Questions and Answers
What is the mechanism of action (MOA) of ondansetron?
Which medication is administered if ondansetron is ineffective?
What are the potential dangerous side effects of metoclopramide?
Which type of medication is promethazine classified as?
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What should a nurse ensure when administering promethazine via IV?
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What action does metoclopramide perform as a prokinetic medication?
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What is the primary side effect of ondansetron?
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What can occur if promethazine infiltrates surrounding tissues during administration?
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Which medications can be combined with ondansetron to enhance its antiemetic effects?
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What is extravasation in the context of IV medication administration?
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Study Notes
Antiemetics Overview
- Bismuth subsalicylate (Pepto-Bismol), benzodiazepines (e.g., Lorazepam), glucocorticoids (e.g., beclomethasone), antihistamines (e.g., scopolamine), and cannabis exhibit antiemetic properties.
Prototype Antiemetic Drugs
- Ondansetron is a key prototype antiemetic drug.
- Metoclopramide is another important prototype antiemetic drug.
Ondansetron
- Mechanism of Action (MOA): Blocks serotonin at the 5HT-3 receptors, preventing initiation of vomiting.
- Administration: Given as a 4mg IV push as needed.
- Alternative for inefficacy: Metoclopramide can be used if ondansetron is ineffective.
- Side Effects: Common side effects include headaches and QT prolongation; “anti-drugs” should be avoided to minimize risks.
- Combination for enhanced effects: Glucocorticoids such as methylprednisone and dexamethasone can be combined with ondansetron.
Metoclopramide
- Mechanism of Action: Acts as a dopamine receptor antagonist, specifically blocking D2 receptors in the CNS to prevent nausea and vomiting.
- Prokinetic Action: Stimulates gastrointestinal muscle movement, enhancing peristalsis.
- Side Effects: Sedation and diarrhea can occur due to increased peristalsis.
- Dangerous Side Effects: Long-term use may lead to extrapyramidal effects, including tardive dyskinesia.
Promethazine
- Classification: It is classified as both an antihistamine and an antiemetic.
- Receptor Binding: Binds to H1 receptors (antihistamine for allergies), dopaminergic receptors (antiemetic effects), and muscarinic receptors (anticholinergic effects for motion sickness).
- Post-Surgery Administration: Commonly administered after surgery due to its sedating and antiemetic effects.
- Side Effects: Can cause bradypnea, nystagmus, tinnitus, and tachycardia.
- Safety Note: Considered a "high alert" medication due to potential severe tissue damage.
- Adverse Effects from Extravasation: If infiltrated into surrounding tissues, it poses a risk for gangrene.
IV Administration Precautions
- When administering promethazine via IV, ensure it is done through a large vein and monitor the injection site closely.
- Burning and pain at the injection site may indicate extravasation.
Extravasation
- Definition: The accidental leakage of IV fluids or medications into surrounding tissue instead of remaining within the vein, leading to potential tissue damage.
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Description
Test your knowledge on antiemetic medications with this quiz. Explore various topics, including mechanisms of action, administration routes, and prototype drugs. Perfect for students in pharmacology or nursing programs.
