patients with severe renal impairment compared to subjects with normal renal function [see Use In Specific Populations].
Patients With Hepatic Impairment
In studies with solifenacin succinate 10 mg in adults, there was a 2-fold increase in the t½ and a 35% increase in AUC of solifenacin in patients with moderate hepatic impairment compared to subjects with normal hepatic function [see Use In Specific Populations]. Solifenacin succinate has not been studied in patients with severe hepatic impairment.
Drug Interaction Studies
Interaction studies have only been performed in adults. In pediatric patients 2 years of age and older, metabolism via CYP3A4 is the major route of elimination and the metabolic capacity of the liver is similar.
Strong CYP3A4 Inhibitors
In a crossover study in adults, following blockade of CYP3A4 by coadministration of the strong 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].
CYP3A4 Inducers
Because solifenacin is a substrate of CYP3A4, inducers of CYP3A4 may decrease the concentration of solifenacin.
Warfarin
In a crossover study in adults, subjects received a single oral dose of warfarin 25 mg on the 10th day of dosing with either solifenacin succinate 10 mg or matching placebo once daily for 16 days. For R-warfarin, when it was coadministered with solifenacin succinate, the mean Cmax increased by 3% and AUC decreased by 2%. For SÂwarfarin, when it was coadministered with solifenacin succinate, the mean Cmax and AUC increased by 5% and 1%, respectively.
Oral Contraceptives
In a crossover study in adults, 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 succinate 10 mg or matching placebo once daily for 10 days starting from the 12th day of receipt of oral contraceptives. For ethinyl estradiol, when it was administered with solifenacin succinate, the mean Cmax and AUC increased by 2% and 3%, respectively. For levonorgestrel, when it was administered with solifenacin succinate, the mean Cmax and AUC decreased by 1%.
Digoxin
In a crossover study in adults, 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 succinate 10 mg or matching placebo with digoxin 0.125 mg for an additional 10 days. When digoxin was coadministered with solifenacin succinate, the mean Cmax and AUC increased by 13% and 4%, respectively.
Drugs Metabolized By Cytochrome P450
Enzymes In vitro studies demonstrated that, at therapeutic concentrations, solifenacin does not inhibit CYP1A1/2, 2C9, 2C19, 2D6, or 3A4 derived from human liver microsomes.
Animal Toxicology And/Or Pharmacology
Juvenile Animal Toxicology Data
Dose-related increased mortality without preceding clinical signs occurred in juvenile mice treated before weaning for a duration of 12 weeks, from day 10 after birth, with doses that achieved a pharmacological effect. Animals dosed from postnatal day 10 onwards had higher mortality compared to the mortality in adult mice. No increased frequency in mortality was observed in juvenile mice that were treated after weaning for a duration of 4 weeks, from day 21 after birth onwards. Plasma exposure at postnatal day 10 was higher than in adult mice; the systemic exposure at postnatal day 21 was comparable to the systemic exposure in adult mice.
Clinical Studies
The efficacy of VESIcare LS oral suspension was evaluated in two 52-week, open-label, baseline-controlled, sequential dose titration studies in a total of 95 pediatric patients 2 years of age and older with neurogenic detrusor overactivity (NDO). Study 1 (NCT01981954) included patients 2 to less than 5 years of age and Study 2 (NCT01565694) included patients 5 to 17 years of age. Entry criteria required that patients had a diagnosis of neurogenic detrusor overactivity (NDO) confirmed by urodynamics demonstrating the presence of involuntary detrusor contractions with detrusor pressure increase greater than 15 cm H2O and that patients or their caregivers practiced clean intermittent catheterization (CIC). VESIcare LS oral suspension was administered once daily. All patients initially received a weight-based starting dose, followed by dose titration to their lowest effective dose, up to a maximum dose. The duration of the dose titration period was up to 12 weeks and this period was followed by a dose maintenance period of at least 40 weeks.
In Study 1, a total of 19 patients aged 2 to less than 5 years of age received VESIcare LS oral suspension. Of these, 17 patients completed treatment through week 24 and had adequate urodynamic measurements for evaluation of efficacy. The optimized maintenance dose within this study population included 63% of patients at the maximum dose, 26% of patients at an intermediate dose, and 5% of patients at the starting dose. The study population included 7 males (41%) and 10 females (59%).
In Study 2, a total of 76 patients aged 5 to 17 years of age received VESIcare LS oral suspension. Of these, 49 patients (24 patients aged 5 to < 12 years and 25 patients aged 12 to 17 years) completed treatment through week 24 and had adequate urodynamic measurements for evaluation of efficacy. The optimized maintenance dose within this study population included 58% of patients at the maximum dose, 15% of patients at an intermediate dose, and 7% of patients at the starting dose. This study population included 24 males (49%) and 25 females (51%).
