OPIOID ANALGESIC AGENTS
Analgesics
•Medications that relieve pain without causing loss of consciousness
•Painkillers
•Painkillers
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
–Sudden in onset
–Usually subsides once treated
•Chronic pain
–Persistent or recurring
–Often difficult to treat
Classification of Pain
•Somatic
•Visceral
•Superficial
•Vascular
•Referred
•Neuropathic
•Phantom
•Cancer
•Psychogenic
•Central
•Visceral
•Superficial
•Vascular
•Referred
•Neuropathic
•Phantom
•Cancer
•Psychogenic
•Central
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
•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
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
•Uses the analogy of a gate to describe how impulses from damaged tissues are sensed in the brain
Pain Transmission
Tissue injury causes the release of:
•Bradykinin
•Histamine
•Potassium
•Prostaglandins
•Serotonin
These substances stimulate nerve endings, starting the pain process.
There are two types of nerves stimulated:
•“A” fibers and
•“C” fibers
“A” Fibers “C” Fibers
Myelin sheath No myelin sheath
Large fiber size Small fiber size
Conduct fast Conduct slowly
Inhibit pain transmission Facilitate pain transmission
Sharp and well-localized Dull and nonlocalized
•Types of pain related to proportion of “A” to “C” fibers in the damaged areas
•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.”
•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.
•Bradykinin
•Histamine
•Potassium
•Prostaglandins
•Serotonin
These substances stimulate nerve endings, starting the pain process.
There are two types of nerves stimulated:
•“A” fibers and
•“C” fibers
“A” Fibers “C” Fibers
Myelin sheath No myelin sheath
Large fiber size Small fiber size
Conduct fast Conduct slowly
Inhibit pain transmission Facilitate pain transmission
Sharp and well-localized Dull and nonlocalized
•Types of pain related to proportion of “A” to “C” fibers in the damaged areas
•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.”
•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.
Instructors may want to use
EIC Image #37:
Gate Theory of Pain Transmission
EIC Image #37:
Gate Theory of Pain Transmission
•Activation of large “A” fibers CLOSES gate
•Inhibits transmission to brain
–Limits perception of pain
•Activation of small “B” fibers OPENS gate
•Allows impulse transmission to brain
–Pain perception
•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
“T” cells
•Cells that control the gate have a threshold
•Impulses must overcome threshold to be sent to the brain
•Body has endogenous neurotransmitters
–Enkephalins
–Endorphins
•Produced by body to fight pain
•Bind to opioid receptors
•Inhibit transmission of pain by closing gate
♦Rubbing a painful area with massage or liniment stimulates large sensory fibers
•Result:
–GATE closed, recognition of pain REDUCED
–Same pathway used by opiates
•Inhibits transmission to brain
–Limits perception of pain
•Activation of small “B” fibers OPENS gate
•Allows impulse transmission to brain
–Pain perception
•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
“T” cells
•Cells that control the gate have a threshold
•Impulses must overcome threshold to be sent to the brain
•Body has endogenous neurotransmitters
–Enkephalins
–Endorphins
•Produced by body to fight pain
•Bind to opioid receptors
•Inhibit transmission of pain by closing gate
♦Rubbing a painful area with massage or liniment stimulates large sensory fibers
•Result:
–GATE closed, recognition of pain REDUCED
–Same pathway used by opiates
Opioid Analgesics
•Pain relievers that contain opium, derived from the opium poppy or
•chemically related to opium
Narcotics: very strong pain relievers
•codeine sulfate
•meperidine HCl (Demerol)
•methadone HCl (Dolophine)
•morphine sulfate
•propoxyphene HCl
Three classifications based on their actions:
•Agonist
•Agonist-antagonist
•Partial agonist
•chemically related to opium
Narcotics: very strong pain relievers
•codeine sulfate
•meperidine HCl (Demerol)
•methadone HCl (Dolophine)
•morphine sulfate
•propoxyphene HCl
Three classifications based on their actions:
•Agonist
•Agonist-antagonist
•Partial agonist
Opioid Analgesics: Site of action
•Large “A” fibers
•Dorsal horn of spinal cord
•Dorsal horn of spinal cord
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
Three types of opioid receptors:
•Mu •Kappa •Delta
•Prevent stimulation of the GATE
•Prevent pain impulse transmission to the brain
Three types of opioid receptors:
•Mu •Kappa •Delta
Opioid Analgesics: Therapeutic Uses
Main use: to alleviate moderate to severe pain
•Opioids are also used for:
–Cough center suppression
–Treatment of constipation
•Opioids are also used for:
–Cough center suppression
–Treatment of constipation
Opioid Analgesics: Side Effects
•Euphoria
•Nausea and vomiting
•Respiratory depression
•Urinary retention
•Diaphoresis and flushing
•Pupil constriction (miosis) Constipation
•Nausea and vomiting
•Respiratory depression
•Urinary retention
•Diaphoresis and flushing
•Pupil constriction (miosis) Constipation
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
naltrexone (Revia)
•Opiate antagonists
•Bind to opiate receptors and prevent a response
Used for complete or partial reversal of opioid-induced respiratory depression
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
•Result: larger dose of opioids are required to maintain the same level of analgesia
Opiates: Physical Dependence
•The physiologic adaptation of the body to the presence of an opioid
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
for effects other than pain relief
Opiates
•Opioid tolerance and physical dependence are expected with long-term opioid treatment and should not be confused with psychological dependence (addiction).
•Misunderstanding of these terms leads to ineffective pain management and contributes to the problem of undertreatment.
•Physical dependence on opioids is seen when the opioid is abruptly discontinued or when an opioid antagonist is administered.
–Narcotic withdrawal
–Opioid abstinence syndrome
Narcotic Withdrawal Opioid Abstinence Syndrome
•Manifested as:
–anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrhea
•Misunderstanding of these terms leads to ineffective pain management and contributes to the problem of undertreatment.
•Physical dependence on opioids is seen when the opioid is abruptly discontinued or when an opioid antagonist is administered.
–Narcotic withdrawal
–Opioid abstinence syndrome
Narcotic Withdrawal Opioid Abstinence Syndrome
•Manifested as:
–anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrhea
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.
•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.”
•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.
•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.
•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
•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.
•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.
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.
Monitor for therapeutic effects:
•Decreased complaints of pain
•Increased periods of comfort
•With improved activities of daily living, appetite, and sense of well-being
•Obtain baseline vital signs and I & O.
•Assess for potential contraindications and drug interactions.
•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.”
•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.
•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.
•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
•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.
•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.
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.
Monitor for therapeutic effects:
•Decreased complaints of pain
•Increased periods of comfort
•With improved activities of daily living, appetite, and sense of well-being
The slideshow above contains examples of Opioid Analgesic Agents.