How to order Keflex (cephalexin) for a patient with paronychia?

How to Order Keflex (Cephalexin) for Paronychia

For acute paronychia with signs of bacterial infection, prescribe cephalexin 500 mg orally every 6 hours (or 250 mg every 6 hours for milder cases) for 7-10 days, targeting the most common gram-positive pathogens including Staphylococcus aureus and Streptococcus species. 1, 2

Dosing Specifications

Adult Dosing

• Standard dose: 250 mg orally every 6 hours for mild to moderate skin and soft tissue infections 2
• Higher dose: 500 mg orally every 6 hours for more severe infections or less susceptible organisms 2
• Alternative regimen: 500 mg every 12 hours may be used for uncomplicated skin and skin structure infections 2
• Maximum daily dose: Do not exceed 4 grams per day; if higher doses are required, consider parenteral cephalosporins 2

Pediatric Dosing

• Standard dose: 25-50 mg/kg/day divided into doses every 6 hours 2
• For skin infections: Total daily dose may be divided and given every 12 hours in children over 1 year 2
• Severe infections: Double the standard dosage 2

When to Prescribe Oral Antibiotics

Indications for cephalexin in paronychia:

• Presence of purulent drainage or abscess after adequate drainage has been performed 3, 4
• Signs of spreading infection including erythema, warmth, or edema extending beyond the nail fold 1
• Moderate to severe infection (Grade 2-3) with systemic signs 1
• Immunocompromised patients even with mild infection 5
• Failed conservative management with topical therapy after 2 weeks 3, 4

Important caveat: Oral antibiotics are usually not needed if adequate drainage is achieved, unless the patient is immunocompromised or severe infection is present 4, 5

Microbiological Considerations

Cephalexin provides excellent coverage for the most common pathogens in paronychia:

• Gram-positive bacteria (72% of isolates): Including Staphylococcus aureus and Streptococcus species 6
• Some gram-negative bacteria (23% of isolates) 6
• Achieves urinary concentrations of 500-1000 mcg/mL, far exceeding MIC for common pathogens 7

Critical limitation: Up to 25% of paronychia cases have secondary bacterial or fungal superinfections 1, 3, 4

When Cephalexin May Fail

If initial treatment with cephalexin fails after 2 weeks, switch to sulfamethoxazole-trimethoprim (Bactrim) as it provides broader coverage including MRSA. 3, 4

Alternative considerations if cephalexin is ineffective:

• For MRSA coverage: Consider trimethoprim-sulfamethoxazole, doxycycline, or clindamycin 1
• Avoid clindamycin as first-line due to inadequate coverage for some streptococcal species and increasing resistance 4
• For broader coverage: Amoxicillin-clavulanate 500/125 mg every 12 hours covers both typical pathogens and beta-lactamase producers 4

Prescription Writing Details

Sample prescription:

• Drug: Cephalexin 500 mg capsules
• Quantity: #56 capsules (for 7 days) or #80 capsules (for 10 days)
• Directions: Take one capsule by mouth every 6 hours for 7-10 days
• Refills: None 2

For liquid suspension (pediatric):

• Prepare suspension at time of dispensing by adding appropriate amount of water 2
• Store in refrigerator after mixing 2
• May be kept for 14 days without significant loss of potency 2

Adjunctive Measures to Prescribe Concurrently

Always combine oral antibiotics with:

• Warm water or white vinegar soaks (1:1 dilution) for 15 minutes 3-4 times daily 4, 5
• Topical 2% povidone-iodine twice daily 1, 3, 4
• Mid to high potency topical corticosteroid ointment to nail folds twice daily 3, 4

Duration and Follow-up

• Treatment duration: 7-10 days for skin and soft tissue infections 1, 2
• Reassessment: Evaluate response after 2 weeks 1, 3, 4
• Escalation: If no improvement after 2 weeks, obtain cultures and consider referral to dermatology or podiatry 3, 4

Special Populations

Renal impairment: Patients with creatinine clearance <30 mL/min require dose reduction proportional to reduced renal function 7

Allergy considerations: Cephalexin has a low incidence of allergy due to its stability and chemical configuration, but cross-reactivity with penicillin allergy occurs in approximately 10% of patients 7

Common Pitfalls to Avoid

• Do not prescribe oral antibiotics without ensuring adequate drainage if an abscess is present 4, 5
• Do not obtain cultures routinely for simple paronychia, but do obtain them in severe cases, treatment failures, or immunocompromised patients 1, 4
• Do not forget to address underlying causes such as ingrown toenail, which may require specific management beyond antibiotics 3
• Do not use cephalexin alone for chronic paronychia, which is primarily an irritant dermatitis requiring topical corticosteroids rather than antibiotics 8, 5