Prime
- o,p'-DDD
- Obi-Nix
- OBY-CAP
- Occlucort
- OCL
- Octamide
- Octicair Otic Suspension
- Octocaine
- Octostim
- octreotide
- ofloxacin
- Ogen
- olanzapine
- Oleum anethi
- olmesartan
- olsalazine
- omalizumab
- omeprazole
- Omnicef
- Omnipen
- Oncaspar
- Oncet
- Oncovin
- ondansetron
- Ontak
- Onxol
- Opcon-A Ophthalmic Solution
- oprelvekin
- Optimine
- Optimoist
- Orabase Gel
- Orabase-HCA
- Oracit
- Orajel Liquid
- Orajel Mouth-Aid
- Oramorph SR
- orange root
- Orap
- Oraphen-PD
- OrapredPediapred
- Orasone
- Orazinc
- Orbenin
- Oretic
- Orfro
- Organidin NR
- Orinase
- orlistat
- Ornex
- Ornex No Drowsiness
- orphenadrine
- Orphenate
- Orphengesic
- Orphengesic forte
- Ortho/CS
- Ortho-cept
- Orthoclone OKT3
- Ortho-cyclen
- Ortho Dienestrol
- Ortho-Est
- Ortho Evra
- Ortho Micronor
- Ortho-Novum
- Ortho-Prefest
- Ortho Tri-Cyclen
- Orudis
- Oruvail
- Os-Cal
- oseltamivir
- Osmitrol
- Osmoglyn
- Osteocalcin
- Ostoforte
- Otocort Otic Suspension
- Ovcon
- Ovcon-50
- Ovide
- Ovol
- Ovol-40
- Ovral
- Ovrette
- oxacillin
- oxaliplatin
- oxaprozin
- oxazepam
- oxcarbazepine
- oxiconazole
- Oxistat
- oxybutynin
- Oxycocet
- Oxycodan
- oxycodone
- oxycodone/acetaminophen
- oxycodone/aspirin
- Oxycontin
- OxyFAST
- OxyIR
- oxymorphone
- oxytocin
- Oxytrol
- Oysco
- Oyst-Cal
- Oystercal