I'm so sorry you have neighbors who are wicked and would give your dogs drugs. I don't think it will hurt him since he ingested it only once, but I bet he was so scared, poor thing! Is there any way to keep your dogs on only one side of your yard for now? Maybe if the neighbors don't interact with them for a while and don't see them or tease them, they will forget about the dogs and move onto something else. If they are taking drugs like ecstacy, they may be irrational while they are high and continue to do stupid and irresponsible things - they may harm your dogs worse next time.

I've had bad neighbors too and found that no matter how angry I get or how much I try to do to change THEM, I have had to alter my own habits or change the way I did things for a while to smooth things out and make my own life liveable. The only exception to that was a problem that I had with noise all day and all night so I just called the police over and over again. Those people finally moved. If you see them teasing your dogs or damaging your property, can you video it for proof? Or maybe call the police while you see them doing it? Don't even say anything to the neighbors, just call the cops to get them caught in the act.

I hope you work something out that will keep yourself and your dogs safe!!