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 dose-proportional 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 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 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
| |
Tolterodine |
5-Hydroxymethyl Metabolite |
| Phenotype (CYP2D6) |
tmax
(h) |
Cmax*
(µg/L) |
Cavg*
(µg/L) |
t1/2
(h) |
CL/F
(L/h) |
tmax (h) |
Cmax*
(µg/L) |
Cavg*
(µg/L) |
t1/2
(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 |
- |
- |
- |
- |
* Parameter was dose-normalized from 4 mg to 2 mg.
Cmax = Maximum plasma concentration; tmax = Time of occurrence of Cmax;
Cavg = Average plasma concentration; t1/2 = Terminal elimination
half-life; CL/F = Apparent oral
EM = Extensive metabolizers; PM = Poor metabolizers.
† - = 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
(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/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 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 QD2 |
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) |
1 At Tmax of 1 hr; 95% Confidence
Interval
2 At Tmax of 2 hr; 90% Confidence Interval
3 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.
|
Last updated on RxList: 4/29/2009