What is the treatment for a single thick and black toenail?

Treatment for a Single Thick and Black Toenail

A single thick and black toenail is most likely onychomycosis (fungal nail infection) and should be treated with oral terbinafine 250mg daily for 12 weeks as first-line therapy. 1, 2

Diagnostic Approach

Before initiating treatment, proper diagnosis is essential:

• Obtain appropriate nail specimens for laboratory testing (KOH preparation, fungal culture, or nail biopsy) to confirm the diagnosis of onychomycosis 2
• Black discoloration may indicate:
  • Fungal infection (most common) 3
  • Subungual hematoma (blood under the nail from trauma)
  • Melanoma (rare but serious) - should be ruled out, especially if there's a longitudinal melanonychia pattern 4

Treatment Algorithm

First-Line Treatment

• Oral terbinafine 250mg daily for 12 weeks for toenail infection 1, 2
  • Highest efficacy with 70% mycological cure rate 2
  • Fungicidal against dermatophytes by inhibiting squalene epoxidase 1
  • Mean time to overall success is approximately 10 months for toenail infections 2

Alternative Oral Treatments

• Itraconazole 200mg twice daily for 1 week per month (pulse therapy), with three pulses for toenails 1
• Consider when terbinafine is contraindicated or not tolerated

Topical Treatment Options

• Topical therapy should only be used for:
  • Very early or superficial infections 1
  • When systemic therapy is contraindicated 1
• Options include:
  • Amorolfine 5% nail lacquer 1
  • Ciclopirox nail lacquer 5
  • Efinaconazole or tavaborole (newer agents) 5

Adjunctive Measures

For thick dystrophic nails:

• Keep nails trimmed straight across 6
• File nail surfaces with an emery board after softening the nails by soaking in warm saline water or bath 6
• Apply urea-based cream (keratolytic agent) daily to weekly to reduce nail thickness 6
• Consider podiatry referral for professional nail reduction 6

Special Considerations

• For diabetic patients: Terbinafine is preferred due to lower risk of drug interactions and hypoglycemia 1
• For immunosuppressed patients: Terbinafine and fluconazole are preferred due to lower risk of interactions with other medications 1
• For severe cases: Consider nail removal via chemical or laser ablation if conservative treatments fail 6

Prevention of Recurrence

Onychomycosis has high recurrence rates (40-70%), necessitating preventive strategies 1:

• Wear protective footwear in public facilities 1
• Use absorbent and antifungal powders in shoes 1
• Keep nails short 1
• Avoid sharing nail clippers 1

Treatment Monitoring

• Patients should understand that visible improvement takes time due to slow nail growth 2
• Optimal clinical effect is seen some months after mycological cure and cessation of treatment 2
• Monitor for potential side effects of oral terbinafine:
  • Liver function abnormalities (measure serum transaminases before starting) 2
  • Taste disturbances 2
  • Skin reactions 2