CLINICAL PHARMACOLOGY
Mechanism Of Action
Desloratadine is a long-acting
tricyclic histamine antagonist with selective H1-receptor histamine antagonist
activity. Receptor binding data indicates that at a concentration of 2-3 ng/mL
(7 nanomolar), desloratadine shows significant interaction with the human
histamine H1-receptor. Desloratadine inhibited histamine release from human
mast cells in vitro. Results of a radiolabeled tissue distribution study in
rats and a radioligand H1-receptor binding study in guinea pigs showed that
desloratadine did not readily cross the blood brain barrier. The clinical
significance of this finding is unknown.
Pharmacodynamics
Wheal And Flare
Human histamine skin wheal
studies following single and repeated 5-mg doses of desloratadine have shown
that the drug exhibits an antihistaminic effect by 1 hour; this activity may
persist for as long as 24 hours. There was no evidence of histamine-induced
skin wheal tachyphylaxis within the desloratadine 5-mg group over the 28-day
treatment period. The clinical relevance of histamine wheal skin testing is
unknown.
Effects On QTc
Single daily doses of 45 mg
were given to normal male and female volunteers for 10 days. All ECGs obtained
in this study were manually read in a blinded fashion by a cardiologist. In
CLARINEX-treated subjects, there was an increase in mean heart rate of 9.2 bpm
relative to placebo. The QT interval was corrected for heart rate (QTc) by both
the Bazett and Fridericia methods. Using the QTc (Bazett) there was a mean
increase of 8.1 msec in CLARINEX-treated subjects relative to placebo. Using QTc
(Fridericia) there was a mean increase of 0.4 msec in CLARINEX-treated subjects
relative to placebo. No clinically relevant adverse events were reported.
Pharmacokinetics
Absorption
Following oral administration of a desloratadine 5-mg
tablet once daily for 10 days to normal healthy volunteers, the mean time to
maximum plasma concentrations (Tmax) occurred at approximately 3 hours post
dose and mean steady state peak plasma concentrations (Cmax) and AUC of 4 ng/mL
and 56.9 ng.hr/mL were observed, respectively. Neither food nor grapefruit
juice had an effect on the bioavailability (Cmax and AUC) of desloratadine.
The pharmacokinetic profile of CLARINEX Oral Solution was
evaluated in a three-way crossover study in 30 adult volunteers. A single dose
of 10 mL of CLARINEX Oral Solution containing 5 mg of desloratadine was
bioequivalent to a single dose of 5-mg CLARINEX Tablet. Food had no effect on
the bioavailability (AUC and Cmax) of CLARINEX Oral Solution.
The pharmacokinetic profile of CLARINEX RediTabs Tablets
was evaluated in a three-way crossover study in 24 adult volunteers. A single
CLARINEX RediTabs Tablet containing 5 mg of desloratadine was bioequivalent to
a single 5-mg CLARINEX RediTabs Tablet (original formulation) for both
desloratadine and 3-hydroxydesloratadine. Food and water had no effect on the
bioavailability (AUC and Cmax) of CLARINEX RediTabs Tablets.
Distribution
Desloratadine and 3-hydroxydesloratadine are
approximately 82% to 87% and 85% to 89% bound to plasma proteins, respectively.
Protein binding of desloratadine and 3-hydroxydesloratadine was unaltered in
subjects with impaired renal function.
