Ch. 28 Flashcards Preview

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Flashcards in Ch. 28 Deck (38):


- applies only to compounds present in opium


Endogenous Opioid Peptides

3 families:
- enkephalins
- endorphins
- dynorphins


Opioid Receptors

Mu receptors: Analgesia, respiratory depression, euphoria, sedation, and physical dependence
Kappa receptors: Analgesia and sedation; kappa activation may underlie psychotometic effects seen with certain opioids
Delta receptors


Pure Opioid Agonists

- activate mu receptors and kappa receptors
- can produce analgesia, euphoria, sedation, respiratory depression, physical dependence, constipations, and other effects
- morphine: strong opioid agonist and moderate to strong opioid agonists
- codeine: moderate to strong agonists


Agonist-Antagonist Opioids

- pentazocine, nalbuphine, butorphanol, and buprenorphine
- when administered alone, produce analgesia
- if administered, can antagonize analgesia caused by the pure agonist
- rarely used


Pure Opioid Antagonists

- Nalozone (Narcan): prototype of the pure opioid antagonists
- antagonists at mu and kappa receptors
- do not produce analgesia or any of the other effects caused by opioid agonists
- reversal of respiratory and central nervous system depression caused by overdose with opioid agonists
- Methylnaltrexone: used to treat opioid-induced constipation



- source: seedpod of the poppy plant
- actions: pain relief, drowsiness, mental clouding, anxiety reduction
- sense of well-being, respiratory depression
- constipation, urinary retention
- orthostatic hypotension, emesis
- miosis, cough suppression
- biliary colic
- tolerance and physical dependence


Morphine: Therapeutic Use

- relief of pain
- without affecting other senses
- no loss of consciousness
- relieve pain by mimicking the actions of endogenous opioid peptides, primarily at mu receptors


Morphine: Adverse Effect- Resp. Depression

resp. depression:
- infants and elderly are sensitive
- onset: IV, 7 mins; IM, 30 mins; SubQ, 90 mins; may persist 4-5 hours; spinal injection; delayed for hours
- tolerance to resp. depression can develop
- increased depression with concurrent use of other drugs that have CNS depressant actions
- can compromise patients with impaired pulmonary function


Morphine: Constipation

- cause: supressed propulsive intestinal contractions, intensified nonpropulsive contractions, increased ton of anal sphincter, and inhibited secretion of fluids into the intestinal lumen
- complications of constipation include fecal impaction, bowel perforation, rectal tearing, and hemorrhoids
- treatment includes physical activity, increased intake of fiber and fluids, stimulant laxatives, stool softeners, and polyethylene glycol


Morphine: Othrostatic Hypotension

- morphine-like drugs lower bp by blunting the baroreceptor relfex and by dilating peripheral arterioles and veins
- patient teaching: symptoms of hypotension (dizziness) and instructions to sit or lie down if they occur
- hypotension can be minimized by moving slowly when changing from a supine or seated position to an upright position


Morphine: Urinary Retention and Hesitancy

- increases tone in bladder sphincter
- increases tone in detrusor muscle, thereby elevating pressure within bladder and causing sense of urinary urgency
- may interfere with voiding by suppressing awareness of bladder stimuli


Morphine: Cough Supression

- acts at opioid receptors in the medulla to suppress cough
- suppression of spontaneous cough ma lead to the accumulation of secretion in airway
- patients should be instructed to actively cough at regular intervals
- codeine-based and hydrocodone-based cough remedies


Morphine: Biliary Colic

- induces spasm of common bile duct
- epigastric distress to biliary colic
- may intensify rather than relieve pain in patients with pre-existing biliary colic
- meperidine causes less smooth muscle spasm than morphine


Morphine: Emesis

- promotes nausea and vomiting through direct stimulation of chemoreceptor trigger zone of medulla
- emetic reactions are greatest with initial dose and then diminish
-nausea and vomiting is uncommon in recumbent patients but occur 15%-40% of ambulatory patients
- can be reduced by pretreatment with an antimetic and by having patient remain still


Morphine: Elevation of Intracranial Pressure

- supressed resp., morphine increases carbon dioxide content of blood, which dilates cerebral vasculuature and causes intracranial pressure to rise
- if resp. is maintained at a normal rate, intracranial pressure will remain normal


