Analgesic narcotics

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Article Objectives

  • Outline the gate theory of pain and explain therapeutic ways to block pain using the gate theory.
  • Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse reactions, and important drug–drug interactions associated with narcotics .
  • Discuss the use of narcotics drugs across the lifespan.
  • Compare and contrast the prototype drugs morphine, pentazocine, naloxone.
  • Outline the nursing considerations, including important teaching points, for patients receiving a narcotic .

Pain

Pain, by definition,

is a sensory and emotional experience associated with actual or potential tissue damage.

The narcotic analgesics drugs are involved in the management of severe pain, whether acute or chronic, all of which work in the central nervous system (CNS)—the brain and the spinal cord—to alter the way that pain impulses arriving from peripheral nerves are processed.

 

Pain perception

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  • When tissue is injured, various chemicals are released and pain results. These chemicals, includes kinins and prostaglandins
  • A-delta and C fibers carry pain impulses to the spinal cord.
  • According to the gate theory of pain, impulses travel from the spine to the cortex via tracts that can be modulated along the way at specific gates.

 

Gate theory

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Opioid Receptors

  • Opioid receptors; are receptors found in CNS (spinal cord and thalamus); these receptors help integrate and relate incoming information about pain.
  • They are activated both by
  • endogenously[naturally] produced opioid peptides (endorphins and the enkephalins), and by
  • exogenously administered opiate compounds[ analgesic narcotics].
  • Activation of this receptors leads to blocking of pain perception.
  • Opioids, narcotics

    • Narcotics are derived from the opium plant; they bind to opioid receptors to
    • relieve pain [ analgesic effect]
    • Sedation
    • and promote feelings of well-being or euphoria.
  • The (µ) mu-receptors which are subtypes of opioid receptors ;are primarily pain-blocking receptors.
  • Besides analgesia, and euphoria mu-receptors also account for.
    • respiratory depression,
    • decreased GI activity,
    • pupil constriction, and
    • the development of physical dependence.
  • Because of the potential for the development of physical dependence and addiction while taking these drugs, the narcotic agonists are classified as
  • controlled substances.

    • The degree of control is determined by the relative ability of each drug to cause physical dependence [addiction].

     

    Schedules of Controlled Substances

    • The Controlled Substances are drugs that are known to have abuse potential.
    • The controlled drugs are divided into five schedules based on their potential for abuse and physical and psychological dependence.
    • Schedule I
    • High abuse potential and no accepted medical use (heroin, marijuana, LSD)
  • Schedule II
    • High abuse potential with severe dependence liability (narcotics, amphetamines, and barbiturates)
  • Schedule III
    • Less abuse potential than schedule II drugs and moderate dependence liability (nonbarbiturate sedatives, nonamphetamine stimulants, limited amounts of certain narcotics)
  • Schedule IV
    • Less abuse potential than schedule III and limited dependence liability (some sedatives, antianxiety agents, and non-narcotic analgesics)
  • Schedule V (C-V):
    • Limited abuse potential. Primarily small amounts of narcotics (codeine) used as antitussives or antidiarrheals.

     

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    Available narcotic Agonists

    • Codeine ;
    • indication
    • relief of mild to moderate pain;
    • As antitussive in case of coughing induced by mechanical or chemical irritation of the respiratory tract.
  • Fentanyl ;
    • Indications
    • for analgesia before, during, and after surgery;
    • transdermal patch for management of chronic pain
    • Narcotic analgesia for patients on mechanical ventilators at ICU.
  • Morphine;
    • Indications
    • Relief of moderate to severe chronic and acute pain;
    • preoperatively and postoperatively.
  • oxymorphone
  • remifentanil
  • sufentanil
  •  

    Therapeutic Actions and Indications

    Indications for narcotic agonists include

    • relief of severe acute or chronic pain[ pain of acute myocardial infarction, pain in patients suffering from malignancy]
    • preoperative medication,
    • analgesia during anesthesia,
    • as antitussives

     

    Pharmacokinetics

    • Intravenous (IV) administration is the most reliable way to achieve therapeutic levels of narcotics.
    • These drugs undergo hepatic metabolism and are generally excreted in the urine and bile.

