CLINICAL PHARMACOLOGY
Tolterodine is a competitive muscarinic receptor
antagonist. Both urinary bladder contraction and salivation are mediated via
cholinergic muscarinic receptors.
After oral administration, tolterodine is metabolized in
the liver, resulting in the formation of the 5- hydroxymethyl derivative, a
major pharmacologically active metabolite. The 5-hydroxymethyl metabolite,
which exhibits an antimuscarinic activity similar to that of tolterodine,
contributes significantly to the therapeutic effect. Both tolterodine and the
5-hydroxymethyl metabolite exhibit a high specificity for muscarinic receptors,
since both show negligible activity or affinity for other neurotransmitter
receptors and other potential cellular targets, such as calcium channels.
Tolterodine has a pronounced effect on bladder function.
Effects on urodynamic parameters before and 1 and 5 hours after a single 6.4 mg
dose of tolterodine immediate release were determined in healthy volunteers.
The main effects of tolterodine at 1 and 5 hours were an increase in residual
urine, reflecting an incomplete emptying of the bladder, and a decrease in
detrusor pressure. These findings are consistent with an antimuscarinic action
on the lower urinary tract.
Pharmacokinetics
Absorption
In a study with 14C-tolterodine solution in
healthy volunteers who received a 5 mg oral dose, at least 77% of the
radiolabeled dose was absorbed. Tolterodine immediate release is rapidly
absorbed, and maximum serum concentrations (Cmax) typically occur within 1 to 2
hours after dose administration. Cmax and area under the concentration-time
curve (AUC) determined after dosage of tolterodine immediate release are
doseproportional over the range of 1 to 4 mg.
Effect Of Food
Food intake increases the bioavailability of tolterodine
(average increase 53%), but does not affect the levels of the 5-hydroxymethyl
metabolite in extensive metabolizers. This change is not expected to be a
safety concern and adjustment of dose is not needed.
Distribution
Tolterodine is highly bound to plasma proteins, primarily
α1 -acid glycoprotein. Unbound concentrations of tolterodine average 3.7%
± 0.13% over the concentration range achieved in clinical studies. The 5-
hydroxymethyl metabolite is not extensively protein bound, with unbound fraction
concentrations averaging 36% ± 4.0%. The blood to serum ratio of tolterodine
and the 5-hydroxymethyl metabolite averages 0.6 and 0.8, respectively,
indicating that these compounds do not distribute extensively into
erythrocytes. The volume of distribution of tolterodine following
administration of a 1.28 mg intravenous dose is 113 ± 26.7 L.
Metabolism
Tolterodine is extensively metabolized by the liver
following oral dosing. The primary metabolic route involves the oxidation of
the 5-methyl group and is mediated by the cytochrome P450 2D6 (CYP2D6) and
leads to the formation of a pharmacologically active 5-hydroxymethyl
metabolite. Further metabolism leads to formation of the 5-carboxylic acid and
N-dealkylated 5-carboxylic acid metabolites, which account for 51% ± 14% and
29% ± 6.3% of the metabolites recovered in the urine, respectively.
Variability In Metabolism
A subset (about 7%) of the population is devoid of
CYP2D6, the enzyme responsible for the formation of the 5- hydroxymethyl
metabolite of tolterodine. The identified pathway of metabolism for these
individuals (“poor metabolizers”) is dealkylation via cytochrome P450
3A4 (CYP3A4) to N-dealkylated tolterodine. The remainder of the population is
referred to as “extensive metabolizers.” Pharmacokinetic studies
revealed that tolterodine is metabolized at a slower rate in poor metabolizers
than in extensive metabolizers; this results in significantly higher serum
concentrations of tolterodine and in negligible concentrations of the
5-hydroxymethyl metabolite.
Excretion
Following administration of a 5 mg oral dose of
C-tolterodine solution to healthy volunteers, 77% of radioactivity was
recovered in urine and 17% was recovered in feces in 7 days. Less than 1%
( < 2.5% in poor metabolizers) of the dose was recovered as intact
tolterodine, and 5% to 14% ( < 1% in poor metabolizers) was recovered as the
active 5-hydroxymethyl metabolite.
