What is the dosage of Keflex (Cephalexin) for skin infections?

Keflex (Cephalexin) Dosage for Skin Infections

For skin infections in adults, Keflex (cephalexin) should be administered at a dose of 500 mg orally four times daily for 5-7 days. 1, 2

Adult Dosing Options

• Standard regimen: 500 mg orally four times daily (every 6 hours) for 5-7 days 3, 1
• Alternative regimen: 500 mg orally twice daily (every 12 hours) for uncomplicated skin infections 2
• Severe infections: May require higher doses up to 4g total daily dose (divided into 4 doses) 2

Pediatric Dosing

• Standard regimen: 25-50 mg/kg/day divided into 4 doses 2
• Alternative regimen for streptococcal skin infections: Total daily dose may be divided and administered every 12 hours 2
• Severe infections: Dosage may be doubled 2

Dosing Based on Weight (Pediatric Suspension)

Using 125 mg/5 mL suspension (4 times daily dosing):

• 10 kg (22 lb): 1/2 to 1 teaspoon (2.5-5 mL) four times daily
• 20 kg (44 lb): 1 to 2 teaspoons (5-10 mL) four times daily
• 40 kg (88 lb): 2 to 4 teaspoons (10-20 mL) four times daily 2

Treatment Duration

• Uncomplicated skin/soft tissue infections: 5-7 days 1
• Streptococcal infections: Minimum 10 days to prevent complications 2

Clinical Considerations

Type of Infection

• Non-purulent infections (cellulitis, erysipelas): Cephalexin is an excellent first-line choice 1
• Purulent infections (abscesses): Incision and drainage is primary treatment; cephalexin is appropriate if MRSA is not suspected 1

Efficacy

• Cephalexin has demonstrated high clinical cure rates (87-91%) in clinical trials for skin infections 4, 5
• Particularly effective against streptococci and methicillin-susceptible Staphylococcus aureus (MSSA) 1

Important Limitations

• Not effective against MRSA - consider alternative coverage if MRSA is suspected 1
• Penicillin allergy: Up to 10% of penicillin-allergic patients may also be allergic to cephalosporins; avoid in patients with immediate (anaphylactic-type) hypersensitivity to penicillin 1

Monitoring

• Reevaluate patient within 48-72 hours to assess treatment response 1
• Consider hospitalization if no improvement within 24-48 hours of outpatient treatment 1

Special Populations

Renal Impairment

• Dose adjustment required for patients with creatinine clearance less than 30 ml/min 1

Pregnancy

• Category B - generally considered safe in pregnancy 3

Common Adverse Effects

• Diarrhea (most common)
• Nausea
• Headache
• Allergic reactions (rash, pruritus) 4, 5

When to Consider Hospitalization

• Concern for deeper or necrotizing infection
• Poor adherence to therapy anticipated
• Severely immunocompromised patient
• Outpatient treatment failing (no improvement within 24-48 hours) 1

Cephalexin remains a highly effective first-line option for skin and soft tissue infections, particularly when MRSA is not suspected. The recommended dosing schedule balances efficacy with convenience and tolerability.