- Oestrogen vaginal cream
- Olanzapine
- Olodaterol + tiotropium
- Olsalazine
- Omega-3 and fish oil supplements
- Omeprazole
- Omezol Relief
- Onbrez®
- Ondansetron
- Onrex®
- Opioid medicines – lowering my dose
- Opioid medicines overview
- Opioid overdose
- Opioid topics
- Opioids in palliative care
- Oral rehydration salts
- Oral rehydration solution
- Oratane®
- Orlistat
- Orphenadrine
- Oseltamivir
- Otrivin®
- Ovestin®
- Oxazepam
- Oxis turbuhaler
- Oxybutynin
- Oxycodone