CLINICAL PHARMACOLOGY
Granisetron is a selective 5-hydroxytryptamine3 (5-HT3)
receptor antagonist with little or no affinity for other serotonin receptors,
including 5-HT1; 5-HT1A; 5-HT1B/C; 5-HT2;
for alpha1-, alpha2-, or beta-adrenoreceptors; for dopamine-D2;
or for histamine-H1; benzodiazepine; picrotoxin or opioid receptors.
Serotonin receptors of the 5-HT3 type are located peripherally on
vagal nerve terminals and centrally in the chemoreceptor trigger zone of the
area postrema. During chemotherapy that induces vomiting, mucosal enterochromaffin
cells release serotonin, which stimulates 5-HT3 receptors. This evokes
vagal afferent discharge, inducing vomiting. Animal studies demonstrate that,
in binding to 5-HT3 receptors, granisetron blocks serotonin stimulation
and subsequent vomiting after emetogenic stimuli such as cisplatin. In the ferret
animal model, a single granisetron injection prevented vomiting due to high-dose
cisplatin or arrested vomiting within 5 to 30 seconds.
In most human studies, granisetron has had little effect on blood pressure,
heart rate or ECG. No evidence of an effect on plasma prolactin or aldosterone
concentrations has been found in other studies.
Following single and multiple oral doses, KYTRIL (granisetron) Tablets slowed colonic transit
in normal volunteers. However, KYTRIL (granisetron) had no effect on oro-cecal transit time
in normal volunteers when given as a single intravenous (IV) infusion of 50
mcg/kg or 200 mcg/kg.
Pharmacokinetics
In healthy volunteers and adult cancer patients undergoing chemotherapy, administration
of KYTRIL (granisetron) Tablets produced mean pharmacokinetic data shown in Table 1.
Table 1 : Pharmacokinetic Parameters (Median [range]) Following
KYTRIL Tablets (granisetron hydrochloride)
|
Peak Plasma Concentration
(ng/mL) |
Terminal Phase Plasma Half-Life (h) |
Volume of Distribution (L/kg) |
Total Clearance (L/h/kg) |
Cancer Patients
1 mg bid, 7 days (n=27) |
5.99
[0.63 to 30.9] |
N.D.1 |
N.D. |
0.52
[0.09 to 7.37] |
Volunteers
single 1 mg dose (n=39) |
3.63
[0.27 to 9.14] |
6.23
[0.96 to 19.9] |
3.94
[1.89 to 39.4] |
0.41
[0.11 to 24.6] |
1 Not determined after oral administration;
following a single intravenous dose of 40 mcg/kg, terminal phase half-life
was determined to be 8.95 hours.
N.D. Not determined. |
A 2 mg dose of KYTRIL (granisetron) Oral Solution is bioequivalent to the corresponding dose
of KYTRIL (granisetron) Tablets (1 mg x 2) and may be used interchangeably.
Absorption
When KYTRIL (granisetron) Tablets were administered with food, AUC was decreased by 5% and
Cmax increased by 30% in non-fasted healthy volunteers who received a single
dose of 10 mg.
Distribution
Plasma protein binding is approximately 65% and granisetron distributes freely
between plasma and red blood cells.
Metabolism
Granisetron metabolism involves N-demethylation and aromatic ring oxidation
followed by conjugation. In vitro liver microsomal studies show that granisetron's
major route of metabolism is inhibited by ketoconazole, suggestive of metabolism
mediated by the cytochrome P-450 3A subfamily. Animal studies suggest that some
of the metabolites may also have 5-HT3 receptor antagonist activity.
Elimination
Clearance is predominantly by hepatic metabolism. In normal volunteers, approximately
11% of the orally administered dose is eliminated unchanged in the urine in
48 hours. The remainder of the dose is excreted as metabolites, 48% in the urine
and 38% in the feces.
Subpopulations
Gender
The effects of gender on the pharmacokinetics of KYTRIL (granisetron) Tablets have not been
studied. However, after intravenous infusion of KYTRIL (granisetron) , no difference in mean
AUC was found between males and females, although males had a higher Cmax generally.
In elderly and pediatric patients and in patients with renal failure or hepatic
impairment, the pharmacokinetics of granisetron was determined following administration
of intravenous KYTRIL (granisetron) .
