Methylnaltrexone is a peripherally acting mu-opioid receptor antagonist (PAMORA) used in pharmaceutical formulations for the management of opioid-induced constipation (OIC). It is a quaternary ammonium derivative of naltrexone designed to act primarily on peripheral opioid receptors while having limited penetration into the central nervous system.
Methylnaltrexone blocks opioid activity at peripheral mu-opioid receptors in the gastrointestinal tract. This helps counteract opioid-related inhibition of intestinal motility and secretion without substantially reversing centrally mediated opioid analgesia when used as directed.
Methylnaltrexone API is used in qualified pharmaceutical manufacturing, formulation development, analytical testing and research applications.
Methylnaltrexone is a mu-opioid receptor antagonist that acts predominantly in peripheral tissues. Opioids can activate peripheral mu-opioid receptors in the gastrointestinal tract and reduce intestinal motility and secretion.
By blocking these peripheral receptors, methylnaltrexone helps restore gastrointestinal motility and facilitates bowel movements in patients experiencing opioid-induced constipation.
Its quaternary ammonium structure limits its ability to cross the blood-brain barrier compared with centrally acting opioid antagonists.
Methylnaltrexone API is associated with:
The approved indication, dosage form and route of administration depend on the specific pharmaceutical product and applicable regulatory jurisdiction.
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 5.0% |
| Residue on Ignition | NMT 0.5% |
| pH (1% Solution) | 4.0–8.0 |
| Total Impurities | NMT 2.0% |
| Water Content | NMT 5.0% |