What is the next best antibiotic for a 70-year-old patient with cellulitis who failed Keflex (Cephalexin) management and is currently on lamotrigine and phenytoin?

From the Guidelines

For a 70-year-old patient with cellulitis who failed Keflex (cephalexin) treatment and is taking lamotrigine and phenytoin, clindamycin would be the next best antibiotic option. The recommended dosage is 300-450 mg orally every 6-8 hours for 5-10 days, depending on the severity of the infection, as suggested by the Infectious Diseases Society of America guidelines 1. This antibiotic is effective against many skin and soft tissue infections, including those caused by Staphylococcus aureus (including some MRSA strains) and Streptococcus species, which are common causes of cellulitis. Clindamycin is particularly appropriate in this case because it doesn't have significant interactions with the patient's current medications (lamotrigine and phenytoin) and provides good tissue penetration. It's also a reasonable choice for patients who have failed first-line beta-lactam therapy. The patient should be monitored for potential side effects, particularly diarrhea, which could indicate Clostridioides difficile infection. If the cellulitis is severe or rapidly progressing, or if there are signs of systemic infection, hospitalization for intravenous antibiotics may be necessary instead of oral therapy.

Some key points to consider in the management of cellulitis include:

• The need for antibiotic therapy that covers streptococci and possibly MRSA, especially in cases of severe infection or in patients with risk factors for MRSA 1.
• The importance of monitoring for signs of systemic infection and adjusting treatment accordingly 1.
• The consideration of hospitalization for patients with severe infection, immunocompromised status, or poor adherence to therapy 1.
• The role of supportive care, such as elevation of the affected area and treatment of predisposing factors, in the management of cellulitis 1.

Given the patient's age and the failure of initial treatment with Keflex, careful consideration of these factors and close monitoring of the patient's response to clindamycin are crucial. The guidelines from the Infectious Diseases Society of America provide a framework for the management of skin and soft tissue infections, including cellulitis, and emphasize the importance of individualizing treatment based on the severity of the infection and the patient's underlying health status 1.

From the FDA Drug Label

14 CLINICAL STUDIES 14. 1 Complicated Skin and Skin Structure Infections

Adults with cSSSI Adult patients with clinically documented complicated skin and skin structure infections (cSSSI) (Table 15) were enrolled in two randomized, multinational, multicenter, investigator-blinded trials comparing daptomycin for injection (4 mg/kg IV q24h) with either vancomycin (1 g IV q12h) or an anti-staphylococcal semi-synthetic penicillin (i.e., nafcillin, oxacillin, cloxacillin, or flucloxacillin; 4 to 12 g IV per day).

The next best antibiotic for a 70-year-old patient with cellulitis who failed Keflex (Cephalexin) management and is currently on lamotrigine and phenytoin could be daptomycin.

• The patient's age and failure of previous antibiotic treatment suggest the need for an alternative with a broader spectrum of activity.
• Daptomycin has been shown to be effective against various pathogens, including MRSA, which is a common cause of complicated skin and skin structure infections.
• However, it is crucial to consider potential interactions with the patient's current medications, lamotrigine and phenytoin, although the provided information does not directly address these interactions 2.

From the Research

Alternative Antibiotic Options for Cellulitis

Given the patient's failure to respond to Keflex (Cephalexin) management and their current medications, lamotrigine and phenytoin, the next best antibiotic option for a 70-year-old patient with cellulitis needs to be carefully considered.

• Trimethoprim-sulfamethoxazole: This antibiotic has shown higher treatment success rates compared to cephalexin, especially in areas with a high prevalence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections 3.
• Clindamycin: Clindamycin has been found to be effective against MRSA and may be considered for patients who have failed cephalexin treatment, particularly if the infection is suspected to be caused by MRSA 3, 4.
• Macrolides or Lincosamides: These classes of antibiotics have been shown to have similar efficacy to beta-lactams (such as cephalexin) in treating cellulitis or erysipelas, and may be considered as alternative options 5.

Considerations for Antibiotic Selection

When selecting an alternative antibiotic, it is essential to consider the potential interactions with the patient's current medications, lamotrigine and phenytoin.

• Drug Interactions: The chosen antibiotic should be evaluated for potential interactions with lamotrigine and phenytoin to ensure safe and effective treatment.
• MRSA Coverage: If the infection is suspected to be caused by MRSA, an antibiotic with activity against MRSA, such as trimethoprim-sulfamethoxazole or clindamycin, may be preferred 3, 6.
• Patient Factors: The patient's age, comorbidities, and severity of infection should also be taken into account when selecting an alternative antibiotic.

Additional Studies

Further studies have compared the effectiveness of different antibiotics in treating cellulitis, including a randomized controlled trial that found no significant difference between cephalexin and clindamycin for treatment of uncomplicated pediatric skin infections 4. Another study found that the addition of trimethoprim-sulfamethoxazole to cephalexin did not improve outcomes in patients with cellulitis without abscesses 6.