Thought I'd do a quick google search on isoxazolines and found this interesting web page: http://parasitipedia.net/index.php?option=com_content&view=article&id=2668&Itemid=2951
Isoxazolines are "non-competitive GABA (gamma-aminobutyric acid)receptor antagonists, much more selective for GABA receptors in insects or ticks, than for those in mammals, including humans. They bind to chloride channels in nerve and muscle cells, which blocks the transmission of neuronal signals."
There are some names of veterinary drugs that might be worth chasing up too...
