Potential side effects of opioids

• Constipation
• Nausea
• Vomiting
• Drowsiness
• Dizziness
• Weakness
• Dry mouth
• Confusion
• Difficulty urinating
• Itching
• Respiratory depression (slowed rate of breathing, one of the more serious concerns)

Side effects can be so intense that some patients stop taking the pain-relieving medication. But doctors can often successfully manage side effects, so it's important to discuss them. For instance, sedation side effects often diminish and nausea can be treated, says Charles Cleeland, PhD, chair of the Department of Symptom Research at University of Texas M. D. Anderson Cancer Center in Houston.