What is the appropriate dosing of Keflex (Cephalexin) for an 81-year-old male with mildly impaired renal function (eGFR of 80) and left lower leg cellulitis/stasis dermatitis?

From the Guidelines

For an 81-year-old male with mildly impaired renal function (eGFR of 80) and left lower leg cellulitis/stasis dermatitis, the appropriate dosing of Keflex (cephalexin) would be 500 mg orally every 6 hours for 5 days, as a 5-day course is as effective as a 10-day course for uncomplicated cellulitis 1. This standard adult dosing is appropriate since the patient's renal function is only mildly impaired with an eGFR of 80, which does not warrant dose adjustment. For cellulitis, it is essential to cover the common causative organisms, particularly Streptococcus species and methicillin-sensitive Staphylococcus aureus. Some key points to consider in the management of cellulitis include:

• Elevation of the affected area to promote gravity drainage of the edema and inflammatory substances
• Appropriate therapy for any underlying condition that may have predisposed to the infection, such as tinea pedis, venous eczema (“stasis dermatitis”), or trauma
• Monitoring for improvement within 48-72 hours; if the infection worsens or shows no signs of improvement, reassessment is necessary as this could indicate resistance to cephalexin or an alternative diagnosis
• Completing the full course of antibiotics even if symptoms improve before completion The patient should take the medication with or without food, though taking it with food may help reduce gastrointestinal side effects. Cephalexin works by inhibiting bacterial cell wall synthesis and is effective against many of the common causative organisms in cellulitis, particularly Streptococcus species and methicillin-sensitive Staphylococcus aureus 1. In cases where the patient does not respond to cephalexin, consideration should be given to the possibility of methicillin-resistant Staphylococcus aureus (MRSA) infection, and alternative antibiotics such as clindamycin, doxycycline, or linezolid may be necessary 1.

From the FDA Drug Label

The usual adult dose is 250 mg every 6 hours For the following infections, a dosage of 500 mg may be administered every 12 hours: streptococcal pharyngitis, skin and skin structure infections, and uncomplicated cystitis in patients over 15 years of age.

For an 81-year-old male with mildly impaired renal function (eGFR of 80) and left lower leg cellulitis/stasis dermatitis, the appropriate dosing of Keflex (Cephalexin) is 500 mg every 12 hours or 250 mg every 6 hours, as the patient's condition falls under skin and skin structure infections.

• The patient's renal function is mildly impaired, but the provided drug label does not specify dosage adjustments for patients with an eGFR of 80 2.
• Given the patient's age and mildly impaired renal function, it is essential to monitor for potential adverse effects and adjust the dosage as needed.

From the Research

Appropriate Keflex Dosing for 81-Year-Old Male with eGFR of 80

• The patient's condition of left lower leg cellulitis/stasis dermatitis requires antibiotic treatment, and Keflex (Cephalexin) is a commonly used antibiotic for such conditions 3.
• However, the patient's mildly impaired renal function (eGFR of 80) needs to be considered when determining the appropriate dosing of Keflex.
• According to the study on renal function assessment in older people, the BIS1 equation is the most accurate formula for calculating eGFR values in persons aged more than 70 years old 4.
• Although there is no direct evidence on the appropriate dosing of Keflex for an 81-year-old male with an eGFR of 80, the study on assessment of antibiotic treatment of cellulitis and erysipelas suggests that the optimum antibiotic treatment for cellulitis lacks consensus, and data are limited on the most appropriate route of administration or duration of therapy 3.
• Another study on prevention and management of acneiform rash associated with EGFR inhibitor therapy found that oral antibiotics had the greatest efficacy in preventing grade 2 or higher acneiform eruptions, with a relative risk reduction of 40% 5.
• The study on stasis dermatitis highlights the importance of compression therapy, topical treatments, and interventional treatment options to correct the underlying causes of venous reflux, but does not provide guidance on antibiotic dosing 6.
• The study on antibiotic prophylaxis for skin toxicity induced by antiepidermal growth factor receptor agents suggests that prophylactic antibiotics may reduce the occurrence and severity of anti-EGFR drug-related skin rashes, but does not provide specific guidance on Keflex dosing 7.

Considerations for Keflex Dosing

• The patient's renal function should be closely monitored, and the dose of Keflex should be adjusted accordingly to prevent accumulation of the drug 4.
• The patient's age and comorbidities should also be considered when determining the appropriate dosing of Keflex.
• The duration of therapy and the route of administration (oral or intravenous) should be determined based on the severity of the patient's condition and the clinical response to treatment 3.