Pharmacokinetics

Chemotherapy-Induced Nausea and Vomiting

In adult cancer patients undergoing chemotherapy and in volunteers, mean pharmacokinetic data obtained from an infusion of a single 40 mcg/kg dose of granisetron hydrochloride injection are shown in Table 1.

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 12% of the administered dose is eliminated unchanged in the urine in 48 hours.  The remainder of the dose is excreted as metabolites, 49% in the urine, and 34% in the feces.

Subpopulations

Gender

There was high inter- and intra-subject variability noted in these studies.  No difference in mean AUC was found between males and females, although males had a higher Cmax generally.

Elderly

The ranges of the pharmacokinetic parameters in elderly volunteers (mean age 71 years), given a single 40 mcg/kg intravenous dose of granisetron hydrochloride injection, were generally similar to those in younger healthy volunteers; mean values were lower for clearance and longer for half-life in the elderly patients (see Table 1).

Pediatric Patients

A pharmacokinetic study in pediatric cancer patients (2 to 16 years of age), given a single 40 mcg/kg intravenous dose of granisetron hydrochloride 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.

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 granisetron hydrochloride injection.

Hepatically Impaired Patients

A pharmacokinetic study 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 and the good tolerance of doses well above the recommended 10 mcg/kg dose, dosage adjustment in patients with possible hepatic functional impairment is not necessary.

Chemotherapy-Induced Nausea and Vomiting

Single-Day Chemotherapy

Cisplatin-Based Chemotherapy

In a double-blind, placebo-controlled study in 28 cancer patients, granisetron hydrochloride injection, administered as a single intravenous infusion of 40 mcg/kg, was significantly more effective than placebo in preventing nausea and vomiting induced by cisplatin chemotherapy (see Table 2).

Granisetron hydrochloride injection was also evaluated in a randomized dose response study of cancer patients receiving cisplatin ≥75 mg/m2.  Additional chemotherapeutic agents included:  anthracyclines, carboplatin, cytostatic antibiotics, folic acid derivatives, methylhydrazine, nitrogen mustard analogs, podophyllotoxin derivatives, pyrimidine analogs, and vinca alkaloids. 

Table 1.  Pharmacokinetic Parameters in Adult Cancer Patients Undergoing Chemotherapy and in Volunteers, Following a Single Intravenous 40 mcg/kg Dose of Granisetron Hydrochloride Injection

*5-minute infusion.

†3-minute infusion.

Table 2.  Prevention of Chemotherapy-Induced Nausea and Vomiting — Single-Day Cisplatin Therapy1

1 Cisplatin administration began within 10 minutes of granisetron hydrochloride injection infusion and continued for 1.5 to 3 hours.  Mean cisplatin dose was 86 mg/m2 in the granisetron hydrochloride injection group and 80 mg/m2 in the placebo group.

2 No vomiting and no moderate or severe nausea.

Granisetron hydrochloride injection doses of 10 and 40 mcg/kg were superior to 2 mcg/kg in preventing cisplatin-induced nausea and vomiting, but 40 mcg/kg was not significantly superior to 10 mcg/kg (see Table 3).

Granisetron hydrochloride injection was also evaluated in a double-blind, randomized dose response study of 353 patients stratified for high (≥80 to 120 mg/m2) or low (50 to 79 mg/m2) cisplatin dose.  Response rates of patients for both cisplatin strata are given in Table 4.

For both the low and high cisplatin strata, the 10, 20, and 40 mcg/kg doses were more effective than the 5 mcg/kg dose in preventing nausea and vomiting within 24 hours of chemotherapy administration.  The 10 mcg/kg dose was at least as effective as the higher doses.

Moderately Emetogenic Chemotherapy

Granisetron hydrochloride injection, 40 mcg/kg, was compared with the combination of chlorpromazine (50 to 200 mg/24 hours) and dexamethasone (12 mg) in patients treated with moderately emetogenic chemotherapy, including primarily carboplatin >300 mg/m2, cisplatin 20 to 50 mg/m2 and cyclophosphamide >600 mg/m2.  Granisetron hydrochloride injection was superior to the chlorpromazine regimen in preventing nausea and vomiting (see Table 5).

