CNS pain (opioids)
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Questions and Answers

A drug's ability to cross the blood-brain barrier is primarily dependent on what property?

  • Its lipid solubility, facilitating diffusion across the barrier. (correct)
  • Its protein-binding capacity within the plasma.
  • Its molecular weight and structural complexity.
  • Its degree of ionization in the bloodstream.

    • What is the most accurate description of tolerance as it relates to prolonged drug exposure?

  • A complete cessation of therapeutic benefit due to receptor saturation.
  • An increased sensitivity to a drug's effects over time.
  • A need to increase the dosage to achieve the same therapeutic effect. (correct)
  • The development of new side effects with continued use.

    • What physiological response is expected when a patient abruptly discontinues a drug they have been taking for a prolonged period and has developed physical dependence?

  • An immediate return to the patient's pre-treatment baseline.
  • The onset of a withdrawal syndrome. (correct)
  • A heightened sensitivity to other medications.
  • A paradoxical increase in the drug's therapeutic effects.

    • Which statement best differentiates analgesics from other types of pain-relieving medications?

    <p>Analgesics relieve pain without causing loss of consciousness. (D)</p> Signup and view all the answers

    Among the families of endogenous opioid peptides, which of the of options are correct? (Select all the apply)

    <p>Enkephalins (A), Dynorphins (D)</p> Signup and view all the answers

    When a patient chronically takes a CNS drug, what adaptation is most likely to occur regarding side effects?

    <p>The intensity of side effects diminish but the therapeutic effect remains. (D)</p> Signup and view all the answers

    Which of the following characteristics of a drug would most likely prevent it from crossing the blood-brain barrier?

    <p>High protein binding and ionization. (C)</p> Signup and view all the answers

    Which effect is primarily associated with the activation of mu receptors?

    <p>Respiratory depression (B)</p> Signup and view all the answers

    What distinguishes pure opioid agonists from agonist-antagonist opioids?

    <p>Pure opioid agonists activate both mu and kappa receptors, while agonist-antagonists may block one receptor while activating another. (C)</p> Signup and view all the answers

    Which of the following is a potential consequence of administering an agonist-antagonist opioid to a patient already taking a pure opioid agonist?

    <p>Reversal of analgesia (D)</p> Signup and view all the answers

    What is the primary mechanism of action of naloxone [Narcan] in the treatment of opioid overdose?

    <p>Antagonism of both mu and kappa receptors (B)</p> Signup and view all the answers

    A patient is receiving morphine for post-operative pain. Which of the side effects below is most likely to require intervention?

    <p>Respiratory depression (B)</p> Signup and view all the answers

    What is the main difference between codeine and morphine?

    <p>Codeine is a moderate to strong opioid agonist, while morphine is a strong opioid agonist. (A)</p> Signup and view all the answers

    Which receptor activation may lead to psychotomimetic effects with certain opioids?

    <p>Kappa receptors (C)</p> Signup and view all the answers

    A patient taking buprenorphine regularly experiences a reduced analgesic effect when administered morphine. What is the most likely reason for this?

    <p>Buprenorphine blocks the mu receptors, preventing morphine from binding and exerting its effect (D)</p> Signup and view all the answers

    Which of the following is NOT an effect of pure opioid agonists?

    <p>Reversal of CNS depression (D)</p> Signup and view all the answers

    What is the typical duration of untreated morphine abstinence syndrome?

    <p>7 to 10 days (D)</p> Signup and view all the answers

    Approximately how long after the last dose of morphine do initial abstinence symptoms typically appear?

    <p>10 hours (B)</p> Signup and view all the answers

    Which of the following is an initial symptom observed in morphine abstinence syndrome?

    <p>Rhinorrhea (A)</p> Signup and view all the answers

    What is the primary concern regarding morphine withdrawal?

    <p>It is intensely unpleasant, but typically not lethal (C)</p> Signup and view all the answers

    Which drug class, when combined with morphine, poses the greatest risk of severe respiratory depression?

    <p>CNS depressants (A)</p> Signup and view all the answers

    Why should morphine be used cautiously in patients with head injuries?

    <p>It masks neurological symptoms (D)</p> Signup and view all the answers

    Which route of fentanyl administration is commonly used for surgical anesthesia?

    <p>Parenteral (C)</p> Signup and view all the answers

    Which factor can accelerate the absorption of fentanyl from a transdermal patch?

    <p>Heat (A)</p> Signup and view all the answers

    What is the relative potency of fentanyl compared to morphine?

    <p>100 times more potent (A)</p> Signup and view all the answers

    Which of the following is a transmucosal formulation of fentanyl?

    <p>Sublingual spray (D)</p> Signup and view all the answers

    What is the primary mechanism of action for Pentazocine (Talwin)?

