Mechanism of Action
Dexlansoprazole is a PPI that suppresses gastric acid secretion by specific
inhibition of the (H+,K+)-ATPase in the gastric parietal
cell. By acting specifically on the proton pump, dexlansoprazole blocks the
final step of acid production.
Pharmacodynamics
Antisecretory Activity
The effects of KAPIDEX 60 mg (n = 20) or lansoprazole 30 mg (n = 23) once daily
for five days on 24-hour intragastric pH were assessed in healthy subjects in
a multiple-dose crossover study. The results are summarized in Table 3.
Table 3: Effect on 24-hour Intragastric pH on Day 5 After
Administration of KAPIDEX or Lansoprazole
KAPIDEX
60 mg |
Lansoprazole
30 mg |
| Mean Intragastric pH |
| 4.55 |
4.13 |
| % Time Intragastric pH > 4 (hours) |
| 71 |
60 |
| (17 hours) |
(14 hours) |
Serum Gastrin Effects
The effect of KAPIDEX on serum gastrin concentrations was evaluated in approximately
3460 patients in clinical trials up to 8 weeks and in 1023 patients for up to
6 to 12 months. The mean fasting gastrin concentrations increased from baseline
during treatment with KAPIDEX 30 mg and 60 mg doses. In patients treated for
more than 6 months, mean serum gastrin levels increased during approximately
the first 3 months of treatment and were stable for the remainder of treatment.
Mean serum gastrin levels returned to pre-treatment levels within one month
of discontinuation of treatment.
Enterochromaffin-Like Cell (ECL) Effects
There were no reports of ECL cell hyperplasia in gastric biopsy specimens obtained
from 653 patients treated with KAPIDEX 30 mg, 60 mg or 90 mg for up to 12 months.
During lifetime exposure of rats dosed daily with up to 150 mg per kg per day
of lansoprazole, marked hypergastrinemia was observed followed by ECL cell proliferation
and formation of carcinoid tumors, especially in female rats [see Nonclinical
Toxicology].
Effect on Cardiac Repolarization
A study was conducted to assess the potential of KAPIDEX to prolong the QT/QTc
interval in healthy adult subjects. KAPIDEX doses of 90 mg or 300 mg did not
delay cardiac repolarization compared to placebo. The positive control (moxifloxacin)
produced statistically significantly greater mean maximum and time-averaged
QT/QTc intervals compared to placebo.
Pharmacokinetics
The dual delayed release formulation of KAPIDEX results in a dexlansoprazole
plasma concentration-time profile with two distinct peaks; the first peak occurs
1 to 2 hours after administration, followed by a second peak within 4 to 5 hours
(see Figure 1). Dexlansoprazole is eliminated with a half-life of approximately
1 to 2 hours in healthy subjects and in patients with symptomatic GERD. No accumulation
of dexlansoprazole occurs after multiple, once daily doses of KAPIDEX 30 mg
or 60 mg, although mean AUCt and Cmax values of dexlansoprazole were
slightly higher (less than 10%) on day 5 than on day 1.
Figure 1: Mean Plasma Dexlansoprazole Concentration – Time
Profile Following Oral Administration of 30 or 60 mg KAPIDEX Once Daily for
5 Days in Healthy Subjects
The pharmacokinetics of dexlansoprazole are highly variable, with percent coefficient
of variation (CV%) values for C max, AUC, and CL/F of greater than 30% (see
Table 4).
Table 4: Mean (CV%) Pharmacokinetic Parameters for Subjects
on Day 5 After Administration of KAPIDEX
Dose
(mg) |
Cmax
(ng/mL) |
AUC24
(ng•h/mL) |
CL/F
(L/h) |
| 30 |
658 (40%) |
3275 (47%) |
11.4 (48%) |
| (N=44) |
(N=43) |
(N=43) |
| 60 |
1397 (51%) |
6529 (60%) |
11.6 (46%) |
| (N=79) |
(N=73) |
(N=41) |
Absorption
After oral administration of KAPIDEX 30 mg or 60 mg to healthy subjects and
symptomatic GERD patients, mean Cmax and AUC values of dexlansoprazole increased
approximately dose proportionally (see Figure 1).
