Azithromycin-Ivermectin is Nonsuperior to Ivermectin Alone for Preventing Scabies, Impetigo

A combination regimen comprised of azithromycin and ivermectin is associated with similar reductions in scabies and impetigo compared with ivermectin monotherapy in communities featuring typically high rates of these infections, according to a study in Clinical Infectious Diseases.

“In many tropical countries scabies is a major cause of secondary bacterial infection,” lead study author Michael Marks, PhD, of the London School of Hygiene & Tropical Medicine, told Contagion^®. “We tried to understand if giving antibiotics alongside treating scabies reduced the prevalence of bacterial skin infections more than just treating scabies. The amount of scabies fell by about 90% in both sets of communities (those that received scabies treatment and those that received scabies treatment plus an antibiotic).”

A total of 6 communities from the Malaita province of the Solomon Islands, all of which feature high prevalence of scabies and impetigo, were included in the open-label study. To prevent contamination, the chosen communities were isolated from each other. Investigators randomized community residents to receive either 200 μg/kg ivermectin monotherapy (n = 717) or a combined-treatment regimen consisting of 30 mg/kg azithromycin plus 200 μg/kg ivermectin (n = 705). Assessments were performed at baseline, 3 months, and 12 months. In addition to determining the superiority of the combined treatment over ivermectin monotherapy, the investigators also monitored each community for antibiotic resistance.

The scabies prevalence rates at baseline in the ivermectin-only and combined treatment arms were 11.8% (95% CI 9.4%-14.6%) and 9.2% (95% CI 7.1-11.7%), respectively. Additionally, the prevalence rates of active impetigo at baseline were 10.1% (95% CI 8.1%-13.0%) in the ivermectin monotherapy arm and 12.1% (95% CI 9.7%-14.9%) in the combination therapy group.

Scabies prevalence at 12-month follow-up was similar in the ivermectin-only (1.0%; 95% CI 0.3%-2.6%) and combination therapy arms (2.5%; 95% CI 1.4%-4.5). Scabies was slightly higher in the combination-treatment arm (3.3%; 95% CI 2.1%-5.1%) compared with the monotherapy arm (0.7%; 95% CI 0.2%-1.8%) at 12 months. No significant differences were observed between the groups in regard to the change in scabies (91.5% vs 92.4%; P =.31) or impetigo (75.2% vs 72.7%; P =.49) prevalence at 12 months.

At each time point, there was no evidence of macrolide resistance among streptococci in either treatment group. Although 1 Staphylococcus aureus isolate was macrolide-resistant in the combination treatment arm at baseline and 8 S. aureus isolates were resistant at 3 months, there was no resistance detected in any of the isolates tested at 12-month follow-up.

“In a subset of patients, we found a temporary increase in antibiotic resistance amongst people treated with antibiotics as well as the scabies drug, but this went away by 12 months,” Dr Marks added. “Overall, we found no additional benefit from giving antibiotics at the same time as community treatment of scabies in terms of reducing secondary bacterial infections.”

Limitations of the analysis include its unblinded design as well as the variation in follow-up rates between each arm. Also, the study did not identify the safety of ivermectin and azithromycin coadministration.