# 一位62歲的個案因慢性神經性疼痛，開始使用methadone 5 mg口服每日三次。該個案同時服用ondansetron及ciprofloxacin。優先的護理評估及介入計畫為何？

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=375164&lang=zh-tw  
> language: zh-TW  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PA

## 題目

一位62歲的個案因慢性神經性疼痛，開始使用methadone 5 mg口服每日三次。該個案同時服用ondansetron及ciprofloxacin。優先的護理評估及介入計畫為何？

## 選項

1. methadone為短效藥，每12小時加量直到疼痛緩解。
2. 立即停用ondansetron與ciprofloxacin，因會抵銷methadone止痛效果。
3. 取得基線12導程ECG評估QTc，檢視藥物清單(ondansetron、ciprofloxacin、amiodarone、抗精神病藥等QT延長藥)；因半衰期長且差異大，調整間隔需5~7天；自第3天起密切監測鎮靜與呼吸；衛教低劑量開始且緩慢加量。 **✔ 正確答案**
4. methadone不會影響QT，不需ECG監測。

**正確答案: 3**

## 解析

Methadone為長效μ受體致效劑，具N-甲基-D-天門冬胺酸（NMDA）拮抗作用，用於慢性疼痛及鴉片類藥物使用疾患的治療。三個藥理學陷阱在NCLEX教學中佔主導地位：(1) 變異性大、長的排除半衰期（15至60小時，遠長於止痛作用的半衰期4至8小時）─開始使用或劑量調整後第3至7天，藥物蓄積是主要風險，此時呼吸抑制達到高峰；應每5至7天調整劑量，而非每日；絕不可指示個案若頭幾天疼痛未受控制就服用更多藥物；(2) QTc間期延長及torsades de pointes（多型性心室心搏過速）風險─應取得基礎心電圖，30天後及每年重複，或當劑量增加超過每日30至40毫克、出現新症狀，或併用會延長QT的藥物時重複（ondansetron、氟喹諾酮類如ciprofloxacin、amiodarone、抗精神病藥物、某些抗生素、methadone本身、低血鉀及低血鎂等電解質異常）；可能時應避免合併使用；(3) 透過CYP3A4及CYP2D6的藥物交互作用─phenytoin、rifampin、ritonavir、fluvoxamine及許多其他藥物會改變methadone血中濃度。Naloxone逆轉可能需以輸注方式給予，因為methadone的作用時間比naloxone長。每12小時增加劑量、否認QT效應、以及在沒有替代方案下立即停用交互作用藥物，都是不安全的。

## 深入解析

緩慢調整加上QT警戒加上3~7天呼吸監測高峰是methadone安全三角。注意QT延長藥併用。

## 重要概念

- **methadone** — μ受體促效加NMDA拮抗，t½ 15-60h，延長QT，CYP3A4/2D6，治療SUD
- **QT prolongation** — 基線ECG加30天/年、加量時、QT延長藥群、torsades風險
- **titration interval** — 5-7天、不可每日加量、開始3-7天呼吸抑制最劇、累積風險

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