皮膚科的切開排膿之後：吃點抗生素撲菌特（Baktar, Trimethoprim-Sulfamethoxazole）可能是更好的選擇。

皮膚上的感染性膿包光是切開排膿與擦藥是不夠的，應該還要加吃抗生素撲菌特（Trimethoprim-Sulfamethoxazole）來減少後續的感染性併發症。

皮膚科的切開排膿大致就是在皮膚上看到有包膿，中間摸起來已經有點軟（fluctuating）或是黃色膿頭出現的時候，可以拿支18號粗針頭或是尖刀片在那個地方戳個小洞，把裡面的膿擠出來。其中最常排的是表皮囊腫的膿（很多非感染性），其次的則是毛囊炎、甲溝炎的膿（大多是感染性）。這個動作往往很痛，但痛得很有價值。因為再大、再腫、就算是對methicillin有抗藥性之金黃色葡萄球菌（MASA）造成的膿瘍，經過適當的切開排膿，往往兩三天內就會明顯緩解。有些人甚至主張對於這類皮膚的膿瘍，切開排膿才是最好的『抗生素』。

然而，事情不總是這麼順利，偶而切開排膿還是會跑出一些併發症，例如今天晚上筆者帶老婆與小孩去逛街，居然被急診call了！原來是先前有位毛囊炎的病人在門診（不是筆者的）做完切開排膿之後居然發燒，又跑回急診。

雖然最後發現是找錯人，但筆者在接到電話後的這段時間裡讀了一下相關的期刊論文，發現皮膚科很常做的切開排膿治療，看似數十年如一日的例行公事，實則近幾年來還是有些新的進展。

近期內的一個新發現剛好和這次事件有關：切開排膿後應該使用適當的口服抗生素，會比完全不用還好（參1）。這一篇居然還是醫界龍頭--新英格蘭醫學期刊（NEJM）的文章，顯然這個結論有相當的重要性與正確性。會做這個研究是因為過去的研究覺得切開排膿後給抗生素似乎沒什麼用(參2)，但這研究的參與人數較少，而且這個結論跟臨床經驗明顯不太一致。

這次的雙盲研究共找了1247個皮膚膿瘍的病人來分析，當中45.3%的人是對methicillin有抗藥性之金黃色葡萄球菌感染。其中630位使用了四顆撲菌特（Trimethoprim-Sulfamethoxazole，80mg/400mg）每次四顆一天兩次，持續七天，另外617位則用安慰劑。結果發現有用藥的治癒率為80.5%，沒用藥則為73.6%，兩者相差6.9%，顯然用藥的結果較佳，有明顯的統計上差異(P=0.005)。而且用藥還可以降低之後要進一步手術排膿、跑出其他新病灶、與感染家中其他成員的風險。

當然很多醫師會覺得使用撲菌特這個藥有其他風險，例如會引發再生不良性貧血（aplastic anemia）、蠶豆症惡化、引起嚴重過敏反應（例如史蒂芬斯-強森Stevens-Johnson症候群）。但再生不良性貧血很少見，蠶豆症與史蒂芬斯-強森症候群的都可以藉由病史詢問來避免。就算病人先前沒用過撲菌特，第一次使用要變成史蒂芬斯-強森症候群的機會其實沒有想像中的高（參3）。雖然撲菌特是引起的著名藥物之一，但在台灣史蒂芬斯-強森症候群的盛行率大約每年每百萬人僅8人，而且很多其實是carbanazepine與allopurinol所引起。NEJM的研究也顯示使用撲菌特的人只有輕度腸胃不適的機會略增。

依照上述結論，為了避免切開排膿後的感染性問題，應該要給大部分病人開立撲菌特（Trimethoprim-Sulfamethoxazole)才是，只是筆者要強調內文提到的給藥劑量很高（每次四顆一天兩次，是一般常規劑量（每次兩顆一天兩次）的兩倍。反覆讀了內文三四遍確認，連讀者來信裡都是寫這個劑量。根據個人經驗，常規劑量的撲菌特就可以輕鬆化解大部分的皮膚科感染病。因此在台灣是否要用到這麼高的劑量，或許需要再做進一步的研究。因此筆者建議給每次兩顆，一天兩次，持續一週即可。如果病人有住院或慢性疾病病史，屬於感染MASA高危險群，則可給每次四顆，一天兩次，持續一週。這時就要多喝水，避免藥物結晶在腎小管沉澱。不過臨床上遇到的膿包可能有不同感染原的考量，實際給藥還是要以專業醫師的臨床裁量為準。

參考資料

1. Trimethoprim-Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess. Talan DA, Mower WR, Krishnadasan A, Abrahamian FM, Lovecchio F, Karras DJ, Steele MT, Rothman RE, Hoagland R, Moran GJ. N Engl J Med. 2016 Mar 3;374(9):823-32. doi: 10.1056/NEJMoa1507476.

