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

PainPain

Most common Most common reason people seek reason people seek health carehealth care

Tissue damage Tissue damage activates free activates free nerve endings nerve endings (pain receptors)(pain receptors)

Generally indicates Generally indicates tissue damage tissue damage

PainPain

Defined as Defined as whatever the whatever the patient says it ispatient says it is

It exists whenever It exists whenever he or she says it he or she says it doesdoes

Gate TheoryGate TheoryPg 122 Fig 9-1Pg 122 Fig 9-1

Injury results in release (from the tissues) Injury results in release (from the tissues) of of Bradykinin Bradykinin HistamineHistamine ProstoglandinsProstoglandins

Action potential along nerve fiberAction potential along nerve fiber Activates pain receptorActivates pain receptor Enter the spinal cord via the dorsal hornEnter the spinal cord via the dorsal horn If impulses can be stopped here…pain stopsIf impulses can be stopped here…pain stops

Gate TheoryGate Theory

Brain can evaluate, identify and Brain can evaluate, identify and localize painlocalize pain

BradykininBradykinin

Strongest pain producing substancesStrongest pain producing substances May be involved in acute painMay be involved in acute pain Prostglandins increase sensitivity to Prostglandins increase sensitivity to

painpain Chemical mediators activate and Chemical mediators activate and

sensitize pain receptors or stimulate sensitize pain receptors or stimulate the release of pain producing the release of pain producing substancessubstances

Endogenous AnalgesiaEndogenous Analgesia

Activated by nerve Activated by nerve signals or by signals or by morphine-like morphine-like substances substances entering the brainentering the brain

Opiate receptorsOpiate receptors Endogenous Endogenous

peptidespeptides

Pain TreatmentPain Treatment Often UNDER treatedOften UNDER treated Cancer pain Cancer pain

management in management in particularparticular Not aimed at Not aimed at

prevention of addictionprevention of addiction Patient comfortPatient comfort

Tolerance may occur Tolerance may occur Pg 123 (do not confuse Pg 123 (do not confuse

with addiction)with addiction)

Opiod AnalgesicsOpiod Analgesics

Moderate to Moderate to severe painsevere pain

Reduction of pain Reduction of pain sensationsensation

SedationSedation Decreases Decreases

emotional upsetemotional upset Most are schedule Most are schedule

IIII

Opioid AnalgesicsOpioid Analgesics

Oral, IM, SQ, & IVOral, IM, SQ, & IV PO requires high doses PO requires high doses Prevent or relieve acute or chronic Prevent or relieve acute or chronic

pain pain Bind to opioid receptors in the brain Bind to opioid receptors in the brain

and spinal cord and activate the and spinal cord and activate the endogenous systemendogenous system

Agonist-binds to a receptor site and Agonist-binds to a receptor site and causes a responsecauses a response

Partial agonist-binds to a receptor Partial agonist-binds to a receptor and causes only limited actionsand causes only limited actions

Antagonist-bind to a receptor and Antagonist-bind to a receptor and produce no responseproduce no response

AgonistsAgonistsPrototype: Morphine Prototype: Morphine

SulfateSulfate Morphine and morphine like drugsMorphine and morphine like drugs Activity at Mu, Kappa, & ??? Delta Activity at Mu, Kappa, & ??? Delta

receptorsreceptors Severe & Chronic PainSevere & Chronic Pain IV, IM, SQ, Suppository, Epidural,&, POIV, IM, SQ, Suppository, Epidural,&, PO Impaired kidney function may cause Impaired kidney function may cause

prolonged drug action and accumulationprolonged drug action and accumulation Nonceiling drugNonceiling drug

Prototype:Prototype:CodeineCodeine

PO onset 15-30 PO onset 15-30 minutes duration 4-6 minutes duration 4-6 hourshours

Naturally occurring Naturally occurring opium alkaloidopium alkaloid

ANTI-TUSSIVEANTI-TUSSIVE AnalgesicAnalgesic Milder adverse Milder adverse

effects than effects than morphinemorphine

May be combined May be combined with Acetaminophenwith Acetaminophen

ContraindicationsContraindications

Respiratory Respiratory depressiondepression

Chronic lung Chronic lung diseasedisease

Liver or kidney Liver or kidney diseasedisease

Prostatic Prostatic hypertrophyhypertrophy

Increased ICPIncreased ICP

Agonist/AntagonistAgonist/AntagonistPrototype: Nalbuphine Prototype: Nalbuphine

(Nubain)(Nubain) Agonist activity at some sites and Agonist activity at some sites and

antagonist at othersantagonist at others Low abuse potentialLow abuse potential Potent analgesicsPotent analgesics May produce withdrawal symptoms May produce withdrawal symptoms

in those with opiate dependencein those with opiate dependence SyntheticSynthetic

Opioid AntagonistOpioid AntagonistPrototype: Naloxone Prototype: Naloxone

(Narcan)(Narcan) Reverse or block Reverse or block

analgesia, analgesia, respiratory respiratory depressiondepression

Onset within Onset within minutes and last 1-2 minutes and last 1-2 hourshours

Shorter duration Shorter duration than opioidsthan opioids

May give repeated May give repeated injectionsinjections

WithdrawalWithdrawalPg 125Pg 125

Anxiety, aggressiveness, Anxiety, aggressiveness, restlessness, lacrimation, rhinorhea, restlessness, lacrimation, rhinorhea, perspiration, pupil dilation, perspiration, pupil dilation, piloerection, elevated body temp, piloerection, elevated body temp, diarrhea, BPdiarrhea, BP