In other studies of moderately emetogenic chemotherapy, no significant difference in efficacy was found between granisetron hydrochloride doses of 40 mcg/kg and 160 mcg/kg.

Repeat-Cycle Chemotherapy

In an uncontrolled trial, 512 cancer patients received granisetron hydrochloride injection, 40 mcg/kg, prophylactically, for two cycles of chemotherapy, 224 patients received it for at least four cycles, and 108 patients received it for at least six cycles.  Granisetron hydrochloride injection efficacy remained relatively constant over the first six repeat cycles, with complete response rates (no vomiting and no moderate or severe nausea in 24 hours) of 60% to 69%.  No patients were studied for more than 15 cycles.

Pediatric Studies

A randomized double-blind study evaluated the 24-hour response of 80 pediatric cancer patients (age 2 to 16 years) to granisetron hydrochloride injection 10, 20 or 40 mcg/kg.  Patients were treated with cisplatin ≥60 mg/m2, cytarabine ≥3 g/m2, cyclophosphamide ≥1 g/m2 or nitrogen mustard ≥6 mg/m2 (see Table 6).

A second pediatric study compared granisetron hydrochloride injection 20 mcg/kg to chlorpromazine plus dexamethasone in 88 patients treated with ifosfamide ≥3 g/m2/day for two or three days.  Granisetron hydrochloride injection was administered on each day of ifosfamide treatment.  At 24 hours, 22% of granisetron hydrochloride injection patients achieved complete response (no vomiting and no moderate or severe nausea in 24 hours) compared with 10% on the chlorpromazine regimen.  The median number of vomiting episodes with granisetron hydrochloride injection was 1.5; with chlorpromazine it was 7.

Drug Interactions

Granisetron does not induce or inhibit the cytochrome P-450 drug-metabolizing enzyme system in vitro.  There have been no definitive drug-drug interaction studies to examine pharmacokinetic or pharmacodynamic interaction with other drugs; but in humans, granisetron hydrochloride injection has been safely administered with drugs representing benzodiazepines, neuroleptics and anti-ulcer medications commonly prescribed with antiemetic treatments.  Granisetron hydrochloride injection also does not appear to interact with emetogenic cancer chemotherapies.  Because granisetron is metabolized by hepatic cytochrome P-450 drug-metabolizing enzymes, inducers or inhibitors of these enzymes may change the clearance and, hence, the half-life of granisetron.  No specific interaction studies have been conducted in anesthetized patients.  In addition, the activity of the cytochrome P-450 subfamily 3A4 (involved in the metabolism of some of the main narcotic analgesic agents) is not modified by granisetron hydrochloride in vitro.

In in vitro human microsomal studies, ketoconazole inhibited ring oxidation of granisetron hydrochloride.  However, the clinical significance of in vivo pharmacokinetic interactions with ketoconazole is not known.  In a human pharmacokinetic study, hepatic enzyme induction with phenobarbital resulted in a 25% increase in total plasma clearance of intravenous granisetron hydrochloride.  The clinical significance of this change is not known.

Table 3. Prevention of Chemotherapy-Induced Nausea and Vomiting — Single-Day High-Dose Cisplatin Therapy1

1 Cisplatin administration began within 10 minutes of granisetron hydrochloride injection infusion and continued for 2.6 hours (mean).  Mean cisplatin doses were 96 to 99 mg/m2.

2 No vomiting and no moderate or severe nausea.

Table 4. Prevention of Chemotherapy-Induced Nausea and Vomiting — Single-Day High-Dose and Low-Dose Cisplatin Therapy1

1 Cisplatin administration began within 10 minutes of granisetron hydrochloride injection infusion and continued for 2 hours (mean).  Mean cisplatin doses were 64 and 98 mg/m2 for low and high strata.

