drugged SO

I just need to talk about what happened. So the 11th was my SO's birthday. It was also my friend's birthday who is homeless and crashing in our couch. We decided to celebrate both their birthdays at home. I invited our mutual friends, and my friend decided to invite some coworkers and of course people bring people, so needless to say, there were people in our house that we didn't know. A friend of mine made jungle juice with everclear and I stayed sober. Towards the end of the night I check on my SO and he's acting weird. He is wobbly and furious saying he is going to fight someone. I've been around my SO when he is drunk and this is not normal. I lure him away from the party realize how bad off he is, and tell my friend the party is over. She and the guests leave to continue the party elsewhere, I made sure there was a DD and called to see that the made it to their destination. I tend to my SO who is getting worse off. He was stringing together words that didn't make a coherent thought, vomiting profusely, and getting upset that I can't understand him. Hours of this goes on with me babysitting and eventually his words start making more sense. He tells me he doesn't feel right and this isn't normal. He feels like he is flying. I asked him if someone could've slipped him something and he says he thinks so. I ask him what he wants to do and he wants to try to wait it out. I call my friends who had been at our house to check on them and give them the heads up and they just brush everything off. They keep saying, "Oh he's just drunk." The next day he would seem to get better, then have another episode of incoherent words, he would fall, his vision was going in and out of being blurry or doubled, he had a migraine for the first time ever, he would start puking again, and he was able to see colors when he is colorblind. I was able to take him to the hospital by 6pm, we had to get a babysitter. The hospital ran tests and the good thing is they came back clear, and the hospital got his migraine under control. The doctor believes someone slipped him one of the new synthetic drugs because they wouldn't show up on the tests. Now I'm not sure what to do. I personally do not want the people who were acquaintances or strangers back in my home. We have two suspects in particular. The deal is my friend is interested in one and I know she will invite him over and if I put my foot down she will get upset. She was one of the ones brushing the whole thing off. I have kids and we don't do drugs. I also suffer from mental illness and I personally am weary of putting substances in my body because it can affect me dangerously.