Begin within few hours of last doseBegin within few hours of last dose Early recognition and treatment keyEarly recognition and treatment key

Side Effects & Side Effects & AssessmentsAssessments

Respiratory Respiratory depressiondepression

HypotensionHypotension N & VN & V ConstipationConstipation

Monitor Monitor respirationsrespirations

Orthostatic Orthostatic pressurespressures

BPBP Bowel regimenBowel regimen

TeachingTeaching

No EtohNo Etoh Do not increase Do not increase

dose (unless Rx’d)dose (unless Rx’d) Stay in bed 30-60 Stay in bed 30-60

minutes after minutes after receivingreceiving

No heavy No heavy machinerymachinery

High fiber foods & High fiber foods & increase fluidsincrease fluids

Non Opioid AnalgesicsNon Opioid Analgesics

Analgesic, Antipyretic, & Analgesic, Antipyretic, &

Anti-inflammatory DrugsAnti-inflammatory Drugs

Acetylsalic Acid (Aspirin)Acetylsalic Acid (Aspirin) Acetominophen (Tylenol)Acetominophen (Tylenol) Ibuprofen (Motrin)Ibuprofen (Motrin)

PrototypePrototypeAcetominophenAcetominophen

Does not cause N & V or GI bleedingDoes not cause N & V or GI bleeding Does not interfere with clottingDoes not interfere with clotting Lacks anti-inflammatory activityLacks anti-inflammatory activity Metabolized in liverMetabolized in liver Alters pain perceptionAlters pain perception

Side EffectsSide Effects

Hepatic necrosis (Acute overdose)Hepatic necrosis (Acute overdose) Nephropathy (Chronic overuse)Nephropathy (Chronic overuse) Liver toxicity increase with alcohol Liver toxicity increase with alcohol

ingestion!ingestion!

Mucolytic Mucolytic Prototype: Acetylcysteine Prototype: Acetylcysteine

(Mucomyst)(Mucomyst) Antidote to Antidote to

Acetaminophen Acetaminophen overdoseoverdose

Give POGive PO Must be given Must be given

within 24 hourswithin 24 hours Bad smellBad smell 17 doses17 doses Pg 132Pg 132

Activated Charcoal Activated Charcoal

May be given for an overdose of May be given for an overdose of AcetaminophenAcetaminophen

Other NSAIDSOther NSAIDS

Arachidonic Acid Arachidonic Acid PathwayPathway

Released after injuryReleased after injury MetabolizedMetabolized Both paths result in inflammation Both paths result in inflammation

and painand pain

GI DistressGI Distress

Prostaglandins maintain the Prostaglandins maintain the integrity of stomachintegrity of stomach

Inhibition sets upInhibition sets up UlcerationUlceration GI bleedsGI bleeds

MisoprostolMisoprostol

PrototypePrototypeASA (Aspirin)ASA (Aspirin)

Inhibits the Inhibits the synthesis of synthesis of prostaglandinsprostaglandins

Non selective COX Non selective COX inhibitorinhibitor

Antiplatelet and Antiplatelet and AntipyreticAntipyretic

Prevent sensitization Prevent sensitization of pain receptors to of pain receptors to various chemical various chemical substancessubstances

ContraindicationsContraindications

PUDPUD GI or other bleeding disordersGI or other bleeding disorders HypersensitivityHypersensitivity Impaired renal functionImpaired renal function Children with viral infections (pg Children with viral infections (pg

671)671) Intoxication (table 42-2)Intoxication (table 42-2)

PrototypePrototypeIbuprofen (Motrin)Ibuprofen (Motrin)

Anti-inflammatory agentAnti-inflammatory agent OTCOTC May be better tolerated than aspirin May be better tolerated than aspirin

but work in a similar fashionbut work in a similar fashion Hypersensitivity may occur in people Hypersensitivity may occur in people

with allergy to aspirinwith allergy to aspirin Contraindications similar to ASA Contraindications similar to ASA

(except Reye’s)(except Reye’s)

Selective COX-2 InhibitorSelective COX-2 InhibitorPrototype: Celecoxib Prototype: Celecoxib

(Celebrex)(Celebrex) Designed to relieve Designed to relieve

pain, fever, and pain, fever, and inflammationinflammation

Fewer side effects Fewer side effects than older NSAIDSthan older NSAIDS

Contraindicated with Contraindicated with ulcers, GI bleeds, ulcers, GI bleeds, asthma, severe renal asthma, severe renal impairment, & impairment, & allergy to other allergy to other NSAIDSNSAIDS

FeverfewFeverfew

Relieves HA, fever, and menstrual Relieves HA, fever, and menstrual irregularitiesirregularities

Can increase bleeding with aspirin, Can increase bleeding with aspirin, dipyridamole, warfarindipyridamole, warfarin

Contraindicated in pregnant patients, Contraindicated in pregnant patients, breastfeeding, and children < 2 y/obreastfeeding, and children < 2 y/o

http://www.merck.com/pubs/http://www.merck.com/pubs/mmanual_home2/sec02/ch019/ch019a.htmmmanual_home2/sec02/ch019/ch019a.htm