Objective: To evaluate the pediculicidal and ovicidal activity of 5 head lice products.
Design: In vitro pediculicidal and ovicidal product comparison.
Setting: Tropical field station in Panama.
Participants: Head lice and eggs were harvested from healthy children infested with Pediculus capitis.
Intervention: Within 2 hours of capture, lice were placed in continuous, direct contact with the pediculicide products and observed at regular intervals. Fresh, viable eggs were immersed in the pediculicides for 10 minutes, rinsed, air-dried, and incubated for 2 weeks.
Main outcome measures: Percentage of lice dead at regular observation intervals between 5 minutes and 3 hours of continuous exposure to the pediculicide and percentage of eggs not hatched after 2 weeks.
Results: All lice treated with Ovide lotion (0.5% malathion) were dead within 10 minutes and none of the eggs hatched. There was no significant change in the effectiveness of 0.5% malathion lotion or A-200 shampoo compared with the results of an earlier study (1986). There were significant declines in the pediculicidal activity of RID and the ovicidal activity of lindane. Nix (1% permethrin), which was not on the market at the time of the original study, killed lice in less than 30 minutes, and ovicidal activity ranged from 73% to 90% (diluted and undiluted, respectively).
Conclusions: Ovide lotion (0.5% malathion) was the fastest-killing pediculicide and the most effective ovicide. One percent lindane shampoo was the slowest-acting pediculicide and least effective ovicide. Nix was highly effective in both undiluted and diluted forms.