Pharmacological Management of Pain

1. Pharmacological Management of Pain Frank Ferris, MD Charles F. von Gunten, MD, PhD

2. Epidemiology-Cancer Pain • 30-45% of all patients • 75% of those with advanced disease • Of those with pain • 40-50% moderate to severe • 25-35% excruciating

3. Epidemiology-Cancer Pain • Causes of Pain • 70% related to cancer • 25% cancer treatment • 5% unrelated • 70-90% relieved with oral analgesics

4. Epidemiology-Other Pain • AIDS • 40-60% • Chronically Ill elderly • 60-80%

5. Assessment of Pain • Leading cause of poor pain management • Location and Radiation • Severity • Timing • Exacerbating and Relieving • Effects on Activity • Previous Therapy

6. Pathophysiology • Nociceptive • intact, normally functioning nerves • somatic or visceral • Neuropathic • disrupted functioning of nerves • surgery, infection, pressure, drugs

7. Total Pain • Physical • Psychological • Social • Spiritual

8. Management Strategies • Pharmacological • Physical • Neurolytic • Cognitive-Behavioral • Intraspinal

9. Acute vs Chronic Pain • Acute • less than 6 weeks • related to discernible incident • Chronic • more than 6 weeks • ongoing pathophysiology • Intractable • non-remediable cause

10. WHO 3-step ladder 3severe Morphine Hydromorphone Fentanyl Methadone Oxycodone 2 moderate A/Codeine A/Propoxyphene A/Oxycodone 1mild ASA Acetaminophen NSAID’s

11. Routes of Administration • Oral • Rectal • Buccal • Transcutaneous • Subcutaneous • Intravenous

12. Analgesic Dosing • Chronic Pain • Around-the-Clock • Breakthrough doses prn • Acute Pain • prn dosing

13. Analgesic Dosing • For ROUTINE dosing, dose every half-life (t 1/2) • Morphine t 1/2 = 3 1/2 hrs • Morphine 15 mg po q 4h • For TITRATION and BREAKTHROUGH dose every Cmax. • Morphine Cmax = 1 hr • Morphine 5 mg po q 1h

14. Titration • Five half-lives to reach steady-state • Change routine dosing every 24 hr.

15. Sustained-release analgesics • Don’t use for titration • After dose established, change to sustained-release product for quality-of-life reasons • q 12 h (morphine, hydromorphone) • q 24 h (morphine) • q 72 h (fentanyl)

16. Breakthrough Dosing • Chronic Pain is rarely rock-stable • Breakthrough dose is 10-20% of 24 hr dose • MS Contin 60 mg po q 12 h • Morphine 10-20 mg po q 1 h • More than 2-4 breakthrough doses per day means change the baseline dose

17. Common Opioid Side-Effects • Constipation • Nausea/Vomiting • Drowsiness • Dry Mouth • Sweating • Tolerance develops to all in 5-7 days except constipation

18. Uncommon Side-Effects • Dysphoria/Delirium • Bad dreams/Hallucinations • Pruritus/urticaria • Urinary Retention • Myoclonus/seizures • Respiratory Depression

19. Opioid Side-Effects Addiction = Physical Dependence Out of control Inappropriate Preoccupation Diminished QOL Abstinence Syndrome

20. Pharmacological Tolerance • Diminished effect with repeated dosing • Uncommon in chronic pain • Not clinically limiting • Most common reason for increased dose is increased pain

21. Adjuvant Pain Medicines • Drugs added to opioids which given additional or synergistic pain relief • Primary Analgesics • e.g. tricyclics or aspirin • Non-analgesics • e.g. steroids

22. Pain Syndromes • Neuropathic Pain • Bone Pain

23. Adjuvant Analgesics • Anti-inflammatory • NSAIDs, Steroids • Tricyclic Analgesics • amitriptyline, imipramine • nortriptyline, desipramine • Antiepileptics • carbamazepine, valproate, gabapentin • Antispasmodics • diazepam, baclofen • scopolamine