Transcript Opioid Analgesic Agents

Opioid Analgesic Agents
Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.
Analgesics
• Medications that relieve pain without causing
loss of consciousness
• Painkillers
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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
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Pain Transmission
Tissue injury causes the release of:
• Bradykinin
• Histamine
• Potassium
• Prostaglandins
• Serotonin
These substances stimulate nerve endings,
starting the pain process.
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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.”
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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.
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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
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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
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Opioid Analgesics
• Pain relievers that contain opium,
derived from the opium poppy
or
• chemically related to opium
Narcotics: very strong pain relievers
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Opioid Analgesics
• codeine sulfate
• meperidine HCl (Demerol)
• methadone HCl (Dolophine)
• morphine sulfate
• propoxyphene HCl
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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
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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
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Opioid Analgesics: Side Effects
• Euphoria
• Nausea and vomiting
• Respiratory depression
• Urinary retention
• Diaphoresis and flushing
• Pupil constriction (miosis)
• Constipation
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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
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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
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Opiates: Physical Dependence
• The physiologic adaptation of the body to
the presence of an opioid
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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
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Opiates
• Opioid tolerance and physical dependence
are expected with long-term opioid treatment
and should not be confused with
psychological dependence (addiction).
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Opiates
• Misunderstanding of these terms leads to
ineffective pain management and contributes
to the problem of undertreatment.
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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
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Opiates
Narcotic Withdrawal Opioid Abstinence
Syndrome
• Manifested as:
– anxiety, irritability, chills and hot flashes, joint
pain, lacrimation, rhinorrhea, diaphoresis,
nausea, vomiting, abdominal cramps, diarrhea
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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.
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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.”
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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.
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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.
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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
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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.
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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.
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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.
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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
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Central Nervous System
Depressants
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CNS Depressants
Sedatives
• Drugs that have an inhibitory effect on the
CNS to the degree that they reduce:
– Nervousness
– Excitability
– Irritability
– without causing sleep
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CNS Depressants
Hypnotics
• Calm or soothe the CNS to the point that they
cause sleep
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CNS Depressants
Sedative-Hypnotics—dose dependent:
• At low doses, calm or soothe the CNS
without inducing sleep
• At high doses, calm or soothe the CNS to the point
of causing sleep
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Sedative-Hypnotics: Barbiturates
Barbiturates have a very narrow therapeutic index.
Therapeutic Index
• Dosage range within which the drug is effective
but above which is rapidly toxic.
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Sedative-Hypnotics: Barbiturates
Mechanism of Action
• Site of action:
– Brain stem (reticular formation)
– Cerebral cortex
• By inhibiting GABA, nerve impulses traveling in
the cerebral cortex are also inhibited.
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Sedative-Hypnotics: Barbiturates
Drug Effects
• Low doses:
Sedative effects
• High doses:
Hypnotic effects
(also lowers respiratory rate)
Notorious enzyme inducers
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Sedative-Hypnotics: Barbiturates
Therapeutic Uses
• Hypnotics
• Sedatives
• Anticonvulsants
• Surgical procedures
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Sedative-Hypnotics: Barbiturates
Side Effects
Body System
Effects
CNS
Drowsiness, lethargy, vertigo
mental depression, coma
Respiratory
Respiratory depression, apnea,
bronchospasms, cough
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Sedative-Hypnotics: Barbiturates
Side Effects
Body System
Effects
GI
Nausea, vomiting, diarrhea
Other
Agranulocytosis,
vasodilation, hypotension,
Stevens-Johnson syndrome
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Sedative-Hypnotics: Barbiturates
Toxicology
• Overdose frequently leads to respiratory depression,
and subsequently, respiratory arrest.
• Can be therapeutic:
– Anesthesia induction
– Uncontrollable seizures: “phenobarbital coma”
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CNS Depressants: Benzodiazepines
Mechanism of Action
• Depress CNS activity
• Affect hypothalamic, thalamic, and limbic
systems of the brain
• Benzodiazepine receptors
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CNS Depressants: Benzodiazepines
Drug Effects
• Calming effect on the CNS
• Useful in controlling agitation and anxiety
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CNS Depressants:
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,
including supine and erect BPs.
• Assess for potential disorders or conditions
that may be contraindications, and for
potential drug interactions.
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CNS Depressants:
Nursing Implications
• Give 15 to 30 minutes before bedtime for
maximum effectiveness in inducing sleep.
• Most benzodiazepines (except flurazepam)
cause REM rebound and a tired feeling the
next day; use with caution in the elderly.
• Patients should be instructed to avoid
alcohol and other CNS depressants.
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CNS Depressants:
Nursing Implications
• Check with physician before taking any other
medications, including OTC medications.
• It may take 2 to 3 weeks to notice improved
sleep when taking barbiturates.
• Abruptly stopping these medications,
especially barbiturates, may cause rebound
insomnia.
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CNS Depressants:
Nursing Implications
• Safety is important
– Keep side rails up
– Do not permit smoking
– Assist patient with ambulation
(especially the elderly)
– Keep call light within reach
• Monitor for side effects
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CNS Depressants:
Nursing Implications
• Monitor for therapeutic effects
– Increased ability to sleep at night
– Fewer awakenings
– Shorter sleep induction time
– Few side effects, such as hangover effects
– Improved sense of well-being because of
improved sleep
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