What antibiotic should be prescribed for a 69-year-old patient with a history of diabetes and right foot cellulitis?

From the Guidelines

For a 69-year-old patient with diabetes and right foot cellulitis, I recommend starting with cephalexin 500 mg orally four times daily for 7-10 days. This first-generation cephalosporin effectively covers the most common causative organisms in uncomplicated cellulitis, particularly Streptococcus and methicillin-sensitive Staphylococcus aureus 1. For patients with penicillin allergy, clindamycin 300-450 mg orally three times daily is an appropriate alternative. Given the patient's diabetes and age, close monitoring is essential as diabetic foot infections can progress rapidly.

Key Considerations

• If there are signs of severe infection (fever, extensive erythema, lymphangitis), or if MRSA is suspected based on local prevalence or previous history, consider adding trimethoprim-sulfamethoxazole or switching to doxycycline 1.
• The patient should elevate the affected foot, monitor blood glucose levels closely as infection may worsen glycemic control, and return for evaluation if symptoms worsen or fail to improve within 48-72 hours.
• Diabetic patients with foot infections require particularly careful assessment as they may have impaired sensation and delayed healing.

Duration of Therapy

• A course of antibiotic therapy of 1–2 weeks is usually adequate for most soft tissue DFIs 1.

Selection of Antibiotic Regimen

• Select specific antibiotic agents for treatment based on the likely or proven causative pathogens, their antibiotic susceptibilities, the clinical severity of the infection, evidence of efficacy for DFI and costs 1.
• Consider adding an agent active against MRSA if there is substantial risk of infection with this organism 1.
• Empiric anti-pseudomonal therapy is usually not required unless risk factors for Pseudomonas infection are present 1.
• Empiric anti-anaerobic therapy is appropriate for necrotic, gangrenous or foul-smelling wounds, which also require debridement 1.

From the FDA Drug Label

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 Diabetic Foot Infections 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 In the ITT population, the cure rates were 68. 5% (165/241) in linezolid-treated patients and 64% (77/120) in comparator-treated patients

For a 69-year-old patient with a history of diabetes and right foot cellulitis, linezolid may be considered as a treatment option. The cure rates for linezolid-treated patients with diabetic foot infections were 68.5% in the intent-to-treat population and 83% in clinically evaluable patients. However, it is essential to consider the patient's overall clinical condition, potential allergies, and possible interactions with other medications before making a treatment decision 2.

From the Research

Antibiotic Treatment Options for Diabetic Foot Infections

The choice of antibiotic for a 69-year-old patient with a history of diabetes and right foot cellulitis depends on several factors, including the severity of the infection, the presence of any underlying conditions, and the local prevalence of microbial causal agents.

• Linezolid: A study published in 2004 3 compared the efficacy and safety of linezolid with ampicillin-sulbactam/amoxicillin-clavulanate in the treatment of foot infections in diabetic patients. The results showed that linezolid was at least as effective as the comparator drugs, with clinical cure rates of 81% versus 71%, respectively.
• Moxifloxacin: Another study published in 2007 4 compared the efficacy of moxifloxacin with piperacillin-tazobactam/amoxicillin-clavulanate in the treatment of diabetic foot infections. The results showed that moxifloxacin was as effective as the comparator drugs, with clinical cure rates of 68% versus 61%, respectively.
• Amoxicillin-Clavulanate plus Ciprofloxacin: A study published in 2019 5 recommended amoxicillin-clavulanate plus ciprofloxacin as the empiric antibiotic regimen of choice for soft tissue infections in diabetic foot, based on the local prevalence of microbial causal agents.
• Individualized Optimization of Amoxicillin/Clavulanate Therapy: A study published in 2004 6 suggested that individualized optimization of amoxicillin/clavulanate therapy based on pharmacokinetic/pharmacodynamic parameters can enhance the antimicrobial effect and the treatment of infected non-critical ischemic diabetic foot ulcers.

Considerations for Antibiotic Selection

When selecting an antibiotic for the treatment of diabetic foot infections, it is essential to consider the following factors:

• The severity of the infection
• The presence of any underlying conditions, such as renal impairment or allergies
• The local prevalence of microbial causal agents
• The susceptibility of the causative microorganisms to different antibiotics
• The potential for antibiotic resistance

Specific Antibiotic Regimens

Some specific antibiotic regimens that have been studied for the treatment of diabetic foot infections include:

• Amoxicillin-clavulanate 1.2 g (of amoxicillin) i.v. every 12 hours plus ciprofloxacin 200 mg i.v. every 12 hours 7
• Linezolid 600 mg i.v. every 12 hours 3
• Moxifloxacin 400 mg i.v. every 24 hours 4