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Opioid Management in the Chronic Back Pain Patient

Opioid Management in the Chronic Back Pain Patient. Kenneth Reed, M.D. Interventional Pain Management St. John Medical Center. Objectives. Immediate Release Opioids Extended Release Opioids Nonopioid adjuvants. Opioid Receptors. Mu, Kappa, Delta Located on dorsal horn of spinal cord

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Opioid Management in the Chronic Back Pain Patient

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  1. Opioid Management in the Chronic Back Pain Patient Kenneth Reed, M.D. Interventional Pain Management St. John Medical Center

  2. Objectives • Immediate Release Opioids • Extended Release Opioids • Nonopioid adjuvants

  3. Opioid Receptors • Mu, Kappa, Delta • Located on dorsal horn of spinal cord • Mu receptors – modulate mechanical, chemical, and thermal stimuli • Kappa – thermal nociception and chemical visceral pain • Delta – mechanical and thermal pain

  4. Adverse Effects • Constipation • Nausea/Emesis • Sedation • Pruritus • Respiratory depression • Urinary retention

  5. Constipation • Most common side effect • Usually no tolerance • Can lead to other side effects (N/V) • Binds to Mu receptors in gut, slowing gut motility • Treatment • Laxative i.e. senna, bisacodyl, lactulose • Stool softeners (may not work as well)

  6. Nausea and Vomiting • Usually lasts 2-3 days • Activation of medullary chemoreceptor trigger zone • Activation of the vestibular system • Constipation • Vestibular – worse with ambulation • Treat with meclizine or scopolamine • Chemoreceptor – ondansetron • Decrease dose and then re-increase med slower • Change opioid

  7. Pruritus • Tolerance develops quickly • Related to histamine release activating C-fiber itch fibers • Face • Treatment with antihistamine • Nalbuphine – mu receptor antagonist

  8. Sedation • Usually temporary • Study showed stable dose of opioids for 7d rarely have psychomotor involvement • Recommend not to drive on opioids • Consider other causes of sedation (other medications or organ disease causing build up of metabolites

  9. Respiratory depression • Mu receptor induced in brainstem • Epidural or intrathecal administration can be delayed up to 12 hrs. • Naloxone for reversal – careful of severe withdrawal symptoms and congestive heart failure

  10. Opioid tolerance • Fixed dose of an opioid results in decreasing analgesia, thus requiring higher doses of medication to achieve similar effect • NMDA receptor involved • Increased pain secondary to progression of disease • Opioid rotation – doesn’t always require equipotent doses

  11. Physical Dependence and Withdrawal • Physiologic state that manifests when a medication is stopped, resulting in withdrawal • Adrenergic mediated (clonidine, beta blocker) • Withdrawal lasts 3-7 days • Irritability, insomnia, anxiety, diaphoresis, yawning, lacrimation, rhinorrhea • Chills, myalgias, abdominal cramping, nausea, diarrhea, tachycardia • Taper 10-20% every 48-72 hours

  12. Addiction • Opioid use resulting in physical, psychological, and/or social dysfunction and continued use of the opioid • Dopaminergic system in the brain • With increased doses of opioids, pain remains unchanged • Difficult diagnosis to make • Rate ranges from 3%-19%

  13. Codeine • Derived from opium or morphine • Weak mu opioid agonist, half life 2.5-3 hrs. • Needs to be converted to morphine by the body for analgesic effect • CYP2D6 poor metabolizers • Urinary excretion • Codeine, Morphine, Hydrocodone (1%)

  14. Morphine • Hydrophilic phenanthrene derivative • All opioids compared to morphine to determine equipotency • Bioavailability 33% • Delayed onset secondary to slow transport across blood brain barrier • Longer duration of action 4-5 hours • Metabolites • Morphine 6-glucuronide (M6G) and morphine 3-glucuronide (M3G)

  15. Morphine • M6G has mu opioid activity • M3G (50% of metabolite) • No analgesic action • Allodynia, hyperalgesia, myoclonus, seizures • Oral and chronic administration • Increasing amounts of metabolites • Can become higher than the parent compound • UDS can show hydromorphone • Liver disease – use with caution • Kidney disease – AVOID

  16. Meperidine • 1/10 as potent as morphine • Rapid onset, short duration • Less sedation and pruritus • Anticholinergic, cardiac, and local anesthetic properties • Potential for neurotoxicity • Metabolite normeperidine • CNS hyperactivity => seizures • Avoid in renal insufficiency • Chronic administration not recommended

  17. Oxycodone • Semisynthetic closely related to morphine • Derived from opium • High bioavailability - 60% • Active metabolite is oxymorphone (up to 14 times more potent than its parent) • Genetic polymorphism in 10% of population • Difficulty metabolizing to oxymorphone • Competition for CYP2D6 • Tricyclic antidepressants, neuroleptics, SSRIs

