8.Clostridioides difficile 初次感染，依其嚴重程度，下列處方何者最適當？
(A)nonsevere，metronidazole 250 mg PO Q8H
(B)severe，vancomycin 125 mg PO Q6H
(C)severe，fidaxomicin 200 mg PO Q8H
(D)fulminant with ileus，metronidazole 500 mg IV Q8H＋vancomycin 250 mg rectal enema Q6H

• 直接回答你：

  CDI (艱難梭菌感染) 總共分成三級：

  1. 輕症 (Non-severe)

  2. 重症 (Severe)

  3. 猛爆性 (Fulminant) $\leftarrow$ 只有這一級會有「腸阻塞 (Ileus)」！

  ❌ (A) nonsevere：metronidazole 250 mg PO Q8H

  • 錯誤點 1 (藥物地位)： 現在就算是輕症 (Non-severe)，首選也是 Fidaxomicin 或 Vancomycin。Metronidazole 只是替代方案。

  • 錯誤點 2 (劑量)： 就算真的要用 Metronidazole，劑量標準是 500 mg PO TID (Q8H)。250 mg 劑量太低，治療失敗率高。

• ✅ (B) severe：vancomycin 125 mg PO Q6H

  • 正確！

  • 指引建議： 不論是輕症 (Non-severe) 還是重症 (Severe) 的初次感染，口服 Vancomycin 的標準劑量都是 125 mg QID (一天四次, Q6H) 吃 10 天。

  • 這是一個非常標準且安全的答案。

• ❌ (C) severe：fidaxomicin 200 mg PO Q8H

  • 錯誤點 (頻次)： Fidaxomicin 是長效且很貴的藥。

  • 正確用法： 200 mg PO BID (一天兩次, Q12H) 吃 10 天。不是 Q8H。

• ❌ (D) fulminant with ileus：metronidazole 500 mg IV Q8H + vancomycin 250 mg rectal enema Q6H

  • 錯誤點 (缺角)： 猛爆性 (Fulminant) 感染的治療核心是 「口服高劑量 Vancomycin」。

  • 正確指引建議：

    1. Vancomycin 500 mg PO/NG Q6H (一定要給高劑量口服，若腸阻塞則透過鼻胃管給)。<-- 選項漏了這個最重要的！

    2. Metronidazole 500 mg IV Q8H (這部分選項有寫對)。

    3. 若有腸阻塞 (Ileus)，加用 Vancomycin Rectal enema (灌腸)，通常劑量是 500 mg in 100 ml NS Q6H (選項寫 250 mg 偏低，且最致命的是漏掉了口服 Vancomycin)。

Primary Regimens

• Treatment considerations
  • If possible, stop the inciting antibiotic
  • Up to 20-25% patients relapse though less frequent with fidaxomicin
  • In general, avoid antiperistaltic medicine during acute phase
  • Generally 10 days recommended, but course can be extended to 14 days if improving but not resolved.
• Mild Disease or Moderate disease, initial episode: 
  • Fidaxomicin 200 mg po bid x 10 days
  • Vancomycin 125 mg po qid x 10 days
• Fulminant (Severe) disease, initial episode:
  • Vancomycin 500 mg q6h po or via nasogastric tube ± Metronidazole 500 mg IV q8h, particularly if ileus is present
    • For patients with ileus, administer Vancomycin 500 mg in 100 mL normal saline per rectum as a retention enema q6h.
    • In retrospective study of ICU patients, Vancomycin + Metronidazole combination associated with decrease in mortality from 36 to 16%.
• Severe disease with toxic megacolon: treatment as above PLUS
  • Sometimes only option is colectomy
    • Alternative: loop ileostomy coupled with antegrade colonic irrigation with Vancomycin + intravenous Metronidazole (Ann Surg 254:423, 2011)
  • No data on the efficacy of Fidaxomicin in patients with severe life-threatening disease.
  • Fecal microbiota transplant (FMT) is promising; supportive evidence in one retrospective cohort study (Open Forum Infect Dis 6:ofz398, 2019)
• Recurrent CDI:
  • First Recurrence (use a regimen different from original, if possible) 
    • Fidaxomicin 200 mg po bid x 10 days
    • Fidaxomicin (extended regimen) 200 mg po bid x 5 days, 200 mg po qod x 20 days
    • Vancomycin 125 mg po qid x 10 days
    • Vancomycin taper as follows:
      • 125 mg po qid x 10 days, followed by
      • 125 mg tid x 1 week, then
      • 125 mg bid x 1 week, then
      • 125 mg q24h x 1 week, then
      • 125 mg q48h x 1 week, then
      • 125 mg q3w x 1 week
  • Recurrence following treatment with Metronidazole as primary regimen  
    
    • Vancomycin 125 mg po qid x 10 days
    • Fidaxomicin 200 mg po bid x 10 days
  • Multiple recurrences:
    • Fecal microbiota transplantation (FMT) emerging as a treatment of choice for recurrent infections.
    • For details of donor screening  used for commercial product from Open Biome see N Engl J Med 2019; 381:2070.
    • Vancomycin 125 mg po qid x 10 days followed by Rifaximin 400 po tid x 20 days
    • FMT is becoming more logistically difficult due to emergence MDR fecal contents, increased regulations (see comments)
    • Commercial fecal microbiota products approved by FDA for recurrent episodes reviewed in Clin Infect Dis 77:S487 2023.
      •  Rebyota (rectally-administered, live fecal microbiota suspension): Per rectum as single dose enema. No need for prior bowel prep. Treatment success at 8 weeks: 75%. See Med Lett Drugs Ther 65:35, 2023
      • Vowst  (oral fecal microbiota spore capsules): Give 10 oz magnsesium citrate. After 24 hr, 4 capsules po daily for 3 consecutive days. Treatment success at  8 weeks: 83%. See Med Lett Drugs Ther. 65:81, 2023
• Prophylaxis to prevent recurrent CDI in patients requiring on-going systemic antimicrobial therapy for another indication:
  • Retrospective study of treatment doses of oral Vancomycin while patient was receiving systemic antibiotics found reduced incidence of recurrent CDI to 4.2% versus 26.6% in patients not treated with concurrent vancomycin (Clin Infect Dis 63:651, 2016).
  • Prevention of C. difficile in allogeneic hematopoietic stem cell recipients with oral vancomycin prophylaxis. Compared frequency of C. diff. over 2 sequential periods. CDI occurred in 31 of 131 (23.6% in the control group and 1 of 71 of those given vancomycin prophylaxis