Metabolism
Desloratadine (a major metabolite of loratadine) is
extensively metabolized to 3-hydroxydesloratadine, an active metabolite, which
is subsequently glucuronidated. The enzyme(s) responsible for the formation of
3-hydroxydesloratadine have not been identified. Data from clinical trials
indicate that a subset of the general population has a decreased ability to
form 3hydroxydesloratadine, and are poor metabolizers of desloratadine. In
pharmacokinetic studies (n=3748), approximately 6% of subjects were poor
metabolizers of desloratadine (defined as a subject with an AUC ratio of
3-hydroxydesloratadine to desloratadine less than 0.1, or a subject with a
desloratadine half-life exceeding 50 hours). These pharmacokinetic studies
included subjects between the ages of 2 and 70 years, including 977 subjects
aged 2 to 5 years, 1575 subjects aged 6 to 11 years, and 1196 subjects aged 12 to
70 years. There was no difference in the prevalence of poor metabolizers across
age groups. The frequency of poor metabolizers was higher in Blacks (17%,
n=988) as compared to Caucasians (2%, n=1,462) and Hispanics (2%, n=1,063). The
median exposure (AUC) to desloratadine in the poor metabolizers was
approximately 6-fold greater than in the subjects who are not poor
metabolizers. Subjects who are poor metabolizers of desloratadine cannot be
prospectively identified and will be exposed to higher levels of desloratadine
following dosing with the recommended dose of desloratadine. In multidose
clinical safety studies, where metabolizer status was identified, a total of 94
poor metabolizers and 123 normal metabolizers were enrolled and treated with
CLARINEX Oral Solution for 15-35 days. In these studies, no overall differences
in safety were observed between poor metabolizers and normal metabolizers.
Although not seen in these studies, an increased risk of exposure-related
adverse events in patients who are poor metabolizers cannot be ruled out.
Elimination
The mean plasma elimination half-life of desloratadine
was approximately 27 hours. Cmax and AUC values increased in a dose
proportional manner following single oral doses between 5 and 20 mg. The degree
of accumulation after 14 days of dosing was consistent with the half-life and
dosing frequency. A human mass balance study documented a recovery of
approximately 87% of the 14C-desloratadine dose, which was equally
distributed in urine and feces as metabolic products. Analysis of plasma
3hydroxydesloratadine showed similar Tmax and half-life values compared to
desloratadine.
Special Populations
Geriatric Subjects
In older subjects (≥65 years old; n=17) following
multiple-dose administration of CLARINEX Tablets, the mean Cmax and AUC values
for desloratadine were 20% greater than in younger subjects (<65 years old).
The oral total body clearance (CL/F) when normalized for body weight was
similar between the two age groups. The mean plasma elimination half-life of
desloratadine was 33.7 hr in subjects ≥65 years old. The pharmacokinetics
for 3-hydroxydesloratadine appeared unchanged in older versus younger subjects.
These age-related differences are unlikely to be clinically relevant and no
dosage adjustment is recommended in elderly subjects.
Pediatric Subjects
In subjects 6 to 11 years old, a single dose of 5 mL of
CLARINEX Oral Solution containing 2.5 mg of desloratadine, resulted in
desloratadine plasma concentrations similar to those achieved in adults
administered a single 5-mg CLARINEX Tablet. In subjects 2 to 5 years old, a
single dose of 2.5 mL of CLARINEX Oral Solution containing 1.25 mg of desloratadine,
resulted in desloratadine plasma concentrations similar to those achieved in
adults administered a single 5-mg CLARINEX Tablet. However, the Cmax and AUC of
the metabolite (3-hydroxydesloratadine) were 1.27 and 1.61 times higher for the
5-mg dose of Oral Solution administered in adults compared to the Cmax and AUC
obtained in children 2 to 11 years of age receiving 1.25-2.5 mg of CLARINEX
Oral Solution.
A single dose of either 2.5 mL or 1.25 mL of CLARINEX
Oral Solution containing 1.25 mg or 0.625 mg, respectively, of desloratadine
was administered to subjects 6 to 11 months of age and 12 to 23 months of age.
The results of a population pharmacokinetic analysis indicated that a dose of 1
mg for subjects aged 6 to 11 months and 1.25 mg for subjects 12 to 23 months of
age is required to obtain desloratadine plasma concentrations similar to those
achieved in adults administered a single 5-mg dose of CLARINEX Oral Solution.
The CLARINEX RediTabs 2.5-mg tablet has not been
evaluated in pediatric patients. Bioequivalence of the CLARINEX RediTabs Tablet
and the original CLARINEX RediTabs Tablets was established in adults. In
conjunction with the dose-finding studies in pediatrics described, the
pharmacokinetic data for CLARINEX RediTabs Tablets supports the use of the
2.5-mg dose strength in pediatric patients 6 to 11 years of age.
