Is Bactrim (trimethoprim/sulfamethoxazole) effective for treating boils?

From the Guidelines

Bactrim (trimethoprim/sulfamethoxazole) should not be used as the primary treatment for simple boils, as incision and drainage is the recommended initial treatment. According to the most recent guidelines 1, incision and drainage is the primary treatment for simple abscesses or boils, and antibiotics are not needed unless there are signs of systemic illness, severe disease, or lack of response to incision and drainage alone.

For patients with boils caused by methicillin-resistant Staphylococcus aureus (MRSA), Bactrim may be considered as an empirical treatment option, particularly in outpatients with purulent cellulitis or abscesses associated with MRSA 1. The typical adult dosage is one double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) taken twice daily for 7-10 days. However, it is essential to note that Bactrim works by inhibiting bacterial folate synthesis, which prevents bacteria from producing DNA and proteins necessary for survival, and common side effects include rash, nausea, and sun sensitivity.

Some key points to consider when treating boils include:

• Incision and drainage is the primary treatment for simple abscesses or boils
• Antibiotics may be necessary for patients with severe disease, systemic illness, or lack of response to incision and drainage alone
• Bactrim may be considered as an empirical treatment option for MRSA-related boils
• It is crucial to complete the full course of antibiotics even if symptoms improve quickly
• If the boil does not improve within 2-3 days of starting antibiotics, becomes larger, or if you develop fever or spreading redness, seek medical attention promptly.

From the Research

Effectiveness of Bactrim for Boils

• Bactrim, also known as trimethoprim/sulfamethoxazole (TMP-SMX), is an antibiotic that has been studied for its effectiveness in treating boils and other skin infections 2, 3, 4, 5.
• A study published in 2021 found that there is limited evidence to support the use of oral antibiotics, including TMP-SMX, for the treatment of bacterial folliculitis and boils 2.
• However, a 2017 study published in the New England Journal of Medicine found that TMP-SMX, in conjunction with incision and drainage, improved short-term outcomes in patients with simple abscesses, including those caused by Staphylococcus aureus 3.
• Another study published in 2016 found that TMP-SMX may help with abscess cure and decrease abscess formation at new sites 4.
• A 2017 study compared TMP-SMX with placebo for uncomplicated skin abscesses and found that the addition of TMP-SMX resulted in improved clinical resolution at 7 to 14 days after treatment 5.

Mechanism of Action and Resistance

• Trimethoprim, a component of Bactrim, exerts antimicrobial activity by blocking the reduction of dihydrofolate to tetrahydrofolate, the active form of folic acid, by susceptible organisms 6.
• Resistance to trimethoprim may be either intrinsic or acquired, with acquired resistance most commonly stemming from a chromosomal mutation that results in the production of a dihydrofolate reductase enzyme which is less vulnerable to trimethoprim inhibition 6.

Adverse Reactions and Therapeutic Indications

• The most common adverse reactions to trimethoprim include gastrointestinal intolerance and skin eruptions 6.
• Trimethoprim is currently approved for the treatment of uncomplicated urinary tract infections, and is being investigated for the treatment of other infections, including bacterial exacerbations of chronic bronchitis, bacterial pneumonia, and typhoid fever 6.