Deaths associated with ivermectin for scabies

Abstract

Robert Barkwell and Susanne Shields (April 19, p 1144)1Barkwell R Shields S Death associated with ivermectin treatment of scabies.Lancet. 1997; 349: 1144-1145Summary Full Text Full Text PDF PubMed Scopus (156) Google Scholar report that treatment of scabies with ivermectin seems associated with an increased risk of death within the first 6 months after treatment in elderly patients. This finding is worrying and will inspire further investigations into the safety of this effective2Meinking TL Taplin D Hermida JL Pardo R Kerdel FA The treatment of scabies with ivermectin.N Engl && Med. 1996; 333: 26-30Crossref Scopus (315) Google Scholar and practical therapy for scabies. This study raises some questions. The two groups of residents that were compared might differ by other factors than just the fact that one group was treated with ivermectin. How strong was the influence of selection? Residents were matched for age but not for dementia, and the severity of dementia is known to affect time to death.3Brodaty H McGilchrist C Harris L Peters KE Time until institutionalization and death in patients with dementia: role of caregivers training and risk factors.Arch Neurol. 1993; 50: 643-650Crossref PubMed Scopus (204) Google Scholar What was the effect of other factors or possible confounders-ie, distress, isolation, &c? It would also be interesting to know more about the disease specific mortality and other underlying conditions to get an idea of what could be a biological explanation for the statistically significant association. We analysed our data in a similar way to Barkwell and Shields. Between 1994 and 1996 several scabies outbreaks occurred in a psychogeriatric nursing home.4Reintjes R Oostendorp JJHM Carsauw HHC van der Lans SMGA Conyn-vanSpaendonck MAE Investigation of recurring scabies outbreaks in a nursing home.Infectieziek Bull. 1997; 8: 51-54Google Scholar All 220 residents were effectively treated with ivermectin in August, 1996. We looked at mortality over the past 3 years, comparing the 6 months after ivermectin treatment with the 30 months before. Age and medical conditions were much the same for the group of residents within this period. The Figure shows the number of deaths per 6 months. Seasonal variation with more deaths in the winter months can be seen. The winter of 1994/95 shows the largest number of deaths. By contrast with Barkwell and Shields we did not find any significant variation on statistical testing. The mortality rate in the month after treatment did not differ significantly from that before (Kruskal-Wallis test). The odds ratio was 1·33 (95% CI 0·91–1·94). Ivermectin has been used extensively and has been associated with a low frequency of side-effects.5Orkin N Scabies: what's new?.Curr Prob Dermatol. 1995; 22: 105-111PubMed Google Scholar Barkwell and Shields' conclusion that ivermectin should not be used for treatment of scabies in elderly patients is not supported by our results. Deaths associated with ivermectin for scabiesAuthors' reply Full-Text PDF