This paper describes that the previous addition of Verapamil does not block the spastic response to Praziquantel (Pz) in larvae of Taenia pisiformis kept in vitro, where opposite results were found in the literature using mammalian tissue. It is possible that Pz stimulates other Ca++ transport channels not sensitive to Verapamil action and promotes Ca++ liberation from calcareous corpuscles stimulating phospholipase C of the tegument surface generating inositol triphosphate. These hypotheses require experimental approaches to define the exact mechanism of action.