Elderly
The ranges of the pharmacokinetic parameters in elderly volunteers (mean age
71 years), given a single 40 mcg/kg intravenous dose of KYTRIL (granisetron) Injection, were
generally similar to those in younger healthy volunteers; mean values were lower
for clearance and longer for half-life in the elderly.
Renal Failure Patients
Total clearance of granisetron was not affected in patients with severe renal
failure who received a single 40 mcg/kg intravenous dose of KYTRIL (granisetron) Injection.
Hepatically Impaired Patients
A pharmacokinetic study with intravenous KYTRIL (granisetron) in patients with hepatic impairment
due to neoplastic liver involvement showed that total clearance was approximately
halved compared to patients without hepatic impairment. Given the wide variability
in pharmacokinetic parameters noted in patients, dosage adjustment in patients
with hepatic functional impairment is not necessary.
Pediatric Patients
A pharmacokinetic study in pediatric cancer patients (2 to 16 years of age),
given a single 40 mcg/kg intravenous dose of KYTRIL (granisetron) Injection, showed that volume
of distribution and total clearance increased with age. No relationship with
age was observed for peak plasma concentration or terminal phase plasma half-life.
When volume of distribution and total clearance are adjusted for body weight,
the pharmacokinetics of granisetron are similar in pediatric and adult cancer
patients.
Clinical Trials
Chemotherapy-Induced Nausea and Vomiting
KYTRIL (granisetron) Tablets prevent nausea and vomiting associated with initial and repeat
courses of emetogenic cancer therapy, as shown by 24-hour efficacy data from
studies using both moderately- and highly-emetogenic chemotherapy.
Moderately Emetogenic Chemotherapy
The first trial compared KYTRIL (granisetron) Tablets doses of 0.25 mg to 2 mg twice a day,
in 930 cancer patients receiving, principally, cyclophosphamide, carboplatin,
and cisplatin (20 mg/m² to 50 mg/m²). Efficacy was based on complete
response (ie, no vomiting, no moderate or severe nausea, no rescue medication),
no vomiting, and no nausea. Table 2 summarizes the results of this study.
Table 2 : Prevention of Nausea and Vomiting 24 Hours PostÂChemotherapy1
|
Percentages of Patients
KYTRIL Tablet Dose |
Efficacy Measures |
0.25 mg
twice a day
(n=229)
% |
0.5 mg
twice a day
(n=235)
% |
1 mg
twice a day
(n=233)
% |
2 mg
twice a day
(n=233)
% |
Complete Response2 |
61 |
70* |
81*† |
72* |
No Vomiting |
66 |
77* |
88* |
79* |
No Nausea |
48 |
57 |
63* |
54 |
1 Chemotherapy included oral and injectable cyclophosphamide,
carboplatin, cisplatin (20 mg/m² to 50 mg/m²), dacarbazine,
doxorubicin, epirubicin.
2 No vomiting, no moderate or severe nausea, no rescue medication.
*Statistically significant (P < 0.01) vs. 0.25 mg bid.
†Statistically significant (P < 0.01) vs. 0.5 mg bid. |
Results from a second double-blind, randomized trial evaluating KYTRIL (granisetron) Tablets
2 mg once a day and KYTRIL (granisetron) Tablets 1 mg twice a day were compared to prochlorperazine
10 mg twice a day derived from a historical control. At 24 hours, there was
no statistically significant difference in efficacy between the two KYTRIL (granisetron) Tablet
regimens. Both regimens were statistically superior to the prochlorperazine
control regimen (see Table 3).
Table 3 : Prevention of Nausea and Vomiting 24 Hours PostÂChemotherapy1
Efficacy Measures |
Percentages of Patients |
KYTRIL (granisetron) Tablets
1 mg twice a day
(n = 354)
% |
KYTRIL (granisetron) Tablets
2 mg once a day
(n = 343)
% |
Prochlorperazine2
10 mg twice daily (n=111)
% |
Complete Response3 |
69* |
64* |
41 |
No Vomiting |
82* |
77* |
48 |
No Nausea |
51* |
53* |
35 |
Total Control4 |
51* |
50* |
33 |
1 Moderately emetogenic chemotherapeutic agents
included cisplatin (20 mg/m² to 50 mg/m²), oral and intravenous
cyclophosphamide, carboplatin, dacarbazine, doxorubicin.