  18. Oxycodone • Fewer side effects than morphine • Oxycodone, OxyIR, Roxicodone (single agents) • Percocet, Endocet, Roxicet (acetaminophen) • Percodan or Endodan (aspirin) • Oxycontin (sustained release) • Kidneys excrete oxycodone – use caution

  19. Oxymorphone • Semi-synthetic opioid • Opana in 2006 • Mu and delta activity • Delta opioid receptor reduces tolerance and potentiates mu receptor analgesia • More lipid soluble than morphine/oxycodone • Bioavailability only 10% - extensive hepatic first pass metabolism • High lipid solubility

  20. Oxymorphone • Oxymorphone IR – onset 30 minutes, half-life 7-9 hours • Oxymorphone ER – steady state in 3 days, half life 9-11 hours • Dose adjustment for hepatic and renal impairment • Moderate to severe hepatic impairment – contraindicated • Alcohol increases plasma concentration 300% • Avoid eating 1 hour prior to administration and 2 hours after

  21. Hydromorphone • Strong affinity for mu receptor • Derivative of morphine • Also formed from hydrocodone • Pruritus, sedation, nausea less frequent • Five times more potent than morphine orally • Highly lipophilic therefore can be given subcutaneously • Onset orally 30 min. with peak in 8-20 min • Avoid in renal failure • Neuroexcitation properties • However more preferable in renal insufficiency compared to morphine

  22. Fentanyl • Highly lipophilic, high affinity for mu opioid receptor • 75-125 times more potent than morphine • Transmucosal • 47% bioavailability • Cancer and palliative care • Start at lowest dose • Transdermal • Avoid heat • Helpful in patients with nausea/emesis/short-gut syndrome • Difficult to titrate • Therapeutic serum levels 1-30 hrs. • Steady state up to 6 days • 16 hour half life after patch is removed

  23. Methadone • Unrelated to other opioids • High bioavailability of 80% • Cheap • Three times more people are using this for chronic pain versus treatment programs • Mu receptor affinity lower than morphine • Fewer side effects • NMDA receptor antagonist • Inhibits serotonin and norepinephrine reuptake

  24. Methadone • Higher affinity for delta receptor compared to morphine • Decreases opioid induced tolerance and dependence ( NMDA antagonism as well) • High lipophilicity and extensive tissue distribution => slow elimination • Half life 27 hrs. • Biphasic elimination

  25. Methadone – Biphasic elimination • Alpha elimination – distribution phase • 8-12 hours • Analgesia does not exceed 6-8 hours • Initial dosing frequent to meet steady state • Analgesia 6-12 hours • Beta elimination – clearance • 30-60 hours • Sufficient for preventing withdrawal • Q24 hours

  26. Methadone • Autoinducible enzyme • Can bring about its own metabolism and clearance over time • Gastric pH affects absorption • Increase pH causes increased absorption (omeprazole) • Decreases in urinary pH increase excretion • Doesn’t accumulate in renal failure • Short gut syndrome • Can be chewed or comes in elixir

  27. Methadone • Prolongation of QTc interval => torsade de pointes • Methadone tends to have higher potency in patients switching from high dose opioids • Secondary to antagonism of NMDA receptor by morphine • Safe starting dose for opioid naive 2.5 mg Q8 hours with dose increase weekly • Starting dose for opioid tolerant should not exceed 30-40 mg per day

  28. Buprenorphine • Schedule III semisynthetic opioid • Alternative to methadone maintenance therapy • Subutex and Suboxone • 30-40 times more potent than morphine • Naloxone in the latter – cause withdrawal if injected • Mu receptor agonist • Kappa and delta receptor antagonist • Causes less euphoria • Analgesic efficacy is limited and even get antagonism at higher doses

  29. Buprenorphine • Slow onset of action (90 minutes) • Relatively long half-life (4-5 hours) • Slow dissociation from opioid receptor and high affinity • Blocks other opioids from binding • Higher doses of narcotic may be required • Starting buprenorphine may precipitate withdrawal if already on another opioid • Naloxone may not readily reverse induced respiratory depression

  30. Specific Short-Acting Opioids • Schedule I – Have no currently accepted medical use and high potential for abuse, addiction, or physical dependence • Schedule II – Have accepted medical use and high potential for abuse, addiction, or physical dependence • Schedule III – Have accepted medical use and potential for abuse, addiction, or physical dependence less than drugs in schedule I & II • Schedule IV and V

