List of Medicines K | List of Medicines L | List of Medicines M | List of Medicines N |
| Octreotide | Octreotide is an octapeptide that mimics natural somatostatin pharmacologically, though it is a more potent inhibitor of growth | 
| Ofloxacin | Ofloxacin is a fluoroquinolone antibiotic | 
| Olanzapine | Olanzapine is an atypical antipsychotic | 
| Omeprazole | Omeprazole is a proton pump inhibitor used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome | 
| Ondansetron | Ondansetron is a serotonin 5-HT3 receptor antagonist used mainly as an antiemetic | 
| Orciprenaline | Orciprenaline is a bronchodilator | 
| Orlistat | It is a drug designed to treat obesity | 
| Ormeloxifene | Ormeloxifene is one of the selective estrogen receptor modulators, or SERMs | 
| Ornidazole | Ornidazole is a drug that cures some protozoan infections | 
| Orphenadrine | Orphenadrine is an anticholinergic drug of the ethanolamine antihistamine | 
| Oxaliplatin | Oxaliplatin is a platinum-based cancer chemotherapy drug | 
| Oxazepam | Oxazepam is a drug which is a benzodiazepine derivative | 
| Oxcarbazepine | Oxcarbazepine is an anticonvulsant and mood stabilizing drug, used primarily in the treatment of epilepsy | 
| Oxiconazole | Oxiconazole is an antifungal agent | 
| Oxprenolol | Oxprenolol is a non-selective beta blocker with some intrinsic sympathomimetic activity | 
| Oxybutynin | Oxybutynin is an anticholinergic medication | 
| Oxyfedrine | Oxyfedrine is a vasodilator | 
| Oxymetazoline | Oxymetazoline is an adrenergic used as the hydrochloride salt as a vasoconstrictor to reduce nasal or conjunctival congestion | 
| Oxyphenonium | |
| Oxytetracycline | Oxytetracycline is a broad-spectrum tetracycline group of antibiotic | 
| Oxytocin | Oxytocin is a hormone that also acts as a neurotransmitter in the brain | 
| Ofloxacin + Tinidazole | |
| Olopatadine | Olopatadine is an antihistamine | 
| Omeprazole + Domperidone | |
| Olmesartan Medoxomil | Olmesartan medoxomil is an angiotensin II receptor antagonist used to treat high blood pressure | 
| Oseltamivir | Oseltamivir, an anti-viral drug | 
| Oxycodone | Oxycodone, a narcotic analgesic | 
| Omega-3 triglycerides | Omega-3 triglycerides are one of the ethyl esters of polyunsaturated fatty acids is used to treat or reduce circulatory levels of triglycerides | 
| Ofloxacin + Ornidazole | Ofloxacin + Ornidazole, a combined formulation of antibiotics, are prescribed for the treatment of peridonitis, diarrhoea, dysentery, gingivitis and pelvic inflammatory disease. | 
| Omega-3 fatty acid | Omega-3 fatty acid is indicated for the treatment of omega-3 fatty acid deficiency associated with cardiovascular disorders and hypertriglyceridemia | 
| Oxatomide | Oxatomide, a piperazine derivative, is indicated as a systemic anti-histaminic drug to treat allergies | 
List of Medicines K | List of Medicines L | List of Medicines M | List of Medicines N |