Treatment of Tinea (Dermatophytosis)

Overview

Treatment by Site

1. Tinea Corporis (body) and Tinea Cruris (groin)

• Topical therapy is first-line
  • Allylamines: terbinafine, naftifine
  • Benzylamines: butenafine
  • Azoles: econazole, luliconazole, miconazole, clotrimazole
  • Ciclopirox
  • Allylamines/benzylamines may provide a more sustained cure compared to azoles
• For tinea cruris, keep the area as dry as possible; lotions or sprays are easier to apply than creams on large areas

• Oral therapy required:
  • Terbinafine 250 mg/day for 1-2 weeks
  • Itraconazole 200 mg/day for 1-2 weeks
  • Alternatives: fluconazole, griseofulvin
• Terbinafine is generally preferred as it has fewer drug interactions than itraconazole

2. Tinea Pedis (athlete's foot)

• Topical: azoles, allylamines, benzylamines (same agents as above)
• Systemic (for extensive or refractory cases): terbinafine, itraconazole, fluconazole, griseofulvin
• Note: tinea pedis can be complicated by bacterial superinfection (streptococci/staphylococci entering through toe-web fissures); agents like econazole and ciclopirox have some additional antibacterial coverage and may be useful in those situations

3. Tinea Capitis (scalp)

• Always requires systemic therapy - topical agents do not penetrate the hair shaft
• Griseofulvin has been the traditional agent; treatment failure is often due to inadequate dose or duration
• Terbinafine may be more effective for Trichophyton tonsurans (most common cause in the US)
• Fluconazole and itraconazole are also effective alternatives

4. Onychomycosis (nail, tinea unguium)

• Always requires systemic therapy (topical agents generally ineffective alone)
• Confirm fungal infection before starting oral therapy (about 1/3 of clinically suspected cases are not fungal)

• Terbinafine is slightly superior to itraconazole for dermatophyte onychomycosis; monitor for hepatotoxicity with both
• Itraconazole has frequent drug interactions; use with caution in heart failure

• Ciclopirox lacquer
• Efinaconazole (topical solution, applied for up to 1 year - shown beneficial in trials)
• Tavaborole
• All require ~48 weeks of treatment
• Griseofulvin is no longer preferred for onychomycosis (less efficacious, longer courses)

Summary Table

Important Notes

• Ketoconazole (systemic) is not recommended for superficial infections due to risk of severe hepatotoxicity and QT prolongation
• Relapse of tinea cruris and tinea pedis is common; treat early with topical agents
• Onychomycosis relapses occur in 25-30% of cases after treatment
• Itraconazole capsules require food and gastric acid for absorption; the solution is taken on an empty stomach

Emerging Resistance - 2025 Alert

Fluconazole Tablet - Dosage

Available Formulations

• Tablets: 50 mg, 100 mg, 150 mg, 200 mg
• Oral suspension: 10 mg/mL and 40 mg/mL
• IV solution: 2 mg/mL (in saline or dextrose)

Dosage by Indication

General Dosing Rules

• General range: 50-400 mg once daily (oral or IV)
• Loading dose: On day 1, give twice the maintenance dose
• Maximum studied dose: Up to 1200 mg/day has been used in cryptococcal meningitis trials

Pediatric Dosing

• General infections: 12 mg/kg once daily (max 600 mg/day), no loading dose
• Onychomycosis: 3-6 mg/kg/week
  • Fingernails: 6-12 weeks
  • Toenails: 9-15 weeks

Renal Dose Adjustment

• Fluconazole is primarily renally eliminated (poorly metabolized by liver)
• Dose adjustment required in renal insufficiency
• For patients on dialysis: give full dose after each dialysis session

Key Pharmacokinetic Points

• Oral bioavailability ~90% (nearly equivalent to IV)
• Long half-life: 25-30 hours (allows once-daily or once-weekly dosing)
• Absorption is NOT affected by food, gastric acidity, or disease
• Good CSF and tissue penetration (skin, nail, vitreous)

Important Cautions

• Drug interactions: Fluconazole inhibits CYP3A4 and CYP2C9 - interacts with warfarin, phenytoin, cyclosporine, statins, and many others. Fatal arrhythmias possible with cisapride, pimozide, astemizole
• QT prolongation: Cardiac monitoring if risk factors present
• Pregnancy: Avoid high doses (associated with tetralogy of Fallot and skeletal/cardiac defects in neonates)
• Hepatotoxicity: Rare but serious; reversible alopecia with prolonged high-dose use

