Topical avermectin formulations and methods for elimination and prophylaxis of susceptible and treatment resistant strains of head lice

A method for treatment or prophylaxis of a lice infestation, the method comprising:

• (a) applying a unit dose of between about 1 mL and about 100 mL of a topical pediculicidal shampoo-conditioner formulation to a human scalp infested with lice;
• wherein the formulation comprises:
• about 0.1% to about 2.0% by weight ivermectin;
• at least one suspending agent;
• a nonionic surfactant selected from the group consisting of sorbitan tristerate, erucyl alcohol, ricinolyl alcohol, arachidyl alcohol, capryl alcohol, capric alcohol, behenyl alcohol, lauryl alcohol, myristyl alcohol, palmitoleyl alcohol, linoleyl alcohol, elaidyl alcohol, elaidolinoleyl alcohol, glycerine, polydextrose, quillaia, and combinations thereof;
• ivermectin solubilizers consisting of polysorbate 80, cetyl acetate and acetylated lanolin alcohol;
• a conditioner;
• and
• water, wherein the formulation does not include glycols,
• (b) maintaining the topical pediculicidal formulation on the scalp for about 1 to about 60 minutes to provide treated lice;
• and
• (c) removing the pediculicidal formulation from the scalp,
• wherein the treated lice have a faster mortality response than lice treated with 0.5% ivermectin in a solution consisting of deionized water.