Name of the 5HT3 Antagonists Antiemetic Drugs
- Ondansetron
- Granisetron
1.Ondansetron
| Ondansetron |
| Availability Injection: 2 mg/ml in 2- and 20-ml vials Injection (premixed): 32 mg/50 ml single-dose containers Injection USP (preservative-free): 2 mg/ ml in 2-ml single-dose vials Oral solution: 4 mg/5 ml Tablets: 4 mg, 8 mg, 24 mg Tablets (orally disintegrating): 4 mg, 8 mg |
| Indications and dosages To prevent nausea and vomiting caused by moderately emetogenic chemotherapy Adults and children older than age 12: 8 mg (tablet) or 10 ml (oral solution) P.O. b.i.d.; give first dose 30 minutes before chemotherapy and repeat dose 8 hours later. Give 8 mg (tablet) or 10 ml (oral solution) P.O. q 12 hours for 1 to 2 days after chemotherapy ends. Children ages 4 to 11: 4 mg (tablet) or 5 ml (oral solution) P.O. q 8 hours; give first dose 30 minutes before chemotherapy and repeat dose 4 and 8 hours later. Give 4 mg (tablet) or 5 ml (oral solution) P.O. q 8 hours for 1 to 2 days after chemotherapy ends. To prevent nausea and vomiting caused by highly emetogenic chemotherapy Adults and children older than age 12: 32 mg I.V. as a single dose infused over 15 minutes, starting 30 minutes before chemotherapy; or three 0.15-mg/kg doses I.V., with first dose infused over 15 minutes, starting 30 minutes before chemotherapy and repeated 4 hours and 8 hours later. To prevent nausea and vomiting caused by radiation Adults and children older than age 12: 8 mg (tablet) or 10 ml (oral solution) P.O. 1 to 2 hours before radiation and repeated q 8 hours, depending on radiation type, location, and extent Prevention and treatment of postoperative nausea and vomiting Adults and children older than age 12: 16 mg (tablet) or 20 ml (oral solution) P.O. 1 hour before anesthesia induction, or 4 mg I.V. or I.M. before anesthesia or postoperatively Children ages 2 to 12 weighing more than 40 kg (88 lb): 4 mg I.V. before anesthesia or postoperatively Children ages 2 to 12 weighing less than 40 kg (88 lb): 0.1 mg/kg I.V. before anesthesia or postoperatively |
Mechanism of Action:
Blocks serotonin receptors centrally in the chemoreceptor trigger zone and peripherally at vagal nerve terminals in the intestine. This action reduces nausea and vomiting by preventing serotonin release in the small intestine (probable cause of chemotherapyand radiation-induced nausea and vomiting) and by blocking signals to the CNS. Ondansetron may also bind to other serotonin receptors and to mu-opioid receptors.
Pharmacokinetics
- Bioavailability: 56-71% (PO); food increases extent of absorption (17%)
- Metabolism: Extensive hepatic metabolism,
- Metabolites: Glucuronide conjugate, sulfate conjugate (inactive)
- Half-life: 2-7 hr (children <15 years); 3-7 hr (adults); patients with mild to moderate hepatic impairment, 12 hr; patients with severe hepatic impairment (Child-Pugh class C), 20 hr
- Excretion: Primarily urine (30-70%); feces (25%)
Administration
- Give first dose before emetogenic event.
- Remove orally disintegrating tablet by peeling back foil with dry hands; don’t push tablet through foil backing. After removing, place tablet on patient’s tongue, where it will dissolve within seconds. Tell patient to swallow saliva.
- Give undiluted when administering I.M. before anesthesia induction.
- Give undiluted by direct I.V. immediately before anesthesia induction, or postoperatively if nausea and vomiting occur. Administer slowly, over at least 30 seconds (preferably over 2 to 5 minutes).
- For intermittent I.V. infusion, dilute in 50 ml of dextrose 5% in water (D5W) and normal saline solution or D5W and half-normal saline solution. Infuse over 15 minutes.
- When giving I.V., don’t use flexible plastic container in series connection.
Contraindications
Hypersensitivity to drug
Concurrent use of apomorphine
Precautions :
- Hepatic disease
- Congenital long QT syndrome (avoid use)
- Hypersensitivity to other selective 5-HT3 receptor antagonists
- Phenylketonuria (with orally disintegrating tablets)
- Pregnant or breastfeeding patients
- Children younger than age 12.
Adverse reactions
- CNS: headache, dizziness, malaise, drowsiness, fatigue, weakness, extrapyramidal reactions
- CV: chest pain, hypotension, ECG changes including QT-interval prolongation (rare and mostly with I.V. use), torsades de pointes (postmarketing reports)
- GI: constipation, diarrhea, abdominal pain, dry mouth
- GU: urinary retention Respiratory: bronchospasm
- Skin: rash
- Other: pain at injection site, shivering, anaphylaxis
Patient monitoring
- Monitor GI status.
- Assess for extrapyramidal reactions.
- Check vital signs. Watch for hypotension and bronchospasm.
- Monitor fluid intake and output. Stay alert for urinary retention.
- Be aware that cases of torsades de pointes have been reported. Monitor ECG in patients with electrolyte abnormalities (such as hypokalemia orhypomagnesemia), congestive heart failure, or bradyarrhythmias, and in patients taking other drugs that lead to prolonged QT interval.
