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CHAPTER 18 Gastrointestinal System 1

Seretonin Antagonist

Use Prevention, treatment of Half-life: Onset: Peaks: Duration:

nausea and vomiting due 4 h 30 min 12 h 1224 hto cancer chemotherapy,

including high-dose

cisplatin. Prevention of

postop nausea, vomiting.

Prevention of radiation-

induced nausea, vomiting.

Example Ondanestron Route: Pregnancy Pharmacokinetic:

(Zofran) PO/IM/IV category: B Readily absorbed from

GI tract; PB: 7076%;

metabolized in liver;

excreted in urine.Unknown if removed

by hemodialysis.

How it works Action may be central (CTZ) or peripheral (vagus nerveterminal), preventing nausea/vomiting associated with

cancer chemotherapy.

Adult dose Note: All oral doses given 30 minutes before chemotherapy

and repeated at 8 h intervals.

Nausea, vomiting: chemotherapy.

PO: 24 mg once a day or 8 mg 3 times/day; IV: 3 doses

0.15 mg/kg. First dose given 30 min before chemotherapy;then 4 h and 8 h after first dose of ondanestron.

Nausea, vomiting: postop.

IM/IV: 4 mg undiluted over 25 min.

Nausea, vomiting: radiation.

PO: 8 mg 3 times/day.

Before administration Assess for dehydration if excessive vomiting occurs.

Provide emotional support.

Assess medical and drug history (reduced dose for hepaticimpairment).

Assess bowel and nutritional status.

Assess electrolytes.

Assess baseline vital signs.

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Pharmacology Demystified2

Seretonin Antagonist (continued)

Administration PO: Give without regard to food.

IM: Inject into large muscle mass.

IV: Give IV push over 25 min; infusion over 15 min.

After administration Monitor patient in environment for safety.

Assess bowel sounds for peristalsis.

Assess mental status.

Monitor daily bowel activity and stool consistency and recordtime of evacuation.

Monitor for dehydration.

Monitor patient comfort.

Contraindications None significant.

Side effects/ Frequent: Anxiety, dizziness, drowsiness, headache, fatigue,adverse reaction constipation, diarrhea, hypoxia, urinary retention.

Occasional: Abdominal pain, xerostomia (diminished salivasecretion), fever, feeling of cold, redness/pain at injection site,

paresthesia, weakness.

Rare: Hypersensitivity reaction (rash, itching), blurred vision.

Adverse/toxic:

Overdose may produce combination of CNS stimulation anddepressant effects.

Patient education Relief from nausea/vomiting generally occurs shortly afterdrug administration.

Avoid alcohol, barbiturates.

Report persistent vomiting.