Renally Impaired
Desloratadine pharmacokinetics following a single dose of
7.5 mg were characterized in patients with mild (n=7; creatinine clearance
51-69 mL/min/1.73 m²), moderate (n=6; creatinine clearance 34-43 mL/min/1.73 m²),
and severe (n=6; creatinine clearance 5-29 mL/min/1.73 m²) renal impairment or
hemodialysis dependent (n=6) patients. In patients with mild and moderate renal
impairment, median Cmax and AUC values increased by approximately 1.2-and
1.9-fold, respectively, relative to subjects with normal renal function. In
patients with severe renal impairment or who were hemodialysis dependent, Cmax and
AUC values increased by approximately 1.7-and 2.5-fold, respectively. Minimal
changes in 3-hydroxydesloratadine concentrations were observed. Desloratadine
and 3-hydroxydesloratadine were poorly removed by hemodialysis. Plasma protein
binding of desloratadine and 3-hydroxydesloratadine was unaltered by renal
impairment. Dosage adjustment for patients with renal impairment is recommended
[see DOSAGE AND ADMINISTRATION].
Hepatically Impaired
Desloratadine pharmacokinetics were characterized
following a single oral dose in patients with mild (n=4), moderate (n=4), and
severe (n=4) hepatic impairment as defined by the Child-Pugh classification of
hepatic function and 8 subjects with normal hepatic function. Patients with
hepatic impairment, regardless of severity, had approximately a 2.4-fold
increase in AUC as compared with normal subjects. The apparent oral clearance
of desloratadine in patients with mild, moderate, and severe hepatic impairment
was 37%, 36%, and 28% of that in normal subjects, respectively. An increase in
the mean elimination half-life of desloratadine in patients with hepatic
impairment was observed. For 3-hydroxydesloratadine, the mean Cmax and AUC
values for patients with hepatic impairment were not statistically
significantly different from subjects with normal hepatic function. Dosage
adjustment for patients with hepatic impairment is recommended [see DOSAGE
AND ADMINISTRATION].
Gender
Female subjects treated for 14 days with CLARINEX Tablets
had 10% and 3% higher desloratadine Cmax and AUC values, respectively, compared
with male subjects. The 3-hydroxydesloratadine Cmax and AUC values were also
increased by 45% and 48%, respectively, in females compared with males.
However, these apparent differences are not likely to be clinically relevant
and therefore no dosage adjustment is recommended.
Race
Following 14 days of treatment with CLARINEX Tablets, the
Cmax and AUC values for desloratadine were 18% and 32% higher, respectively, in
Blacks compared with Caucasians. For 3-hydroxydesloratadine there was a corresponding
10% reduction in Cmax and AUC values in Blacks compared to Caucasians. These
differences are not likely to be clinically relevant and therefore no dose
adjustment is recommended.
Drug Interactions
In two controlled crossover clinical pharmacology studies
in healthy male (n=12 in each study) and female (n=12 in each study)
volunteers, desloratadine 7.5 mg (1.5 times the daily dose) once daily was
coadministered with erythromycin 500 mg every 8 hours or ketoconazole 200 mg
every 12 hours for 10 days. In three separate controlled, parallel group
clinical pharmacology studies, desloratadine at the clinical dose of 5 mg has
been coadministered with azithromycin 500 mg followed by 250 mg once daily for
4 days (n=18) or with fluoxetine 20 mg once daily for 7 days after a 23-day
pretreatment period with fluoxetine (n=18) or with cimetidine 600 mg every 12
hours for 14 days (n=18) under steady-state conditions to normal healthy male
and female volunteers. Although increased plasma concentrations (Cmax and AUC0-24
hrs) of desloratadine and 3hydroxydesloratadine were observed (see Table 2),
there were no clinically relevant changes in the safety profile of
desloratadine, as assessed by electrocardiographic parameters (including the
corrected QT interval), clinical laboratory tests, vital signs, and adverse
events.