A summary of mean (± standard deviation) pharmacokinetic
parameters of tolterodine immediate release and the 5-hydroxymethyl metabolite
in extensive (EM) and poor (PM) metabolizers is provided in Table 1. These data
were obtained following single and multiple doses of tolterodine 4 mg
administered twice daily to 16 healthy male volunteers (8 EM, 8 PM).
Table 1: Summary of Mean (±SD) Pharmacokinetic
Parameters of Tolterodine and its Active Metabolite (5-hydroxymethyl
metabolite) in Healthy Volunteers
Phenotype (CYP2D6) |
Tolterodine |
5-Hydroxymethyl Metabolite |
tmax (h) |
Cmax* (μg/L) |
Cavg* (μg/L) |
t½ (h) |
CL/F (L/h) |
tmax (h) |
Cmax* (μg/L) |
Cavg* (μg/L) |
t½ (h) |
Single-dose |
EM |
1.6 ± 1.5 |
1.6 ± 1.2 |
0.50 ± 0.35 |
2.0 ± 0.7 |
534 ± 697 |
1.8 ± 1.4 |
1.8 ± 0.7 |
0.62 ± 0.26 |
3.1 ± 0.7 |
PM |
1.4 ± 0.5 |
10 ± 4.9 |
8.3 ± 4.3 |
6.5 ± 1.6 |
17 ± 7.3 |
† |
† |
† |
† |
Multiple- dose |
EM |
1.2 ± 0.5 |
2.6 ± 2.8 |
0.58 ± 0.54 |
2.2 ± 0.4 |
415 ± 377 |
1.2 ± 0.5 |
2.4 ± 1.3 |
0.92 ± 0.46 |
2.9 ± 0.4 |
PM |
1.9 ± 1.0 |
19 ± 7.5 |
12 ± 5.1 |
9.6 ± 1.5 |
11 ± 4.2 |
† |
† |
† |
† |
Cmax = Maximum plasma concentration; tmax = Time of
occurrence of Cmax; Cavg = Average plasma concentration; t½ = Terminal
elimination half-life; CL/F = Apparent oral clearance.
EM = Extensive metabolizers; PM = Poor metabolizers
*Parameter was dose-normalized from 4 mg to 2 mg.
†= not applicable |
Pharmacokinetics In Special Populations
Age
In Phase 1, multiple-dose studies in which tolterodine
immediate release 4 mg (2 mg bid) was administered, serum concentrations of
tolterodine and of the 5-hydroxymethyl metabolite were similar in healthy
elderly volunteers (aged 64 through 80 years) and healthy young volunteers
(aged less than 40 years). In another Phase 1 study, elderly volunteers (aged
71 through 81 years) were given tolterodine immediate release 2 or 4 mg (1 or 2
mg bid). Mean serum concentrations of tolterodine and the 5-hydroxymethyl metabolite
in these elderly volunteers were approximately 20% and 50% higher,
respectively, than reported in young healthy volunteers. However, no overall
differences were observed in safety between older and younger patients on
tolterodine in Phase 3, 12-week, controlled clinical studies; therefore, no
tolterodine dosage adjustment for elderly patients is recommended (see PRECAUTIONS,
Geriatric Use).
Pediatric
The pharmacokinetics of tolterodine have not been
established in pediatric patients.
Gender
The pharmacokinetics of tolterodine immediate release and
the 5-hydroxymethyl metabolite are not influenced by gender. Mean Cmax of
tolterodine (1.6 μg/L in males versus 2.2 μg/L in females) and the
active 5- hydroxymethyl metabolite (2.2 μg/L in males versus 2.5 μg/L
in females) are similar in males and females who were administered tolterodine
immediate release 2 mg. Mean AUC values of tolterodine (6.7 μg•h/L
in males versus 7.8 μg•h/L in females) and the 5-hydroxymethyl
metabolite (10 μg•h/L in males versus 11 μg•h/L in
females) are also similar. The elimination half-life of tolterodine for both
males and females is 2.4 hours, and the half-life of the 5-hydroxymethyl
metabolite is 3.0 hours in females and 3.3 hours in males.
Race
Pharmacokinetic differences due to race have not been
established.
Renal Insufficiency
Renal impairment can significantly alter the disposition
of tolterodine immediate release and its metabolites. In a study conducted in
patients with creatinine clearance between 10 and 30 mL/min, tolterodine
immediate release and the 5-hydroxymethyl metabolite levels were approximately
2-3 fold higher in patients with renal impairment than in healthy volunteers.
