REM sleep?

I only enter REM sleep after I have taken something.  I don’t know why this is but it is true.   After taking a prescription narcotic, I fell out of a chair, I thought it was the drug but it wasn’t it was because I had gone for more than 6 months without adequate sleep.   There was a shift of some sort that prevented me from accessing the state of sleep deprivation that had been created during the 6+ months that I had gone without it.