Distribution
Plasma protein binding of dexlansoprazole ranged from 96.1% to 98.8% in healthy
subjects and was independent of concentration from 0.01 to 20 mcg per mL. The
apparent volume of distribution (Vz/F) after multiple doses in symptomatic
GERD patients was 40.3 L.
Metabolism
Dexlansoprazole is extensively metabolized in the liver by oxidation, reduction,
and subsequent formation of sulfate, glucuronide and glutathione conjugates
to inactive metabolites. Oxidative metabolites are formed by the cytochrome
P450 (CYP) enzyme system including hydroxylation mainly by CYP2C19, and oxidation
to the sulfone by CYP3A4.
CYP2C19 is a polymorphic liver enzyme which exhibits three phenotypes in the
metabolism of CYP2C19 substrates; extensive metabolizers (*1/*1), intermediate
metabolizers (*1/mutant) and poor metabolizers (mutant/mutant). Dexlansoprazole
is the major circulating component in plasma regardless of CYP2C19 metabolizer
status. In CYP2C19 intermediate and extensive metabolizers, the major plasma
metabolites are 5-hydroxy dexlansoprazole and its glucuronide conjugate, while
in CYP2C19 poor metabolizers dexlansoprazole sulfone is the major plasma metabolite.
Elimination
Following the administration of KAPIDEX, no unchanged dexlansoprazole is excreted
in urine. Following the administration of [14C]dexlansoprazole to
6 healthy male subjects, approximately 50.7% (standard deviation (SD): 9.0%)
of the administered radioactivity was excreted in urine and 47.6% (SD: 7.3%)
in the feces. Apparent clearance (CL/F) in healthy subjects was 11.4 to 11.6
L/h, respectively, after 5-days of 30 or 60 mg once daily administration.
Effect of CYP2C19 Polymorphism on Systemic Exposure of Dexlansoprazole
Systemic exposure of dexlansoprazole is generally higher in intermediate and
poor metabolizers. In male Japanese subjects who received a single dose of KAPIDEX
30 mg or 60 mg (N=2 to 6 subjects/group), mean dexlansoprazole Cmax and AUC
values were up to 2 times higher in intermediate compared to extensive metabolizers;
in poor metabolizers, mean Cmax was up to 4 times higher and mean AUC was up
to 12 times higher compared to extensive metabolizers. Though such study was
not conducted in Caucasians and African Americans, it is expected dexlansoprazole
exposure in these races will be affected by CYP2C19 phenotypes as well.
Effect of Food on Pharmacokinetics and Pharmacodynamics
In food-effect studies in healthy subjects receiving KAPIDEX under various
fed conditions compared to fasting, increases in Cmax ranged from 12% to 55%,
increases in AUC ranged from 9% to 37%, and tmax varied (ranging from a decrease
of 0.7 hours to an increase of 3 hours). No significant differences in mean
intragastric pH were observed between fasted and various fed conditions. However,
the percentage of time intragastric pH exceeded 4 over the 24-hour dosing interval
decreased slightly when KAPIDEX was administered after a meal (57%) relative
to fasting (64%), primarily due to a decreased response in intragastric pH during
the first 4 hours after dosing. Because of this, while KAPIDEX can be taken
without regard to food, some patients may benefit from administering the dose
prior to a meal if post-meal symptoms do not resolve under post-fed conditions.
Special Populations
Pediatric Use
The pharmacokinetics of dexlansoprazole in patients under the age of 18 years
have not been studied.
Geriatric Use
The terminal elimination half-life of dexlansoprazole is significantly increased
in geriatric subjects compared to younger subjects (2.23 and 1.5 hours, respectively);
this difference is not clinically relevant. Dexlansoprazole exhibited higher
systemic exposure (AUC) in geriatric subjects (34.5% higher) than younger subjects.
No dosage adjustment is needed in geriatric patients [see Use
in Specific Populations].
