| NSI-189 | | | 1 |
| NSI-189 phosphate | 179324-69-7 | | 1 |
| Nonivamide | 2319-84-8 | | 1 |
| Noradrenaline Bitartrate | 923288-95-3 | | 1 |
| Noradrenaline Bitartrate Monohydrate | 108341-18-0 | | 1 |
| Noradrenaline hydrochloride | | Adrenergic agents | 1 |
| Noroxycodone | 57664-96-7 | Opioid analgesics | 1 |
| Noroxycodone hydrochloride | 52446-25-0 | Opioid analgesics | 1 |
| Nutmeg flower powder | | Herbal remedies | 1 |
| Nutmeg tree seed | | Herbal remedies | 1 |
| Oak bark | | Herbal remedies | 1 |
| Obeticholic Acid | 459789-99-2 | | 1 |
| Oclacitinib maleate | 1208319-27-0 | | 1 |
| Octisalate | | | 1 |
| Octocrylene | | | 1 |
| Oflea-wort seed | | Herbal remedies | 1 |
| Olaparib intermediates | 218301-22-5 | | 1 |
| Olive tree leaf cut | | Herbal remedies | 1 |
| Olodaterol | 868049-49-4 | Adrenergic agents | 1 |
| Omadacycline | 389139-89-3 | Tetracyclines | 1 |
| Omalizumab | 242138-07-4 | Immunosuppressants | 1 |
| Omega-3 Acid Ethyl Ester 90 | 99685-96-8 | Other therapeutic nutrients/minerals/electrolyte | 1 |
| Omega-3-acid ethyl esters 60 | | Lipid-lowering agents | 1 |
| Ondansetron Compound A | 119812-29-2 | 5HT3 antagonists | 1 |
| Orange petals | | Herbal remedies | 1 |
| Orris root | | Herbal remedies | 1 |
| Orthodichlorobenzene | 95-50-1 | Disinfectants | 1 |
| Osimertinib intermediates | 142-25-6 | | 1 |
| Oteseconazole | 1340593-59-0 | Antimycotics | 1 |
| Otilonium | 105360-89-2 | Antispasmodics | 1 |
| Oxalate salt of Benzyl (2S,5R)-5-((Benzyloxy)amino)piperidine
-2-carboxylate | 1171080-45-7 | Intermediates | 1 |
| Oxerutin | 17673-25-5 | | 1 |
| Oxolamine Citrate | 83886-84-6 | Antitussives | 1 |
| Oxolinic Acid | 14698-29-4 | Quinolones | 1 |
| Oxymel of squill | | | 1 |
| Oxytetracycline Hydrochloride | 2058-46-0 | | 1 |
| Ozagrel sodium | 189224-26-8 | | 1 |
| Ozanimod | 1306760-87-1 | | 1 |
| Ozenoxacin | 245765-41-7 | | 1 |
| Ozenoxacin Intermediates | | | 1 |