Constipation and bowel cleansers:


Opioid-induced constipation (OIC) in adults with chronic non-cancer pain, including chronic pain related to prior cancer or its treatment in patients who do not require frequent opioid dosage escalation. OIC in adults with advanced illness or pain caused by active cancer who require opioid dosage escalation for palliative care.

Limitations of Use:

Use for >4 months has not been studied in the advanced illness population.


Give by SC inj in upper arm, abdomen, or thigh; rotate inj sites. Chronic non-cancer pain: Discontinue all maintenance laxatives prior to initiation; may be used if suboptimal methylnaltrexone response after 3 days. Reevaluate if opioid regimen is changed. Give 12mg once daily. Advanced illness: Give once every other day as needed (max 1 dose/24hrs). <38kg or >114kg: 0.15mg/kg. 38–<62kg: 8mg. 62–114kg: 12mg. Moderate or severe renal impairment (CrCl<60mL/min): reduce dose by ½ (see full labeling). Severe hepatic impairment: may consider reducing weight-based dose by ½ (non-cancer pain only). Prefilled syringes: use only for 8mg or 12mg fixed doses.


Not established.


Known or suspected GI obstruction and at increased risk of recurrent obstruction.


Discontinue if concurrent opioid pain medication is also discontinued. GI perforation; monitor for severe, persistent, or worsening abdominal pain; discontinue if occurs. Discontinue if severe or persistent diarrhea occurs. Increased risk of opioid withdrawal and/or reduced analgesia in those with blood-brain barrier disruptions; monitor for symptoms. Bowel movement may occur within 30 mins of dosing. Elderly. Pregnancy. Nursing mothers: not recommended.

See Also:

Pharmacologic Class:

Opioid antagonist (peripheral).


Potential additive effects and increased risk of opioid withdrawal with concomitant other opioid antagonists; avoid.

Adverse Reactions:

Abdominal pain, flatulence, nausea, dizziness, diarrhea, headache, abdominal distention, vomiting, hyperhidrosis, anxiety, muscle spasms, rhinorrhea, chills, tremor, hot flush; GI perforation, opioid withdrawal.

Generic Availability:


How Supplied:

Tabs—60, 90; Single-use vial (12mg/0.6mL)—1; Prefilled syringes (8mg/0.4mL)—7; Prefilled syringes (12mg/0.6mL)—1, 7