Peripheral μ-opioid receptor antagonist Pregnancy: No available data in pregnant women to inform a drug-associated risk of major birth defects and miscarriage. There is a potential for opioid withdrawal in a fetus when used in pregnant women. Should be used during pregnancy only if the potential benefit justifies the potential risk.

Naldemedine

Brand names: Rizmoic

Naldemedine is a peripherally acting mu-opioid receptor antagonist taken orally to treat opioid-induced constipation in adults who have had an inadequate response to laxatives.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 0.2 mg once daily, with or without food

Route: Oral

Frequency: Once daily

Alteration of the analgesic dosing regimen prior to initiating naldemedine is not required. Patients receiving opioids for less than 4 weeks may be less responsive. Discontinue naldemedine if treatment with the opioid pain medication is also discontinued. Paediatric: safety and effectiveness have not been established. Geriatric: no overall differences in safety or effectiveness were observed in patients 65 years and over, but greater sensitivity of some older individuals cannot be ruled out; no age-related alterations in pharmacokinetics were observed. SOURCE CAVEAT: no UK SPC section was captured in the bundle; the regimen above is from the US prescribing information for Symproic and must be verified against the UK SPC before publication.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known or suspected gastrointestinal obstruction, and patients at increased risk of recurrent obstruction, due to the potential for gastrointestinal perforation
History of a hypersensitivity reaction to naldemedine (reactions have included bronchospasm and rash)

Side effects

Abdominal pain
Diarrhoea
Nausea
Gastroenteritis
Gastrointestinal perforation and symptoms of opioid withdrawal (serious, described in warnings)

Interactions

Strong CYP3A inducers (e.g. rifampin, carbamazepine, phenytoin, St John's Wort) — significant decrease in plasma naldemedine concentrations which may reduce efficacy; avoid use
Other opioid antagonists — potential for additive opioid receptor antagonism and increased risk of opioid withdrawal; avoid concomitant use
Moderate CYP3A inhibitors (e.g. fluconazole, atazanavir, aprepitant, diltiazem, erythromycin) and strong CYP3A inhibitors (e.g. itraconazole, ketoconazole, clarithromycin, ritonavir, saquinavir) — increase plasma naldemedine concentrations; monitor for naldemedine-related adverse reactions
P-glycoprotein inhibitors (e.g. amiodarone, captopril, ciclosporin, quercetin, quinidine, verapamil) — increase plasma naldemedine concentrations; monitor

Clinical monograph

How it works

It antagonises mu-opioid receptors in the gastrointestinal tract; its limited penetration of the central nervous system means it relieves opioid-induced constipation without reversing central analgesia.

Prescribing in practice

Contraindicated in known or suspected gastrointestinal obstruction because of the risk of perforation.
It is taken orally once daily and may be given with or without food.
Discontinue if opioid treatment is stopped, and consider stopping if severe diarrhoea develops.

Monitoring

Monitor for severe abdominal pain or diarrhoea and for symptoms suggesting opioid withdrawal, particularly in patients with disrupted blood-brain barrier integrity.

Counselling the patient

Advise patients to report severe, persistent or worsening abdominal pain or diarrhoea promptly.
Explain that the medicine targets constipation in the gut and should not reduce pain control from their opioid.

Evidence & guidelines

Naldemedine is recommended by NICE as an option for treating opioid-induced constipation in adults who have had an inadequate response to laxatives.

Reference: NICE TA651; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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