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.
๐น Pharmacological Considerations in the Elderly
Age-related changes affecting opioids:
- โ GI motility and gastric acidity โ altered absorption.
- โ Fat, โ lean mass and total body water โ affects drug distribution.
- โ Hepatic blood flow โ reduced first-pass metabolism.
- โ Renal clearance โ accumulation of renally-excreted opioids (e.g., morphine, hydromorphone).
Dosing recommendations:
- Start at 25โ50% 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).
๐น Commonly Used Opioids
- Step 2 WHO ladder: Oxycodone, hydrocodone + paracetamol/NSAID.
- Short-acting options: Morphine, oxycodone, codeine, hydromorphone.
- Avoid multiple opioidsโuse one agent and titrate.
- Titrate:
- Mild pain: โ by 25โ50%
- Moderate-severe pain: โ by 50โ100%
- Dose escalation intervals depend on formulation (e.g., 24h for SR opioids, 72h for fentanyl/methadone).
- Use PRN orders carefullyโdose ranges should be no more than 4x the minimum.
๐น Side Effects of Opioids in the Elderly
| Adverse Effect | Mechanism / Notes |
|---|---|
| Nausea | CTZ stimulation, vestibular activation. Most common (14%). |
| Constipation | Mu-opioid receptor agonism โ โ GI motility. No tolerance develops โ prophylactic laxatives essential. |
| Urinary Retention | Anticholinergic effect and from constipation. |
| Sedation/Cognitive Impairment | CNS depression; โ risk with benzodiazepines/antidepressants; polypharmacy risk. |
| Myoclonus | Accumulates with chronic therapy; more common with morphine (active metabolite). |
| Pruritus | Seen in 2โ10%, usually self-resolving. |
| Respiratory Depression | Dose-dependent ฮผ-receptor effect. Use naloxone if RR < 8 or SpOโ < 90%. |
| Opioid-induced Hyperalgesia | โ pain sensitivity due to toxic metabolites (M3G/H3G), NMDA activation. |
| QT Prolongation | Associated with methadone, especially in HIV+ patients. |
| Endocrine effects | โ LH/testosterone/cortisol; โ prolactin โ โ libido, bone density, sexual dysfunction. |
๐น Management of Side Effects
- Dose reduction (25โ50%) for adverse effects without compromising analgesia.
- Symptomatic treatment (e.g., antiemetics, laxatives).
- Opioid rotation for intolerable side effects.
- Change route (e.g., oral โ transdermal) if needed.
- Add adjuvants (e.g., TCAs, gabapentinoids, steroids) if opioid dose is insufficient or poorly tolerated.
๐น Additional Prescribing Principles
- Document response to PRNs to guide ongoing management.
- Equianalgesic conversions should factor in cross-tolerance:
- Reduce dose by 33โ50% (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.
๐น Key Recommendations from AGS/WHO
- Prefer scheduled over โon demandโ 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.