The active ingredient in ondansetron tablets, USP is ondansetron hydrochloride (HCl) as the dihydrate, the racemic form of ondansetron and a selective blocking agent of the serotonin 5-HT3 receptor type. Chemically it is (±) 1, 2, 3, 9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one, monohydrochloride, dihydrate. It has the following structural formula:

The molecular formula is C18H19N3O•HCl•2H2O, representing a molecular weight of 365.9. Ondansetron hydrochloride USP (dihydrate) is a white to off-white powder that is soluble in water and normal saline.



Ondansetron tablets, USP for oral administration contain ondansetron hydrochloride USP (dihydrate) equivalent to 4 mg or 8 mg or 24 mg of ondansetron. Each film-coated tablet also contains the inactive ingredients anhydrous lactose, microcrystalline cellulose, pregelatinized starch (maize), magnesium stearate, triacetin, titanium dioxide and hypromellose. In addition 8 mg tablet also contains iron oxide yellow and 24 mg tablet also contains iron oxide red.



Meets USP dissolution test 6.

Pharmacodynamics

 

Ondansetron is a selective 5-HT3 receptor antagonist. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist. Serotonin receptors of the 5-HT3 type are present both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone of the area postrema. It is not certain whether ondansetron’s antiemetic action is mediated centrally, peripherally, or in both sites. However, cytotoxic chemotherapy appears to be associated with release of serotonin from the enterochromaffin cells of the small intestine. In humans, urinary 5-HIAA (5-hydroxyindoleacetic acid) excretion increases after cisplatin administration in parallel with the onset of emesis. The released serotonin may stimulate the vagal afferents through the 5-HT3 receptors and initiate the vomiting reflex.



In animals, the emetic response to cisplatin can be prevented by pretreatment with an inhibitor of serotonin synthesis, bilateral abdominal vagotomy and greater splanchnic nerve section, or pretreatment with a serotonin 5-HT3 receptor antagonist.



In normal volunteers, single intravenous doses of 0.15 mg/kg of ondansetron had no effect on esophageal motility, gastric motility, lower esophageal sphincter pressure, or small intestinal transit time. Multiday administration of ondansetron has been shown to slow colonic transit in normal volunteers. Ondansetron has no effect on plasma prolactin concentrations.



Ondansetron does not alter the respiratory depressant effects produced by alfentanil or the degree of neuromuscular blockade produced by atracurium. Interactions with general or local anesthetics have not been studied.

1.

Prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy, including cisplatin ≥50 mg/m2.

2.

Prevention of nausea and vomiting associated with initial and repeat courses of moderately emetogenic cancer chemotherapy.

3.

Prevention of nausea and vomiting associated with radiotherapy in patients receiving either total body irradiation, single high-dose fraction to the abdomen, or daily fractions to the abdomen.

4.

Prevention of postoperative nausea and/or vomiting. As with other antiemetics, routine prophylaxis is not recommended for patients in whom there is little expectation that nausea and/or vomiting will occur postoperatively. In patients where nausea and/or vomiting must be avoided postoperatively, ondansetron tablets, USP are recommended even where the incidence of postoperative nausea and/or vomiting is low.

The concomitant use of apomorphine with ondansetron is contraindicated based on reports of profound hypotension and loss of consciousness when apomorphine was administered with ondansetron.



Ondansetron tablets are contraindicated for patients known to have hypersensitivity to the drug.

Hypersensitivity reactions have been reported in patients who have exhibited hypersensitivity to other selective 5-HT3 receptor antagonists.



ECG changes including QT interval prolongation has been seen in patients receiving ondansetron. In addition, postmarketing cases of Torsade de Pointes have been reported in patients using ondansetron. Avoid ondansetron hydrochloride in patients with congenital long QT syndrome. ECG monitoring is recommended in patients with electrolyte abnormalities (e.g., hypokalemia or hypomagnesemia), congestive heart failure, bradyarrhythmias or patients taking other medicinal products that lead to QT prolongation.



The development of serotonin syndrome has been reported with 5-HT3 receptor antagonists alone. Most reports have been associated with concomitant use of serotonergic drugs (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors, mirtazapine, fentanyl, lithium, tramadol, and intravenous methylene blue). Some of the reported cases were fatal. Serotonin syndrome occurring with overdose of ondansetron hydrochloride alone has also been reported. The majority of reports of serotonin syndrome related to    5-HT3 receptor antagonist use occurred in a post-anesthesia care unit or an infusion center.



Symptoms associated with serotonin syndrome may include the following combination of signs and symptoms: mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, with or without gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of ondansetron hydrochloride and other serotonergic drugs. If symptoms of serotonin syndrome occur, discontinue ondansetron hydrochloride and initiate supportive treatment. Patients should be informed of the increased risk of serotonin syndrome, especially if ondansetron hydrochloride is used concomitantly with other serotonergic drugs (see PRECAUTIONS and OVERDOSAGE).

The following have been reported as adverse events in clinical trials of patients treated with ondansetron, the active ingredient of ondansetron hydrochloride. A causal relationship to therapy with ondansetron hydrochloride has been unclear in many cases.



