Couple of points here…
1. Our HR Director here at work is a good friend of mine and has advised me in these matters in the past. At the end of the day, HR will weigh one thing, can you sue? Their job is supposed to be to advocate for the employee, but in most cases they will just figure out if something is violating your rights or the law and if it is borderline or not in direct violation, they will side with the company. If laws are being broken, they will side with the employee. In your case, so many laws are being broken that with careful documentation, you could probably get a large out of court settlement.
2. Blackmail is illegal. So is giving someone your prescription meds. Also, in most states, giving someone a substance they are unaware of, such as a laxative, is a felony and is considered poisoning. Don’t mess around with any of this any longer. You might go directly to the district attorney, explain what has been going on and see if they want to investigate.
At the end of the day, you need to make a strong case to HR, sue or get a different job. The situation you are in is unhealthy to say the least and is probably holding you back from leading a more fulfilled life! I am truly sorry you have to go through this, ignorant people suck.REPORT ABUSE