  31. Scheduled Medications • Schedule I – Marijuana, heroin • Schedule II – morphine, hydromorphone, methadone, oxycodone, cocaine, amphetamine, fentanyl • Schedule III – lortab (meds combined with non-narcotic), suboxone • Schedule IV – Benzodiazepines, phenobarbital, Soma • Schedule V – Antitussives, Lyrica

  32. Percocet • Schedule II • Don’t prescribe more than five times per day • If 10mg not strong enough consider switching to oxycodone • Stronger than hydrocodone • High abuse potential especially with long acting • UDS • Oxycodone • Oxymorphone

  33. Hydrocodone • Schedule III • Abuse potential close to percocet • Almost equipotent to morphine • Half life 3.8 hours • Don’t prescribe more than fives times per day • UDS • Hydrocodone • Hydromorphone

  34. Tramadol • Schedule IV in Oklahoma • 1/10 potency of morphine • Mu opioid receptor • Inhibits reuptake of norepinephrine and serotonin • Abuse potential • Seizures and serotonin syndrome

  35. Tapentadol • Schedule II • 1/6 potency of morphine • Analgesia in 1.5-2 hours • Half life 4 hours • Mu opioid receptor • Norepinephrine reuptake inhibition • Abuse potential similar to hydrocodone and oxycodone • Avoid with SSRIs, SNRIs, triptans

  36. Nonopioid Adjuvants • Membrane stabalizers • Gabapentin • Pregabalin • Carbamazepine • Lidocaine • NSAIDs • Skeletal Muscle Relaxants

  37. Gabapentin • Calcium-Channel Blocker • Decreased release of glutumate, norepinephrine, substance P • Initial dose 100 or 300 mg daily • Can increase every 2-5 days • Common side effects • Fatigue, somnolence, dizziness • Edema, rash • Side effects reduced with slow titration

  38. Gabapentin • Reduce dose in renal insufficiency • Uses • Postherpatic neuralgia, chronic regional pain syndrome, diabetic neuropathy, neuropathic pain, spinal stenosis, multiple sclerosis • Improves analgesic efficacy of opioids in neuropathic cancer pain • Synergistic analgesic effect with TCAs

  39. Pregabalin (Lyrica) • Calcium channel blocker • Initial dose 150 mg/day but recommend starting lower • Given BID or TID • Maximum dose of 600 mg/day • More rapid onset of pain relief • Fewer side effects than Gabapentin • Reduce in decreased kidney function • Postherpatic neuralgia, diabetic neuropathy

  40. Lidocaine • Lidoderm 5% patches • Postherpatic neuralgia • Post-thoracotomy pain • Intercostal neuralgia • Meralgia Parasthetica • Muscle/myofascial pain

  41. Carbamazepine • Sodium channel blocker • Initial dosage 100-200 mg BID • Titrate up to 300-1200 mg/day • Uses • Trigeminal neuralgia, Thalamic-mediated post stroke pain, Postherpatic neuralgia, Diabetic neuropathy • Side effects – limited by slow titration • Drowsiness, dizziness, nausea/emesis

  42. Carbamazepine • Severe side effects • Pancytopenia • Stevens Johnson syndrome • Toxic epidermal necrolysis • Monitoring • CBC for baseline and then every 2-4 months

  43. NSAIDs • Reversible or irreversible acetylation of cyclooxygenase (COX) • COX-1 and COX-2 • COX-1 • Hemostasis, platelet aggregation, production of prostacyclin • COX-2 • Fever, inflammation, pain

  44. NSAIDs • Highly protein bound to plasma proteins • Rapidly and completely absorbed by GI tract • Food delays absorption • Work both peripherally and centrally • Metabolized by liver • Specific Medications • Naproxen, Ibprofen, Ketoprofen, Diclofenac, Meloxicam, Celebrex

  45. Specific NSAIDs • Naproxen (BID) • Half-life 14 hrs. • Steady state in 48 hrs. • Most of drug excreted in urine • Maximum 750-1000 mg per day • Ibprofen (QID) • Rapidly absorbed • Half-life 2-2.5 hrs. • Maximum dose 1200-2400 mg per day

  46. Diclofenac • COX-2 selectivity • Rapidly absorbed • Large first pass metabolism (50%) • Peaks in 2-3 hrs. • Highest cardiac risk • Hepatotoxicity – monitor transaminases • Voltaren gel • Flector Patch

  47. Specific medications • Meloxicam • COX-2 • Dose of 7.5 mg more selective than 15 mg • Peak concentration 5-10 hrs. • Half life of 15-20 hrs. • Celebrex • Only selective COX-2 inhibitor in United States • Peak in 2-3 hrs. • Half life 11 hrs. • Doesn’t interfere with platelet aggregation • Usually doesn’t cause gastric upset

  48. Muscle Relaxants

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