| O | ||
| Octreotide Acetate | Sandostatin | |
| Ofloxacin | Floxin, Ocuflox | |
| Olsalazine Sodium | Dipentum | |
| Omeprazole | Prilosec | |
| Ondansetron HCI | Zofran | |
| Opium Tincture, Camphorated | Paregoric | |
| Orphenadrine Citrate | Norflex | |
| Orphenadrine Citrate, ASA & Caffeine | Norgesic | |
| Oxacillin Sodium | Prostaphlin, Bactocill | |
| Oxamniquine | Vansil | |
| Oxaprozin | DayPro | |
| Oxazepam | Serax | |
| Oxtriphyline | Choledyl | |
| Oxybutynin Chloride | Ditropan | |
| Oxycodone HCI & Acetaminophen | Percocet, Roxicet | |
| Oxycodone HCI, Acetaminophen & Sodium | ||
| Metabisulfite | Tylox | |
| Oxycodone HCI & Aspirin | Percodan | |
| Oxymetazoline HCI (Nasal) | Afrin, Allerest, | |
| Dristan Long Lasting, | Duration, Sinex Long Acting | |
| Oxymetholone | Anadrol 50 | |
| Oxymorphone HCI | Numorphan | |
| Oxyphencyclimine HCI | Daricon | |
| Oxytetracycline HCI | Terramycin, Uri-Tet | |
| Oxytocin | Pitocin, Syntocinon |