昂丹司瓊
昂丹司瓊是一種強效的、具有中樞與周邊作用的**止吐藥**，屬於 5-HT3 受體拮抗劑。 主要臨床重點： * **頑固性嘔吐**：當常規療法（如馬羅匹坦或甲氧氯普胺）無效時，常作為救援或二線止吐藥。 * **化療與嚴重疾病**：被視為預防和治療化療引起之噁心與嘔吐（CINV）的黃金標準，特別是針對順鉑等高致吐性藥物。廣泛應用於**犬小病毒腸炎**、**胰臟炎**及**尿毒症**的嚴重病例。 * **物種考量**：犬隻通常耐受性良好。過去在貓的使用上存在爭議，但目前在貓科臨床上頻繁用於治療頑固性嘔吐及嚴重胰臟炎，且臨床效果良好。 > **臨床提示**：昂丹司瓊不具備促腸胃動力作用。若存在胃排空延遲或腸阻塞，它無法解決動力問題，且可能掩蓋潛在的胃擴張症狀。
作用機制: Ondansetron is a highly selective and competitive **5-HT3 (serotonin type 3) receptor antagonist**. * **Peripheral Action**: Cytotoxic drugs, severe inflammation (e.g., pancreatitis), or viral infections (e.g., parvovirus) cause cellular damage in the GI tract, triggering the release of serotonin from enterochromaffin cells. This serotonin binds to 5-HT3 receptors on vagal afferent nerve terminals, sending emetogenic signals to the brain. Ondansetron blocks these peripheral receptors. * **Central Action**: It also directly antagonizes 5-HT3 receptors located in the **Chemoreceptor Trigger Zone (CTZ)** within the area postrema of the brainstem, preventing central emetic signaling to the vomiting center. * **Net Effect**: Profound inhibition of the vomiting reflex without altering GI motility or causing significant sedation.
各物種劑量
- Empiric dose · 0.5 mg/kg IV or PO twice daily. · IV/PO · q12h
- Anti-emetic for intractable vomiting · 0.1-0.15 mg/kg slow IV push q6-12h as needed · IV · q6-12h · as needed
- Antiemetic for adjunctive treatment of severe pancreatitis · 0.1-1 mg/kg PO or IV q12-24h · PO/IV · q12-24h
- All uses (nausea and vomiting) · 0.5 mg/kg loading dose followed by 0.5 mg/kg/h infusion · IV · infusion for 6 hours · 6 hours · Used when signs are not controlled by other drugs.
- All uses (nausea and vomiting) · 0.5-1 mg/kg · PO · q12-24h · As needed · Oral bioavailability is considered to be low. Subcutaneous administration is more bioavailable.
- Severe vomiting (including parvovirus or pancreatitis) · 0.1-0.3 mg/kg IV given as a slow push every 8 to 12 hours (based on patient response). · IV · q8-12h · Has produced dramatic results in controlling or decreasing frequency of vomiting.
- Chemotherapy-related vomiting · 0.5-1 mg/kg PO q8-12h; 0.1-0.5 mg/kg IV over 15 minutes q8h or 30 minutes before cisplatin infusion. · PO/IV · q8-12h
- Adjunctive therapy of acute diarrhea · 0.5-1 mg/kg PO twice daily. · PO · q12h · Antagonizes neuronal 5-HT3 receptors and inhibits Cl- and H2O secretion from intestinal epithelial cells.
- Antiemetic · 0.1-0.2 mg/kg IV q6-12h or 0.1-1 mg/kg PO q1224h · IV/PO · q6-12h (IV) or q12-24h (PO)
給藥途徑
禁忌症
- Hypersensitivity to ondansetron or other 5-HT3 antagonists
- Concurrent use with apomorphine (due to risk of severe hypotension)
- Intestinal obstruction
不良反應
- Constipation
- Sedation
- Extrapyramidal clinical signs (head shaking)
- Arrhythmias
- Hypotension
- Headaches (reported in humans)
- Alterations in liver enzymes
- Hypersensitivity reactions (rare)
藥物相互作用
- Apomorphine · Severe hypotension reported in humans; concurrent use is contraindicated.
- Drugs affecting QTc interval (e.g., amiodarone, cisapride, halothane, isoflurane, sotalol) · Theoretically may have additive effects on QTc interval, potentially resulting in serious arrhythmias.
- Tramadol · May reduce the efficacy of both drugs (human data); veterinary significance is unknown. · moderate
監測
- Clinical efficacy (reduction or cessation of vomiting)
- Hydration status and electrolyte balance (due to underlying vomiting)
- Resolution of nausea and vomiting
- Liver enzymes (with prolonged use)
- Bowel movements (monitor for constipation)
過量
Overdoses of up to 10X did not cause significant morbidity in human subjects. If an overdose occurs, treat supportively.
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