For patients on opioids who have or are at risk for constipation, the preferred regimen is two senna tabs qhs.
For patients on opiods who are severely constipated and may require manual disimpaction: subcutaneous methylnaltrexone 8-12 mg (.15 mg/kg) depending on weight.
Based on a conversation with Arthur Lipman, a pharmacist at the University of Utah who has particular expertise in constipation.