How is Nystop (nystatin) used to treat fungal infections such as athlete's foot or jock itch?

Nystop (Nystatin Topical Powder) Is NOT Appropriate for Athlete's Foot or Jock Itch

Nystatin topical powder should not be used to treat athlete's foot (tinea pedis) or jock itch (tinea cruris) because it is only effective against Candida yeast infections, not the dermatophyte fungi that cause these conditions. 1

Why Nystatin Doesn't Work for These Infections

Mechanism and Spectrum of Activity

• Nystatin is specifically indicated for cutaneous or mucocutaneous mycotic infections caused by Candida albicans and other Candida species only 1
• The drug works by binding to sterols in fungal cell membranes, but it exhibits no appreciable activity against dermatophytes (the fungi that cause athlete's foot and jock itch) 1
• Nystatin is active against yeasts including C. albicans, C. parapsilosis, C. tropicalis, and others, but not against Trichophyton rubrum or T. mentagrophytes—the primary causative organisms of athlete's foot and jock itch 1, 2

What Actually Causes These Infections

Athlete's Foot (Tinea Pedis)

• Caused predominantly by T. rubrum and T. mentagrophytes, not Candida species 2
• Presents as fine scaly or vesiculopustular eruptions, commonly affecting toe web spaces and soles 2
• Affects up to 22% of swimmers and runners 2

Jock Itch (Tinea Cruris)

• Also caused by dermatophyte fungi, not Candida 2
• Requires antidermatophyte therapy, not antiyeast therapy 2

Correct Treatment Options

For Athlete's Foot (Tinea Pedis)

First-line topical therapy:

• Terbinafine 1% cream applied once daily for 1 week achieves approximately 94% mycological cure rates and offers the advantage of brief treatment duration 2
• Ciclopirox olamine 0.77% cream or gel applied twice daily for 4 weeks achieves 60% cure at end of treatment and 85% cure two weeks post-treatment 2
• Clotrimazole 1% cream applied twice daily for 4 weeks is an over-the-counter alternative 2
• Butenafine applied twice daily for 2 weeks is another OTC option 2

Oral therapy for chronic or refractory cases:

• Oral terbinafine 250 mg once daily for 1 week has similar efficacy to 4 weeks of topical clotrimazole but with faster clinical resolution 2
• Oral itraconazole 100 mg once daily for 2 weeks is an alternative 2

For Jock Itch (Tinea Cruris)

• Terbinafine 1% cream applied daily for 1 week achieves approximately 94% mycological cure rate and is approved for children 12 years and older 2
• Butenafine applied twice daily for 2 weeks (adults only) 2
• Clotrimazole applied twice weekly for 4 weeks 2
• Oral itraconazole 100 mg daily for 2 weeks or 200 mg daily for 1 week for more extensive disease 2

Important Clinical Pearls

Prevention Strategies

• Thorough drying between toes after showers is essential 2
• Daily sock changes and periodic cleaning of athletic footwear 2
• Use of foot powder after bathing reduces T. pedis rates from 8.5% to 2.1% 2
• For jock itch prevention: cover active foot lesions with socks before wearing underwear to prevent spread from concurrent tinea pedis 2

Common Pitfalls to Avoid

• Do not confuse Candida intertrigo (yeast infection) with dermatophyte infections—only the former responds to nystatin 1
• Confirm diagnosis with KOH preparation or culture before treatment, as clinical appearance alone can be misleading 1
• Recognize that nystatin is not absorbed from intact skin and has zero systemic or dermatophyte activity 1