Exposure levels of other metabolites of tolterodine (e.g., tolterodine acid,
N-dealkylated tolterodine acid, N-dealkylated tolterodine, and N-dealkylated
hydroxylated tolterodine) were significantly higher (10-30 fold) in renally
impaired patients as compared to the healthy volunteers. The recommended dosage
for patients with significantly reduced renal function is DETROL 1 mg twice
daily (see PRECAUTIONS, General and DOSAGE AND ADMINISTRATION).
Hepatic Insufficiency
Liver impairment can significantly alter the disposition
of tolterodine immediate release. In a study conducted in cirrhotic patients,
the elimination half-life of tolterodine immediate release was longer in
cirrhotic patients (mean, 7.8 hours) than in healthy, young, and elderly
volunteers (mean, 2 to 4 hours). The clearance of orally administered
tolterodine was substantially lower in cirrhotic patients (1.0 ± 1.7 L/h/kg)
than in the healthy volunteers (5.7 ± 3.8 L/h/kg). The recommended dose for
patients with significantly reduced hepatic function is DETROL 1 mg twice daily
(see PRECAUTIONS, General and DOSAGE AND ADMINISTRATION).
Drug-Drug Interactions
Fluoxetine
Fluoxetine is a selective serotonin reuptake inhibitor
and a potent inhibitor of CYP2D6 activity. In a study to assess the effect of
fluoxetine on the pharmacokinetics of tolterodine immediate release and its
metabolites, it was observed that fluoxetine significantly inhibited the
metabolism of tolterodine immediate release in extensive metabolizers,
resulting in a 4.8-fold increase in tolterodine AUC. There was a 52% decrease
in Cmax and a 20% decrease in AUC of the 5-hydroxymethyl metabolite. Fluoxetine
thus alters the pharmacokinetics in patients who would otherwise be extensive
metabolizers of tolterodine immediate release to resemble the pharmacokinetic
profile in poor metabolizers. The sums of unbound serum concentrations of
tolterodine immediate release and the 5-hydroxymethyl metabolite are only 25%
higher during the interaction. No dose adjustment is required when DETROL and
fluoxetine are coadministered.
Other Drugs Metabolized By Cytochrome P450 Isoenzymes
Tolterodine immediate release does not cause clinically
significant interactions with other drugs metabolized by the major drug
metabolizing CYP enzymes. In vivo drug-interaction data show that tolterodine
immediate release does not result in clinically relevant inhibition of CYP1A2,
2D6, 2C9, 2C19, or 3A4 as evidenced by lack of influence on the marker drugs
caffeine, debrisoquine, S-warfarin, and omeprazole. In vitro data show that
tolterodine immediate release is a competitive inhibitor of CYP2D6 at high
concentrations (Ki 1.05 μM), while tolterodine immediate release as well
as the 5-hydroxymethyl metabolite are devoid of any significant inhibitory
potential regarding the other isoenzymes.
CYP3A4 Inhibitors
The effect of 200 mg daily dose of ketoconazole on the pharmacokinetics
of tolterodine immediate release was studied in 8 healthy volunteers, all of
whom were poor metabolizers (see Pharmacokinetics, Variability in
Metabolism for discussion of poor metabolizers). In the presence of
ketoconazole, the mean Cmax and AUC of tolterodine increased by 2 and 2.5 fold,
respectively. Based on these findings, other potent CYP3A inhibitors such as
other azole antifungals (e.g., itraconazole, miconazole) or macrolide
antibiotics (e.g., erythromycin, clarithromycin) or cyclosporine or vinblastine
may also lead to increases of tolterodine plasma concentrations (see
PRECAUTIONS and DOSAGE AND ADMINISTRATION).
Warfarin
In healthy volunteers, coadministration of tolterodine
immediate release 4 mg (2 mg bid) for 7 days and a single dose of warfarin 25
mg on day 4 had no effect on prothrombin time, Factor VII suppression, or on
the pharmacokinetics of warfarin.
Oral Contraceptives
Tolterodine immediate release 4 mg (2 mg bid) had no
effect on the pharmacokinetics of an oral contraceptive (ethinyl
estradiol 30 μg/levonorgestrel 150 μg) as evidenced by the monitoring
of ethinyl estradiol and levonorgestrel over a 2-month cycle in healthy female
volunteers.
