- Oaknet Healthcare
- Oaknet Life Sciences
- Obsurge
- Ochoa
- Octane
- Octavia
- Olcare
- Olcare (Cardium)
- Olcare (Evacare)
- Olcare (Excare)
- Olcare (Fusion)
- Olcare (Olski)
- Olcare (Paed Care)
- Olcare (Psycare)
- Olive
- Om Biotec
- Omega Bio
- Omenta Pharma
- Oncare
- Oncobiotek Drugs
- Oncomed
- Onika
- Ontop
- Ophtechnics
- Optho Remedies
- Optica Pharma
- Orbit
- Orchid
- Orchid (Cardiovascular)
- Orchid (Critical Care)
- Orchid (Diabetes)
- Orchid (Mano)
- Orchid (Psychiatry)
- Organic Labs
- Organon
- Orgus Health Care
- Origo Pharma
- Orion
- Oriva LS
- Orris Pharma
- Oscar Remedies
- Osmed
- Osper
- Ostrich Pharma
- Overseas
- Overseas (Medicare)
- Oxford Pharma
- Oxygen Pharma
- Oxytech
- Ozone Pharma