- Depression of consciousness
- Depression of respiratory drive
- Hypotension
- Nausea, vomiting, constipation (or ileus)
- Drug interactions
- Tolerance
- Withdrawal
| - Hallucination and delirium
- Histamine release
- Peripheral vasodilation
- Urinary retention
- Pruritis
- Increased intracranial pressure
- Hyperalgesia
|