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Page 1: opioid analgesics

Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Opioid Analgesic AgentsOpioid Analgesic Agents

Page 2: opioid analgesics

Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

AnalgesicsAnalgesics

• Medications that relieve pain without causing Medications that relieve pain without causing loss of consciousnessloss of consciousness

• PainkillersPainkillers

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Classification of Pain Classification of Pain By Onset and DurationBy Onset and Duration• Acute painAcute pain

– Sudden in onsetSudden in onset

– Usually subsides once treatedUsually subsides once treated

• Chronic painChronic pain

– Persistent or recurringPersistent or recurring

– Often difficult to treatOften difficult to treat

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Classification of PainClassification of Pain• SomaticSomatic• VisceralVisceral• SuperficialSuperficial• VascularVascular• ReferredReferred• NeuropathicNeuropathic• PhantomPhantom• CancerCancer• PsychogenicPsychogenic• CentralCentral

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Classification of Pain By SourceClassification of Pain By Source

Vascular painVascular pain• Possibly originates from vascular or Possibly originates from vascular or

perivascular tissuesperivascular tissues

Neuropathic painNeuropathic pain• Results from injury to peripheral nerve fibers or Results from injury to peripheral nerve fibers or

damage to the CNSdamage to the CNS

Superficial painSuperficial pain• Originates from skin or mucous membranesOriginates from skin or mucous membranes

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Pain Transmission Gate TheoryPain Transmission Gate Theory

• Most common and well-describedMost common and well-described

• Uses the analogy of a gate to describe how Uses the analogy of a gate to describe how impulses from damaged tissues are sensed impulses from damaged tissues are sensed in the brainin the brain

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Pain TransmissionPain Transmission

Tissue injury causes the release of:Tissue injury causes the release of:

• BradykininBradykinin

• HistamineHistamine

• PotassiumPotassium

• ProstaglandinsProstaglandins

• SerotoninSerotonin

These substances stimulate nerve endings, These substances stimulate nerve endings, starting the pain process.starting the pain process.

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Pain TransmissionPain Transmission

There are two types of nerves stimulated:There are two types of nerves stimulated:

• ““A” fibersA” fibers

andand

• ““C” fibersC” fibers

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Pain TransmissionPain Transmission

““A” FibersA” Fibers “C” Fibers“C” Fibers

Myelin sheathMyelin sheath No myelin sheathNo myelin sheath

Large fiber sizeLarge fiber size Small fiber sizeSmall fiber size

Conduct fastConduct fast Conduct slowlyConduct slowly

Inhibit painInhibit pain Facilitate pain Facilitate pain transmissiontransmission transmissiontransmission

Sharp andSharp and Dull andDull andwell-localizedwell-localized nonlocalizednonlocalized

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Pain TransmissionPain Transmission

• Types of pain related to proportion of Types of pain related to proportion of “A” to “C” fibers in the damaged areas“A” to “C” fibers in the damaged areas

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Pain TransmissionPain Transmission

• These pain fibers enter the spinal cord These pain fibers enter the spinal cord and travel up to the brain.and travel up to the brain.

• The point of spinal cord entry is the The point of spinal cord entry is the DORSAL HORN.DORSAL HORN.

• The DORSAL HORN is the location The DORSAL HORN is the location of the “GATE.”of the “GATE.”

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Pain TransmissionPain Transmission

• This gate regulates the flow of sensory This gate regulates the flow of sensory impulses to the brain.impulses to the brain.

• Closing the gate stops the impulses.Closing the gate stops the impulses.

• If no impulses are transmitted to higher If no impulses are transmitted to higher centers in the brain, there is NO pain centers in the brain, there is NO pain perception.perception.

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Instructors may want to useInstructors may want to useEIC Image #37:EIC Image #37:

Gate Theory of Pain TransmissionGate Theory of Pain Transmission

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Pain TransmissionPain Transmission

• Activation of large “A” fibers CLOSES gateActivation of large “A” fibers CLOSES gate

• Inhibits transmission to brainInhibits transmission to brain

– Limits perception of painLimits perception of pain

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Pain TransmissionPain Transmission

• Activation of small “B” fibers OPENS gateActivation of small “B” fibers OPENS gate

• Allows impulse transmission to brainAllows impulse transmission to brain

– Pain perceptionPain perception

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Pain TransmissionPain Transmission

• Gate innervated by nerve fibers from brain, Gate innervated by nerve fibers from brain, allowing the brain some control over gateallowing the brain some control over gate

• Allows brain to:Allows brain to:

– Evaluate, identify, and localize the painEvaluate, identify, and localize the pain

– Control the gate before the gate is openControl the gate before the gate is open

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Pain TransmissionPain Transmission

““T” cellsT” cells

• Cells that Cells that controlcontrol the gate have a threshold the gate have a threshold

