Pain Most common reason people seek health care Tissue damage activates free nerve endings (pain receptors) Generally indicates tissue damage

Pain Defined as whatever the patient says it is It exists whenever he or she says it does

Gate Theory Pg 122 Fig 9-1 Injury results in release (from the tissues) of Injury results in release (from the tissues) of Bradykinin Bradykinin Histamine Histamine Prostoglandins Prostoglandins Action potential along nerve fiber Action potential along nerve fiber Activates pain receptor Activates pain receptor Enter the spinal cord via the dorsal horn Enter the spinal cord via the dorsal horn If impulses can be stopped here…pain stops If impulses can be stopped here…pain stops

Gate Theory Brain can evaluate, identify and localize pain Brain can evaluate, identify and localize pain

Bradykinin Strongest pain producing substances Strongest pain producing substances May be involved in acute pain May be involved in acute pain Prostglandins increase sensitivity to pain Prostglandins increase sensitivity to pain Chemical mediators activate and sensitize pain receptors or stimulate the release of pain producing substances Chemical mediators activate and sensitize pain receptors or stimulate the release of pain producing substances

Endogenous Analgesia Activated by nerve signals or by morphine- like substances entering the brain Activated by nerve signals or by morphine- like substances entering the brain Opiate receptors Opiate receptors Endogenous peptides Endogenous peptides

Pain Treatment Often UNDER treated Cancer pain management in particular Not aimed at prevention of addiction Patient comfort Tolerance may occur Pg 123 (do not confuse with addiction)

Opiod Analgesics Moderate to severe pain Moderate to severe pain Reduction of pain sensation Reduction of pain sensation Sedation Sedation Decreases emotional upset Decreases emotional upset Most are schedule II Most are schedule II

Opioid Analgesics Oral, IM, SQ, & IV Oral, IM, SQ, & IV PO requires high doses PO requires high doses Prevent or relieve acute or chronic pain Prevent or relieve acute or chronic pain Bind to opioid receptors in the brain and spinal cord and activate the endogenous system Bind to opioid receptors in the brain and spinal cord and activate the endogenous system

Agonist-binds to a receptor site and causes a response Agonist-binds to a receptor site and causes a response Partial agonist-binds to a receptor and causes only limited actions Partial agonist-binds to a receptor and causes only limited actions Antagonist-bind to a receptor and produce no response Antagonist-bind to a receptor and produce no response

Agonists Prototype: Morphine Sulfate Morphine and morphine like drugs Morphine and morphine like drugs Activity at Mu, Kappa, & ??? Delta receptors Activity at Mu, Kappa, & ??? Delta receptors Severe & Chronic Pain Severe & Chronic Pain IV, IM, SQ, Suppository, Epidural,&, PO IV, IM, SQ, Suppository, Epidural,&, PO Impaired kidney function may cause prolonged drug action and accumulation Impaired kidney function may cause prolonged drug action and accumulation Nonceiling drug Nonceiling drug

Prototype: Codeine PO onset minutes duration 4-6 hours Naturally occurring opium alkaloid ANTI-TUSSIVE Analgesic Milder adverse effects than morphine May be combined with Acetaminophen

Contraindications Respiratory depression Respiratory depression Chronic lung disease Chronic lung disease Liver or kidney disease Liver or kidney disease Prostatic hypertrophy Prostatic hypertrophy Increased ICP Increased ICP

Agonist/Antagonist Prototype: Nalbuphine (Nubain) Agonist activity at some sites and antagonist at others Agonist activity at some sites and antagonist at others Low abuse potential Low abuse potential Potent analgesics Potent analgesics May produce withdrawal symptoms in those with opiate dependence May produce withdrawal symptoms in those with opiate dependence Synthetic Synthetic

Opioid Antagonist Prototype: Naloxone (Narcan) Reverse or block analgesia, respiratory depression Reverse or block analgesia, respiratory depression Onset within minutes and last 1-2 hours Onset within minutes and last 1-2 hours Shorter duration than opioids Shorter duration than opioids May give repeated injections May give repeated injections

