There is evidence from randomized controlled trials (RCTs) that topical fusidic acid and mupirocin are effective in the treatment of localized non-bullous impetigo. Their use in extensive impetigo may be limited by practical issues. There is evidence that a newer topical antibiotic, retapamulin, is as effective as fusidic acid.

• A Cochrane systematic review (search date: March 2002) identified 57 RCTs (n = 3533) that investigated a variety of interventions in the treatment of impetigo [Koning et al, 2003]. The primary outcome of these studies was clinical cure or improvement at 1 week, as assessed by the investigator.
• The main results were:
• A meta-analysis of five placebo-controlled trials in people with non-bullous impetigo found that, overall, topical antibiotics resulted in better cure rates than placebo (odds ratio [OR] 6.49, 95% CI 3.93 to 10.73). Three trials found mupirocin to be more effective than placebo (OR 5.40, 95% CI 2.79 to 10.45), and one trial found fusidic acid to be more effective than placebo (OR 8.65, 95% CI 3.88 to 19.29).
• Twelve RCTs compared different topical antibiotics with each other in people with non-bullous impetigo; no significant differences were found.
• A meta-analysis of 10 RCTs found mupirocin to be more effective than oral erythromycin (OR 1.76, 95% CI 1.05 to 2.97) in people with non-bullous impetigo. Topical fusidic acid was also found to be superior to erythromycin in one trial.
• One RCT in people with bullous impetigo found no significant difference (OR 3.57, 95% CI 0.53 to 23.95) between topical fusidic acid and oral erythromycin.
• The authors concluded that topical fusidic acid or mupirocin are superior to oral antibiotics in the treatment of limited impetigo.
• Another systematic review (search date: August 2002) identified 16 RCTs that met its inclusion criteria; trials that excluded people on the basis of results from skin swabs were not included in the review [George and Rubin, 2003].
• Meta-analysis showed that topical antibiotics were more effective than placebo (OR 2.69, 95% CI 1.49 to 4.86) and were superior to oral erythromycin (OR 0.48, 95% CI 0.23 to 1.00).
• On the basis of the available evidence, the authors recommended the use of a topical antibiotic for 7 days for people with limited impetigo.
• Topical retapamulin is a newer topical antibiotic, developed and licensed since the above systematic reviews [DTB, 2008].
• A placebo-controlled trial (n = 213) found a superior clinical response in people with non-bullous impetigo who received retapamulin compared with vehicle alone (85% compared with 52%, p < 0.0001) [Koning et al, 2008].
• An RCT (n = 519), powered to show non-inferiority of the interventions, compared the effectiveness of treatment with retapamulin for 5 days or fusidic acid for 7 days [Oranje et al, 2007].
• In those people completing the trial as per protocol, there was a clinical response of 99.1% with retapamulin compared with 94.0% for fusidic acid. This indicated a significant benefit for retapamulin (difference 5.1 percentage points, 95% CI 1.1 to 9.0, p = 0.003).
• However, using intent-to-treat analysis, there was no significant difference between the treatments: clinical response 94.8% with retapamulin compared with 90.1% with fusidic acid (difference 4.7 percentage points, 95% CI –0.4 to +9.7, p = 0.062).