2 Historical control from a previous double-blind KYTRIL (granisetron) trial.
3 No vomiting, no moderate or severe nausea, no rescue medication.
4 No vomiting, no nausea, no rescue medication.
*Statistically significant (P < 0.05) vs. prochlorperazine historical
control. |
Results from a KYTRIL (granisetron) Tablets 2 mg daily alone treatment arm in a third double-blind,
randomized trial, were compared to prochlorperazine (PCPZ), 10 mg bid, derived
from a historical control. The 24-hour results for KYTRIL (granisetron) Tablets 2 mg daily
were statistically superior to PCPZ for all efficacy parameters: complete response
(58%), no vomiting (79%), no nausea (51%), total control (49%). The PCPZ rates
are shown in Table 3.
Cisplatin-Based Chemotherapy
The first double-blind trial compared KYTRIL (granisetron) Tablets 1 mg bid, relative to
placebo (historical control), in 119 cancer patients receiving high-dose cisplatin
(mean dose 80 mg/m²). At 24 hours, KYTRIL (granisetron) Tablets 1 mg bid was significantly
(P < 0.001) superior to placebo (historical control) in all efficacy parameters:
complete response (52%), no vomiting (56%) and no nausea (45%). The placebo
rates were 7%, 14%, and 7%, respectively, for the three efficacy parameters.
Results from a KYTRIL (granisetron) Tablets 2 mg once a day alone treatment arm in a second
double-blind, randomized trial, were compared to both KYTRIL (granisetron) Tablets 1 mg twice
a day and placebo historical controls. The 24-hour results for KYTRIL (granisetron) Tablets
2 mg once a day were: complete response (44%), no vomiting (58%), no nausea
(46%), total control (40%). The efficacy of KYTRIL (granisetron) Tablets 2 mg once a day was
comparable to KYTRIL (granisetron) Tablets 1 mg twice a day and statistically superior to
placebo. The placebo rates were 7%, 14%, 7%, and 7%, respectively, for the four
parameters.
No controlled study comparing granisetron injection with the oral formulation
to prevent chemotherapy-induced nausea and vomiting has been performed.
Radiation-Induced Nausea and Vomiting
Total Body Irradiation
In a double-blind randomized study, 18 patients receiving KYTRIL (granisetron) Tablets, 2
mg daily, experienced significantly greater antiemetic protection compared to
patients in a historical negative control group who received conventional (non-5-HT3
antagonist) antiemetics. Total body irradiation consisted of 11 fractions of
120 cGy administered over 4 days, with three fractions on each of the first
3 days, and two fractions on the fourth day. KYTRIL (granisetron) Tablets were given one hour
before the first radiation fraction of each day.
Twenty-two percent (22%) of patients treated with KYTRIL (granisetron) Tablets did not experience
vomiting or receive rescue antiemetics over the entire 4-day dosing period,
compared to 0% of patients in the historical negative control group (P < 0.01).
In addition, patients who received KYTRIL (granisetron) Tablets also experienced significantly
fewer emetic episodes during the first day of radiation and over the 4-day treatment
period, compared to patients in the historical negative control group. The median
time to the first emetic episode was 36 hours for patients who received KYTRIL (granisetron)
Tablets.
Fractionated Abdominal Radiation
The efficacy of KYTRIL (granisetron) Tablets, 2 mg daily, was evaluated in a double-blind,
placebo-controlled randomized trial of 260 patients. KYTRIL (granisetron) Tablets were given
1 hour before radiation, composed of up to 20 daily fractions of 180 to 300
cGy each. The exceptions were patients with seminoma or those receiving whole
abdomen irradiation who initially received 150 cGy per fraction. Radiation was
administered to the upper abdomen with a field size of at least 100 cm².
The proportion of patients without emesis and those without nausea for KYTRIL (granisetron)
Tablets, compared to placebo, was statistically significant (P < 0.0001) at
24 hours after radiation, irrespective of the radiation dose. KYTRIL (granisetron) was superior
to placebo in patients receiving up to 10 daily fractions of radiation, but
was not superior to placebo in patients receiving 20 fractions.
Patients treated with KYTRIL (granisetron) Tablets (n=134) had a significantly longer time
to the first episode of vomiting (35 days vs. 9 days, P < 0.001) relative to
those patients who received placebo (n=126), and a significantly longer time
to the first episode of nausea (11 days vs. 1 day, P < 0.001). KYTRIL (granisetron) provided
significantly greater protection from nausea and vomiting than placebo.