2. Management of skin abscesses in the era of methicillin-resistant Staphylococcus aureus. Singer AJ, Talan DA. N Engl J Med 2014;370:1039-1047

3. A case of toxic epidermal necrolysis caused by trimethoprim-sulfamethoxazole. Rijal JP, Pompa T, Giri S, Bhatt VR.BMJ Case Rep. 2014 Jul 9;2014. pii: bcr2013203163. doi: 10.1136/bcr-2013-203163.

4. 台大皮膚部網頁 http://derm.ntuh.gov.tw/Article.asp?BlockName=ArtView&AT_ID=115

摘要原文

N Engl J Med. 2016 Mar 3;374(9):823-32. doi: 10.1056/NEJMoa1507476.

Trimethoprim-Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess.

Talan DA1, Mower WR1, Krishnadasan A1, Abrahamian FM1, Lovecchio F1, Karras DJ1, Steele MT1, Rothman RE1, Hoagland R1, Moran GJ1.

Abstract

BACKGROUND:

U.S. emergency department visits for cutaneous abscess have increased with the emergence of methicillin-resistant Staphylococcus aureus (MRSA). The role of antibiotics for patients with a drained abscess is unclear.

METHODS:

We conducted a randomized trial at five U.S. emergency departments to determine whether trimethoprim-sulfamethoxazole (at doses of 320 mg and 1600 mg, respectively, twice daily, for 7 days) would be superior to placebo in outpatients older than 12 years of age who had an uncomplicated abscess that was being treated with drainage. The primary outcome was clinical cure of the abscess, assessed 7 to 14 days after the end of the treatment period.

RESULTS:

The median age of the participants was 35 years (range, 14 to 73); 45.3% of the participants had wound cultures that were positive for MRSA. In the modified intention-to-treat population, clinical cure of the abscess occurred in 507 of 630 participants (80.5%) in the trimethoprim-sulfamethoxazole group versus 454 of 617 participants (73.6%) in the placebo group (difference, 6.9 percentage points; 95% confidence interval [CI], 2.1 to 11.7; P=0.005). In the per-protocol population, clinical cure occurred in 487 of 524 participants (92.9%) in the trimethoprim-sulfamethoxazole group versus 457 of 533 participants (85.7%) in the placebo group (difference, 7.2 percentage points; 95% CI, 3.2 to 11.2; P<0.001). Trimethoprim-sulfamethoxazole was superior to placebo with respect to most secondary outcomes in the per-protocol population, resulting in lower rates of subsequent surgical drainage procedures (3.4% vs. 8.6%; difference, -5.2 percentage points; 95% CI, -8.2 to -2.2), skin infections at new sites (3.1% vs. 10.3%; difference, -7.2 percentage points; 95% CI, -10.4 to -4.1), and infections in household members (1.7% vs. 4.1%; difference, -2.4 percentage points; 95% CI, -4.6 to -0.2) 7 to 14 days after the treatment period. Trimethoprim-sulfamethoxazole was associated with slightly more gastrointestinal side effects (mostly mild) than placebo. At 7 to 14 days after the treatment period, invasive infections had developed in 2 of 524 participants (0.4%) in the trimethoprim-sulfamethoxazole group and in 2 of 533 participants (0.4%) in the placebo group; at 42 to 56 days after the treatment period, an invasive infection had developed in 1 participant (0.2%) in the trimethoprim-sulfamethoxazole group.

CONCLUSIONS:

In settings in which MRSA was prevalent, trimethoprim-sulfamethoxazole treatment resulted in a higher cure rate among patients with a drained cutaneous abscess than placebo. (Funded by the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number,NCT00729937.).