MEDICATIONS,  PAIN MEDICINE

Opiates and elderly

General Overview

  • Pain is prevalent in older adults, especially in long-term care settings.
  • Up to 80% of long-term care residents experience significant pain.
  • Opiates are effective for nociceptive and neuropathic pain.
  • Older adults are at higher risk of adverse effects due to pharmacokinetic and pharmacodynamic changes.

πŸ”Ή Pharmacological Considerations in the Elderly

Age-related changes affecting opioids:

  • ↓ GI motility and gastric acidity β†’ altered absorption.
  • ↑ Fat, ↓ lean mass and total body water β†’ affects drug distribution.
  • ↓ Hepatic blood flow β†’ reduced first-pass metabolism.
  • ↓ Renal clearance β†’ accumulation of renally-excreted opioids (e.g., morphine, hydromorphone).

Dosing recommendations:

  • Start at 25–50% of usual adult dose.
  • “Start low and go slow”.
  • Avoid: Meperidine, Propoxyphene, Tramadol (neurotoxicity, ineffectiveness, serotonin syndrome/seizures).
  • Codeine: variable effect due to CYP2D6 metabolism (30% are poor metabolizers).

πŸ”Ή Commonly Used Opioids

  • Step 2 WHO ladder: Oxycodone, hydrocodone + paracetamol/NSAID.
  • Short-acting options: Morphine, oxycodone, codeine, hydromorphone.
  • Avoid multiple opioidsβ€”use one agent and titrate.
  • Titrate:
    • Mild pain: ↑ by 25–50%
    • Moderate-severe pain: ↑ by 50–100%
  • Dose escalation intervals depend on formulation (e.g., 24h for SR opioids, 72h for fentanyl/methadone).
  • Use PRN orders carefullyβ€”dose ranges should be no more than 4x the minimum.

πŸ”Ή Side Effects of Opioids in the Elderly

Adverse EffectMechanism / Notes
NauseaCTZ stimulation, vestibular activation. Most common (14%).
ConstipationMu-opioid receptor agonism β†’ ↓ GI motility. No tolerance develops β†’ prophylactic laxatives essential.
Urinary RetentionAnticholinergic effect and from constipation.
Sedation/Cognitive ImpairmentCNS depression; ↑ risk with benzodiazepines/antidepressants; polypharmacy risk.
MyoclonusAccumulates with chronic therapy; more common with morphine (active metabolite).
PruritusSeen in 2–10%, usually self-resolving.
Respiratory DepressionDose-dependent ΞΌ-receptor effect. Use naloxone if RR < 8 or SpOβ‚‚ < 90%.
Opioid-induced Hyperalgesia↑ pain sensitivity due to toxic metabolites (M3G/H3G), NMDA activation.
QT ProlongationAssociated with methadone, especially in HIV+ patients.
Endocrine effects↓ LH/testosterone/cortisol; ↑ prolactin β†’ ↓ libido, bone density, sexual dysfunction.

πŸ”Ή Management of Side Effects

  • Dose reduction (25–50%) for adverse effects without compromising analgesia.
  • Symptomatic treatment (e.g., antiemetics, laxatives).
  • Opioid rotation for intolerable side effects.
  • Change route (e.g., oral β†’ transdermal) if needed.
  • Add adjuvants (e.g., TCAs, gabapentinoids, steroids) if opioid dose is insufficient or poorly tolerated.

πŸ”Ή Additional Prescribing Principles

  • Document response to PRNs to guide ongoing management.
  • Equianalgesic conversions should factor in cross-tolerance:
    • Reduce dose by 33–50% (except fentanyl/methadone).
    • Methadone requires specialist knowledge due to nonlinear conversion.
  • Long-acting opioids require careful initiation and titration; avoid frequent changes.
  • Involve patient/family in education and decision-making.

πŸ”Ή Key Recommendations from AGS/WHO

  • Prefer scheduled over β€œon demand” dosing.
  • Monitor closely for side effects and adjust accordingly.
  • Assess pain routinely, even in patients with cognitive impairment.
  • Premedicate known pain-triggering procedures in cognitively impaired patients.

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