Opioids should never be prescribed without laxative/stool softener
Little to no tolerance to constipation develops
Uncertain relationship between opioid dose and amount of laxatives needed
Fentanyl and methadone may cause less constipation than morphine
Methylnaltrexone given by subcutaneous injection and FDA approved for opioid-induced constipation in patients with advanced illness receiving palliative care after failing laxative therapy.