Medication Summary
Topical antibiotics, systemic antibiotics, or a combination of both is effective therapy for impetigo. Empiric bacterial coverage is aimed at eradicating Staphylococcus aureus and group A beta-hemolytic streptococci (GABHS; also known as Streptococcus pyogenes). Antihistamines may be prescribed for symptomatic relief in patients with pruritus.
Mupirocin applied topically has been shown to be effective for localized impetigo, but resistance has emerged. Retapamulin is a newer option. [50, 65] Bacitracin is no longer recommended, as it is not as efficacious and causes frequent allergic skin reactions and occasional-to-rare anaphylaxis. [55]
The advantages of topical antibiotics include the following [55, 66] :
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Low risk of systemic adverse events and drug interactions
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Higher concentration of the antibiotic when applied to the affected area
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Smaller amount of drug is used
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Lack of effect on intestinal florae
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Low cost
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Ease of administration to young children
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Preferred by patients and their parents over oral treatment
The disadvantages of topical antibiotics include the following [55] :
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Potential production of irritant and allergic contact dermatitis
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Decreased penetration in the affected area
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Potential rapid appearance of bacterial resistance
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Potential alteration of cutaneous flora
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Potential systemic absorption and consequent toxic effects
Systemic antibiotic treatment is indicated for widespread infections, complicated infections, or those associated with systemic manifestations. A cephalosporin, semisynthetic penicillin, or beta-lactam/beta-lactamase inhibitor combination is generally suitable for first-line therapy.
Methicillin-resistant Staphylococcus aureus (MRSA) should be suspected in cases of spontaneous abscess or cellulitis and in lesions that do not resolve with traditional antimicrobial therapy, in which case alternative antibiotics should be considered. These include trimethoprim-sulfamethoxazole, tetracycline, clindamycin, fluoroquinolones, and linezolid.
In areas with a high percentage of community-acquired MRSA, the empiric antibiotic choice should provide coverage for this possibility.
Topical Antimicrobials
Class Summary
Topical antibiotic treatment with mupirocin is the treatment of choice for uncomplicated localized pyoderma, although S aureus resistance to mupirocin has been increasing.
Mupirocin (Bactroban, Centany)
Mupirocin is a naturally occurring antibiotic produced by fermentation of Pseudomonas fluorescens. The mechanism of action of mupirocin is via inhibition of bacterial protein synthesis.
Retapamulin (Altabax)
Retapamulin is a topical antibiotic available as a 1% ointment. It is the first of a new antibiotic class called pleuromutilins. This agent inhibits protein synthesis by binding to the 50S subunit on the ribosome. It is indicated for impetigo caused by S aureus or Streptococcus pyogenes.
Ozenoxacin (Xepi)
Ozenoxacin, a quinolone antimicrobial drug, works by inhibiting the bacterial DNA replication enzymes, DNA gyrase A and topoisomerase IV. It has been shown to be bactericidal against S. aureus and S. pyogenes organisms.
Antibiotics, Other
Class Summary
Systemic antibiotic treatment is indicated for widespread or complicated pyoderma.
Amoxicillin and clavulanate (Augmentin)
This oral antibiotic combines the broad-spectrum antibiotic amoxicillin with the beta-lactamase inhibitor clavulanate. Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, while clavulanate inhibits beta-lactamase producing bacteria.
For children older than 3 months, dosing is based on the amoxicillin content. Because of different amoxicillin-clavulanate ratios in the 250-mg tab (250mg/125mg) versus the 250-mg chewable tab (250mg/62.5mg), do not use the 250-mg tab until the child weighs more than 40 kg.
Dicloxacillin
Dicloxacillin binds to one or more penicillin-binding proteins, which, in turn, inhibits synthesis of bacterial cell walls. It is indicated for treatment of infections caused by penicillinase-producing staphylococci. This agent may be used to initiate therapy when staphylococcal infection is suspected.
Erythromycin (E.E.S., Ery-Tab, Erythrocin)
Erythromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It is used for the treatment of staphylococcal and streptococcal infections. However, macrolide resistance in the United States has been increasing. Erythromycin is used only when other options are unavailable or contraindicated.
In children, the patient's age and weight and the severity of the infection determine the proper dosage. When twice-daily dosing is desired, a half-total daily dose may be taken every 12 hours. For more severe infections, double the dose.
Clindamycin (Cleocin)
Clindamycin is a lincosamide used for the treatment of serious skin and soft tissue staphylococcal infections. It is also effective against aerobic and anaerobic streptococci (except enterococci). It inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Trimethoprim-sulfamethoxazole (Bactrim DS, Septra DS)
Trimethoprim-sulfamethoxazole selectively inhibits bacterial dihydrofolate reductase. It has good susceptibility against community-acquired MRSA but is not effective against S pyogenes.
Levofloxacin (Levaquin)
This agent inhibits DNA gyrase and topoisomerase IV, resulting in bactericidal activity. It is used as an alternative agent for MRSA infection.
Ciprofloxacin (Cipro)
Ciprofloxacin inhibits DNA gyrase and topoisomerase IV, resulting in bactericidal activity. Use this agent as an alternative for MRSA infection.
Linezolid (Zyvox)
Linezolid binds to the 50S ribosomal subunit, interfering with protein synthesis. This agent is used for MRSA or complicated skin infections.
Antihistamines, 2nd Generation
Class Summary
If pruritus is significant, antihistamines can be prescribed to possibly help minimize scratching. Avoidance of trauma to the skin may prevent or limit the spread of impetigo by autoinoculation. These agents selectively inhibit peripheral histamine H1 receptors to histamine.
Desloratadine (Clarinex)
Desloratadine is a long-acting tricyclic histamine antagonist that is selective for the H1 receptor. It relieves nasal congestion and systemic effects of seasonal allergy. It is the major metabolite of loratadine, which, after ingestion, is metabolized extensively to the active metabolite 3-hydroxydesloratadine.
Cetirizine (Zyrtec)
Cetirizine selectively inhibits histamine H1 receptor sites in blood vessels, the GI tract, and the respiratory tract, which, in turn, inhibits physiologic effects that histamine normally induces at H1 receptor sites. Once-daily dosing is convenient. Bedtime dosing may be useful if sedation is a problem.
Loratadine (Claritin, Alavert, Loradamed, Tavist ND)
Loratadine is nonsedating and selectively inhibits peripheral histamine H1 receptors.
Antihistamines, 1st Generation
Class Summary
These agents selectively inhibit peripheral histamine H1 receptors to histamine.
Hydroxyzine (Vistaril)
Hydroxyzine antagonizes H1 receptors in the periphery. It may suppress histamine activity in the subcortical region of the CNS. It is often administered before sleep because of its sedating properties.
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Bullous impetigo with circumscribed lesions with a thin collarette of scale.
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Bullous impetigo on the buttocks. Courtesy of Medical University of South Carolina, Department of Dermatology.
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Following dermabrasion, this patient developed nonbullous impetigo in the same area as several herpes simplex lesions. Note the grouped vesicles which are classic for herpetic lesions, as well as additional crusted pink plaques. Concurrent bacterial impetigo can often be seen with herpes simplex and aerobic bacterial cultures are important to identify secondary impetigo.
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A nummular eczema lesion on the knee, impetiginized with Staphylococcus aureus.
