Is opioid induced constipation readily treatable in the majority of patients using OTC laxatives?
In many patients, OIC can be treated with OTC stimulant laxatives, with or without emollient laxatives (stool softeners). OIC is caused when opioid agonists combine with and activate mu-opioid receptors within the gastric mucosa. This results in reduced peristalsis, decreased fluid resorption, increased fluid absorption, and decreased rectal sphincter tone. Therefore, emollients such as docusate which does not promote peristalsis, will not generally be effective as single agents—in layman’s terms, “mush with no push.” Therefore, a stimulant laxative will be the most likely OTC agent to successfully treat OIC.
OIC does not resolve in up to 54% of patients treated with OTC agents. Peripherally acting mu-opioid receptor antagonist (PAMORA) provides targeted relief that pharmacologically is specific to the pathology of OIC. These drugs block the intestinal mu receptors from mu-agonists, but do not cross into the central nervous system (CNS) and therefore do not detract from the analgesic effects of opioids. The first PAMORA approved for OIC in the United States was subcutaneous methylnaltrexone (Relistor) in 2008, intended for palliative care patients; however, in 2014 naloxegol (Movantik) was approved for OIC in the noncancer patient requiring chronic opioid therapy.