2 No vomiting and no use of rescue antiemetic. 

Table 5.  Prevention of Chemotherapy-Induced Nausea and Vomiting— Single-Day Moderately Emetogenic Chemotherapy

1 Patients also received dexamethasone, 12 mg.

2 No vomiting and no moderate or severe nausea.

  Table 6.  Prevention of Chemotherapy-Induced Nausea and Vomiting in Pediatric Patients

1 No vomiting and no moderate or severe nausea.

Carcinogenesis, Mutagenesis, Impairment of Fertility

In a 24-month carcinogenicity study, rats were treated orally with granisetron 1, 5 or 50 mg/kg/day (6, 30 or 300 mg/m2/day).  The 50 mg/kg/day dose was reduced to 25 mg/kg/day (150 mg/m2/day) during week 59 due to toxicity.  For a 50 kg person of average height (1.46 m2 body surface area), these doses represent 16, 81 and 405 times the recommended clinical dose (0.37 mg/m2, IV) on a body surface area basis.  There was a statistically significant increase in the incidence of hepatocellular carcinomas and adenomas in males treated with 5 mg/kg/day (30 mg/m2/day, 81 times the recommended human dose based on body surface area) and above, and in females treated with 25 mg/kg/day (150 mg/m2/day, 405 times the recommended human dose based on body surface area).  No increase in liver tumors was observed at a dose of 1 mg/kg/day (6 mg/m2/day, 16 times the recommended human dose based on body surface area) in males and 5 mg/kg/day (30 mg/m2/day, 81 times the recommended human dose based on body surface area) in females.  In a 12-month oral toxicity study, treatment with granisetron 100 mg/kg/day (600 mg/m2/day, 1622 times the recommended human dose based on body surface area) produced hepatocellular adenomas in male and female rats while no such tumors were found in the control rats.  A 24-month mouse carcinogenicity study of granisetron did not show a statistically significant increase in tumor incidence, but the study was not conclusive.

Because of the tumor findings in rat studies, granisetron hydrochloride injection should be prescribed only at the dose and for the indication recommended (see INDICATIONS AND USAGE and DOSAGE AND ADMINISTRATION).

Granisetron was not mutagenic in an in vitro Ames test and mouse lymphoma cell forward mutation assay, and in vivo mouse micronucleus test and in vitro and ex vivo rat hepatocyte UDS assays.  It, however, produced a significant increase in UDS in HeLa cells in vitro and a significant increased incidence of cells with polyploidy in an in vitro human lymphocyte chromosomal aberration test.

Granisetron at subcutaneous doses up to 6 mg/kg/day (36 mg/m2/day, 97 times the recommended human dose based on body surface area) was found to have no effect on fertility and reproductive performance of male and female rats.

Pregancy

Teratogenic Effects: Pregnancy Category B.

Reproduction studies have been performed in pregnant rats at intravenous doses up to 9 mg/kg/day (54 mg/m2/day, 146 times the recommended human dose based on body surface area) and pregnant rabbits at intravenous doses up to 3 mg/kg/day (35.4 mg/m2/day, 96 times the recommended human dose based on body surface area) and have revealed no evidence of impaired fertility or harm to the fetus due to granisetron.  There are, however, no adequate and well-controlled studies in pregnant women.  Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Nursing Mothers

It is not known whether granisetron is excreted in human milk.  Because many drugs are excreted in human milk, caution should be exercised when granisetron hydrochloride injection is administered to a nursing woman.

Pediatric Use

See DOSAGE AND ADMINISTRATION for use in chemotherapy-induced nausea and vomiting in pediatric patients 2 to 16 years of age.  Safety and effectiveness in pediatric patients under 2 years of age have not been established.

Geriatric Use

During chemotherapy clinical trials, 713 patients 65 years of age or older received granisetron hydrochloride injection.  Effectiveness and safety were similar in patients of various ages.

