According to several systematic reviews, mupirocin was as effective as several oral antibiotics (dicloxacillin [Dynapen], cephalexin [Keflex], ampicillin). Oral antibiotics are recommended for patients who do not tolerate a topical antibiotic, and should be considered for those with more extensive or systemic disease. Basic prescribing information is summarized in Table 3 . One study comparing fusidic acid and cefuroxime found no difference in effectiveness, and both mupirocin and fusidic acid were consistently more effective than oral erythromycin. 4 , 7 Although patients with more extensive impetigo and those with systemic symptoms often are treated with oral antibiotics, there were no studies comparing oral and topical antibiotics in this subset of patients. Oral antibiotics can be used, however, based on expert opinion and traditional practice. 8 Adverse effects, particularly nausea, are more common with oral antibiotics, especially erythromycin, than with topical antibiotics. 8
In extreme cases, the infection invades a deeper layer of skin and develops into ecthyma, a deeper form of the condition. Ecthyma forms small, pus-filled ulcers with a crust much darker and thicker than that of ordinary impetigo. Ecthyma can be very itchy, and scratching the irritated area spreads the infection quickly. Left untreated, the ulcers may cause permanent scars and pigment changes. The gravest potential complication of impetigo is post-streptococcal glomerulonephritis, a severe kidney disease that occurs following a streptococcal infection in about 2% to 5% of cases, mainly in children.