What are the dosing recommendations for Keflex (cephalexin) and Bactrim (trimethoprim-sulfamethoxazole) for an infected ingrown toenail, and what are the steps for partial nail avulsion?

Antibiotic Dosing and Partial Nail Avulsion for Infected Ingrown Toenail

Antibiotic Dosing Recommendations

For an infected ingrown toenail, prescribe either Keflex (cephalexin) 500 mg orally four times daily OR Bactrim DS (trimethoprim-sulfamethoxazole 160/800 mg) 1-2 tablets orally twice daily for 5-7 days. 1

Keflex (Cephalexin) Dosing

• Adult dose: 500 mg orally four times daily (every 6 hours) 1
• Duration: 5-7 days depending on clinical response 1
• Covers methicillin-susceptible Staphylococcus aureus (MSSA) and streptococci, the most common pathogens in skin and soft tissue infections 1
• Well-tolerated with minimal gastrointestinal side effects and rapid absorption from the upper intestine 2

Bactrim (Trimethoprim-Sulfamethoxazole) Dosing

• Adult dose: 1-2 double-strength tablets (160/800 mg) orally twice daily 1
• Duration: 5-7 days depending on clinical response 1
• Provides coverage against both MSSA and MRSA (methicillin-resistant S. aureus) 1
• Consider this option if MRSA colonization is suspected, there is evidence of MRSA infection elsewhere, or the patient is an injection drug user 1

Important Antibiotic Considerations

• Antibiotics are NOT necessary if performing partial nail avulsion with phenolization - multiple studies demonstrate no benefit in healing time or infection rates when antibiotics are added to the surgical procedure 3, 4
• If cellulitis extends proximal to the hallux interphalangeal joint or systemic signs of infection are present, broader coverage may be warranted 1, 4
• Obtain bacterial cultures if there is treatment failure, severe infection, or immunocompromised state 1

---

Partial Nail Avulsion Procedure Steps

Partial nail avulsion with phenolization is the most effective treatment for ingrown toenails, with lower recurrence rates than surgical excision alone. 5, 3

Pre-Procedure Preparation

• Obtain informed consent and explain the procedure 5
• Assess for contraindications: peripheral vascular disease, immunocompromised state, or severe cellulitis extending beyond the toe 4
• No pre-procedural antibiotics are needed 3, 4

Anesthesia

• Perform a digital ring block using 1-2% lidocaine without epinephrine 5
• Inject along both sides of the base of the great toe at the level of the metatarsophalangeal joint 5
• Wait 5-10 minutes for complete anesthesia 5

Nail Avulsion Steps

1. Apply a tourniquet at the base of the toe using a penrose drain or rubber band to create a bloodless field 5

2. Separate the ingrown nail border from the nail bed using a straight hemostat or nail elevator, advancing from the distal edge to the proximal nail fold 5

3. Cut the nail longitudinally using straight scissors, creating a 3-4 mm strip from the distal edge to the proximal nail matrix 5

4. Grasp and remove the nail strip using a hemostat, rotating it outward and pulling toward the center of the nail to completely extract it from under the proximal nail fold 5

5. Inspect the nail bed to ensure complete removal of the nail strip and any spicules 5

Phenolization (Chemical Matricectomy)

• Apply 88% liquefied phenol to the exposed nail matrix using a cotton-tipped applicator 5, 3
• Apply for 60-90 seconds, ensuring contact with the entire matrix area 5
• Repeat the phenol application 2-3 times for optimal matrix destruction 5
• Flush thoroughly with isopropyl alcohol after phenol application to neutralize the chemical 5
• Phenolization produces significantly better results than surgical matrix excision, with lower recurrence rates (including regrowth and spike formation) at 1 year 3

Post-Procedure Care

• Remove the tourniquet 5
• Apply antibiotic ointment and a non-adherent dressing 5
• Instruct the patient to soak the toe in warm, soapy water twice daily starting 24-48 hours post-procedure 5
• No post-procedural antibiotics are necessary - they do not reduce infection rates or improve healing time 3, 4
• Expected healing time is approximately 2 weeks 4

Common Pitfalls to Avoid

• Incomplete nail strip removal leads to recurrence - ensure the entire strip is extracted from under the proximal nail fold 5
• Inadequate phenol application to the matrix results in nail regrowth - apply for the full 60-90 seconds and repeat 2-3 times 5, 3
• Prescribing unnecessary antibiotics - reserve antibiotics only for cases with significant cellulitis or systemic signs of infection 3, 4
• Using phenol in patients with peripheral vascular disease - phenol can cause tissue necrosis in compromised circulation 5