What is the recommended dosage and treatment plan for Keflex (cephalexin)?

Cephalexin (Keflex) Dosage and Treatment Recommendations

For adults, the recommended dosage of cephalexin is 250-500 mg orally every 6 hours or 500 mg every 12 hours, with a total daily dose ranging from 1-4 grams depending on infection severity. 1

Adult Dosing Regimens

Standard Adult Dosing:

• Mild to moderate infections: 250 mg every 6 hours 1
• More severe infections: 500 mg every 6 hours 1
• Alternative dosing for certain infections: 500 mg every 12 hours for:
  • Streptococcal pharyngitis
  • Skin and skin structure infections
  • Uncomplicated cystitis in patients over 15 years 1

Specific Infection Types and Duration:

• Skin and soft tissue infections: 500 mg every 6 hours or 500 mg every 12 hours for 5-7 days 2, 3
• Streptococcal pharyngitis: 500 mg every 12 hours for at least 10 days 1
• Uncomplicated cystitis: 500 mg every 12 hours for 7-14 days 1

Pediatric Dosing

• Standard pediatric dose: 25-50 mg/kg/day divided into 4 doses 1
• Streptococcal pharyngitis and skin infections: Total daily dose may be divided and administered every 12 hours 1
• Otitis media: Higher dosage of 75-100 mg/kg/day in 4 divided doses 1
• β-hemolytic streptococcal infections: Treatment should continue for at least 10 days 1

Special Considerations

Renal Impairment

• Dose adjustment required for patients with creatinine clearance less than 30 ml/min 4
• Reduction should be proportional to reduced kidney function 4

Maximum Daily Dose

• If daily doses greater than 4 g are required, parenteral cephalosporins should be considered 1

Treatment Duration

• Mild infections: 5-7 days 3
• Moderate infections: 10-14 days 3
• Severe infections: 14-21 days 3
• Streptococcal infections: Minimum of 10 days to prevent rheumatic fever 1

Efficacy and Clinical Applications

Cephalexin is effective for:

• Skin and soft tissue infections (particularly MSSA) 2, 5
• Upper and lower respiratory tract infections 4
• Uncomplicated urinary tract infections 4

Clinical studies have demonstrated high efficacy rates:

• 90-96% clinical cure rates for skin and soft tissue infections 5
• Comparable efficacy to other antibiotics like ofloxacin for skin infections 6

Important Considerations and Pitfalls

1. Allergic cross-reactivity: Up to 10% of penicillin-allergic patients may also be allergic to cephalosporins. Cephalexin should not be used in patients with immediate (anaphylactic-type) hypersensitivity to penicillin 3

2. Bacterial resistance: Consider local resistance patterns when prescribing. For suspected MRSA infections, cephalexin alone is not appropriate 2, 3

3. Combination therapy: Adding trimethoprim-sulfamethoxazole to cephalexin has not shown significant benefit for uncomplicated cellulitis in controlled trials 7

4. Adjunctive measures: Proper wound care and drainage are essential for treatment success in skin infections 3

5. Storage of suspension: After reconstitution, the suspension should be refrigerated and may be kept for 14 days without significant loss of potency 1

Remember that cephalexin is rapidly cleared by the kidneys, with 70-100% of the dose found in urine 6-8 hours after administration, making it particularly effective for urinary tract infections 4.