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Opioid Analgesic Agents

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					Opioid Analgesic Agents

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

Analgesics
• Medications that relieve pain without causing loss of consciousness • Painkillers

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

Classification of Pain By Onset and Duration
• Acute pain
– Sudden in onset

– Usually subsides once treated

• Chronic pain
– Persistent or recurring
– Often difficult to treat

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

Classification of Pain
• • • • • • • • • • Somatic Visceral Superficial Vascular Referred Neuropathic Phantom Cancer Psychogenic Central

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

Classification of Pain By Source
Vascular pain
• Possibly originates from vascular or perivascular tissues

Neuropathic pain
• Results from injury to peripheral nerve fibers or damage to the CNS

Superficial pain
• Originates from skin or mucous membranes
Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Pain Transmission Gate Theory
• Most common and well-described • Uses the analogy of a gate to describe how impulses from damaged tissues are sensed in the brain

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

Pain Transmission
Tissue injury causes the release of:
• Bradykinin

• Histamine • Potassium • Prostaglandins
• Serotonin

These substances stimulate nerve endings, starting the pain process.
Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Pain Transmission
There are two types of nerves stimulated:
• ―A‖ fibers

and • ―C‖ fibers

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Pain Transmission
―A‖ Fibers
Myelin sheath

―C‖ Fibers
No myelin sheath

Large fiber size Conduct fast Inhibit pain

Small fiber size Conduct slowly Facilitate pain transmission transmission Dull and nonlocalized

Sharp and well-localized

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

Pain Transmission
• Types of pain related to proportion of ―A‖ to ―C‖ fibers in the damaged areas

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

Pain Transmission
• These pain fibers enter the spinal cord and travel up to the brain. • The point of spinal cord entry is the DORSAL HORN.

• The DORSAL HORN is the location of the ―GATE.‖

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

Pain Transmission
• This gate regulates the flow of sensory impulses to the brain. • Closing the gate stops the impulses.

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

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

Instructors may want to use EIC Image #37: Gate Theory of Pain Transmission

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

Pain Transmission
• Activation of large ―A‖ fibers CLOSES gate • Inhibits transmission to brain
– Limits perception of pain

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

Pain Transmission
• Activation of small ―B‖ fibers OPENS gate • Allows impulse transmission to brain
– Pain perception

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

Pain Transmission
• Gate innervated by nerve fibers from brain, allowing the brain some control over gate • Allows brain to:
– Evaluate, identify, and localize the pain – Control the gate before the gate is open

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

Pain Transmission
―T‖ cells
• Cells that control the gate have a threshold

• Impulses must overcome threshold to be sent to the brain

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

Pain Transmission
• Body has endogenous neurotransmitters
– Enkephalins

– Endorphins

• Produced by body to fight pain
• Bind to opioid receptors

• Inhibit transmission of pain by closing gate

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

Pain Transmission
Rubbing a painful area with massage or liniment stimulates large sensory fibers
• Result:

– GATE closed, recognition of pain REDUCED – Same pathway used by opiates

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

Opioid Analgesics
• Pain relievers that contain opium, derived from the opium poppy or

• chemically related to opium
Narcotics: very strong pain relievers

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

Opioid Analgesics
• codeine sulfate • meperidine HCl (Demerol)

• methadone HCl (Dolophine)
• morphine sulfate

• propoxyphene HCl

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

Opioid Analgesics
Three classifications based on their actions:
• Agonist

• Agonist-antagonist • Partial agonist

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

Opioid Analgesics: Site of action
• Large ―A‖ fibers • Dorsal horn of spinal cord

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

Opioid Analgesics: Mechanism of Action
• Bind to receptors on inhibitory fibers, stimulating them • Prevent stimulation of the GATE

• Prevent pain impulse transmission to the brain

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

Opioid Analgesics: Mechanism of Action
Three types of opioid receptors:
• Mu

• Kappa • Delta

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Opioid Analgesics: Therapeutic Uses
Main use: to alleviate moderate to severe pain
• Opioids are also used for:

– Cough center suppression – Treatment of constipation

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

Opioid Analgesics: Side Effects
• Euphoria • Nausea and vomiting

• Respiratory depression • Urinary retention • Diaphoresis and flushing • Pupil constriction (miosis)
• Constipation
Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Opiate Antagonists
naloxone (Narcan) naltrexone (Revia)
• Opiate antagonists • Bind to opiate receptors and prevent a response Used for complete or partial reversal of opioid-induced respiratory depression

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

Opiates: Opioid Tolerance
• A common physiologic result of chronic opioid treatment • Result: larger dose of opioids are required to maintain the same level of analgesia

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

Opiates: Physical Dependence
• The physiologic adaptation of the body to the presence of an opioid

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

Opiates: Psychological Dependence (addiction)
• A pattern of compulsive drug use characterized by a continued craving for an opioid and the need to use the opioid for effects other than pain relief

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

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

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

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

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

Opiates
• Physical dependence on opioids is seen when the opioid is abruptly discontinued or when an opioid antagonist is administered.
– Narcotic withdrawal
– Opioid abstinence syndrome

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

Opiates
Narcotic Withdrawal Opioid Abstinence Syndrome • Manifested as:
– anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrhea

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

Opioid Analgesics: Nursing Implications
• Before beginning therapy, perform a thorough history regarding allergies, use of other medications,health history, and medical history.

• Obtain baseline vital signs and I & O. • Assess for potential contraindications and drug interactions.

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

Opioid Analgesics: Nursing Implications
• Perform a thorough pain assessment, including nature and type of pain, precipitating and relieving factors, remedies, and other pain treatments.
– Assessment of pain is now being considered a ―fifth vital sign.‖

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

Opioid Analgesics: Nursing Implications
• Be sure to medicate patients before the pain becomes severe as to provide adequate analgesia and pain control.

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

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

Opioid Analgesics: Nursing Implications
• Oral forms should be taken with food to minimize gastric upset. • Ensure safety measures, such as keeping side rails up, to prevent injury.

• Withhold dose and contact physician if there is a decline in the patient’s condition or if VS are abnormal—especially if respiratory rate is below 12 breaths/minute.
Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Opioid Analgesics: Nursing Implications
• Follow proper administration guidelines for IM injections, including site rotation. • Follow proper guidelines for IV administration, including dilution, rate of administration, and so forth. CHECK DOSAGES CAREFULLY

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

Opioid Analgesics: Nursing Implications
• Constipation is a common side effect and may be prevented with adequate fluid and fiber intake.

• Instruct patients to follow directions for administration carefully, and to keep a record of their pain experience and response to treatments. • Patients should be instructed to change positions slowly to prevent possible orthostatic hypotension.
Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Opioid Analgesics: Nursing Implications
• Patients should not take other medications or OTC preparations without checking with their physician.

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

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

Opioid Analgesics: Nursing Implications
Monitor for side effects:
• Should VS change, patient’s condition decline, or pain continue, contact physician immediately. • Respiratory depression may be manifested by respiratory rate of less than 12/min, dyspnea, diminished breath sounds, or shallow breathing.

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

Opioid Analgesics: Nursing Implications
Monitor for therapeutic effects:
• Decreased complaints of pain

• Increased periods of comfort • With improved activities of daily living, appetite, and sense of well-being

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


				
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