# 一位護理師準備對一位接受化療的個案靜脈注射 ondansetron 8 mg。哪一項基礎檢查結果最應該暫停給藥？

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391807&lang=zh-tw  
> language: zh-TW  
> subject: Medical Emergencies  
> category: PA

## 題目

一位護理師準備對一位接受化療的個案靜脈注射 ondansetron 8 mg。哪一項基礎檢查結果最應該暫停給藥？

## 選項

1. QTc 510 ms、血清鉀3.3且併用methadone — 顯著QT延長風險 **✔ 正確答案**
2. 體溫37.0°C
3. 血紅素11.5 g/dL
4. 血壓124/78

**正確答案: 1**

## 解析

正確答案（2）：Ondansetron 會延長 QT 間期。當基礎 QTc ≥500 ms、電解質異常（低血鉀／低血鎂），以及併用其他會延長 QT 的藥物（如 methadone）時，發生 torsades de pointes 的風險很高。應暫停 ondansetron，矯正血鉀／血鎂，通知醫療提供者；可考慮替代的止吐藥（例如 scopolamine、對 QT 影響較小的 granisetron，或 aprepitant）。 （1、3、4）為正常結果。

## 深入解析

記憶提示 5-HT3拮抗劑，尤其ondansetron，會讓QT變長。給serotonin拮抗止吐藥前先矯正K/Mg；便秘也常見。

## 臨床情境

情境 55歲女性正在接受化療；因噁心開立ondansetron 8 mg IV。心電圖：QTc 510 ms，K+ 3.3，也正在使用methadone。

## 重要概念

- **5-HT3受體拮抗劑** — Ondansetron、granisetron、palonosetron、dolasetron；serotonin受體止吐藥。
- **QT延長** — Torsades de pointes風險；QTc >500 ms或增加>60 ms需處理。
- **藥物誘發torsades** — QT延長藥造成的多型性心室頻脈；以IV magnesium治療。

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