Efficacy of chemical and botanical over-the-counter pediculicides available in Brazil, and off-label treatments, against head lice ex vivo

Abstract

Background:  There is a lack of reliable data on the efficacy of over-the-counter (OTC) pediculicides in Brazil.

Methods:  We performed ex vivo assays of eight marketed pediculicides: 1% permethrin (Kwell®, Clean Hair®, Keltrina®, Nedax®), 0.02% deltamethrin (Deltacid®, Pediderm®), and two “natural” products (Piolho e Lêndea®, Pilogenio®). We also tested 5% permethrin (Keltrina Plus®), traditional home remedies and an ivermectin-based product used in veterinary medicine. Head lice (49–52 per group) were immersed in the compound for 3 min and washed after 20 min to simulate the typical in vivo treatment protocol. Lice were examined for activity up to 24 h using stringent criteria for survival.

Results:  Of the permethrin containing products, highest mortality was observed with Kwell® and Clean Hair® (97.9 and 90.2% after 4 h). Keltrina®, Nedax®, Keltrina Plus®, and the two deltamethrin-based products showed only a low efficacy of <60% after 4 h. With exception of pure coconut oil (80% mortality after 4 h), home remedies showed a very low efficacy, and both marketed products killed few lice. The ivermectin-based product caused a mortality of 100% after 4 h.

Conclusions:  Most Brazilian OTC products did not show a satisfactory efficacy against head lice. Resistance may be present. Ivermectin and coconut oil are promising compounds for topical treatment. Laboratory-based tests should be used to assess resistance patterns and to identify formulations of the active ingredient that increase the efficacy. Standardized testing should be performed before a product is licensed for head lice treatment.