The primary efficacy endpoint was change from baseline in the patients’ maximum cystometric (bladder) capacity (MCC) after 24 weeks of treatment with VESIcare LS oral suspension. As shown in Table 4, an improvement in MCC was observed in patients aged 2 to less than 5 years of age and in patients aged 5 to 17 years of age. The magnitude of the observed changes from baseline in the primary and secondary efficacy endpoints were comparable between patients 5 to less than 12 years of age and patients 12 to 17 years of age.
The results for the primary efficacy endpoint in the 2 clinical studies of VESIcare LS oral suspension in pediatric patients with neurogenic detrusor overactivity (NDO) are shown in Table 4. Treatment effects were maintained over 52 weeks.
Table 4: Change from Baseline in Maximum Cystometric Capacity (MCC) at 24 Weeks in Pediatric Patients with Neurogenic Detrusor Overactivity (NDO) Treated with VESIcare LS Oral Suspension in Studies 1 and 2
| Aged 2 to Less than 5 Years (N=17) Mean (SD) | Aged 5 to 17 Years (N=49) Mean (SD) |
Maximum Cystometric Capacity (mL) |
Baseline | 98 (40) | 224 (133)0 |
Week 24 | 137 (37) | 279 (127) |
Change from baseline | 39 (36) | 57 (108) |
95% CI: 21, 57 | 95% CI: 26, 88 |
N is the number of patients who took at least one dose and provided valid values for MCC at baseline and Week 24. 1. Baseline values for patients aged 5 to 17 years are based on patients who took at least one dose and provided valid baseline and at least one post-baseline values for MCC. |
Results for other urodynamic parameters and from patient urinary diaries, which were secondary efficacy endpoints in Studies 1 and 2, are shown in Tables 5 and 6, respectively.
Table 5: Changes from Baseline in Other Urodynamic Parameters at Week 24 in Pediatric Patients with Neurogenic Detrusor Overactivity (NDO) Treated with VESIcare LS Oral Suspension in Studies 1 and 2
| Aged 2 to Less than 5 Years (N=17) Mean (SD) | Aged 5 to 17 Years (N=49) Mean (SD) |
Bladder Compliance (mL/cm H2O) |
Baseline | 5.7 (4.9) | 14.6 (36.4)0 |
Change from baseline | 5.8 (7.3) | 9.1 (28.6) |
| 95% CI: 2.2, 9.6 | 95% CI: 1.0, 17.2 |
Number of Overactive Detrusor Contractions (> 15 cm H2O) |
Baseline | 9.9 (11.6) | 3.9 (4.7)0 |
Change from baseline | -7.0 (9.3) | -2.3 (5.1) |
| 95% CI: -11.8, -2.2 | 95% CI: -3.7, -0.8 |
Percentage of Expected Bladder Volume Prior To First Detrusor Contraction > 15 cm H2O2 |
Baseline (median) | 15.8% | 27.7%1 |
Change from baseline (median) | 31.1% | 13.3% |
N is the number of patients who took at least one dose and provided valid values for MCC at baseline and Week 24. 1 Baseline values for patients aged 5 to 17 years are based on patients who took at least one dose and provided valid baseline and at least one post-baseline values for MCC. 2For patients who showed a detrusor contraction during the urodynamic assessment at Week 24. |
Table 6: Changes from Baseline in Maximum Catheterized Urine Volume and Number of Incontinence Episodes at Week 24 in Pediatric Patients with Neurogenic Detrusor Overactivity (NDO) Treated with VESIcare LS Oral Suspension in Studies 1 and 2
| Aged 2 to Less than 5 Years (N=17) | Aged 5 to 17 Years (N=49) |
Maximum Catheterized Urine Volume/Day (mL) |
Baseline | 77 (43.0) | 204 (92.7) |
Change from baseline | 45 (54.7) | 68 (88.1) |
95% CI: 15, 76 | 95% CI: 43, 92 |
Number of Incontinence Episodes/24 hours1 |
Baseline | 3.9 (0.8) | 3.4 (2.9) |
Change from baseline | -1.6 (1.2) | -1.6 (2.0) |
95% CI: -2.3, -0.9 | 95% CI: -2.2, -1.0 |
1. For patients aged 2 to less than 5 years, the number of incontinence episodes per 24 hours was evaluated as the number of periods between clean intermittent catheterizations with incontinence per 24 hours. |