Table 2: Changes in Desloratadine and
3-Hydroxydesloratadine Pharmacokinetics in Healthy Male and Female Volunteers
|
Desloratadine |
3-Hydroxydesloratadine |
Cmax |
AUC0-24 hrs |
Cmax |
AUC0-24 hrs |
Erythromycin
(500 mg Q8h) |
+ 24% |
+ 14% |
+ 43% |
+ 40% |
Ketoconazole
(200 mg Q12h) |
+ 45% |
+ 39% |
+ 43% |
+ 72% |
Azithromycin
(500 mg day 1, 250 mg QD x 4 days) |
+ 15% |
+ 5% |
+ 15% |
+ 4% |
Fluoxetine (20 mg QD) |
+ 15% |
+ 0% |
+ 17% |
+ 13% |
Cimetidine (600 mg Q12h) |
+ 12% |
+ 19% |
-11% |
-3% |
Animal Toxicology And/Or Pharmacology Reproductive
Toxicology Studies
Desloratadine was not teratogenic in rats at doses up to
48 mg/kg/day (estimated desloratadine and desloratadine metabolite exposures
were approximately 210 times the AUC in humans at the recommended daily oral
dose) or in rabbits at doses up to 60 mg/kg/day (estimated desloratadine
exposures were approximately 230 times the AUC in humans at the recommended
daily oral dose). In a separate study, an increase in pre-implantation loss and
a decreased number of implantations and fetuses were noted in female rats at 24
mg/kg (estimated desloratadine and desloratadine metabolite exposures were
approximately 120 times the AUC in humans at the recommended daily oral dose).
Reduced body weight and slow righting reflex were reported in pups at doses of
9 mg/kg/day or greater (estimated desloratadine and desloratadine metabolite
exposures were approximately 50 times or greater than the AUC in humans at the
recommended daily oral dose). Desloratadine had no effect on pup development at
an oral dose of 3 mg/kg/day (estimated desloratadine and desloratadine
metabolite exposures were approximately 7 times the AUC in humans at the
recommended daily oral dose).
Clinical Studies
Seasonal Allergic Rhinitis
The clinical efficacy and safety of CLARINEX Tablets were
evaluated in over 2300 patients 12 to 75 years of age with seasonal allergic
rhinitis. A total of 1838 patients received 2.5 to 20 mg/day of CLARINEX in 4
double-blind, randomized, placebo-controlled clinical trials of 2 to 4 weeks'
duration conducted in the United States. The results of these studies
demonstrated the efficacy and safety of CLARINEX 5 mg in the treatment of adult
and adolescent patients with seasonal allergic rhinitis. In a dose-ranging
trial, CLARINEX 2.5 to 20 mg/day was studied. Doses of 5, 7.5, 10, and 20
mg/day were superior to placebo; and no additional benefit was seen at doses
above 5.0 mg. In the same study, an increase in the incidence of somnolence was
observed at doses of 10 mg/day and 20 mg/day (5.2% and 7.6%, respectively),
compared to placebo (2.3%).
In two 4-week studies of 924 patients (aged 15 to 75
years) with seasonal allergic rhinitis and concomitant asthma, CLARINEX Tablets
5 mg once daily improved rhinitis symptoms, with no decrease in pulmonary
function. This supports the safety of administering CLARINEX Tablets to adult
patients with seasonal allergic rhinitis with mild to moderate asthma.
CLARINEX Tablets 5 mg once daily significantly reduced
the Total Symptom Score (the sum of individual scores of nasal and non-nasal
symptoms) in patients with seasonal allergic rhinitis. See Table 3.
Table 3: TOTAL SYMPTOM SCORE (TSS) Changes in a 2-Week
Clinical Trial in Patients with Seasonal Allergic Rhinitis
Treatment Group (n) |
Mean Baseline* (SEM) |
Change from Baseline† (SEM) |
Placebo Comparison (P-value) |
CLARINEX 5.0 mg (171) |
14.2 (0.3) |
-4.3 (0.3) |
P<0.01 |
Placebo (173) |
13.7 (0.3) |
-2.5 (0.3) |
|
SEM=Standard Error of the Mean
* At baseline, a total nasal symptom score (sum of 4 individual symptoms) of at
least 6 and a total non-nasal symptom score (sum of 4 individual symptoms) of
at least 5 (each symptom scored 0 to 3 where 0=no symptom and 3=severe
symptoms) was required for trial eligibility. TSS ranges from 0=no symptoms to
24=maximal symptoms.