    <p>Agonist activity at Kappa opioid receptors and antagonist activity at Mu opioid receptors. (B)</p> Signup and view all the answers

    Why is opioid pain status generally evaluated both before and after opioid administration?

    <p>To assess the effectiveness of the opioid dosage and adjust for individual variation. (B)</p> Signup and view all the answers

    In the context of opioid therapy, what distinguishes patient-controlled analgesia (PCA) from traditional intramuscular (IM) therapy?

    <p>IM injections can cause negative side effects such as bruising and hematoma formation. (C)</p> Signup and view all the answers

    What is a crucial consideration when discontinuing opioid therapy for a patient who has been receiving opioids regularly?

    <p>Abrupt cessation should always be avoided to prevent withdrawal symptoms. (B)</p> Signup and view all the answers

    Beyond overdose treatment, what is another principal use of opioid antagonists?

    <p>Relief of opioid-induced constipation. (B)</p> Signup and view all the answers

    What is the primary mechanism by which morphine relieves pain?

    <p>By mimicking the actions of endogenous opioid peptides at mu receptors. (A)</p> Signup and view all the answers

    Which route of administration of morphine is likely to have the slowest onset of action?

    <p>Oral (A)</p> Signup and view all the answers

    What is the most appropriate first-line treatment for morphine toxicity characterized by severe respiratory depression?

    <p>Providing ventilatory support. (D)</p> Signup and view all the answers

    Why does only a small fraction of a morphine dose reach the site of analgesic action in the body?

    <p>Morphine is not very lipid-soluble and does not cross the blood-brain barrier easily. (D)</p> Signup and view all the answers

    Which of the following physiological responses is an uncommon effect of morphine?

    <p>Diarrhea (C)</p> Signup and view all the answers

    What vital sign should be most closely monitored before administering a dose of morphine?

    <p>Respiratory rate (C)</p> Signup and view all the answers

    A patient is exhibiting pinpoint pupils and a decreased respiratory rate. Which condition should be suspected?

    <p>Morphine toxicity (C)</p> Signup and view all the answers

    Morphine-induced orthostatic hypotension is due to which of the following mechanisms?

    <p>Peripheral vasodilation. (B)</p> Signup and view all the answers

    A patient on long-term morphine therapy requires a higher dose to achieve the same level of pain relief. Which of the following best explains this phenomenon?

    <p>Tolerance. (C)</p> Signup and view all the answers

    Which of the following actions of Morphine could exacerbate symptoms of a patient with chronic Obstructive Pulmonary Disease (COPD)?

    <p>Cough suppression (C)</p> Signup and view all the answers

    Flashcards

    Blood-Brain Barrier

    A barrier that limits drug entry into the brain, allowing only lipid-soluble drugs to pass.

    Lipid-Soluble Drugs

    Drugs that can easily cross the blood-brain barrier due to their fat affinity.

    Tolerance

    A decreased response to a drug after prolonged use.

    Physical Dependence

    A condition where stopping a drug leads to withdrawal symptoms.

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    Analgesics

    Drugs designed to relieve pain without causing loss of consciousness.

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    Opioids

    A class of drugs that are the most effective for pain relief.

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    Endogenous Opioid Peptides

    Natural peptides in the body that relieve pain; includes enkephalins, endorphins, and dynorphins.

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    Morphine Source

    Derived from the seedpod of the poppy plant.

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    Pharmacologic Actions of Morphine

    Includes pain relief, drowsiness, and anxiety reduction.

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    Respiratory Depression

    Reduced breathing rate caused by morphine use.

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    Classic Triad of Morphine Toxicity

    Coma, respiratory depression, and pinpoint pupils.

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    Naloxone

    An antagonist used to reverse morphine overdose effects.

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    Admin Routes for Morphine

    Can be administered orally, intramuscularly, or IV.

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    Miosis

    Constricted pupils that occur with morphine use.

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    Biliary Colic

    Pain caused by issues in the biliary system, sometimes from morphine.

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    Euphoria/Dysphoria

    Overactive pleasure or intense discomfort from morphine.

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    Therapeutic Use of Morphine

    Relief of pain without loss of consciousness or other senses.

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    Opioid Receptors

    The three main classes: Mu, Kappa, and Delta receptors. Mu involves analgesia, euphoria, and dependence.

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    Mu Receptors

    Opioid receptors responsible for analgesia, sedation, euphoria, and physical dependence.

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    Kappa Receptors

    Opioid receptors that provide analgesia and sedation; may cause psychotomimetic effects.

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    Delta Receptors

    Opioid receptors involved in modulating analgesia but not deeply discussed like Mu and Kappa.