• Impulses must overcome threshold to be sent Impulses must overcome threshold to be sent to the brainto the brain

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Pain TransmissionPain Transmission

• Body has endogenous neurotransmittersBody has endogenous neurotransmitters

– EnkephalinsEnkephalins

– EndorphinsEndorphins

• Produced by body to fight painProduced by body to fight pain

• Bind to opioid receptorsBind to opioid receptors

• Inhibit transmission of pain by closing gateInhibit transmission of pain by closing gate

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Pain TransmissionPain Transmission

Rubbing a painful area with massage or Rubbing a painful area with massage or liniment stimulates large sensory fibersliniment stimulates large sensory fibers

• Result:Result:

– GATE closed, recognition of pain REDUCEDGATE closed, recognition of pain REDUCED

– Same pathway used by opiatesSame pathway used by opiates

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Opioid AnalgesicsOpioid Analgesics

• Pain relievers that contain opium, Pain relievers that contain opium, derived from the opium poppy derived from the opium poppy

oror

• chemically related to opiumchemically related to opium

Narcotics: very strong pain relieversNarcotics: very strong pain relievers

Page 21: opioid analgesics

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Opioid AnalgesicsOpioid Analgesics

• codeine sulfatecodeine sulfate

• meperidine HCl (Demerol)meperidine HCl (Demerol)

• methadone HCl (Dolophine)methadone HCl (Dolophine)

• morphine sulfatemorphine sulfate

• propoxyphene HClpropoxyphene HCl

Page 22: opioid analgesics

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Opioid AnalgesicsOpioid Analgesics

Three classifications based on their actions:Three classifications based on their actions:

• AgonistAgonist

• Agonist-antagonistAgonist-antagonist

• Partial agonistPartial agonist

Page 23: opioid analgesics

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Opioid Analgesics: Site of actionOpioid Analgesics: Site of action

• Large “A” fibersLarge “A” fibers

• Dorsal horn of spinal cordDorsal horn of spinal cord

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Opioid Analgesics: Opioid Analgesics: Mechanism of ActionMechanism of Action

• Bind to receptors on inhibitory fibers, Bind to receptors on inhibitory fibers, stimulating themstimulating them

• Prevent stimulation of the GATEPrevent stimulation of the GATE

• Prevent pain impulse transmission Prevent pain impulse transmission to the brainto the brain

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Opioid Analgesics: Opioid Analgesics: Mechanism of ActionMechanism of Action

Three types of opioid receptors:Three types of opioid receptors:

• MuMu

• KappaKappa

• DeltaDelta

Page 26: opioid analgesics

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Opioid Analgesics: Therapeutic UsesOpioid Analgesics: Therapeutic Uses

Main use: to alleviate moderate to severe painMain use: to alleviate moderate to severe pain

• Opioids are also used for:Opioids are also used for:

– Cough center suppressionCough center suppression

– Treatment of constipationTreatment of constipation

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Opioid Analgesics: Side EffectsOpioid Analgesics: Side Effects

• EuphoriaEuphoria

• Nausea and vomitingNausea and vomiting

• Respiratory depressionRespiratory depression

• Urinary retentionUrinary retention

• Diaphoresis and flushingDiaphoresis and flushing

• Pupil constriction (miosis)Pupil constriction (miosis)

• Constipation Constipation

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Opiate AntagonistsOpiate Antagonists

naloxone (Narcan)naloxone (Narcan)

naltrexone (Revia)naltrexone (Revia)

• Opiate antagonistsOpiate antagonists

• Bind to opiate receptors and prevent a responseBind to opiate receptors and prevent a response

Used for complete or partial reversal of Used for complete or partial reversal of opioid-induced respiratory depressionopioid-induced respiratory depression

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Opiates: Opioid ToleranceOpiates: Opioid Tolerance

• A common physiologic result of chronic A common physiologic result of chronic opioid treatmentopioid treatment

• Result:Result: larger dose of opioids are larger dose of opioids are requiredrequired

to maintain the same level ofto maintain the same level ofanalgesiaanalgesia

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Opiates: Physical DependenceOpiates: Physical Dependence

• The physiologic adaptation of the body to The physiologic adaptation of the body to the presence of an opioidthe presence of an opioid

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Opiates: Psychological Dependence Opiates: Psychological Dependence (addiction)(addiction)

• A pattern of compulsive drug use A pattern of compulsive drug use characterized by a continued craving for characterized by a continued craving for an opioid and the need to use the opioid an opioid and the need to use the opioid for effects other than pain relieffor effects other than pain relief

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OpiatesOpiates

• Opioid tolerance and physical dependence Opioid tolerance and physical dependence are expected with long-term opioid treatment are expected with long-term opioid treatment and should not be confused with and should not be confused with psychological dependence (addiction).psychological dependence (addiction).

