Someone at work is stealing my medecine what can i do?

I stopped bringing it in, but my bag still got rifled through. I told my boss but he has done NOTHING. I feel really uncomfortable working someplace where someone felt it was okay to go through my bag and steal from me. What can I do? Is my boss obliged to do anything? What happens if I file a police report? Are there any measures I can take through OSHA?