Morphine: Euphoria/Dysphoria

- exaggerated sense of well-being caused by activation of mu receptors
- a sense of anxiety and unease; uncommon among patients in pain, but may occur when morphine is taken in absence of pain


Morphine: Sedation

- drowsiness and some mental clouding
- avoid hazardous activities


Morphine: Miosis

- cause pupilary constriction
- toxic doses: pupils constrict to pinpoint size
- bright lights


Morphine: Neurotoxicity

- delirum, agitation, hyperalgesia
- renal impairment, prolonged high-dose opioid use
- manage: hydration and dose reducation


Adverse Effects From Prologned Morphine Use

- hormonal changes: declinein cortisol levels, increase in prolactin, decrease in LH and FH, testosterone and estrogen
- altered and suppressed immune function


Morphine: Pharacokinetics

- admin by several routes
- not very lipid-soluble
- does not cross BBB easily
- only small fraction of each dose reaches site of analgesic action


Morphine: Tolerance

- increased doses needed to obtain same response
- develops with analgesia, euphoria, sedation, and resp. depression
- cross-tolerance to other opioid agonists
- no tolerance to miosis or constipation develops


Morphine: Physical Dependence

- abstinence sydnrome with abrupt discontinuation
- about 10 hours after last dose, the intial reaction occurs and includes yawning, rhinorrhea, and sweating
- progressing to sneezing, weakness, nausea, vomiting, diarhea, abdominal crmaps, bone and muscle pain, spasms, and kicking movements
- lasts 7-10 days if untreated
- withdrawl is unpleasent but not lethal


Morphine: Drug Interactions

- CNS depressants: intesnify sedation and resp. depression
- Anticholinergic drugs
- Hypotensive drugs
- MAO inhibitors
- agonist-anatagonist opiods
- opioid antagonist


Morphine: Toxicity

- clinical manifestation: classic triad (coma, resp. depression, pimpoint pupils)
- treat: vent support; anatagonist (Narcan)
- guidelines: monitor vital signs before giving, give on a fixed schedule



- 10% converts to morphine in liver
- pain and cough supression
- orally usually



- analgesic actions = to those of codeine
- long-acting analgesics
- immediate release



- 100x more potent than morphine


Dosing Guidelines

- assessment of pain: should be evaluated before opioid admin and about 1 hour after
- dosage determination: opioid analgesic must be adjusted to accomodate individual variation
- dosing schedule: as a rule, opioid should be admin on a fixed schedule
- avoiding withdrawal


Clinical Use of Opioids

- physical dependence: state in which an abstinence sydnrome will occur if the dependence-producing drug is abruptly withdrawn; it is NOT equated with addiction
- abus: drug use that is inconsistent with medical social norms
- addiction: behaviour pattern characterized by continued use of a psychoactive substance despite physical, psychologic, or social harm


Patient-controlled analgesia

- drug selection and dosage regulations
- comparision of patient-controoled analgesia with traditional intramuscular therapy
- IM painful to patient; cause negative side effects (bruising and hematoma formation)
- patient education and family education


Indications for Clinical Use

- postoperative pain
- obstetric analgesia
- myocardinal infarction
- head injury
- cancer-related pain
- chronic noncancer pain


Opiod Anatagonist: Principle Use

- treat opioid overdose and relief of opiod-induced constipation
- reversal of postoperative opioid effects
- reversal of neonatal resp. depression
- management of opiod addiction


Pure Opioid Antagonists

- Narcan (Naloxone)



- action: competitive antagonist
- pharmacolgic effects
- pharmacokinetics
- therapeutic uses: reversal of opioid overdose; reversal of postoperative opioid effects; reversal of neonetal resp. depression (during labour and delivery)



- pure opiod antagonist
- opioid and alcohol abuse
- opioid abuse: prevents euphoria if abuser takes and opiod
- candidates for treatment must be rendered opioid free before naltrexone is started
- does not prevent craving for opioids


Nonopioid Centrally Acting Analgesics

- relieve pain by mechanism largely or completely unrelated to opioid receptors
- do not cause resp. depression, physical dependence or abuse
- not regulated under controlled substances act
ex. Tramadol (suicide risk), Clonidine, Ziconotide, Dexmedetomidine