As the area under the curve is not significantly different with or without a meal, the drug can be taken independently of food. Once in the bloodstream, 93 to 94% of the substance is bound to plasma proteins, mainly to albumin.Naldemedine is mainly metabolized by the enzyme CYP3A4 to nor-naldemedine (which makes up about 9–13% of the circulating substance), and to a much lesser extent by UGT1A3 to naldemedine 3-glucuronide. Minor metabolites are the 6-glucuronide, the 7-(R/S)-hydroxy-derivates, and two products formed by enterobacteria through cleaving the oxadiazole ring: naldemedine carboxylic acid and benzamidine. Nor-naldemedine, the glucuronides, and the carboxylic acid are opioid receptor antagonists, but less potent than the original substance. Naldemedine and its metabolites are excreted via urine and faeces. The part of the molecule "left" of the cleavage line (the sum of original substance, nor-naldemedine, glucuronides, hydroxy-derivative, and carboxylic acid) is found to 20.4% in the urine and to 64.3% in the faeces, while the part "right" to the line (the sum of original substance, nor-naldemedine, glucuronides, hydroxy-derivative, and benzamidine) is found to 57.3% in the urine and to 34.8% in the faeces. This indicates that benzamidine is predominantly excreted in the urine and the carboxylic acid is predominantly excreted in the faeces. The terminal half-life is about 11 hours. Chemistry
Naldemedine is used in form of the tosylate, a white to light tan powder. It is not hygroscopic and has a high water solubility at a physiologic pH.
Naldemedine (brand name Symproic in the US and Rizmoic in the European Union) is a medication that is used for the treatment of opioid-induced constipation in adults with chronic non-cancer pain. It is a peripherally acting μ-opioid receptor antagonist and was developed by Shionogi. Clinical studies have found it to possess statistically significant effectiveness for these indications and to be generally well tolerated, with predominantly mild to moderate gastrointestinal side effects. Effects indicative of central opioid withdrawal or impact on the analgesic or miotic effects of co-administered opioids have only been observed in a small number of patients. Medical uses
In the US, naldemedine is approved for the treatment of opioid induced constipation in adults with chronic non-cancer pain, including those who have chronic pain related to prior cancer or its treatment and do not need frequent opioid dosage escalation.In the European Union, naldemedine is also approved for the treatment of opioid induced constipation in adults, but as a second-line therapy after treatment with a laxative. Contraindications
The drug is contraindicated in patients with gastrointestinal obstruction or perforation, or those at risk for these problems. Side effects
Side effects in studies were abdominal pain (8–11% of patients as compared to 2–5% under placebo, depending on the study), diarrhea (7% versus 2–3%), nausea (4–6% versus 2–5%), vomiting (3% versus 2%), gastroenteritis (2–3% versus 1%), and opioid withdrawal syndrome (1.5–3.2% versus 0.5–1.5%). The latter was severe but manageable in one patient, and otherwise mild to moderate. Hypersensitivity reactions were rare; they occurred in two patients.