Common opioid‑induced disorders

• Opioid‑induced hyperalgesia (OIH) — paradoxical increase in pain sensitivity with ongoing opioid exposure.
• Opioid‑induced endocrine dysfunction — hypogonadism, adrenal insufficiency (long‑term opioids).
• Opioid‑induced bowel dysfunction — constipation, delayed gastric emptying.
• Opioid‑induced neurocognitive effects — sedation, cognitive slowing; increased fall risk in older adults.
• Opioid‑induced mood and anxiety symptoms — depression, emotional blunting, or dysphoria related to opioid treatment or withdrawal.
• Neonatal abstinence syndrome (NAS) — withdrawal in neonates after in‑utero opioid exposure.
• Immune system effects and risk of infections in people who inject opioids (notably skin/soft tissue infections, endocarditis).

Diagnostic considerations

1. Temporal relationship: correlate symptom onset with opioid initiation, dose escalation, or withdrawal.
2. Differentiate OIH from tolerance or uncontrolled underlying pain — OIH often presents as diffuse pain, increased sensitivity, or decreased opioid efficacy despite dose increases.
3. Screen for endocrine dysfunction with symptoms of low libido, fatigue, amenorrhoea — check morning cortisol, LH/FSH, testosterone, and consider endocrine referral.
4. Rule out alternative causes for constipation, cognitive decline or mood symptoms (medications, metabolic causes, primary psychiatric illness).

Assessment checklist

• Medication review: opioid type, dose, duration, co‑prescribed benzodiazepines, anticholinergics, and other CNS depressants.
• Functional assessment: pain pattern, sleep, mood, sexual function, cognitive screening and bowel habit inquiry.
• Investigations as indicated: endocrine panels, urine drug screen, imaging or specialist tests for focal neurological signs, and neonatal scoring (Finnegan) for NAS.

Management principles

• Address the cause: reduce or rotate opioids, consider opioid tapering where safe and clinically appropriate.
• Use multimodal pain management — non‑opioid analgesics, physiotherapy, psychological therapies (CBT), and interventional options when indicated.
• Treat specific syndromes: laxatives and bowel regimen for opioid‑induced constipation; endocrine replacement when confirmed; consider opioid rotation or reduction for OIH.
• Coordinate multidisciplinary care — pain medicine, endocrinology, psychiatry, obstetrics (for pregnancy), and paediatrics (for NAS).

Specific disorder management

Opioid‑induced hyperalgesia (OIH)

• Consider when worsening pain is diffuse, non‑specific, or occurs after dose escalation.
• Management: reduce dose, change to a different opioid (rotation), or discontinue opioid and use alternative analgesics and adjuvants (gabapentinoids, SNRIs, NMDA antagonists in specialist settings).
• Non‑pharmacological strategies: CBT, physical therapy and interventional pain procedures as appropriate.

Opioid‑induced endocrine dysfunction

• Symptoms: low libido, erectile dysfunction, menstrual irregularities, fatigue and reduced muscle mass.
• Investigations: morning testosterone in men, LH/FSH, estradiol in women, and cortisol if adrenal insufficiency suspected.
• Treatment: consider opioid dose reduction if possible; refer to endocrinology for hormone replacement therapy when indicated.

Opioid‑induced bowel dysfunction

• First‑line: stimulant laxatives (senna), osmotic laxatives (PEG), stool softeners, and regular bowel regimen.
• Consider peripherally‑acting mu‑opioid receptor antagonists (PAMORAs) (e.g., naloxegol, methylnaltrexone) for refractory cases — follow local formularies and specialist advice.

Neonatal abstinence syndrome (NAS)

• Screen pregnant patients for opioid use and provide OAT (methadone or buprenorphine) rather than abrupt cessation; coordinate obstetric and neonatal care.
• Neonates require scoring (e.g., modified Finnegan) and supportive care; pharmacologic treatment (morphine, methadone, or clonidine) may be needed for severe NAS under neonatal guidance.

Harm reduction and prevention

• Use lowest effective opioid dose for shortest duration; avoid co‑prescribing benzodiazepines where possible.
• Provide patient education on side effects, signs of endocrine dysfunction, constipation prevention and seeking help for cognitive or mood changes.
• Offer naloxone to patients at risk of overdose and monitor for infections and complications in people who inject drugs.

Key takeaways

• Consider opioid‑induced causes when new symptoms arise after starting or escalating opioids.
• Prioritise opioid reduction/rotation and multidisciplinary non‑opioid strategies for OIH and other chronic adverse effects.
• Manage constipation aggressively; check endocrine function when symptoms suggest hypogonadism or adrenal insufficiency.