     

    Adverse Effects

    • Respiratory depression with apnea, cardiac arrest, and shock may result from narcotic-caused CNS respiratory depression.
    • GI effects as
    • constipation ,
    • nausea, vomiting, and
    • biliary spasm
  • urinary retention
  •  

    Contraindications and Cautions

    • C/ I;
    • presence of any known allergy to any narcotic agonist;
    • pregnancy, labor, or lactation
    • after biliary surgery or surgical anastomoses because of the effect of narcotics on GI tract which leads to GI depression .
  • Caution
    • patients with respiratory dysfunction e.g heavy smoker or asthmatic patients .
    • recent GI or genitourinary GU surgery;
    • head injuries,
    • cerebral vascular disease, which could be exacerbated by the CNS effects of the drugs;

     

    Narcotic Antagonists[antidote]

    • Are drugs that bind strongly to opioid receptors, but they do not activate the receptors.
    • Indications
    • blocking unwanted adverse effects associated with narcotics, such as respiratory depression,
    • treatment of narcotic overdose.
  • Type
    • Naloxone (Narcan) is used IV, IM, or SC .
  • Reminder
    • Antidote of benzodiazepine (valium) is
  • Flumazenil (anexate),
    • Antidote of morphine
  • Naloxone (narcan)
  •  

    Nursing Considerations for Patients Receiving Narcotic Agonists

    Assessment: History and Examination

    • Screen for the following conditions, which could be cautions or contraindications for the use of the drug:
    • any known allergies to these drugs;
    • respiratory dysfunction;
    • GI or biliary surgery;
    • renal or hepatic dysfunction.
  • Examinations ;Include screening for baseline status before beginning therapy and for any potential adverse effects. Assess the following:
    • pulse, blood pressure, and cardiac function
    • CNS; orientation, affect, reflexes,
    • Pupil size;
    • Respiration and adventitious sounds;
    • Bowel sounds and reported output;
    • Bladder palpation and voiding pattern.
  • Check liver and renal function tests,
  • electroencephalogram (EEG) and
  • electrocardiogram (ECG) as appropriate.
  •  

    Implementation with Rationale

    • Provide a narcotic antagonist and equipment for assisted ventilation on standby during IV administration to support the patient in case severe reaction occurs.
    • Use extreme caution when injecting a narcotic into any body area that is chilled or has poor perfusion or shock because absorption may be delayed. After repeated doses, an excessive amount is absorbed all at once.
    • Use additional measures for relief of pain, such as
    • back rubs,
    • stress reduction,
    • hot packs, and ice packs to increase the effectiveness of the narcotic and reduce pain.
  • Reassure patients that the risk of addiction is minimal. Most patients who receive narcotics for medical reasons do not develop dependency syndromes.
  • Provide thorough patient teaching, including drug name and prescribed dosage, measures for avoidance of adverse effects,
  •  

    Focus Points

    • Narcotic agonists react with opioid receptor sites to stimulate their activity;
    • Narcotic antagonists are used to treat narcotic overdose or to reverse unacceptable adverse effects.

    Points to Remember

    • Pain occurs any time that tissue is injured and various chemicals are released.
    • The pain impulses are carried to the spinal cord by small-diameter A-delta and C fibers,
    • Opioid receptors, which are found throughout various tissues in the body, but specially in the CNS ,react with endogenous endorphins and enkephalins to modulate the transmission of pain impulses.
    • Narcotics, derived from the opium plant, react with opioid receptors to relieve pain. In addition, they lead to constipation, respiratory depression, sedation, and suppression of the cough reflex, and they stimulate feelings of well-being or euphoria.
    • Because narcotics are associated with the development of physical dependence [addiction], they are controlled substances.
    • Narcotic agonists react with opioid receptor sites to stimulate their activity.
    • Narcotic antagonists, which work to reverse the effects of narcotics, are used to treat narcotic overdose or to reverse unacceptable adverse effects.

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