Page 33: opioid analgesics

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OpiatesOpiates

• Misunderstanding of these terms leads to Misunderstanding of these terms leads to ineffective pain management and contributes ineffective pain management and contributes to the problem of undertreatment.to the problem of undertreatment.

Page 34: opioid analgesics

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OpiatesOpiates

• Physical dependence on opioids is seen Physical dependence on opioids is seen when the opioid is abruptly discontinued or when the opioid is abruptly discontinued or when an opioid antagonist is administered.when an opioid antagonist is administered.

– Narcotic withdrawalNarcotic withdrawal

– Opioid abstinence syndromeOpioid abstinence syndrome

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OpiatesOpiates

Narcotic Withdrawal Opioid Abstinence Narcotic Withdrawal Opioid Abstinence SyndromeSyndrome

• Manifested as: Manifested as:

– anxiety, irritability, chills and hot flashes, joint anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrheanausea, vomiting, abdominal cramps, diarrhea

Page 36: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

• Before beginning therapy, perform a Before beginning therapy, perform a thorough history regarding allergies, use of thorough history regarding allergies, use of other medications,health history, and other medications,health history, and medical history.medical history.

• Obtain baseline vital signs and I & O.Obtain baseline vital signs and I & O.

• Assess for potential contraindications and Assess for potential contraindications and drug interactions.drug interactions.

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

• Perform a thorough pain assessment, Perform a thorough pain assessment, including nature and type of pain, including nature and type of pain, precipitating and relieving factors, remedies, precipitating and relieving factors, remedies, and other pain treatments.and other pain treatments.

– Assessment of pain is now being considered Assessment of pain is now being considered a “fifth vital sign.”a “fifth vital sign.”

Page 38: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

• Be sure to medicate patients before the pain Be sure to medicate patients before the pain becomes severe as to provide adequate becomes severe as to provide adequate analgesia and pain control.analgesia and pain control.

• Pain management includes pharmacologic Pain management includes pharmacologic and nonpharmacologic approaches. Be sure and nonpharmacologic approaches. Be sure to include other interventions as indicated.to include other interventions as indicated.

Page 39: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

• Oral forms should be taken with food to Oral forms should be taken with food to minimize gastric upset.minimize gastric upset.

• Ensure safety measures, such as keeping Ensure safety measures, such as keeping side rails up, to prevent injury.side rails up, to prevent injury.

• Withhold dose and contact physician if there Withhold dose and contact physician if there is a decline in the patient’s condition or if VS is a decline in the patient’s condition or if VS are abnormal—especially if respiratory rate are abnormal—especially if respiratory rate is below 12 breaths/minute.is below 12 breaths/minute.

Page 40: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

• Follow proper administration guidelines for Follow proper administration guidelines for IM injections, including site rotation.IM injections, including site rotation.

• Follow proper guidelines for IV Follow proper guidelines for IV administration, including dilution, rate of administration, including dilution, rate of administration, and so forth.administration, and so forth.

CHECK DOSAGES CAREFULLYCHECK DOSAGES CAREFULLY

Page 41: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications• Constipation is a common side effect and Constipation is a common side effect and

may be prevented with adequate fluid and may be prevented with adequate fluid and fiber intake.fiber intake.

• Instruct patients to follow directions for Instruct patients to follow directions for administration carefully, and to keep a administration carefully, and to keep a record of their pain experience and record of their pain experience and response to treatments.response to treatments.

• Patients should be instructed to change Patients should be instructed to change positions slowly to prevent possible positions slowly to prevent possible orthostatic hypotension.orthostatic hypotension.

Page 42: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

• Patients should not take other medications Patients should not take other medications or OTC preparations without checking with or OTC preparations without checking with their physician.their physician.

• Instruct patients to notify physician for signs Instruct patients to notify physician for signs of allergic reaction or adverse effects.of allergic reaction or adverse effects.

Page 43: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

Monitor for side effects:Monitor for side effects:

• Should VS change, patient’s condition decline, Should VS change, patient’s condition decline, or pain continue, contact physician immediately.or pain continue, contact physician immediately.

• Respiratory depression may be manifested by Respiratory depression may be manifested by respiratory rate of less than 12/min, dyspnea, respiratory rate of less than 12/min, dyspnea, diminished breath sounds, or shallow breathing.diminished breath sounds, or shallow breathing.

Page 44: opioid analgesics

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Opioid Analgesics: Opioid Analgesics: Nursing ImplicationsNursing Implications

Monitor for therapeutic effects:Monitor for therapeutic effects:

• Decreased complaints of painDecreased complaints of pain

• Increased periods of comfortIncreased periods of comfort

• With improved activities of daily living, appetite, With improved activities of daily living, appetite, and sense of well-beingand sense of well-being


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