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. Cmax and area under the concentration-time curve (AUC) determined
after dosage of tolterodine immediate release are dose-proportional over the
range of 1 to 4 mg. Based on the sum of unbound serum concentrations of tolterodine
and the 5-hydroxymethyl metabolite ("active moiety"), the AUC of tolterodine
extended release 4 mg daily is equivalent to tolterodine immediate release 4
mg (2 mg bid). Cmax and Cmin levels of tolterodine extended release are about
75% and 150% of tolterodine immediate release, respectively. Maximum serum concentrations
of tolterodine extended release are observed 2 to 6 hours after dose administration.
Effect of Food: There is no effect of food on the pharmacokinetics
of tolterodine extended release.
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 Caucasian
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 14C-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 extended 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 extended release administered daily to 17 healthy male volunteers (13 EM, 4 PM).
Table 1: Summary of Mean (±SD) Pharmacokinetic Parameters
of Tolterodine Extended Release and its Active Metabolite (5-hydroxymethyl metabolite)
in Healthy Volunteers
| |
Tolterodine |
5-hydroxymethyl metabolite |
| |
tmax†
(h) |
Cmax
(µg/L) |
Cavg
(µg/L) |
t½
(h) |
tmax†
(h) |
Cmax
(µg/L) |
Cavg
(µg/L) |
t½
(h) |
Single dose 4 mg*
EM |
4(2-6) |
1.3(0.8) |
0.8(0.57) |
8.4(3.2) |
4(3-6) |
1.6 (0.5) |
1.0(0.32) |
8.8(5.9) |
Multiple dose 4 mg
EM
PM |
4(2-6)
4(3-6) |
3.4(4.9)
19(16) |
1.7(2.8)
13(11) |
6.9(3.5)
18(16) |
4(2-6)
-‡ |
2.7(0.90) - |
1.4(0.6) - |
9.9(4.0) - |
* Parameter dose-normalized from 8 to 4 mg for the single-dose
data.
Cmax = Maximum serum concentration; tmax = Time of occurrence of Cmax;
C avg = Average serum concentration; t1/2 = Terminal elimination
half-life.
†Data presented as median (range).
‡ = 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 the Phase 3, 12-week, controlled
clinical studies; therefore, no tolterodine dosage adjustment for elderly patients
is recommended (see PRECAUTIONS, Geriatric Use).
Pediatric: Efficacy in the pediatric population has not been
demonstrated.
The pharmacokinetics of tolterodine extended release capsules have been evaluated
in pediatric patients ranging in age from 11-15 years. The dose-plasma concentration
relationship was linear over the range of doses assessed. Parent/metabolite
ratios differed according to CYP2D6 metabolizer status: EMs had low serum concentrations
of tolterodine and high concentrations of the active 5-hydroxymethyl metabolite,
while PMs had high concentrations of tolterodine and negligible active metabolite
concentrations.
Gender: The pharmacokinetics of tolterodine immediate release
and the 5- hydroxymethyl metabolite are not influenced by gender. Mean Cmax
of tolterodine immediate release (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 immediate release 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 (eg, tolterodine acid, N-dealkylated
tolterodine acid, N- dealkylated tolterodine and N-dealkylated hydroxy tolterodine)
were significantly higher (10-30 fold) in renally impaired patients as compared
to the healthy volunteers. The recommended dose for patients with significantly
reduced renal function is tolterodine 2 mg daily (see PRECAUTIONS,
General and DOSAGE AND ADMINISTRATION)
Hepatic Insufficiency: Liver impairment can significantly alter
the disposition of tolterodine immediate release. In a study of tolterodine
immediate release 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 immediate release 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 tolterodine 2 mg 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 tolterodine 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 a 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 CYP3A4 inhibitors
such as other azole antifungals (eg, itraconazole, miconazole) or macrolide
antibiotics (eg, 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/levo- norgestrel 150 µg) as evidenced by the monitoring of ethinyl estradiol
and levo- norgestrel over a 2-month period 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 Detrol immediate release (tolterodine
IR) tablets 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 co-administration
of tolterodine 2 mg BID with potent CYP3A4 inhibitors in patients who are CYP2D6
poor metabolizers (see PRECAUTIONS: 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 BID1 |
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 BID1 |
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 2 |
45 |
19.263
(15.49, 23.03) |
8.90
(4.77, 13.03) |
19.103
(15.32, 22.89) |
9.29
(5.34, 13.24) |
1At Tmax of 1 hr; 95% Confidence Interval
2At Tmax of 2 hr; 90% Confidence Interval
3The effect on QT interval with 4 days of moxifloxacin dosing
in this QT trial may be greater than typicallyobserved 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 LA Capsules 2 mg were evaluated in 29 patients in a Phase 2 dose-effect study. DETROL LA 4 mg was evaluated for the treatment of overactive bladder with symptoms of urge urinary incontinence and frequency in a randomized, placebo- controlled, multicenter, double-blind, Phase 3, 12-week study. A total of 507 patients received DETROL LA 4 mg once daily in the morning and 508 received placebo. The majority of patients were Caucasian (95%) and female (81%), with a mean age of 61 years (range, 20 to 93 years). In the study, 642 patients (42%) were 65 to 93 years of age. The study included patients known to be responsive to tolterodine immediate release and other anticholinergic medications, however, 47% of patients never received prior pharmacotherapy for overactive bladder. At study entry, 97% of patients had at least 5 urge incontinence episodes per week and 91% of patients had 8 or more micturitions per day. The primary efficacy endpoint was change in mean number of incontinence episodes per week at week 12 from baseline. Secondary efficacy endpoints included change in mean number of micturitions per day and mean volume voided per micturition at week 12 from baseline.
Table 3: 95% Confidence Intervals (CI) for the Difference
between DETROL LA (4 mg daily) and Placebo for Mean Change at Week 12 from Baseline*
| |
DETROL LA
(n=507) |
Placebo
(n=508)† |
Treatment
Difference, vs. Placebo
(95% Cl) |
Number of incontinence episodes/ week
Mean Baseline
Mean Change from Baseline |
22.1
-11.8 (SD 17.8) |
23.3
-6.9 (SD 15.4) |
-4.8 ‡
(-6.9, -2.8) |
Number of micturitions/day
Mean Baseline
Mean Change from Baseline |
10.9
-1.8 (SD 3.4) |
11.3
-1.2 (SD 2.9) |
-0.6 ‡
(-1.0, -0.2) |
Volume Voided per micturition (mL)
Mean Baseline
Mean Change from Baseline |
141
34 (SD 51) |
136
14 (SD 41) |
20 ‡
(14, 26) |
SD = Standard Deviation.
* Intent-to-treat analysis.
†1 to 2 patients missing in placebo group for each efficacy parameter.
‡ The difference between DETROL LA and placebo was statistically significant. |
Last updated on RxList: 2/14/2008