† Mean reduction in TSS averaged over the 2-week treatment period. |
There were no significant
differences in the effectiveness of CLARINEX Tablets 5 mg across subgroups of
patients defined by gender, age, or race.
Perennial Allergic Rhinitis
The clinical efficacy and
safety of CLARINEX Tablets 5 mg were evaluated in over 1300 patients 12 to 80
years of age with perennial allergic rhinitis. A total of 685 patients received
5 mg/day of CLARINEX in two double-blind, randomized, placebo-controlled
clinical trials of 4 weeks’ duration conducted in the United States and
internationally. In one of these studies CLARINEX Tablets 5 mg once daily was
shown to significantly reduce the Total Symptom Score in patients with
perennial allergic rhinitis (Table 4).
Table 4: TOTAL SYMPTOM SCORE (TSS) Changes in a 4-Week
Clinical Trial in Patients with Perennial Allergic Rhinitis
Treatment Group (n) |
Mean Baseline* (SEM) |
Change from Baselinet (SEM) |
Placebo Comparison (P-value) |
CLARINEX 5.0 mg (337) |
12.37 (0.18) |
-4.06 (0.21) |
P=0.01 |
Placebo (337) |
12.30 (0.18) |
-3.27 (0.21) |
|
SEM=Standard Error of the Mean
* At baseline, average of total symptom score (sum of 5 individual nasal
symptoms and 3 non-nasal symptoms, each symptom scored 0 to 3 where 0=no
symptom and 3=severe symptoms) of at least 10 was required for trial
eligibility. TSS ranges from 0=no symptoms to 24=maximal symptoms.
† Mean reduction in TSS averaged over the 4-week treatment period. |
Chronic Idiopathic Urticaria
The efficacy and safety of
CLARINEX Tablets 5 mg once daily was studied in 416 chronic idiopathic
urticaria patients 12 to 84 years of age, of whom 211 received CLARINEX. In two
double-blind, placebo-controlled, randomized clinical trials of six weeks
duration, at the pre-specified one-week primary time point evaluation, CLARINEX
Tablets significantly reduced the severity of pruritus when compared to placebo
(Table 5). Secondary endpoints were also evaluated, and during the first week
of therapy CLARINEX Tablets 5 mg reduced the secondary endpoints, “Number of
Hives” and the “Size of the Largest Hive,” when compared to placebo.
Table 5: PRURITUS SYMPTOM
SCORE Changes in the First Week of a Clinical Trial in Patients with Chronic
Idiopathic Urticaria
Treatment Group (n) |
Mean Baseline (SEM) |
Change from Baseline* (SEM) |
Placebo Comparison (P-value) |
CLARINEX 5.0 mg (115) |
2.19 (0.04) |
-1.05 (0.07) |
P<0.01 |
Placebo (110) |
2.21 (0.04) |
-0.52 (0.07) |
|
Pruritus scored 0 to 3 where
0=no symptom to 3=maximal symptom
SEM=Standard Error of the Mean
* Mean reduction in pruritus averaged over the first week of treatment. |
The clinical safety of CLARINEX
Oral Solution was documented in three, 15-day, double-blind, placebo-controlled
safety studies in pediatric subjects with a documented history of allergic
rhinitis, chronic idiopathic urticaria, or subjects who were candidates for
antihistamine therapy. In the first study, 2.5 mg of CLARINEX Oral Solution was
administered to 60 pediatric subjects 6 to 11 years of age. The second study
evaluated 1.25 mg of CLARINEX Oral Solution administered to 55 pediatric
subjects 2 to 5 years of age. In the third study, 1.25 mg of CLARINEX Oral
Solution was administered to 65 pediatric subjects 12 to 23 months of age and
1.0 mg of CLARINEX Oral Solution was administered to 66 pediatric subjects 6 to
11 months of age. The results of these studies demonstrated the safety of
CLARINEX Oral Solution in pediatric subjects 6 months to 11 years of age.