ondansetron hydrochloride

ondansetron hydrochloride

(on dan' sah tron)

Zofran, Zofran ODT

Pregnancy Category B

Drug class

Antiemetic

Therapeutic actions

Blocks specific receptor sites (5-HT₃), which are associated with nausea and vomiting in the chemoreceptor trigger zone, centrally and at specific sites peripherally. It is not known whether its antiemetic actions are from actions at the central, peripheral, or combined sites.

Indications

·        Parenteral and oral: Prevention of nausea and vomiting associated with emetogenic cancer chemotherapy in patients > 6 mo of age

·        Prevention of postoperative nausea and vomiting—to prevent further episodes or, when postoperative nausea and vomiting must be avoided (oral), prophylactically (parenteral) in patients > 1 mo of age

·        Prevention of nausea and vomiting associated with radiotherapy

·        Unlabeled uses: Treatment of nausea and vomiting associated with acetaminophen poisoning, prostacyclin therapy; treatment of acute levodopa-induced psychosis; reduction of episodes in bulimia nervosa; treatment of spinal or epidural morphine-induced pruritus

Contraindications and cautions

·        Contraindicated with allergy to ondansetron.

·        Use cautiously with pregnancy, lactation.

Available forms

Tablets—4, 8, 24 mg; orally disintegrating tablets—4, 8 mg; oral solution—4 mg/5 mL; injection—2 mg/mL, 32 mg/50 mL

Dosages

ADULTS

Parenteral

·        Prevention of chemotherapy-induced nausea and vomiting: Three 0.15 mg/kg doses IV: First dose is given over 15 min, beginning 30 min before the chemotherapy; subsequent doses are given at 4 and 8 hr, or a single 32-mg dose is infused over 15 min beginning 30 min before the start of the chemotherapy.

Oral

·        Prevention of nausea and vomiting associated with cancer chemotherapy: 8 mg PO 30 min prior to chemotherapy, then 8 mg 8 hr later; give 8 mg q 12 hr for 1-2 days after completion of chemotherapy.

·        Prevention of nausea and vomiting associated with radiotherapy: 8 mg PO tid. For total body radiotherapy, administer 1–2 hr before radiotherapy each day. For single high-dose radiotherapy to abdomen, give 1–2 hr before therapy then, q 8 hr for 1–2 days after therapy complete. For daily fractionated radiotherapy to abdomen, give 1–2 hr before therapy, then q 8 hrs for each day therapy is given.

Parenteral or oral

·        Prevention of postoperative nausea and vomiting: 4 mg undiluted IV, preferably over 2–5 min, or as a single IM dose immediately prior to induction of anesthesia or 16 mg PO 1 hr before anesthesia.

PEDIATRIC PATIENTS

·        Prevention of chemotherapy-induced nausea and vomiting:

Parenteral

6 mo–18 yr: Three doses of 0.15 mg/kg IV over 15 min given 20 min before the start of the chemotherapy, then 4 and 8 hr later.

Oral

< 4 yr: Safety and efficacy not established.

4–11 yr: 4 mg PO 30 min prior to chemotherapy, 4 mg at 4 and 8 hr, then 4 mg PO tid for 1–2 days after completion of chemotherapy.

> 12 yr: Same as adult.

·        Prevention of postoperative nausea and vomiting:

1 mo–12 yr: 0.1 mg/kg IV if < 40 kg or a single dose of 4 mg IV if > 40 kg, preferably given 2–5 min prior to or following induction of anesthesia. Infuse over at least 30 sec.

PATIENTS WITH HEPATIC IMPAIRMENT

Maximum daily dose of 8 mg IV or PO.

Pharmacokinetics

Route	Onset	Peak
Oral	30–60 min	1.7–2.2 hr
IV	Immediate	Immediate

Metabolism: Hepatic; T_1/2: 3.5–6 hr

Distribution: Crosses placenta; may enter breast milk

Excretion: Urine

IV facts

Preparation: Dilute in 50 mL of 5% dextrose injection or 0.9% sodium chloride injection; stable for 48 hr at room temperature after dilution.

Infusion: Infuse slowly over 15 min diluted or 2–5 min undiluted.

Compatibilities: May be diluted with 0.9% sodium chloride injection, 5% dextrose injection, 5% dextrose and 0.9% sodium chloride injection; 5% dextrose and 0.45% sodium chloride injection; 3% sodium chloride injection.

Incompatibilities: Do not mix with alkaline solutions.

Adverse effects

·        CNS: Headache, dizziness, drowsiness, shivers, malaise, fatigue, weakness, myalgia

·        CV: Chest pain, hypotension

·        Dermatologic: Pruritus

·        GI: Abdominal pain, constipation

·        GU: Urinary retention

·        Local: Pain at injection site

Interactions

Drug-food

·        Increased extent of absorption if taken orally with food

Nursing considerations

Assessment

·        History: Allergy to ondansetron, pregnancy, lactation, nausea and vomiting

·        Physical: Skin color and texture; orientation, reflexes, bilateral grip strength, affect; P, BP; abdominal examination; urinary output

Interventions

·        Ensure that the timing of drug doses corresponds to that of the chemotherapy or radiation.

·        Administer oral drug for 1–2 days following completion of chemotherapy or radiation.

Teaching points

·        Take oral drug for 1–2 days following chemotherapy or radiation therapy to maximize prevention of nausea and vomiting. Take the drug every 8 hours around the clock for best results.

·        You may experience these side effects: Weakness, dizziness (change position slowly to avoid injury); dizziness, drowsiness (do not drive or perform tasks that require alertness).

·        Report continued nausea and vomiting, pain at injection site, chest pain, palpitations.

Adverse effects in Italic are most common; those in Bold are life-threatening.