Diuretics
Coadministration of tolterodine immediate release up to 8
mg (4 mg bid) for up to 12 weeks with diuretic agents, such as indapamide,
hydrochlorothiazide, triamterene, bendroflumethiazide, chlorothiazide,
methylchlorothiazide, or furosemide, did not cause any adverse
electrocardiographic (ECG) effects.
Cardiac Electrophysiology
The effect of 2 mg BID and 4 mg BID of tolterodine
immediate release (IR) on the QT interval was evaluated in a 4-way crossover,
double-blind, placebo- and active-controlled (moxifloxacin 400 mg QD) study in
healthy male (N=25) and female (N=23) volunteers aged 18-55 years. Study
subjects [approximately equal representation of CYP2D6 extensive metabolizers
(EMs) and poor metabolizers (PMs)] completed sequential 4-day periods of dosing
with moxifloxacin 400 mg QD, tolterodine 2 mg BID, tolterodine 4 mg BID, and
placebo. The 4 mg BID dose of tolterodine IR (two times the highest recommended
dose) was chosen because this dose results in tolterodine exposure similar to
that observed upon coadministration of tolterodine 2 mg BID with potent CYP3A4
inhibitors in patients who are CYP2D6 poor metabolizers (see DRUG INTERACTIONS). QT interval was measured over a 12-hour period
following dosing, including the time of peak plasma concentration (Tmax) of
tolterodine and at steady state (Day 4 of dosing).
Table 2 summarizes the mean change from baseline to
steady state in corrected QT interval (QTc) relative to placebo at the time of
peak tolterodine (1 hour) and moxifloxacin (2 hour) concentrations. Both
Fridericia's (QTcF) and a population-specific (QTcP) method were used to
correct QT interval for heart rate. No single QT correction method is known to
be more valid than others. QT interval was measured manually and by machine,
and data from both are presented. The mean increase of heart rate associated with
a 4 mg/day dose of tolterodine in this study was 2.0 beats/minute and 6.3
beats/minute with 8 mg/day tolterodine. The change in heart rate with
moxifloxacin was 0.5 beats/minute.
Table 2: Mean (CI) change in QTc from baseline to steady
state (Day 4 of dosing) at Tmax (relative to placebo)
Drug/Dose |
N |
QTcF (msec) (manual) |
QTcF (msec) (machine) |
QTcP (msec) (manual) |
QTcP (msec) (machine) |
Tolterodine 2 mg BID* |
48 |
5.01
(0.28, 9.74) |
1.16
(-2.99, 5.30) |
4.45
(-0.37, 9.26) |
2.00
(-1.81, 5.81) |
Tolterodine 4 mg BID* |
48 |
11.84
(7.11, 16.58) |
5.63
(1.48, 9.77) |
10.31
(5.49, 15.12) |
8.34
(4.53, 12.15) |
Moxifloxacin 400 mg QD† |
45 |
19.26‡
(15.49, 23.03) |
8.90
(4.77, 13.03) |
19.10‡
(15.32, 22.89) |
9.29
(5.34, 13.24) |
*At T of 1 hr; 95% max Confidence Interval
†At Tmax of 2 hr; 90% Confidence Interval
‡The effect on QT interval with 4 days of moxifloxacin dosing in this QT trial
may be greater than typically observed in QT trials of other drugs. |
The reason for the difference between machine and manual
read of QT interval is unclear.
The QT effect of tolterodine immediate release tablets
appeared greater for 8 mg/day (two times the therapeutic dose) compared to 4
mg/day. The effect of tolterodine 8 mg/day was not as large as that observed
after four days of therapeutic dosing with the active control moxifloxacin.
However, the confidence intervals overlapped.
Tolterodine's effect on QT interval was found to
correlate with plasma concentration of tolterodine. There appeared to be a
greater QTc interval increase in CYP2D6 poor metabolizers than in CYP2D6
extensive metabolizers after tolterodine treatment in this study.
This study was not designed to make direct statistical
comparisons between drugs or dose levels. There has been no association of
Torsade de Pointes in the international post-marketing experience with DETROL
or DETROL LA (see PRECAUTIONS, Patients with Congenital or Acquired
QT Prolongation).
Clinical Studies
DETROL Tablets were evaluated for the treatment of
overactive bladder with symptoms of urge urinary incontinence, urgency, and
frequency in four randomized, double-blind, placebo-controlled, 12-week
studies. A total of 853 patients received DETROL 2 mg twice daily and 685
patients received placebo. The majority of patients were Caucasian (95%) and
female (78%), with a mean age of 60 years (range, 19 to 93 years). At study
entry, nearly all patients perceived they had urgency and most patients had
increased frequency of micturitions and urge incontinence. These
characteristics were well balanced across treatment groups for the studies.
The efficacy endpoints for study 007 (see Table 3)
included the change from baseline for:
- Number of incontinence episodes per week
- Number of micturitions per 24 hours (averaged over 7
days)
- Volume of urine voided per micturition (averaged over 2
days)
The efficacy endpoints for studies 008, 009, and 010 (see
Table 4) were identical to the above endpoints with the exception that the
number of incontinence episodes was per 24 hours (averaged over 7 days).
Table 3: 95% Confidence Intervals (CI) for the
Difference between DETROL (2 mg bid) and Placebo for the Mean Change at Week 12
from Baseline in Study 007
|
DETROL (SD)
N = 514 |
Placebo (SD)
N=508 |
Difference (95% CI) |
Number of Incontinence Episodes per Week |
Mean baseline |
23.2 |
23.3 |
|
Mean change from baseline |
-10.6 (17) |
-6.9 (15) |
-3.7 (-5.7, -1.6) |
Number of Micturitions per 24 Hours |
Mean baseline |
11.1 |
11.3 |
|
Mean change from baseline |
-1.7 (3.3) |
-1.2 (2.9) |
-0.5* (-0.9, -0.1) |
Volume Voided per Micturition (mL) |
Mean baseline |
137 |
136 |
|
Mean change from baseline |
29 (47) |
14 (41) |
15* (9, 21) |
SD = Standard Deviation.
* The difference between DETROL and placebo was statistically significant. |
Table 4: 95% Confidence Intervals (CI) for the
Difference between DETROL (2 mg bid) and Placebo for the Mean Change at Week 12
from Baseline in Studies 008, 009, 010
Study |
DETROL (SD) |
Placebo (SD) |
Difference (95% CI) |
Number of Incontinence Episodes per 24 Hours |
008 Number of patients |
93 |
40 |
|
Mean baseline |
2.9 |
3.3 |
|
Mean change from baseline |
-1.3 (3.2) |
-0.9 (1.5) |
0.5 (-1.3,0.3) |
009 Number of patients |
116 |
55 |
|
Mean baseline |
3.6 |
3.5 |
|
Mean change from baseline |
-1.7 (2.5) |
-1.3 (2.5) |
-0.4 (-1.0,0.2) |
010 Number of patients |
90 |
50 |
|
Mean baseline |
3.7 |
3.5 |
|
Mean change from baseline |
-1.6 (2.4) |
-1.1 (2.1) |
-0.5 (-1.1,0.1) |
Number of Micturitions per 24 Hours |
008 Number of patients |
118 |
56 |
|
Mean baseline |
11.5 |
11.7 |
|
Mean change from baseline |
-2.7 (3.8) |
-1.6 (3.6) |
-1.2* (-2.0,-0.4) |
009 Number of patients |
128 |
64 |
|
Mean baseline |
11.2 |
11.3 |
|
Mean change from baseline |
-2.3 (2.1) |
-1.4 (2.8) |
-0.9* (-1.5,-0.3) |
010 Number of patients |
108 |
56 |
|
Mean baseline |
11.6 |
11.6 |
|
Mean change from baseline |
-1.7 (2.3) |
-1.4 (2.8) |
-0.38 (-1.1,0.3) |
Volume Voided per Micturition (mL) |
008 Number of patients |
118 |
56 |
|
Mean baseline |
166 |
157 |
|
Mean change from baseline |
38 (54) |
6 (42) |
32* (18,46) |
009 Number of patients |
129 |
64 |
|
Mean baseline |
155 |
158 |
|
Mean change from baseline |
36 (50) |
10 (47) |
26* (14,38) |
010 Number of patients |
108 |
56 |
|
Mean baseline |
155 |
160 |
|
Mean change from baseline |
31 (45) |
13 (52) |
18* (4,32) |
SD = Standard Deviation.
* The difference between DETROL and placebo was statistically significant. |