Chemotherapy-Induced Nausea and Vomiting

The following have been reported during controlled clinical trials or in the routine management of patients.  The percentage figures are based on clinical trial experience only.  Table 7 gives the comparative frequencies of the five most commonly reported adverse events (≥3%) in patients receiving granisetron hydrochloride injection, in single-day chemotherapy trials.  These patients received chemotherapy, primarily cisplatin, and intravenous fluids during the 24-hour period following granisetron hydrochloride injection administration.  Events were generally recorded over seven days post-granisetron hydrochloride injection administration.  In the absence of a placebo group, there is uncertainty as to how many of these events should be attributed to granisetron hydrochloride, except for headache, which was clearly more frequent than in comparison groups.

Table 7.  Principal Adverse Events in Clinical Trials — Single-Day Chemotherapy

1 Metoclopramide/dexamethasone and phenothiazines/dexamethasone.

In over 3,000 patients receiving granisetron hydrochloride injection (2 to 160 mcg/kg) in single-day and multiple-day clinical trials with emetogenic cancer therapies, adverse events, other than those in Table 7, were observed; attribution of many of these events to granisetron hydrochloride is uncertain.

Hepatic: In comparative trials, mainly with cisplatin regimens, elevations of AST and ALT (>2 times the upper limit of normal) following administration of granisetron hydrochloride injection occurred in 2.8% and 3.3% of patients, respectively.  These frequencies were not significantly different from those seen with comparators (AST: 2.1%; ALT: 2.4%).

Cardiovascular:  Hypertension (2%); hypotension, arrhythmias such as sinus bradycardia, atrial fibrillation, varying degrees of A-V block, ventricular ectopy including non-sustained tachycardia, and ECG abnormalities have been observed rarely.

Central Nervous System:  Agitation, anxiety, CNS stimulation and insomnia were seen in less than 2% of patients.  Extrapyramidal syndrome occurred rarely and only in the presence of other drugs associated with this syndrome.

Hypersensitivity:  Rare cases of hypersensitivity reactions, sometimes severe (e.g., anaphylaxis, shortness of breath, hypotension, urticaria) have been reported.

Other:  Fever (3%), taste disorder (2%), skin rashes (1%).  In multiple-day comparative studies, fever occurred more frequently with granisetron hydrochloride injection (8.6%) than with comparative drugs (3.4%, P<0.014), which usually included dexamethasone.

Prevention of Chemotherapy-Induced Nausea and Vomiting

The recommended dosage for granisetron hydrochloride injection is 10 mcg/kg administered intravenously within 30 minutes before initiation of chemotherapy, and only on the day(s) chemotherapy is given.

Infusion Preparation

Granisetron hydrochloride injection may be administered intravenously either undiluted over 30 seconds, or diluted with 0.9% Sodium Chloride or 5% Dextrose and infused over 5 minutes.

Stability

Intravenous infusion of granisetron hydrochloride injection should be prepared at the time of administration.  However, granisetron hydrochloride injection has been shown to be stable for at least 24 hours when diluted in 0.9% Sodium Chloride or 5% Dextrose and stored at room temperature under normal lighting conditions.

As a general precaution, granisetron hydrochloride injection should not be mixed in solution with other drugs.  Parenteral drug products should be inspected visually for particulate matter and discoloration before administration whenever solution and container permit.

Pediatric Patients

The recommended dose in pediatric patients 2 to 16 years of age is 10 mcg/kg (see CLINICAL TRIALS).  Pediatric patients under 2 years of age have not been studied.

Geriatric Patients, Renal Failure Patients or Hepatically Impaired Patients

No dosage adjustment is recommended (see CLINICAL PHARMACOLOGY, Pharmacokinetics).

Storage

Store single-use vials and multi-use vials at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Once the multi-use vial is penetrated, its contents should be used within 30 days.

Do not freeze.  Protect from light.  Retain in carton until time of use.

Vial stoppers do not contain natural rubber latex.