What is the oral dose of Bactrim (sulfamethoxazole/trimethoprim) for treating an abscess?

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Last updated: June 16, 2025View editorial policy

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From the Guidelines

For treating an abscess, the recommended oral dose of Bactrim (sulfamethoxazole/trimethoprim) is 1-2 double-strength tablets (800 mg sulfamethoxazole/160 mg trimethoprim) twice daily for adults, and for children, the dosage is trimethoprim 4-6 mg/kg/dose, sulfamethoxazole 20-30 mg/kg/dose PO every 12 hours 1.

Key Considerations

  • The primary treatment for most abscesses is incision and drainage, with antibiotics serving as adjunctive therapy in certain cases, such as those with systemic toxicity, rapid progression, or associated comorbidities 1.
  • Bactrim is effective against many bacteria commonly found in abscesses, particularly Staphylococcus aureus, including some MRSA strains.
  • Treatment duration depends on the severity of the infection and clinical response, typically ranging from 7-14 days.

Important Safety Information

  • Patients should take the full course of antibiotics even if symptoms improve.
  • Drink plenty of fluids to prevent crystalluria.
  • Be aware of potential side effects, including rash, gastrointestinal disturbances, and rare but serious adverse reactions like Stevens-Johnson syndrome.

Special Populations

  • For pregnant women, especially in the third trimester, and for children under 2 months of age, alternative antibiotics should be considered due to the pregnancy category C/D of TMP-SMX 1.
  • Dosage adjustments may be necessary for patients with renal impairment.

From the Research

Bactrim PO Dose for Abscess

  • The oral dose of Bactrim (sulfamethoxazole/trimethoprim) for treating an abscess is not explicitly stated in the provided studies as a standard dose, but one study mentions a specific dosage used in a trial 2.
  • In the study published in The New England Journal of Medicine, the dose used was 320 mg of trimethoprim and 1600 mg of sulfamethoxazole, twice daily, for 7 days 2.
  • This study found that trimethoprim-sulfamethoxazole was superior to placebo in treating uncomplicated skin abscesses, with a higher clinical cure rate and lower rates of subsequent surgical drainage procedures, skin infections at new sites, and infections in household members 2.
  • Another study published in the Annals of Emergency Medicine also evaluated the use of trimethoprim-sulfamethoxazole for uncomplicated skin abscesses but did not specify the dose used in the study 3.
  • The role of antibiotics, including Bactrim, in treating abscesses is discussed in various studies, highlighting the need for effective treatment options, especially in cases involving community-associated methicillin-resistant Staphylococcus aureus (MRSA) 4, 2, 3.
  • Bactrim has been used to treat various infections, including skin and soft-tissue infections, and is generally well-tolerated by most patients 5, 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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