Morphine-6-glucuronide (M6G)

Morphine-6-glucuronide (M6G) is a major active metabolite of morphine formed in the liver through glucuronidation primarily by the enzyme UGT2B7[1][4]. M6G is responsible for significant analgesic effects that are comparable or slightly less than morphine itself[1][2]. Unlike proteins such as receptors, enzymes, or transporters, M6G is not a biological target but rather a drug metabolite that itself exerts pharmacological actions primarily through agonism of the mu-opioid receptor (MOR)[3][5]. Its clinical relevance is most pronounced in the context of morphine metabolism, especially in patients with renal dysfunction where M6G can accumulate and cause toxicity, including respiratory depression[1]. Context and Rationale: Morphine-6-glucuronide is not a receptor, enzyme, transporter, or conventional therapeutic target; it is a small-molecule metabolite of morphine that acts on the mu-opioid receptor, which is the actual pharmacological target[3][5]. Therefore, "6-glucuronide morphine" as a target is incorrect—rather, it is a substrate/drug/ligand, not a molecular target for drugs in the usual sense described by this schema. The proper target to consider for drug interaction or mechanism would be the "Mu-type opioid receptor" (also known as OPRM1)[3].

Other names

Morphine 6-glucuronideMorphine-6-glucuronideM6GMorphine 6-beta-D-glucopyranosiduronideMorphine glucuronide