I assume that it is possible that whatever substances they are using to dose are different enough from their testable counterparts so as to not show up on a toxicology report (or that the report will be otherwise compromised, nearly every healthcare professional I have spoken with has indicated being coopted)
Disambiguation Radioactive Dose
Real effects from subjective experience, priming, and allusions after the fact
Thickener added to eyedrops
Laxative
Stress hormone
Antibiotic
Diuretics
Deja vu? Brain to computer interface
Implied through allusions, intimating
Poison
THC
Neurotoxin
Nightshade
Cocaine
LSD
Melatonin