Renal Impairment
Dexlansoprazole is extensively metabolized in the liver to inactive metabolites,
and no parent drug is recovered in the urine following an oral dose of dexlansoprazole.
Therefore, the pharmacokinetics of dexlansoprazole are not expected to be altered
in patients with renal impairment, and no studies were conducted in subjects
with renal impairment [see Use in Specific Populations].
In addition, the pharmacokinetics of lansoprazole were studied in patients with
mild, moderate or severe renal impairment; results demonstrated no need for
a dose adjustment for this patient population.
Hepatic Impairment
In a study of 12 patients with moderately impaired hepatic function who received
a single oral dose of KAPIDEX 60 mg, plasma exposure (AUC) of bound and unbound
dexlansoprazole in the hepatic impairment group was approximately 2 times greater
compared to subjects with normal hepatic function. This difference in exposure
was not due to a difference in protein binding between the two liver function
groups. No adjustment for KAPIDEX is necessary for patients with mild hepatic
impairment (Child-Pugh Class A). KAPIDEX 30 mg should be considered for patients
with moderate hepatic impairment (Child-Pugh Class B). No studies have been
conducted in patients with severe hepatic impairment (Child-Pugh Class C) [see
Use in Specific Populations].
Gender
In a study of 12 male and 12 female healthy subjects who received a single
oral dose of KAPIDEX 60 mg, females had higher systemic exposure (AUC) (42.8%
higher) than males. No dosage adjustment is necessary in patients based on gender.
Drug-Drug Interactions
Warfarin
In a study of 20 healthy subjects, co-administration of KAPIDEX 90 mg once
daily for 11 days with a single 25 mg oral dose of warfarin on day 6 did not
result in any significant differences in the pharmacokinetics of warfarin or
INR compared to administration of warfarin with placebo. However, there have
been reports of increased INR and prothrombin time in patients receiving PPIs
and warfarin concomitantly [see DRUG INTERACTIONS].
Cytochrome P 450 Interactions
Dexlansoprazole is metabolized, in part, by CYP2C19 and CYP3A4.
In vitro studies have shown that KAPIDEX is not likely to inhibit CYP isoforms
1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1 or 3A4. As such, no clinically
relevant interactions with drugs metabolized by these CYP enzymes would be expected.
Furthermore, clinical drug-drug interaction studies in mainly CYP2C19 extensive
and intermediate metabolizers have shown that KAPIDEX does not affect the pharmacokinetics
of diazepam, phenytoin, or theophylline. The subjects' CYP1A2 genotypes in the
drug-drug interaction study with theophylline were not determined.
Clinical Studies
Healing of Erosive Esophagitis
Two multi-center, double-blind, active-controlled, randomized, 8-week studies
were conducted in patients with endoscopically confirmed EE. Severity of the
disease was classified based on the Los Angeles Classification Grading System
(Grades A-D). Patients were randomized to one of the following three treatment
groups: KAPIDEX 60 mg daily, KAPIDEX 90 mg daily or lansoprazole 30 mg daily.
Patients who were H pylori positive or who had Barrett's Esophagus and/or definite
dysplastic changes at baseline were excluded from these studies. A total of
4092 patients were enrolled and ranged in age from 18 to 90 years (median age
48 years) with 54% male. Race was distributed as follows: 87% Caucasian, 5%
Black and 8% other. Based on the Los Angeles Classification, 71% of patients
had mild EE (Grades A and B) and 29% of patients had moderate to severe EE (Grades
C and D) before treatment.
The studies were designed to test non-inferiority. If non-inferiority was demonstrated
then superiority would be tested. Although non-inferiority was demonstrated
in both studies, the finding of superiority in one study was not replicated
in the other.
The proportion of patients with healed EE at week 4 or 8 is presented below
in Table 5.
