Treatment of Ketoconazole-Resistant Tinea Corporis
For tinea corporis of the arm that fails ketoconazole cream, switch to oral itraconazole 100 mg daily for 15 days or oral terbinafine 250 mg daily for 1-2 weeks. 1, 2, 3
Why Ketoconazole Fails
- Ketoconazole has fallen out of favor for dermatophyte infections due to inferior efficacy compared to newer agents and hepatotoxicity risks with oral formulations 4
- Topical therapy alone is inadequate for treatment-resistant tinea corporis, necessitating systemic antifungal therapy 1
First-Line Oral Treatment Options
Itraconazole is the preferred choice based on guideline evidence:
- Itraconazole 100 mg daily for 15 days achieves 87% mycological cure rates for tinea corporis 1, 3
- This fixed-schedule approach is supported by the drug's affinity for keratinized tissues and continued activity after discontinuation 3
- Itraconazole demonstrates superior efficacy compared to both griseofulvin (87% vs 57% cure rate) and ketoconazole 1, 3
Terbinafine is an equally effective alternative:
- Terbinafine 250 mg daily for 1-2 weeks is highly effective, particularly against Trichophyton tonsurans infections 1, 2
- The shorter treatment duration (1-2 weeks vs 15 days) may improve compliance 2
- Terbinafine appears superior for Trichophyton species infections specifically 1
Treatment Selection Algorithm
If the causative organism is known:
- For Trichophyton species: Choose terbinafine 250 mg daily for 1-2 weeks 1, 2
- For other dermatophytes or unknown species: Choose itraconazole 100 mg daily for 15 days 1, 3
If the organism is unknown (most clinical scenarios):
- Either itraconazole or terbinafine is appropriate as both are effective 1, 2
- Consider itraconazole for broader dermatophyte coverage 3
- Consider terbinafine for shorter treatment duration and better compliance 2
Critical Management Points
Confirm diagnosis before treatment:
- Obtain specimens via scalpel scraping for microscopy and culture to identify the causative organism 1
- Treatment can be initiated empirically while awaiting culture results 1
Monitor for treatment endpoint:
- Mycological cure, not just clinical improvement, is the definitive treatment endpoint 1
- Follow-up with repeat mycology sampling until clearance is documented 1
Preventing Recurrence
Address environmental and contact sources:
- Screen and treat family members, especially for anthropophilic species like T. tonsurans (over 50% of family members may be affected) 1
- Clean contaminated combs, brushes, and towels with disinfectant or 2% sodium hypochlorite solution 1
- Avoid skin-to-skin contact with infected individuals and do not share personal items 1
Important Caveats
Drug interactions with itraconazole:
- Itraconazole has significant drug interactions including enhanced toxicity with warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, and simvastatin 1
- Review medication list before prescribing 1
If treatment fails:
- Consider poor compliance, suboptimal drug absorption, organism insensitivity, or reinfection 1
- Extend treatment duration by 2-4 weeks if clinical improvement occurs but mycology remains positive 1
- Switch to the alternative agent (terbinafine if started on itraconazole, or vice versa) if no clinical improvement 1