O
- O-AMKD
- O-Desmethyl Tramadol
- O-Desmethyl Venlafaxine
- O-desmethyl-etonitazene
- o-MDCK
- Ocfentanil
- Octodrine
- Octyl-CP
- Ofloxacin
- Ohmefentanyl
- Olanzapine
- Olanzapine, N-desmethyl
- Olanzepine-M (2-Hydroxymethyl metabolite)
- Oleandrin
- Olopatadine
- Omeprazole
- Omethoate
- Ondansetron
- Ondansteron-M (7-hydroxy)
- Ondansteron-M (8-hydroxy)
- Opipramol
- Orbencarb
- ORG 27569
- Org 27759
- ORG 28611
- Org 29647
- Oripavine
- Orlistat
- Orphenadrine
- Orphenadrine-Nor (Tofenacin. Elamol)
- ortho-Fluoro Acryl Fentanyl
- ortho-fluoro acrylfentanyl
- ortho-Fluoro Butyryl Fentanyl
- ortho-Fluoro Isobutyryl Fentanyl
- ortho-Fluoro Valeryl Fentanyl
- ortho-fluorobutyryl fentanyl
- ortho-Fluorofentanyl
- ortho-Fluorofuranylfentanyl
- ortho-fluoroisobutyryl fentanyl
- ortho-Isopropyl Furanyl Fentanyl
- ortho-Methoxy Butyryl Fentanyl
- ortho-Methoxy Furanyl Fentanyl
- ortho-Methyl Acetyl Fentanyl
- ortho-Methyl Acryl Fentanyl
- ortho-Methyl Cyclopropyl Fentanyl
- ortho-Methyl Fentanyl
- ortho-Methyl Furanyl Fentanyl
- ortho-Methyl Phenyl Fentanyl
- ortho-Methylmethoxyacetylfentanyl
- Oseltamivir
- Ostarine
- Ouabain
- Oxandrolone
- Oxandrolone-M (17-Epi metabolite)
- Oxazepam
- Oxazepam, glucuronide
- Oxazolam
- Oxcarbazepine
- Oxiracetam
- Oxomemazine
- Oxprenolol
- Oxybutynin
- Oxycodone
- Oxycodone, Nor
- Oxydemeton-Methyl
- Oxymesterone
- Oxymetazoline
- Oxymetholone
- Oxymorphone