Withdrawal Pg 125 Anxiety, aggressiveness, restlessness, lacrimation, rhinorhea, perspiration, pupil dilation, piloerection, elevated body temp, diarrhea, BP Anxiety, aggressiveness, restlessness, lacrimation, rhinorhea, perspiration, pupil dilation, piloerection, elevated body temp, diarrhea, BP Begin within few hours of last dose Begin within few hours of last dose Early recognition and treatment key Early recognition and treatment key

Side Effects & Assessments Respiratory depression Respiratory depression Hypotension Hypotension N & V N & V Constipation Constipation Monitor respirations Orthostatic pressures BP Bowel regimen

Teaching No Etoh Do not increase dose (unless Rx’d) Stay in bed minutes after receiving No heavy machinery High fiber foods & increase fluids

Non Opioid Analgesics Analgesic, Antipyretic, & Anti-inflammatory Drugs Acetylsalic Acid (Aspirin) Acetylsalic Acid (Aspirin) Acetominophen (Tylenol) Acetominophen (Tylenol) Ibuprofen (Motrin) Ibuprofen (Motrin)

Prototype Acetominophen Does not cause N & V or GI bleeding Does not cause N & V or GI bleeding Does not interfere with clotting Does not interfere with clotting Lacks anti-inflammatory activity Lacks anti-inflammatory activity Metabolized in liver Metabolized in liver Alters pain perception Alters pain perception

Side Effects Hepatic necrosis (Acute overdose) Hepatic necrosis (Acute overdose) Nephropathy (Chronic overuse) Nephropathy (Chronic overuse) Liver toxicity increase with alcohol ingestion! Liver toxicity increase with alcohol ingestion!

Mucolytic Prototype: Acetylcysteine (Mucomyst) Antidote to Acetaminophen overdose Antidote to Acetaminophen overdose Give PO Give PO Must be given within 24 hours Must be given within 24 hours Bad smell Bad smell 17 doses 17 doses Pg 132 Pg 132

Activated Charcoal May be given for an overdose of Acetaminophen

Other NSAIDS

Arachidonic Acid Pathway Released after injury Released after injury Metabolized Metabolized Both paths result in inflammation and pain Both paths result in inflammation and pain

GI Distress Prostaglandins maintain the integrity of stomach Prostaglandins maintain the integrity of stomach Inhibition sets up Inhibition sets up Ulceration Ulceration GI bleeds GI bleeds Misoprostol Misoprostol

Prototype ASA (Aspirin) Inhibits the synthesis of prostaglandins Inhibits the synthesis of prostaglandins Non selective COX inhibitor Non selective COX inhibitor Antiplatelet and Antipyretic Antiplatelet and Antipyretic Prevent sensitization of pain receptors to various chemical substances Prevent sensitization of pain receptors to various chemical substances

Contraindications PUD PUD GI or other bleeding disorders GI or other bleeding disorders Hypersensitivity Hypersensitivity Impaired renal function Impaired renal function Children with viral infections (pg 671) Children with viral infections (pg 671) Intoxication (table 42-2) Intoxication (table 42-2)

Prototype Ibuprofen (Motrin) Anti-inflammatory agent Anti-inflammatory agent OTC OTC May be better tolerated than aspirin but work in a similar fashion May be better tolerated than aspirin but work in a similar fashion Hypersensitivity may occur in people with allergy to aspirin Hypersensitivity may occur in people with allergy to aspirin Contraindications similar to ASA (except Reye’s) Contraindications similar to ASA (except Reye’s)

Selective COX-2 Inhibitor Prototype: Celecoxib (Celebrex) Designed to relieve pain, fever, and inflammation Designed to relieve pain, fever, and inflammation Fewer side effects than older NSAIDS Fewer side effects than older NSAIDS Contraindicated with ulcers, GI bleeds, asthma, severe renal impairment, & allergy to other NSAIDS Contraindicated with ulcers, GI bleeds, asthma, severe renal impairment, & allergy to other NSAIDS

Feverfew Relieves HA, fever, and menstrual irregularities Relieves HA, fever, and menstrual irregularities Can increase bleeding with aspirin, dipyridamole, warfarin Can increase bleeding with aspirin, dipyridamole, warfarin Contraindicated in pregnant patients, breastfeeding, and children < 2 y/o Contraindicated in pregnant patients, breastfeeding, and children < 2 y/o sec02/ch019/ch019a.htm