- Be aware that using ondansetron after abdominal surgery or with chemotherapy-induced nausea and vomiting may mask a progressive ileus or gastric distention.
Patient teaching
- Tell patient to remove orally disintegrating tablet by peeling back foil with dry hands—not by pushing tablet through foil backing. Instruct him to place tablet on tongue, where it will dissolve within seconds, and then to swallow saliva.
- Instruct patient to immediately report extrapyramidal symptoms, irregular heartbeats, abdominal distention after abdominal surgery, or allergic reaction.
- Inform patient with phenylketonuria (or caregiver) that powder contains phenylalanine.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above
Nursing Considerations
- Place disintegrating tablet on patient’s tongue immediately after opening package. It dissolves in seconds.
- Use calibrated container or oral syringe to measure dose of oral solution.
- Give up to 4 mg I.V. diluted in 50 ml of D5W or normal saline solution
2.Granisetron
| Granisetron |
| Availability Injection: 1 mg/ml Oral solution: 2 mg/10 ml in 30-ml bottles Tablets: 1 mg Transdermal system (patch): 52-cm2 patch (containing 34.3 mg granisetron delivering 3.1 mg/24 hours) |
| Indications and dosages To prevent nausea and vomiting caused by chemotherapy Adults and children ages 2 to 16: For I.V. use, 10 mcg/kg I.V. within 30 minutes before chemotherapy. For P.O. use (adults only), 1 mg P.O. b.i.d., with first dose given at least 1 hour before chemotherapy and second dose given 12 hours later on days when chemotherapy is administered; or 2 mg P.O. daily at least 1 hour before chemotherapy. For transdermal use (adults only), apply patch for up to 7 days. To prevent nausea and vomiting caused by radiation therapy Adults: 2 mg P.O. daily within 1 hour of radiation therapy Acute postoperative nausea and vomiting Adults: 1 mg I.V. undiluted, administered over 30 seconds |
Mechanism of Action:
Has a high affinity for serotonin receptors along vagal nerve endings in intestines. Because of this affinity, granisetron prevents nausea and vomiting that usually result when serotonin is released by damaged enterochromaffin cells.
Pharmacokinetics
- Half-life: 3-14 h
- Bioavailability: 60% (PO)
- Protein bound: 65%
- Metabolism: Extensively metabolized in liver via N-demethylation, oxidation, conjugation, and CYP3A subfamily
- Metabolites: Inactive
- Excretion: Feces: 38%, Urine: 60%
Administration
- For I.V. infusion, dilute with 20 to 50 ml of normal saline solution or dextrose 5% in water.
- Infuse I.V. over 5 minutes, starting 30 minutes before chemotherapy.
- For direct I.V. injection, give undiluted over 30 seconds.
- Don’t mix I.V. form with other drugs.
- For P.O. use, give first dose 1 hour before chemotherapy and second dose 12 hours after first.
- Apply a single transdermal patch to upper outer arm for 24 to 48 hours before chemotherapy.
- Remove patch a minimum of 24 hours after chemotherapy completion. Patch may be worn up to 7 days depending on duration of chemotherapy
Contraindications
Hypersensitivity to drug
Precautions :
- Pregnant or breastfeeding patients
- Children younger than age 18 (safety of P.O. and transdermal use not established)
- Children younger than age 2 (safety of I.V. use not established).
Adverse reactions
- CNS: headache, anxiety, stimulation, weakness, drowsiness, dizziness
- CV: hypertension
- GI: nausea, vomiting, diarrhea, constipation, abdominal pain
- Hematologic: anemia, leukopenia, thrombocytopenia
- Skin: alopecia, application site reactions (patch)
- Other: altered taste, decreased appetite, fever, chills, shivering
Patient monitoring
- Monitor hepatic enzyme levels and CBC with white cell differential.
- Monitor temperature and blood pressure. Have patient use caution when ambulating, to avoid orthostatic hypotension.
- Know that patch may be degraded by direct exposure to natural or artificial sunlight
Patient teaching
- Instruct patient to apply a single transdermal patch to upper outer arm 24 to 48 hours before chemotherapy.
- Instruct patient to remove patch by gently peeling it off in a minimum of 24 hours after chemotherapy completion.
- Instruct patient to remove patch if a severe or generalized skin reaction (such as rash or itching) occurs.
- Advise patient to avoid direct exposure of application site to natural or artificial sunlight by covering site with clothing while wearing patch and for 10 days after patch removal.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- Advise patient to minimize GI upset by eating frequent, small servings of healthy food.
- Tell patient he’ll undergo regular blood testing during therapy.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the tests and herbs mentioned above.
Nursing Considerations
- Use cautiously in patients with arrhythmias or cardiac conduction disorders because granisetron may prolong QT interval. Patients especially at risk include those with cardiac disease or electrolyte abnormalities and those receiving cardiotoxic chemotherapy or therapy with another drug that prolongs QT interval.
- For use with chemotherapy, dilute I.V. preparation of granisetron with normal saline solution or D5W to total volume of 20 to 50 ml. Mixture may be stored up to 24 hours. Use only on days when chemotherapy is given.
- Apply transdermal patch to patient’s upper outer arm 24 to 48 hours before chemotherapy, and don’t remove it until at least 24 hours after chemotherapy is completed
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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