What to expect
Side effects
Constipation, nausea, and drowsiness are common. Slowed breathing is the effect that can kill.
Common
- Constipation — almost everyone; a stool plan should start on day one
- Nausea and vomiting
- Drowsiness, dizziness, lightheadedness
- Dry mouth
- Itching, flushing
- Urinary retention
- Low blood pressure, especially when standing up
- Confusion, especially in older adults
Serious
- Slow or stopped breathing — the main cause of death
- Overdose, coma, cardiac arrest
- Severe drop in blood pressure
- Adrenal insufficiency after long-term use (fatigue, nausea, low blood pressure)
- Worsening of gallbladder or biliary pain (sphincter of Oddi spasm)
- Opioid-induced hyperalgesia — paradoxically more pain with long, high-dose use