There are basically two classes of dewormers.
One class is the benzimidazoles, which are white liquids or pastes that are administered orally. These dewormers are brands such as Albandazole, Fenbendazole, and Oxfendazole. They kill nearly 100% of adult worms but only about 20 to 95% of arrested larvae and have no residual killing power. This means that if benzimidazoles are used, you cannot deworm until the end of June to ensure that the transmission of gastrointestinal parasites has stopped.
The other type of dewormer is the macrocyclic lactones. These are administered by injection or as a pour-on. The brands that are macrocyclic are Doramecin, Eprinomectin, Ivermectin, and Moxidactin. These also kill 100% of adult worms, but they also kill nearly 100% of the arrested larvae and have a variable number of days of residual killing power. This residual power allows you to deworm earlier in the spring so as not to cause additional stress of deworming in the hotter months.
