levamisole (pour-on, injectable, and oral formulations) is highly effective against the common adult Gl nematodes and lungworms and many larval stages. It lacks efficacy against arrested larvae, such as those of Ostertagia ostertagi. Levamisole slow- release boluses are available in some countries and contain 22.05 mg levamisole. They release 2.5 mg during the first 24 hr and the remainder over a 60-day period.