Chemotherapy-Induced Nausea and Vomiting



The adverse events in Table 5 have been reported in ≥5% of adult patients receiving a single 24 mg ondansetron tablet in 2 trials. These patients were receiving concurrent highly emetogenic cisplatin-based chemotherapy regimens (cisplatin dose ≥50 mg/m2).

 

Table 5. Principal Adverse Events in U.S. Trials: Single Day Therapy With 24 mg Ondansetron Tablets (Highly Emetogenic Chemotherapy)

The adverse events in Table 6 have been reported in ≥5% of adults receiving either 8 mg of ondansetron tablets 2 or 3 times a day for 3 days or placebo in 4 trials. These patients were receiving concurrent moderately emetogenic chemotherapy, primarily cyclophosphamide-based regimens. 

 

Table 6. Principal Adverse Events in U.S. Trials: 3 Days of Therapy With 8 mg Ondansetron Tablets (Moderately Emetogenic Chemotherapy)

Central Nervous System



There have been rare reports consistent with, but not diagnostic of, extrapyramidal reactions in patients receiving ondansetron.



Hepatic



In 723 patients receiving cyclophosphamide-based chemotherapy in U.S. clinical trials, AST and/or ALT values have been reported to exceed twice the upper limit of normal in approximately 1% to 2% of patients receiving ondansetron tablets. The increases were transient and did not appear to be related to dose or duration of therapy. On repeat exposure, similar transient elevations in transaminase values occurred in some courses, but symptomatic hepatic disease did not occur. The role of cancer chemotherapy in these biochemical changes cannot be clearly determined.



There have been reports of liver failure and death in patients with cancer receiving concurrent medications including potentially hepatotoxic cytotoxic chemotherapy and antibiotics. The etiology of the liver failure is unclear.



Integumentary



Rash has occurred in approximately 1% of patients receiving ondansetron.



Other



Rare cases of anaphylaxis, bronchospasm, tachycardia, angina (chest pain), hypokalemia, electrocardiographic alterations, vascular occlusive events, and grand mal seizures have been reported. Except for bronchospasm and anaphylaxis, the relationship to ondansetron hydrochloride was unclear.



Radiation-Induced Nausea and Vomiting



The adverse events reported in patients receiving ondansetron tablets and concurrent radiotherapy were similar to those reported in patients receiving ondansetron tablets and concurrent chemotherapy. The most frequently reported adverse events were headache, constipation, and diarrhea.



Postoperative Nausea and Vomiting



The adverse events in Table 7 have been reported in ≥5% of patients receiving ondansetron tablets at a dosage of 16 mg orally in clinical trials. With the exception of headache, rates of these events were not significantly different in the ondansetron and placebo groups. These patients were receiving multiple concomitant perioperative and postoperative medications.

 

Table 7. Frequency of Adverse Events From Controlled Studies With Ondansetron Tablets (Postoperative Nausea and Vomiting)

Observed During Clinical Practice



In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of oral formulations of ondansetron hydrochloride. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. The events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to ondansetron hydrochloride.



Cardiovascular: Rarely and predominantly with intravenous ondansetron, transient ECG changes including QT interval prolongation have been reported.



General: Flushing. Rare cases of hypersensitivity reactions, sometimes severe (e.g., anaphylaxis/anaphylactoid reactions, angioedema, bronchospasm, shortness of breath, hypotension, laryngeal edema, stridor) have also been reported. Laryngospasm, shock, and cardiopulmonary arrest have occurred during allergic reactions in patients receiving injectable ondansetron.



Hepatobiliary: Liver enzyme abnormalities



Lower Respiratory: Hiccups



Neurology: Oculogyric crisis, appearing alone, as well as with other dystonic reactions



Skin: Urticaria, Stevens-Johnson syndrome, and toxic epidermal necrolysis



Special Senses: Eye Disorders:  Cases of transient blindness, predominantly during intravenous administration, have been reported. These cases of transient blindness were reported to resolve within a few minutes up to 48 hours.

Animal studies have shown that ondansetron is not discriminated as a benzodiazepine nor does it substitute for benzodiazepines in direct addiction studies.

There is no specific antidote for ondansetron overdose. Patients should be managed with appropriate supportive therapy. Individual intravenous doses as large as 150 mg and total daily intravenous doses as large as 252 mg have been inadvertently administered without significant adverse events. These doses are more than 10 times the recommended daily dose.



In addition to the adverse events listed above, the following events have been described in the setting of ondansetron overdose: “Sudden blindness” (amaurosis) of 2 to 3 minutes’ duration plus severe constipation occurred in 1 patient that was administered 72 mg of ondansetron intravenously as a single dose. Hypotension (and faintness) occurred in a patient that took 48 mg of ondansetron tablets. Following infusion of 32 mg over only a 4-minute period, a vasovagal episode with transient second-degree heart block was observed. In all instances, the events resolved completely.



