Final answer:
Rocuronium is the aminosteroid without significant active metabolites, used in muscle relaxation during surgery. Avermectins are the drug class that specifically inhibits neuronal transmission in helminths.
Step-by-step explanation:
The only aminosteroid that does not have significant active metabolites is Rocuronium (Option B). Aminosteroids such as Vecuronium, Pancuronium, and Rocuronium are neuromuscular blocking agents used primarily to produce muscle relaxation during surgery. Rocuronium is unique among these because it is designed to have a rapid onset and does not produce significant metabolites, unlike Vecuronium and Pancuronium which do have active metabolites.
In addressing the secondary question regarding the inhibition of neuronal transmission in helminths, the correct class of drugs is Avermectins (Option B). Avermectins, which include drugs such as ivermectin, are used specifically for this purpose in a variety of parasitic infections caused by helminths. They are known for their ability to enhance the release of gamma-aminobutyric acid (GABA), which subsequently results in the paralysis and eventual death of the helminthe.