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Impetigo - Prescription Guide

Causative Organisms

• Nonbullous (most common): Streptococcus pyogenes (Group A Strep) and/or Staphylococcus aureus
• Bullous: S. aureus exclusively (exfoliative toxin A)

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Step 1: Is it Localized or Widespread?

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Topical Therapy (Localized, Few Lesions)

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Oral (Systemic) Therapy - Widespread or Bullous Impetigo

Presumed/Unknown Etiology (cover both staph + strep)

Confirmed GAS (S. pyogenes) Impetigo

Penicillin/Beta-Lactam Allergy

Bullous Impetigo

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If MRSA Suspected

• Consider trimethoprim-sulfamethoxazole (TMP-SMX) or clindamycin (if susceptible)
• Vancomycin IV for severe/failing cases
• Most impetigo is MSSA; MRSA is less common but should be considered in treatment failures

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Key Clinical Notes

• Fever is NOT a feature of impetigo - if present, suspect deeper tissue infection (cellulitis, SSTI) or an alternative diagnosis
• Topical therapy is preferred for limited lesions to reduce antibiotic resistance
• Impetigo resolves in 3-6 weeks even without treatment, but antibiotics shorten course and reduce spread
• Treatment does NOT reduce the risk of post-streptococcal acute glomerulonephritis (AGN) - a serious but unpredictable complication
• Nasal carriers of S. aureus are at elevated risk - consider mupirocin nasal decolonization in recurrent cases

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Fungal Infection vs. Eczema - Key Differences

Quick Comparison Table

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The Critical Danger: Tinea Incognito

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How to Confirm the Diagnosis

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Treatment

Fungal Infection (Tinea Corporis)

• Topical (localized):
  • Terbinafine 1% cream - once daily x 7 days (most effective, SOR: A)
  • Clotrimazole or miconazole - twice daily x 2-4 weeks
  • Ketoconazole 2% cream - daily x 2-4 weeks
• Oral (widespread or resistant):
  • Terbinafine 250 mg once daily x 2 weeks (superior to griseofulvin)
  • Itraconazole 100-200 mg daily x 2 weeks
  • Griseofulvin 500 mg daily x 4-6 weeks
• Important: Apply to lesion AND 2 cm of surrounding normal skin

Eczema (Atopic Dermatitis)

• Topical corticosteroids - mainstay of treatment (high-potency for flares)
• Emollients/moisturizers - applied liberally, multiple times daily
• Antihistamines (hydroxyzine) - for itch relief
• Topical calcineurin inhibitors - tacrolimus or pimecrolimus (steroid-sparing)
• Avoid triggers - soaps, wool, sweat, stress, allergens
• No systemic steroids routinely - high relapse rate when stopped
• Biologics (dupilumab) for severe refractory cases

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Quick Clinical Clue

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Eczema (Atopic Dermatitis) - Prescription Guide

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Step 1: Skin Care Basics (All Patients - Every Day)

• Moisturizers/Emollients - apply liberally, multiple times daily, especially within 3 minutes of bathing ("soak and smear")
  • Ointments preferred (e.g., white petrolatum, Vaseline) - best barrier, no preservatives
  • Creams acceptable (e.g., Cetaphil, CeraVe)
• Bathing: Lukewarm (not hot) water; gentle fragrance-free soap
• Bleach baths (for recurrent infections): 1/4 cup of household bleach (5-6%) in a full bathtub (20 gallons) - twice weekly; dramatically reduces S. aureus colonization
• Avoid triggers: Wool clothing, sweating, overheating, fragranced products, known allergens

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Step 2: Topical Anti-Inflammatory Therapy (Mild - Moderate Disease)

A. Topical Corticosteroids (First-Line)

• Ointments preferred over creams (also act as emollient, less allergy risk)
• Once-daily application is as effective as more frequent applications in most sites
• Use stronger steroid in short bursts to gain control, then step down
• Maintenance: Apply to commonly flaring areas twice weekly (proactive therapy)
• Do NOT use high-potency steroids on face, groin, axillae long-term

B. Topical Calcineurin Inhibitors (TCIs) - Steroid-Sparing

• No risk of skin atrophy or striae - safe for face and folds long-term
• May cause burning/stinging on first application - warn patients
• Systemic absorption is not significant

C. Topical PDE4 Inhibitor

• Safe on face and skinfolds
• May sting on application
• Best for maintenance or mild-moderate disease

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Step 3: Antipruritic Therapy (Itch Control)

• Apply ice to "break" acute itch paroxysms
• Moisturizers with menthol, phenol, or pramoxine help reduce localized itch between steroid applications

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Step 4: Phototherapy (Moderate-Severe, Topical Therapy Insufficient)

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Step 5: Systemic Therapy (Severe/Refractory Disease)

Biologic (Preferred systemic agent)

Conventional Immunosuppressants

Systemic Corticosteroids

• Avoid routine use - rebound flare when stopped is common and can be severe
• If needed: short courses ≤3 weeks only
• If repeated courses needed, escalate to phototherapy or steroid-sparing systemic agent

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Treating Secondary Infection (S. aureus)

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Treatment Ladder Summary

Step 1: Emollients + skin care + trigger avoidance (ALL patients)
Step 2: Low-potency topical steroid or TCI (mild)
Step 3: Medium-high potency topical steroid (moderate)
Step 4: Phototherapy (NB-UVB) (moderate-severe)
Step 5: Dupilumab or cyclosporine/methotrexate (severe/refractory)

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2024 AAAAI/ACAAI Guidelines (PMID: 38108679) and a network meta-analysis on systemic treatments (PMID: 37678577) confirm dupilumab as the preferred systemic agent with the best efficacy-safety profile for moderate-severe AD.