Age-related changes in blood-brain barrier permeability may cause methylnaltrexone's (peripherally acting µ-opioid receptor antagonist) restricted diffusion and modify opioid-induced central pain-relieving consequences. As per the results of this study, there is no affect of age on the safety and effectiveness of methylnaltrexone for opioid-induced constipation (OIC).

To study if the opioid analgesia is impaired in older population who were given methylnaltrexone for the management of OIC.

Total of 1627 patients (<65 years and ≥65 years) diagnosed with OIC who used opioids for pain relief and who had terminal illness or chronic nonmalignant pain were included. Pain intensity scores, symptoms of opioid withdrawal, adverse events linked with therapy, and rescue-free laxation (RFL) in 4 hours of therapy were the study endpoints.

All in all, 1323 patients were aged < 65 years in which 908 patients were in methylnaltrexone and 415 on placebo. In the same way, 304 patients were aged ≥ 65 years which 171 patients on methylnaltrexone and 133 patients on placebo.

All the groups had nonsignificant pain intensity score decreases. No statistical significant differences were found from starting point of the study in methylnaltrexone or placebo groups, in the older patients. Pain in the abdomen, flatulence, and nausea were commonly described adverse events linked with therapy. Irrespective of age, the adverse events associated with opioid withdrawal waned with the second dose than the first dose and were similar with placebo. The RFL response in 4 hours of methylnaltrexone usage increased significantly in both age groups relative to the placebo.

The use of Methylnaltrexone did not adversely affect opioid withdrawal effects, pain control , or adverse events while offering effective RFL, irrespective of age.