What is the oral (PO) dose of Keflex (Cephalexin) for an abscess?

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Last updated: June 16, 2025View editorial policy

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From the Guidelines

For an abscess, the typical oral dose of Keflex (cephalexin) for adults is 500 mg taken four times daily (every 6 hours) for 7-10 days, as recommended by the Infectious Diseases Society of America 1. Children may receive 20 mg per kg per dose twice daily (maximum = 500 mg per dose) for 10 days, as indicated in the guidelines for managing group A streptococcal pharyngitis 1. The exact dosage and duration should be tailored to the severity of the infection, the patient's age, weight, and kidney function. Keflex is a first-generation cephalosporin antibiotic that works by inhibiting bacterial cell wall synthesis, making it effective against many gram-positive bacteria commonly found in abscesses, including Staphylococcus aureus (except MRSA) 1. It's essential to complete the full course of antibiotics even if symptoms improve before finishing. Patients should take the medication with food if it causes stomach upset. Antibiotic treatment alone may not be sufficient for abscesses; surgical drainage is often necessary as an adjunct to antibiotic therapy, as stated in the clinical practice guidelines for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children 1. If the patient has a penicillin allergy, caution should be exercised as there is approximately 10% cross-reactivity between penicillins and cephalosporins. Some key points to consider when treating abscesses include:

  • Incision and drainage is the primary treatment for cutaneous abscesses 1
  • Antibiotic therapy is recommended for abscesses associated with severe or extensive disease, rapid progression, or signs and symptoms of systemic illness 1
  • The choice of antibiotic should be based on the suspected or confirmed causative pathogen and local epidemiology 1

From the FDA Drug Label

For the following infections, a dosage of 500 mg may be administered every 12 hours: streptococcal pharyngitis, skin and skin structure infections, and uncomplicated cystitis in patients over 15 years of age. The usual adult dose is 250 mg every 6 hours For more severe infections or those caused by less susceptible organisms, larger doses may be needed

The oral (PO) dose of Keflex (Cephalexin) for an abscess (considered a skin and skin structure infection) is 500 mg every 12 hours or 250 mg every 6 hours for adults. For more severe infections, larger doses may be needed 2.

From the Research

Keflex PO Dose for Abscess

  • The oral dose of Keflex (Cephalexin) for an abscess can be determined based on the provided studies.
  • According to the study 3, the daily dose of Keflex used in adults was 1,000 mg, given in four divided doses.
  • Another study 4 compared the efficacy and safety of cefdinir to that of cephalexin in adolescents and adults with mild to moderate uncomplicated skin and skin structure infections, including abscesses. In this study, cephalexin was administered at a dose of 250 mg four times daily.
  • A study 5 specifically looked at the treatment of uncomplicated skin abscesses with cephalexin and found that cephalexin was administered at a dose of 500 mg orally four times for 7 days after incision and drainage of the abscess.
  • It is essential to note that the dosage may vary depending on the specific condition, patient population, and other factors, as seen in the different studies 3, 4, 5.

Dosage Considerations

  • The studies suggest that Keflex can be effective in treating abscesses at various dosages, including 1,000 mg per day in adults 3 and 250 mg four times daily 4.
  • However, the most relevant study for abscess treatment 5 used a dose of 500 mg orally four times for 7 days.
  • It is crucial to consult the specific study or clinical guidelines for the most appropriate dosage and treatment regimen for a particular patient or condition, as supported by the evidence from 3, 4, 5.

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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