Ondansetron HCl

A to Z Drug Facts

 Action Selective serotonin (5-HT₃) receptor antagonist that inhibits serotonin receptors in GI tract or chemoreceptor trigger zone.

 Indications

Parenteral and oral: Prevention of nausea and vomiting with initial and repeat courses of emetogenic cancer chemotherapy, including high-dose cisplatin; prevention of postoperative nausea or vomiting. Oral: 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; prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy, including cisplatin ³ 50 mg/m². Unlabeled use(s): Treatment of nausea and vomiting associated with acetaminophen poisoning or prostacyclin therapy; treatment of acute levodopa-induced psychosis (visual hallucinations); reduction in bulimic episodes due to bulimia nervosa; treatment of spinal or epidural morphine-induced pruritus; management of social anxiety disorder.

 Contraindications Standard considerations.

 Route/Dosage

Prevention of Chemotherapy-Induced Nausea and Vomiting

ADULTS: IV 0.15 mg/kg infused over 15 min beginning 30 min before emetogenic chemotherapy with 2 additional 0.15 mg/kg doses 4 and 8 hrs after the first dose. Alternatively, infuse 32 mg over 15 min, starting 30 min prior to emetogenic chemotherapy. ADULTS & CHILDREN ³ 12 YR: PO (moderately emetogenic cancer chemotherapy) 8 mg bid, administering the first dose 30 min prior to starting emetogenic chemotherapy and the second dose 8 hrs after the first dose; subsequent 8 mg doses may be given q 12 hr for 1 to 2 days after completion of chemotherapy. CHILDREN 4 to 11 YR: PO 4 mg tid, starting 30 min prior to chemotherapy, with subsequent doses 4 and 8 hr after the first dose; give 4 mg q 8 hr for 1 to 2 days after completion of chemotherapy.

Prevention of Radiotherapy-Induced Nausea and Vomiting

ADULTS: PO 8 mg tid.

Total Body Irradiation

ADULTS: PO 8 mg 1 to 2 hr prior to each fraction of radiotherapy administered each day.

Single High-Dose Fraction Radiothreapy to the Abdomen

ADULTS: PO 8 mg 1 to 2 hr prior to radiotherapy, with subsequent doses q 8 hr after the first dose for 1 to 2 days after completion of radiotherapy.

Daily Fractionated Radiotherapy to the Abdomen

ADULTS: PO 8 mg 1 to 2 hr prior to radiotherapy, with subsequent doses q 8 hr after the first dose for each day radiotherapy is given.

Prevention of Postoperative Nausea and Vomiting

ADULTS: IV 4 mg (undiluted) > 30 sec (preferably over 2 to 5 min) or IM 4 mg (undiluted) as a single injection. PO 16 mg as a single dose 1 hr prior to induction of anesthesia. CHILDREN (2 to 12 YR weighing £ 40 kg): IV 0.1 mg/kg CHILDREN (> 40 kg): IV 4 mg single dose. Administer over ³ 30 sec, preferably over 2 to 5 min.

Prevention of Nausea and Vomiting due to Highly Emetogenic Cancer Chemotherapy

ADULTS: PO 24 mg given 30 min prior to start of single-day highly emetogenic chemotherapy, including ³ 50 mg/m² cisplatin.

 Interactions

Rifamycins (eg, rifampin): Plasma levels of ondansetron may be reduced, decreasing the antiemetic effect. INCOMPATIBILITIES: Alkaline solutions.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: Chest pain; tachycardia. CNS: Headache; seizures. DERM: Rash. GI: Dry mouth; constipation; abdominal pain. META: Hypokalemia. RESP: Bronchospasm. OTHER: Fever; anaphylaxis; weakness.

 Precautions

Pregnancy: Category B. Lactation: Undetermined. Children: Dosing in children < 4 yr is not well defined. Hepatic impairment: In patients with severe hepatic impairment, do not exceed 8 mg daily oral dose. For IV use, give single 8 mg daily dose over 15 min beginning 30 min before chemotherapy. Peristalsis: Ondansetron does not stimulate gastric or intestinal peristalsis; may mask progressive ileus or gastric distention.

 Administration/Storage

• Dilute solution in 50 mL of 5% Dextrose in Water or 0.9% Sodium Chloride for Injection.
• Do not mix with solutions for which compatibility has not been established.
• Preparation is stable for 48 hr at room temperature following dilution.
• Rectal suppositories and oral solutions may be extemporaneously compounded.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note hepatic impairment.
• Ensure that baseline hepatic studies have been performed before beginning therapy.
• Assess patient for nausea, vomiting, and bowel sounds.
• Monitor I&O carefully.
• Be prepared to give additional IV fluids to patient who is vomiting, but do not overhydrate.
• Discontinue IV infusion if signs of hypersensitivity develop.

 Patient/Family Education

• Advise patient that headache is a common side effect.
• Advise patient that medication will greatly reduce likelihood of nausea and vomiting, but that these are still possible.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts