What is the dose of Keflex (Cephalexin) for a normal BMI woman of mid-age with a boil?

Cephalexin Dosage for Boil Treatment in Middle-Aged Woman with Normal BMI

For a middle-aged woman with normal BMI presenting with a boil, the recommended dose of cephalexin (Keflex) is 500 mg orally four times daily for 5-7 days. 1, 2

Dosing Regimen

• Standard adult dose: 500 mg every 6 hours (four times daily) for skin and skin structure infections 1
• Alternative dosing: 500 mg every 12 hours (twice daily) may be considered for uncomplicated skin infections 1
• Duration: 5-7 days for uncomplicated skin infections 2

Rationale for Dosing

Cephalexin is an appropriate first-line antibiotic for skin and soft tissue infections like boils because:

1. It provides excellent coverage against Staphylococcus aureus and Streptococcus species, which are the most common causative organisms in boils 2
2. It is well-absorbed orally and achieves high tissue concentrations 3
3. It has a favorable safety profile with low incidence of side effects 3

Clinical Considerations

• If MRSA is suspected (history of previous MRSA infections, failed prior treatment, or high local prevalence), alternative antibiotics should be considered 2
• For severe infections or those with significant surrounding cellulitis, the higher end of the dosing range (up to 4g daily) may be appropriate 1
• Incision and drainage remains the primary treatment for boils; antibiotics are an adjunct therapy 2

Monitoring and Follow-up

• Patient should be reevaluated in 24-48 hours for signs of improvement 2
• Instruct patient to return immediately if experiencing increased pain, redness, swelling, or purulent discharge 2
• If no improvement after 48-72 hours, consider:
  • Need for drainage if not already performed
  • Possible resistant organism requiring different antibiotic coverage
  • Obtaining cultures to guide therapy

Practical Administration Tips

• Cephalexin can be taken with or without food
• If gastrointestinal upset occurs, taking with food may improve tolerance
• Ensure adequate fluid intake while taking the medication
• Complete the full course of antibiotics even if symptoms improve before completion

Caveats

• Recent research suggests twice-daily dosing (500 mg every 12 hours) may be as effective as four-times-daily dosing with potentially better adherence 4, but the FDA-approved dosing for skin infections remains 500 mg every 6 hours 1
• Adjust dosing in patients with severe renal impairment (creatinine clearance <30 mL/min) 3
• Avoid in patients with immediate hypersensitivity reactions to penicillin due to potential cross-reactivity 2