What is the treatment duration of cephalexin (Keflex) for cellulitis?

From the Guidelines

A 5-day course of cephalexin is as effective as a 10-day course for the treatment of uncomplicated cellulitis, as long as clinical improvement has occurred by 5 days. When treating cellulitis with cephalexin, the following key points should be considered:

• The standard adult dosage is typically 500 mg taken orally four times daily, or alternatively 1 gram twice daily 1.
• For more severe infections, the dose may be increased up to 4 grams daily.
• Children require weight-based dosing, usually 25-50 mg/kg/day divided into four doses.
• Treatment should continue until all signs of infection have resolved, including redness, warmth, swelling, and tenderness.
• If symptoms don't improve within 48-72 hours or worsen at any point, medical reassessment is necessary as this may indicate antibiotic resistance or a deeper infection requiring intravenous antibiotics, as noted in the practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of america 1. Some important considerations when using cephalexin for cellulitis include:
• Cephalexin works by inhibiting bacterial cell wall synthesis and is effective against many skin pathogens including Streptococcus and methicillin-sensitive Staphylococcus aureus.
• It's essential to complete the full prescribed course even if symptoms improve before finishing, to prevent recurrence and antibiotic resistance.
• In cases where clinical improvement has occurred by 5 days, a 5-day course of antimicrobial therapy is sufficient, according to the 2014 update by the infectious diseases society of america 1.

From the Research

Treatment Duration of Cephalexin for Cellulitis

• The treatment duration of cephalexin (Keflex) for cellulitis is not directly stated in the provided studies, but we can look at the duration of treatment for cellulitis in general.
• A study from 2005 2 compared the treatment of cellulitis with antibiotic therapy alone for 10 days versus antibiotic therapy for 10 days plus an oral anti-inflammatory for 5 days, and found that the addition of an oral anti-inflammatory agent significantly shortened the time to regression of inflammation and complete resolution of cellulitis.
• A study from 2023 3 compared high-dose (1000 mg) to standard-dose (500 mg) cephalexin to treat patients with cellulitis, and found that treatment failure occurred in 12.9% of patients in the standard-dose arm versus 3.2% in the high-dose arm, with a treatment duration of 7 days.
• Another study from 2020 4 found that there was no association between the duration of antibiotic therapy and outcome as measured at day 10 and day 30, suggesting that a shorter course of treatment may be effective.
• It's worth noting that the optimal treatment duration for cellulitis may depend on various factors, including the severity of the infection and the patient's response to treatment, as suggested by studies 2, 5, 4.

Factors Affecting Treatment Duration

• The severity of the infection, with more severe cases potentially requiring longer treatment durations 2, 4.
• The use of combination therapy, such as antibiotic and anti-inflammatory therapy, which may shorten the time to resolution of cellulitis 2.
• The dose of the antibiotic, with higher doses potentially leading to better outcomes 3, 5.