Background: Subcutaneous (SC) methylnaltrexone (MNTX) is approved for opioid-induced constipation (OIC) in adults with chronic noncancer pain and OIC in adults with advanced illness or with active cancer who require opioid dosage escalation for palliative care. This post hoc analysis evaluated data pooled from 3 randomized studies of patients with advanced illness and OIC.

Methods: Patients received single doses of SC MNTX 0.15 or 0.30 mg/kg or placebo (study 301); SC MNTX 0.15 mg/kg or placebo every other day for 2 weeks (study 302); or SC MNTX 8 or 12 mg in patients 38–<62 or ≥62 kg, respectively, or placebo every other day for 2 weeks (study 4000). Data were stratified by those with/without cancer. Efficacy endpoints included laxation ≤4 hours and rescue-free laxation (RFL) ≤24 hours after the first dose, time to RFL, and pain scores that were assessed using a scale of 0 to 10.

Results: Median baseline opioid use was higher in cancer (MNTX: 190 mg/d, n=198; placebo: 200 mg/d, n=157) versus noncancer patients (MNTX: 120 mg/d, n=82; placebo: 80 mg/d, n=80). MNTX significantly increased the percentage of patients with a laxation response ≤4 hours and RFL ≤24 hours after the first dose in cancer (MNTX: 61.1% and 71.2% vs placebo: 15.3% and 41.4%, respectively; P<0.0001) and noncancer patients (MNTX: 62.2% and 74.4% vs placebo 17.5% and 37.5%, respectively; P<0.0001). MNTX significantly reduced the median time to RFL at 4 hours in cancer (MNTX: 1.1 h, placebo: >4 h; P≤0.0001) and noncancer patients (MNTX: 1.1 h, placebo: >4 h; P≤0.0001). Mean changes in pain scores were similar (cancer patients, MNTX: −0.4 vs placebo: −0.2; noncancer patients, MNTX: −0.4 vs placebo: −0.4).

Conclusions: MNTX increased laxation responses and improved clinical signs of constipation in OIC patients with/without cancer.