| Octotiamine |
| Ofloxacin |
| Olprinone Hydrochloride |
| Omeprazole |
| Ondansetron Hydrochloride |
| Orciprenaline Sulfate* |
| Ornoprostil |
| Osalmid |
| Otastat Potassium |
| Oxapium Iodide* |
| Oxaprozin* |
| Oxatomide |
| Oxazepam |
| Oxazolam* |
| Oxeladin citrate |
| Oxendolone |
| Oxethazaine* |
| Oxiconazole Nitrate |
| Oxiglutatione |
| Oxitropium Bromide |
| trans-p-Oxocamphor |
| Oxprenolol Hydrochloride* |
| Oxybuprocaine Hydrochloride* |
| Oxybutynin Hydrochloride |
| Oxycodone Hydrochloride* |
| Oxydol* |
| Oxymetazoline Hydrochloride |
| Oxymetebanol |
| Oxymetholone* |
| Oxypertine |
| Oxytetracycline Hydrochloride* |
| Oxytetracycline |
| Ozagrel Hydrochloride |
| Ozagrel Sodium |