Management of Cellulitis in Diabetic Patients

Why Diabetics Are Different

• Polymicrobial infections - staphylococcal, streptococcal, pseudomonal, and anaerobic organisms often co-exist (vs. simple strep/staph in non-diabetics)
• Neuropathy - pain may be absent even with severe, deep infection; the true extent of infection is often underestimated clinically
• Peripheral artery disease (PAD) - impaired blood flow reduces antibiotic penetration and wound healing
• Hyperglycemia - worsens neutrophil function and tissue repair
• Gas-producing gram-negative organisms can occur in deeper, more severe infections
• Tinea pedis acts as a common portal of bacterial entry

Step 1 - Assessment and Classification (IDSA/IWGDF)

Step 2 - Investigations

• Wound cultures: Take from deep tissue, not superficial swabs (superficial swabs reflect colonization, not infection - they confuse and delay treatment). Gold standard is surgical debridement with targeted tissue/fluid culture
• Blood cultures: For severe/systemic infection
• Plain X-ray: Detect subcutaneous gas, foreign bodies, bone erosion, Charcot joints
• CT scan: Identifies deep abscesses; detects gas in soft tissues better than plain film
• MRI: Best for early osteomyelitis detection when X-rays are negative but suspicion is high
• Probe-to-bone test: If the wound can be probed to bone, osteomyelitis is almost certain
• Labs: CBC, CRP, ESR (elevated inflammatory markers support diagnosis in equivocal cases), renal function, blood glucose, HbA1c
• Vascular assessment: Pedal and popliteal pulse palpation; ankle-brachial index if PAD suspected; transcutaneous oxygen measurement (TCOM - a tension <40 mmHg indicates impaired wound healing)

Step 3 - Antibiotic Therapy

Mild infections (Grade 2) - Outpatient oral therapy

• Target aerobic gram-positive cocci (Streptococcus, Staphylococcus)
• Oral options: dicloxacillin, cephalexin, amoxicillin-clavulanate
• If MRSA risk factors: trimethoprim-sulfamethoxazole (TMP-SMX) or doxycycline
• Duration: 1-2 weeks (may extend if infection persists)

Moderate infections (Grade 3) - Hospital admission, IV antibiotics

• Broader spectrum required - cover gram-positives, gram-negatives, and possibly anaerobes
• IV options: piperacillin-tazobactam, ampicillin-sulbactam, ticarcillin-clavulanate
• Add vancomycin or daptomycin if MRSA risk factors present
• For recent antibiotic exposure, macerated ulcer, warm climate, or ischemic/necrotic/gas-forming infection: add coverage for Pseudomonas and resistant gram-negatives
• Transition to oral therapy once clinically improving

Severe infections (Grade 4) - ICU-level care + urgent surgery

• Broad-spectrum IV antibiotics covering gram-positives (including MRSA), gram-negatives (including Pseudomonas), and anaerobes
• Regimens: vancomycin + piperacillin-tazobactam or vancomycin + meropenem
• Urgent surgical evaluation mandatory

Step 4 - Surgical Management

• Cellulitis alone (no abscess/necrosis): Non-operative - antibiotics alone
• Deep space abscess: Incision and drainage, leave wound open to drain, inspect for extension to deeper spaces or bone
• Necrotic tissue: Urgent debridement of all non-viable tissue back to healthy margins; wounds left open for secondary healing
• Necrotizing infection (gas in tissue, crepitus, rapid progression): Emergency surgical debridement - resect all diseased soft tissue, muscle, and bone to healthy margins
• Osteomyelitis without bone resection: 6-week course of targeted antibiotics (after debridement, 10 days from surgical debridement); long-term follow-up (at least 1 year) required
• Osteomyelitis with extensive bone involvement: Amputation may be necessary. After major amputation, 5-year survival drops from 70% to 43%
• PAD: Revascularization may be necessary to improve healing - surgical bypasses often required (though they may fail over time)

Step 5 - Supportive and Adjunctive Care

Step 6 - Interdisciplinary Team

• Endocrinology (glycemic optimization)
• General/vascular surgery (debridement, revascularization)
• Podiatry (wound care, offloading)
• Infectious disease (antibiotic stewardship, culture-directed therapy)
• Wound care specialists
• Pharmacists, dieticians, physiotherapy

