What is the standard dosing of Cephalexin (Keflex) for simple cellulitis in an 80-year-old man with normal renal function?

From the Guidelines

For an 80-year-old man with normal renal function, the standard Keflex (cephalexin) dosing for simple cellulitis is 500 mg orally four times daily (every 6 hours) for 5-7 days. This provides adequate coverage against the most common causative organisms of cellulitis, including Streptococcus and Staphylococcus species, as recommended by the Infectious Diseases Society of America guidelines 1. Despite the patient's advanced age, no dose adjustment is necessary with normal renal function, as cephalexin is primarily eliminated by the kidneys. The patient should complete the full course of antibiotics even if symptoms improve before completion to prevent recurrence or development of antibiotic resistance. Common side effects include gastrointestinal disturbances like diarrhea, nausea, and abdominal pain. The medication should be taken with food if stomach upset occurs. If the cellulitis worsens despite 48-72 hours of treatment, shows systemic symptoms, or involves a large area, the patient should seek immediate medical attention as this may indicate treatment failure requiring alternative antibiotics or possibly intravenous therapy. The optimal duration of antibiotic therapy for simple cellulitis is supported by recent guidelines, including those from the American College of Physicians, which suggest a course of 5 to 7 days is adequate 1.

Some key points to consider:

• The patient's normal renal function allows for standard dosing of cephalexin without adjustment.
• The choice of cephalexin provides broad coverage against common pathogens involved in simple cellulitis.
• Completion of the full antibiotic course is crucial to prevent recurrence and resistance.
• Monitoring for side effects and signs of treatment failure is essential for optimal patient care.

From the FDA Drug Label

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. The usual adult dose is 250 mg every 6 hours

• Standard dosing: For an 80-year-old man with normal renal function and simple cellulitis, the standard dosing for Keflex (cephalexin) is 500 mg every 12 hours or 250 mg every 6 hours 2

From the Research

Standard Keflex Dosing for Simple Cellulitis

• The standard dosing for Keflex (cephalexin) in an 80-year-old man with normal renal function for simple cellulitis is not explicitly stated in the provided studies.
• However, according to the study 3, the majority of non-purulent, uncomplicated cases of cellulitis are caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus, and appropriate targeted coverage of this pathogen with oral antibiotics such as penicillin, amoxicillin, and cephalexin is sufficient.
• The study 4 compared the treatment success rates of empiric therapy with cephalexin, trimethoprim-sulfamethoxazole, and clindamycin for outpatients with cellulitis, but did not provide specific dosing information for cephalexin.
• The study 5 discussed the importance of estimating kidney function in geriatric patients and adjusting drug doses accordingly, but did not provide specific guidance on cephalexin dosing.
• The study 6 discussed the age-dependent changes in drug disposition and sensitivity in the elderly, but did not provide specific guidance on cephalexin dosing.
• The study 7 discussed the use of antibiotic prophylaxis to prevent recurrent cellulitis, but did not provide specific guidance on cephalexin dosing for simple cellulitis.
• In general, the dosing of cephalexin for simple cellulitis in an 80-year-old man with normal renal function would typically be 250-500 mg every 6 hours, but this information is not explicitly stated in the provided studies 3, 7, 5, 4, 6.