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    Pure Opioid Agonists

    Drugs that activate Mu and Kappa receptors, producing analgesia and euphoria.

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    Moderate to Strong Agonists

    Opioids like morphine and codeine that produce significant pain relief but vary in strength.

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    Agonist-Antagonist Opioids

    Drugs like pentazocine that act as both agonists and antagonists, producing analgesia alone but can block pure agonists.

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    Pure Opioid Antagonists

    Drugs like naloxone that block agonist effects without producing analgesia.

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    Naloxone (Narcan)

    The prototype pure opioid antagonist used to reverse opioid overdose effects.

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    Abstinence Syndrome

    Withdrawal symptoms that occur with abrupt discontinuation of morphine.

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    Withdrawal Symptoms

    Physical reactions such as yawning, sweating, and nausea due to stopping morphine suddenly.

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    Duration of Withdrawal

    Unpleasant withdrawal symptoms last for 7 to 10 days if untreated.

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    CNS Depressants Interaction

    Morphine can be dangerous when combined with central nervous system depressants.

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    Precautions for Morphine

    Considerations such as respiratory issues and pregnancy before using morphine.

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    Fentanyl Potency

    Fentanyl is 100 times more potent than morphine.

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    Routes of Fentanyl Administration

    Fentanyl can be administered via parenteral, transdermal, or transmucosal routes.

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    Transdermal Fentanyl

    A method of delivering fentanyl through the skin using patches.

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    Transmucosal Fentanyl

    Fentanyl formulations delivered through mucous membranes, such as lozenges.

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    Violent Sneezing in Withdrawal

    A physical symptom that can occur due to morphine withdrawal.

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    Hydrocodone (Vicodin)

    Most widely prescribed opioid in the U.S., often combined with other pain relievers.

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    Buprenorphine

    An opioid used in a patch (Butrans) and sublingual film (Suboxone) for pain and addiction treatment.

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    Patient-Controlled Analgesia

    A system where patients manage their own pain relief with devices, preventing multiple injections.

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    Opioid Antagonists

    Medications used to treat overdose, opioid-induced constipation, and manage addiction.

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    Study Notes

    CNS/Pain Introduction

    • Central Nervous System (CNS) Pharmacology is introduced.

    Blood-Brain Barrier

    • The blood-brain barrier impedes drug entry into the brain.
    • Lipid-soluble drugs can pass through the blood-brain barrier more easily.
    • Protein-bound or highly ionized drugs cannot easily pass through.

    Adaptation to Prolonged Drug Exposure

    • Chronic use of CNS drugs may decrease the intensity of side effects, while therapeutic effects remain strong.
    • Morphine, used for pain relief, commonly causes nausea early on, but the nausea reduces, while analgesic effects persist.

    Tolerance & Physical Dependence

    • Tolerance is a decreased response during prolonged drug use.
    • Physical dependence is where abrupt discontinuation of a drug precipitates withdrawal symptoms.

    Analgesics & Opioids

    • Analgesics relieve pain without causing unconsciousness.
    • Opioids are the most effective pain relievers available.

    Endogenous Opioid Peptides

    • Enkephalins, endorphins, and dynorphins are three families of peptides.

    Opioid Receptors

    • Mu receptors are associated with analgesia, respiratory depression, euphoria, sedation, and physical dependence.
    • Kappa receptors are associated with analgesia and sedation; activation may cause psychotomimetic effects in some opioids.
    • Delta receptors are also present.

    Classification of Drugs as Opioid Receptors

    • Opioid drugs can be agonists, partial agonists, or antagonists.
    • Pure opioid agonists, agonist-antagonist opioids, and pure opioid antagonists exist.

    Pure Opioid Agonists

    • Activate mu and kappa receptors.
    • Can result in analgesia, euphoria, sedation, respiratory depression, physical dependence, constipation, and other effects.
    • Morphine is a strong opioid agonist.
    • Codeine is a moderate to strong opioid agonist.

    Agonist-Antagonist Opioids

    • Pentazocine and buprenorphine produce analgesia when administered alone.
    • Administered with a pure opioid agonist, they can antagonize the analgesia caused by the agonist.

    Pure Opioid Antagonists

    • Naloxone (Narcan) is a prototype pure opioid antagonist.
    • Works on mu and kappa receptors.
    • Do not produce analgesia or related effects.
    • Reverses respiratory or CNS depression caused by opioid overdose.

    Basic Pharmacology of Opioids

    • Strong opioid agonists (includes morphine and other strong opioid agonists).
    • Moderate to strong opioid agonists (includes agonist-antagonist opioids).