Table 5: EE Healing Ratesa: All Grades
| Study |
Number of Patients (N)b |
Treatment Group
(daily) |
Week 4
% Healed |
Week 8c
% Healed |
(95% CI) for the Treatment Difference
(KAPIDEX – Lansoprazole)
by Week 8 |
| 1 |
657 |
KAPIDEX 60 mg |
70 |
87 |
(-1.5, 6.1)d |
| 648 |
Lansoprazole 30 mg |
65 |
85 |
| 2 |
639 |
KAPIDEX 60 mg |
66 |
85 |
(2.2, 10.5)d |
| 656 |
Lansoprazole 30 mg |
65 |
79 |
CI = Confidence interval
a Based on crude rate estimates, patients who did not have
endoscopically documented healed EE and prematurely discontinued were
considered not healed.
b Patients with at least one post baseline endoscopy
c Primary efficacy endpoint
d Demonstrated non-inferiority to lansoprazole |
KAPIDEX 90 mg was studied and did not provide additional clinical benefit over
KAPIDEX 60 mg.
Maintenance of Healed Erosive Esophagitis
A multi-center, double-blind, placebo-controlled, randomized study was conducted
in patients who successfully completed an EE study and showed endoscopically
confirmed healed EE. Maintenance of healing and symptom resolution over a six-month
period were evaluated with KAPIDEX 30 mg or 60 mg once daily compared to placebo.
A total of 445 patients were enrolled and ranged in age from 18 to 85 years
(median age 49 years), with 52% female. Race was distributed as follows: 90%
Caucasian, 5% Black and 5% other.
Sixty-six percent of patients treated with 30 mg of KAPIDEX remained healed
over the six-month time period as confirmed by endoscopy (see Table 6).
Table 6: Maintenance Ratesa of Healed EE at Month
6
Number of Patients
(N)b |
Treatment Group
(daily) |
Maintenance Rate
(%) |
| 125 |
KAPIDEX 30 mg |
66.4c |
| 119 |
Placebo |
14.3 |
a Based on crude rate estimates,
patients who did not have endoscopically documented relapse and prematurely
discontinued were considered to have relapsed.
b Patients with at least one post baseline endoscopy
c Statistically significant vs placebo |
KAPIDEX 60 mg was studied and did not provide additional clinical benefit over
KAPIDEX 30 mg.
KAPIDEX 30 mg demonstrated a higher median percent of 24-hour heartburn-free
days compared to placebo over the 6-month treatment period.
Symptomatic Non-Erosive GERD
A multi-center, double-blind, placebo-controlled, randomized, 4-week study
was conducted in patients with a diagnosis of symptomatic non-erosive GERD made
primarily by presentation of symptoms. These patients who identified heartburn
as their primary symptom, had a history of heartburn for 6 months or longer,
had heartburn on at least 4 of 7 days immediately prior to randomization and
had no esophageal erosions as confirmed by endoscopy. However, patients with
symptoms which were not acid-related may not have been excluded using these
inclusion criteria. Patients were randomized to one of the following treatment
groups: KAPIDEX 30 mg daily, 60 mg daily, or placebo. A total of 947 patients
were enrolled and ranged in age from 18 to 86 years (median age 48 years) with
71% female. Race was distributed as follows: 82% Caucasian, 14% Black and 4%
other.
KAPIDEX 30 mg provided statistically significantly greater percent of days
with heartburn-free 24-hour periods over placebo as assessed by daily diary
over 4 weeks (see Table 7). KAPIDEX 60 mg was studied and provided no additional
clinical benefit over KAPIDEX 30 mg.
Table 7: Median Percentages of 24-Hour Heartburn-Free Periods
During the 4 Week Treatment Period of the Symptomatic Non-Erosive GERD Study
| N |
Treatment Group
(daily) |
Heartburn-Free
24-hour Periods
(%) |
| 312 |
KAPIDEX 30 mg |
54.9a |
| 310 |
Placebo |
18.5 |
| a Statistically significant vs
placebo |
A higher percentage of patients on KAPIDEX 30 mg had heartburn-free 24-hour
periods compared to placebo as early as the first three days of treatment and
this was sustained throughout the treatment period (percentage of patients on
Day 3: KAPIDEX 38% versus placebo 15%; on Day 28: KAPIDEX 63% versus placebo
40%).
Last updated on RxList: 3/10/2009