What are the appropriate antibiotic choices for the treatment of cellulitis?

From the Guidelines

For cellulitis, the first-line antibiotic treatment is typically a 5- to 6-day course of antibiotics active against streptococci, such as cephalexin 500 mg orally four times daily, or dicloxacillin 500 mg orally four times daily, as recommended by the American College of Physicians 1. This approach is based on the most recent guidelines that emphasize the importance of using shorter courses of antibiotics to reduce the risk of resistance and minimize side effects. The choice of antibiotic should be guided by the severity of the infection, the presence of comorbidities, and the potential for MRSA infection. For patients with penicillin allergies, clindamycin 300-450 mg orally three times daily for 5-10 days is an appropriate alternative 1. In cases of suspected MRSA, trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily or doxycycline 100 mg twice daily should be considered 1. For severe infections requiring hospitalization, intravenous options include cefazolin, nafcillin, or vancomycin (for MRSA concerns) 1. Some key points to consider when treating cellulitis include:

• The importance of elevating the affected limb to reduce swelling and promote healing
• Monitoring for signs of worsening infection, such as spreading redness, increasing pain, fever, or streaking
• Completing the full course of antibiotics even if symptoms improve quickly
• Reassessing the choice of antibiotic if there's no improvement within 48-72 hours, as this may indicate resistance or an alternative diagnosis 1. It's also important to note that the treatment duration should be guided by clinical response, with most uncomplicated cases resolving within 5-7 days of therapy 1. Overall, the goal of treatment is to effectively manage the infection while minimizing the risk of resistance and side effects.

From the FDA Drug Label

The cure rates in clinically evaluable patients with complicated skin and skin structure infections were 90% in linezolid-treated patients and 85% in oxacillin-treated patients The cure rates by pathogen for microbiologically evaluable patients are presented in Table 18. Table 18 Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Adult Patients with Complicated Skin and Skin Structure Infections Pathogen Cured ZYVOXn/N (%) Oxacillin/Dicloxacillinn/N (%) Staphylococcus aureus 73/83 (88) 72/84 (86) Methicillin-resistant S aureus 2/3 (67) 0/0 (-) Streptococcus agalactiae 6/6 (100) 3/6 (50) Streptococcus pyogenes 18/26 (69) 21/28 (75) The cure rates in microbiologically evaluable patients with MRSA skin and skin structure infection were 26/33 (79%) for linezolid-treated patients and 24/33 (73%) for vancomycin-treated patients Adult diabetic patients with clinically documented complicated skin and skin structure infections ("diabetic foot infections") were enrolled in a randomized (2:1 ratio), multi-center, open-label trial comparing study medications administered IV or orally for a total of 14 to 28 days of treatment One group of patients received ZYVOX 600 mg q12h IV or orally; the other group received ampicillin/sulbactam 1. 5 to 3 g IV or amoxicillin/clavulanate 500 to 875 mg every 8 to 12 hours (q8–12h) orally.

The appropriate antibiotic choices for the treatment of cellulitis include:

• Linezolid
• Oxacillin
• Vancomycin
• Ampicillin/sulbactam
• Amoxicillin/clavulanate 2

From the Research

Appropriate Antibiotic Choices for Cellulitis

The treatment of cellulitis should initially cover Streptococcus and methicillin-sensitive S. aureus, with expansion for methicillin-resistant S. aureus (MRSA) in cases of cellulitis associated with specific risk factors 3.

• Oral antibiotics such as penicillin, amoxicillin, and cephalexin are sufficient for non-purulent, uncomplicated cases of cellulitis caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus 4.
• For patients with uncomplicated cellulitis, 5 days of therapy with levofloxacin appears to be as effective as 10 days of therapy 5.
• Flucloxacillin, either alone or in combination with phenoxymethylpenicillin, is a commonly prescribed antibiotic for the treatment of cellulitis, particularly in Ireland and the United Kingdom 6.
• In areas with a high prevalence of community-associated MRSA infections, antibiotics with activity against community-associated MRSA, such as trimethoprim-sulfamethoxazole and clindamycin, are preferred empiric therapy for outpatients with cellulitis 7.

Special Considerations

• Coverage for MRSA is generally not recommended for non-purulent cellulitis 4.
• Failure to improve with appropriate first-line antibiotics should prompt consideration for resistant organisms, secondary conditions that mimic cellulitis, or underlying complicating conditions such as immunosuppression, chronic liver disease, or chronic kidney disease 3.
• Risk factors for treatment failure include therapy with an antibiotic that is not active against community-associated MRSA and severity of cellulitis 7.