Pain Management (via Pharmacotherapy)

1. Pain Management (via Pharmacotherapy) Stephanie Riccalarsen, M.D.

2. Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage.

3. Pain • Pain is subjective: there is no test that can measure pain. • Mostly, we have to accept the patients report of pain, which is not always easy. • Perception of pain is influenced by cultural, psychological, and emotional factors.

4. Trying to Objectify Pain • Tachypnea • Grimace • Grinding/Bruxism • Tachycardia • Guarding • Rigidity • Sweating • Rocking • Clutching • Irritability

5. Pain • Acute vs. Chronic • Acute pain is usually related to an easily identified event or condition. • Chronic pain may or may not be related to an easily identified pathophysiologic phenomenon, may be multifactorial, and may be present for an indeterminate period of time.

6. Pain Classifications • Nociceptive pain – involves direct stimulation of intact mechanical, chemical, or thermal nociceptors, and transmission of electrical signals along normally functioning nerves. (Divided into somatic and visceral.) • Neuropathic pain – disordered function of peripheral or central nervous system. Responds best to anti-depressants and anti-convulsants, and occasionally with topical local anesthetics. Otherwise beyond the scope of this presentation.

7. Nociceptive Pain Subtypes • 1. Somatic – skin, soft tissue, muscle, bone. Due to stimulation of somatic nervous system. • 2. Visceral – cardiac, lung, GI and GU tracts. Results from stimulation of the autonomic nervous system. Patients may find this pain difficult to describe or localize.

8. The WHO 3-Step Model • Step 1: Mild pain (1-3/10 on pain scale) • Aspirin • Acetaminophen • Nonsteroidal Anti-Inflammatory Drugs

9. The WHO 3-Step Model • Step 2: Moderate pain (4-6/10) • Acetaminophen or aspirin, plus • Codeine • Hydrocodone • Oxycodone • Oxymorphone or • Tramadol (not available with aspirin, Ultracet is tramadol with acetaminophen)

10. The WHO 3-Step Model • Step 3: Severe pain (7-10/10) • Morphine • Hydromorphone (Dilaudid) • Methadone • Levorphanol • Fentanyl • Oxycodone • +/- Nonopioid analgesics

11. It is not necessary to traverse each step sequentially; a patient with severe pain may need to have step 3 opioids right away.

12. Acetaminophen • Acetaminophen is an effective step 1 analgesic. • It is also useful as a coanalgesic in many situations. • Its site and mechanism of action are not known. It is presumed to have a central mechanism. • It does not have signficant anti-inflammatory effects.

13. Acetaminophen – Adverse effects • Doses greater than 4g per 24 hours are not recommended as they may cause hepatotoxicity. • Hepatic disease or heavy alcohol use increases this risk further. • On the outpatient basis, patients may not realize their Lortab, Percocet, etc., has acetaminophen included (it is called “apap” on the prescription bottle) and they may then take additional separate acetaminophen, increasing risk of accidental overdose and hepatotoxicity.

14. NSAIDs • NSAIDs are effective step 1 analgesics • They may also be useful coanalgesics • They are effective for bone and inflammatory pain. • They work in part by inhibiting cyclo-oxygenase (COX), the enzyme that converts arachidonic acid to prostaglandins. • All NSAIDs inhibit COX but vary in COX-2 selectivity. • Ketorolac (Toradol) is available in an intravenous formulation

15. NSAIDs – Adverse effects • Potential adverse effects, irrespective of route of administration, include gastropathy, renal failure, and inhibition of platelet aggregation. • The nonselective medications are relatively contraindicated in the setting of preexisting renal insufficiency. • If bleeding is a problem, or coagulation or platelet function is impaired, NSAIDs may be contraindicated.

16. Opioid Adverse Effects • Respiratory depression – not seen when titrated to pain control. Pain control is generally achieved before respiratory depression. • Sedation. • Constipation. • Conjugated by the liver and excreted by kidneys, thus disease in either location affects dosing frequency and amount.

17. Opioid Pharmacology • Opioids reach their peak plasma concentration approximately • 60 to 90 minutes after oral or rectal administration • 30 minutes after subQ or IM injection • 6 minutes after intravenous administration • When renal clearance is normal, hydrocodone, hydromorphone, morphine, oxycodone, and their metabolites all have effective half-lives of about 3-4 hours. • When dosed repeatedly, their plasma concentrations approach a steady-state after 4 to 5 half lives.

18. Selecting An Opioid • Extended release formulations are available but are not often used on an inpatient basis for acute pain. • Methadone has a long and variable half-life and is best used on an outpatient basis for chronic pain, thus it has little use on the inpatient service.

19. NOT RECOMMENDED: • Meperidine (Demerol) – Its principal metabolite, normeperidine, has no analgesic properties of its own, has a longer half-life of about 6 hours, is renally excreted, and produces significant adverse effects when it accumulates (tremulousness, dysphoria, myoclonus, and seizures)

20. NOT RECOMMENDED: • Propoxyphene (Darvon) and Propoxyphene with acetaminophen (Darvocet) – Most pain experts believe that these have more dependence and mental status risk, with rather poor pain relief • No better than placebo in most studies • “Low efficacy at commercially available doses.” • “Dose escalation could lead to accumulation of a toxic metabolite”

21. Inpatient Recommended Opioids (Intravenous) • Get comfortable with one or two good IV opioid medications, like morphine and dilaudid, and stick with them. • Remember that dilaudid is 5:1 more potent than morphine; 2 mg of morphine is about equivalent to 0.5 mg of dilaudid. • Common side effects include constipation, nausea, vomiting, itching, and skin flushing. Individual patients may tolerate one but not the other.

22. Oxycodone is available in oral formulation by itself. Percocet is oxycodone with acetaminophen, available with 5/325mg dosing as well as 10/325mg dosing, so 2 tabs may be used every 4 hours instead of every 6 without going over the acetaminophen limit. Oxycodone is more regulated, so an outpatient prescription cannot be called in; a physical prescription must be written and received by the patient. Hydrocodone is not available in oral formulation by itself. Lortab/Vicodin is hydrocodone 5/500mg so each tablet comes with more acetaminophen, meaning if you use a 2 tablet dose, it cannot be given more frequently than q 6 hours. Hydrocodone is less regulated than oxycodone, and a prescription containing it may be called in to a pharmacy over the phone. Commonly Used Oral Inpatient Opioids

23. Sources 1. Mark Goodman, M.D., “Pain Management in Obstetrics and Gynecology” Grand Rounds, 2006. Department of Family Medicine, Creighton University. 2. Frederick E. Youngblood, M.D., CME Presentation October 14, 2005. Department of Anesthesiology, Creighton University. 3. Robert H. Lurie Comprehensive Cancer Center of Northwestern University: http://endoflife.northwestern.edu Module 4: Pain Management. 4. Journal of Pain and Symptom Management Issue 29 Vol 1, Jan 2005 pg 2-13. 5. Whitecar, Jonas, & Clasen. “Managing Pain in the Dying Patient.” American Family Physician. Feb 1,2000/Vol 61, No 3.