Pediatric cases consistent with serotonin syndrome have been reported after inadvertent oral overdoses of ondansetron (exceeding estimated ingestion of 5 mg/kg) in young children. Reported symptoms included somnolence, agitation, tachycardia, tachypnea, hypertension, flushing, mydriasis, diaphoresis, myoclonic movements, horizontal nystagmus, hyperreflexia, and seizure. Patients required supportive care, including intubation in some cases, with complete recovery without sequelae within 1 to 2 days.

Prevention of Nausea and Vomiting Associated With Highly Emetogenic Cancer Chemotherapy



The recommended adult oral dosage of ondansetron tablets is 24 mg given as three 8 mg tablets administered 30 minutes before the start of single-day highly emetogenic chemotherapy, including cisplatin ≥50 mg/m2. Multiday, single-dose administration of a 24 mg dosage has not been studied.



Pediatric Use



There is no experience with the use of a 24 mg dosage in pediatric patients.



Geriatric Use



The dosage recommendation is the same as for the general population.



Prevention of Nausea and Vomiting Associated With Moderately Emetogenic Cancer Chemotherapy

 

The recommended adult oral dosage is one 8 mg ondansetron tablet given twice a day. The first dose should be administered 30 minutes before the start of emetogenic chemotherapy, with a subsequent dose 8 hours after the first dose. One 8 mg ondansetron tablet should be administered twice a day (every 12 hours) for 1 to 2 days after completion of chemotherapy.



Pediatric Use



For pediatric patients 12 years of age and older, the dosage is the same as for adults. For pediatric patients 4 through 11 years of age, the dosage is one 4 mg ondansetron tablet given 3 times a day. The first dose should be administered 30 minutes before the start of emetogenic chemotherapy, with subsequent doses 4 and 8 hours after the first dose. One 4 mg ondansetron tablet should be administered 3 times a day (every 8 hours) for 1 to 2 days after completion of chemotherapy.



Geriatric Use



The dosage is the same as for the general population.



Prevention of Nausea and Vomiting Associated With Radiotherapy, Either Total Body Irradiation, or Single High-Dose Fraction or Daily Fractions to the Abdomen

 

The recommended oral dosage is one 8 mg ondansetron tablet given 3 times a day.



For total body irradiation, one 8 mg ondansetron tablet should be administered 1 to 2 hours before each fraction of radiotherapy administered each day.



For single high-dose fraction radiotherapy to the abdomen, one 8 mg ondansetron tablet should be administered 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for 1 to 2 days after completion of radiotherapy.



For daily fractionated radiotherapy to the abdomen, one 8 mg ondansetron tablet should be administered 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for each day radiotherapy is given.



Pediatric Use



There is no experience with the use of ondansetron tablets in the prevention of radiation-induced nausea and vomiting in pediatric patients.



Geriatric Use



The dosage recommendation is the same as for the general population.



Postoperative Nausea and Vomiting

 

The recommended dosage is 16 mg given as two 8 mg ondansetron tablets 1 hour before induction of anesthesia.



Pediatric Use



There is no experience with the use of ondansetron tablets in the prevention of postoperative nausea and vomiting in pediatric patients.



Geriatric Use



The dosage is the same as for the general population.



Dosage Adjustment for Patients With Impaired Renal Function

 

The dosage recommendation is the same as for the general population. There is no experience beyond first-day administration of ondansetron.



Dosage Adjustment for Patients With Impaired Hepatic Function 



In patients with severe hepatic impairment (Child-Pugh2 score of 10 or greater), clearance is reduced and apparent volume of distribution is increased with a resultant increase in plasma half-life. In such patients, a total daily dose of 8 mg should not be exceeded.

 

Ondansetron Tablets USP, 8 mg are yellow colored, oval shaped, film-coated tablets debossed with ‘F’ on one side and ‘92’ on the other side.



            Unit of 6                      NDC 63187-709-06

Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. Protect from light.

1.

Britto MR, Hussey EK, Mydlow P, et al. Effect of enzyme inducers on ondansetron (OND) metabolism in humans. Clin Pharmacol Ther. 1997;61:228.

2.

Pugh RNH, Murray-Lyon IM, Dawson JL, Pietroni MC, Williams R. Transection of the oesophagus for bleeding oesophageal varices. Brit J Surg. 1973;60:646-649.

3.

Villikka K, Kivisto KT, Neuvonen PJ. The effect of rifampin on the pharmacokinetics of oral and intravenous ondansetron. Clin Pharmacol Ther. 1999;65:377-381.

4.

De Witte JL, Schoenmaekers B, Sessler DI, et al. Anesth Analg. 2001;92:1319-1321.

5.

Arcioni R, della Rocca M, Romanò R, et al. Anesth Analg. 2002;94:1553-1557.

Manufactured for:

Aurobindo Pharma USA, Inc.

2400 Route 130 North

Dayton, NJ  08810

 

Manufactured by:

Aurobindo Pharma Limited

Hyderabad–500 072, India

Relabeled by:

Proficient Rx LP

Thousand Oaks, CA 91320

Revised: 10/2014

NDC 63187-709-30

Ondansetron Tablets, USP

8 mg*

Rx only           30 Tablets