    Morphine

    • Source: Seedpod of the poppy plant.
    • Overview of pharmacologic 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 occur. Euphoria/Dysphoria.
    • Toxicity: Clinical manifestations (classic triad - coma, respiratory depression, pinpoint pupils), treatment (ventilatory support, antagonist Naloxone (Narcan), general guidelines, monitor vital signs, give on a fixed schedule).
    • Therapeutic use: Pain relief without impairing other senses. Mimicking endogenous opioids primarily at mu receptors.
    • Pharmacokinetics: Administered via several routes (oral, intramuscular, intravenous, subcutaneous, epidural, intrathecal). Not very lipid-soluble, does not cross blood-brain barrier easily,only a small fraction of each dose reaches site of analgesic action.
    • Tolerance and physical dependence: physical dependence, abstinence syndrome with abrupt discontinuation, reactions about 10 hours after last dose include yawning, rhinorrhea, and sweating. Progresses to violent sneezing, weakness, nausea, vomiting, diarrhea, abdominal cramps and kicking movements. Lasts about 7-10 days if untreated. Withdrawal is unpleasant but not always lethal unlike some CNS depressants.
    • Abuse liability precautions: Decreased respiratory reserve, pregnancy, labor and delivery, head injury, other precautions.
    • Drug interactions: CNS depressants, anticholinergic drugs, hypotensive drugs, monoamine oxidase inhibitors, agonist-antagonist opioids, opioid antagonists, other interactions.

    Other Strong Opioid Agonists

    • Fentanyl (Duragesic, Abstral, Actiq, Fentora, Onsolis, Lazanda, Subsys) - 100 times more potent than morphine, delivered via parenteral, transdermal, transmucosal routes.
    • Alfentanil, sufentanil, remifentanil, meperidine and methadone are discussed as separate classes.
    • Hydromorphone (Dilaudid): Morphine derivative, potent, given to those with severe pain, highly addictive.

    Moderate to Strong Opioid Agonists

    • Include codeine, oxycodone, hydrocodone (Vicodin).
    • Codeine's actions and uses, preparations, dosage, and administration. 30mg provides same effect as 325mg of acetaminophen
    • Oxycodone analgesic actions equivalent to codeine, long-acting analgesics, controlled-release formulations (OxyContin).
    • Hydrocodone (Vicodin): Most widely prescribed in the United States, combined with aspirin, acetaminophen, or ibuprofen.

    Agonist-Antagonist Opioids

    • Pentazocine (Talwin): Agonist at Kappa receptors, antagonist at Mu receptors, limited respiratory depression, ability to precipitate withdrawal in opioid-addicted pts.
    • Buprenorphine (Butrans, Suboxone): 7-day patch (Butrans), sublingual film (Suboxone); used for pain management and opioid addiction treatment.

    Dosing Guidelines

    • Assessment of pain (evaluated before and after administration).
    • Dosage determination (adjusted to accommodate individual variations).
    • Dosing schedule (fixed schedule, as a rule).
    • Avoiding withdrawal.

    Clinical Use of Opioids

    • Balancing pain relief with minimizing abuse potential.
    • Minimizing fears about: physical dependence, addiction.
    • Patient-controlled analgesia (devices, drug selection, dosage regulations, comparison with IM therapy).
    • Multiple intramuscular injections (patient discomfort, potential for bruising, hematoma).
    • Pain relief via patient education and involvement, including family education.

    Opioid Antagonists

    • Principal uses: treatment of opioid overdose, opioid-induced constipation, reversal of postoperative opioid effects, reversal of neonatal respiratory depression, management of opioid addiction.

    Naloxone

    • Mechanism of action: Competitive antagonist.
    • Pharmacologic effects.
    • Pharmacokinetics
    • Therapeutic uses: Reversal of opioid overdose, drug of choice for pure opioid agonist overdose, reversal of postoperative opioid effects. Titrate cautiously when physical dependence is present. Reversal to achieve adequate ventilation and pain management. Reversal of neonatal respiratory depression.

    Nonopioid Centrally Acting Analgesics

    • Relieve pain through mechanisms unrelated to opioid receptors.
    • Does not cause respiratory depression, physical dependence, or abuse.
    • Not subject to the Controlled Substances Act.

    Nonopioid Centrally Acting Analgesics (cont'd)

    • Tramadol (Ultram): Combination agonist and nonopioid actions, moderate to moderately severe pain relief. Side effects include sedation and dry mouth. Drug interactions include CNS depressants; abuse risk exists. Suicide risk. Preparations include immediate-release and extended-release formulations.

    • Clonidine (Duraclon): Treatment of hypertension and severe pain; Alpha2-adrenergic agonist in pain relief mechanism. Advers effects include cardiovascular issues such as severe hypotension, rebound hypertension, and bradycardia. Also has contraindications.

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