Prognosis and Recurrence

• Nearly 50% of healed diabetic foot infections recur within 1 year, and >90% within 10 years
• ~15% progress to osteomyelitis
• Superficial wound swabs should not guide antibiotic choices - they reflect colonization, not true infection
• Long-term follow-up (minimum 1 year) is required to confirm remission

Inj. Amoxicillin-Clavulanate (Co-amoxiclav) - IV Dosage

Available Formulations (Injectable)

Adult Dosage (IV)

Note on frequency: The q8h interval is standard for SSTI/RTI. For infections involving Gram-negative (Enterobacterales) organisms, q6h dosing is preferred based on pharmacokinetic-pharmacodynamic (PK/PD) principles - beta-lactams require free drug above MIC for 40-50% of the dosing interval. For CrCl >190 mL/min (hyperfiltrators), 1.2 g q4h may be needed.

Pediatric Dosage (IV)

Renal Dose Adjustment (Adults)

Administration

• IV bolus (slow): Reconstitute in WFI; inject over 3-5 minutes
• IV infusion: Dilute in 100 mL of 0.9% NaCl; infuse over 30-40 minutes
• Use immediately after reconstitution; discard unused portion
• Do not mix with blood products, lipid emulsions, or aminoglycosides in the same line
• Each 1.2 g vial contains ~1.0 mmol potassium and ~2.7 mmol sodium (relevant in fluid-restricted patients)

Step-Down to Oral

• Switch to oral therapy (amoxicillin-clavulanate 625 mg or 1 g tablet) as soon as the patient can tolerate oral medications and shows clinical improvement
• IV-to-oral switch is preferred to reduce hospital stay and line-related risks

Key Points

• No dose adjustment needed in hepatic impairment (dose as for adults); monitor liver function with prolonged use
• Contraindicated in patients with prior jaundice/hepatic dysfunction with amoxicillin-clavulanate
• Penicillin allergy - use with caution; cross-reactivity with cephalosporins ~1-2%
• Not active against Pseudomonas - use piperacillin-tazobactam if Pseudomonas coverage needed

Tinea Corporis (Ringworm of the Body) - Treatment

First-Line: Topical Antifungals (Localized Disease)

Twice-Daily Agents

Once-Daily Agents

Allylamines (terbinafine, naftifine) and benzylamines (butenafine) may provide a more sustained clinical cure compared to azoles.

Important Caution - Topical Steroids

• Inferior effectiveness
• Risk of causing Majocchi granuloma (fungal invasion into hair follicle/dermis)
• Higher relapse rate
• Potential corticosteroid adverse effects
• If steroids have been used erroneously, tinea may present as tinea incognito (diminished erythema, absent scaling borders) - a diagnostic trap

Systemic (Oral) Therapy - When Indicated

• Extensive/widespread involvement
• Unresponsive to topical therapy after 2 weeks
• Majocchi granuloma (oral mandatory - topical cannot penetrate)
• Immunocompromised patients
• Involvement of hair follicles

• Terbinafine 250 mg/day for 2-4 weeks is also effective for tinea barbae, tinea faciei, tinea cruris
• Itraconazole and fluconazole lack FDA approval specifically for tinea corporis but are widely used off-label
• Griseofulvin is less preferred but remains an option especially in children

Pediatric Notes

• Topical: Clotrimazole, tolnaftate, and econazole safe at all ages
• Oral (for extensive/refractory):
  • Griseofulvin: children ≥2 years
  • Terbinafine: children ≥4 years (oral granules)
  • Fluconazole: children ≥6 months (off-label for this indication)

Diagnosis Confirmation (if in doubt)

• KOH mount of skin scrapings from the scaly edge of the lesion - look for hyphae
• Fungal culture on Sabouraud dextrose agar (2-4 weeks incubation)
• Wood lamp: Only fluoresces blue-green if Microsporum species (ectothrix); most tinea corporis in adults (Trichophyton) does NOT fluoresce

Control Measures

• Treat all dermatophyte infections at other sites concurrently
• Avoid direct contact with infected persons, animals, or fomites
• Infected pets should also receive antifungal treatment
• Athletes with tinea corporis may participate in contact sports 72 hours after starting topical therapy, and only when the affected area can be covered