Chapter 19 Flashcards
addiction
a chronic neurobiological disease in which genetic, psychosocial and environmental factor induce changes in the individuals behavior to compulsively use drugs despite the harm that may result
Opioid agonists
-drug that attaches to a receptor and initiates an action
Opioid receptor agonists
-Bind to opioid receptors and mimic the effects of the endogenous analgesic peptides
- Interact with mu and kappa receptors
- Inhibit neurotransmitter release and nociceptor signals
- Reduce nerve excitability and alter pain perception
- Pure (mu) agonists - Bind to receptors and produce a response
- Partial agonists - Initiate kappa receptors and partially block mu receptors
analgesics
substance (synthetic or naturally occurring) that inhibits the body’s reaction to painful stimuli or perception of pain
analgesia
relief from pain
Opioid antagonist
- drug that attaches to a receptor, does not initiate an action, but blocks an agonist from producing an effect
- Bind to receptors to prevent agonist from binding - naloxone
- Reverse the mu effects of opioids
antidiuretic hormone (ADH)
substance produced in the hypothalamus and secreted by the pituitary gland that modulates urine production and allows the kidneys to reabsorb water in order to conserve body water
antitussive
a drug that suppressed coughing at a therapeutic dose
examples-Codeine
Hydrocodone
Dextromethorphan
Combined with agents in order to relieve other cold symptoms - may counteract the potential for abuse
Expectorants alter the volume and viscosity of mucus.
Sympathomimetic amines produce nasal decongestion.
Antihistamines decrease mucus secretion.
Alcohol acts as a CNS depressant.
anuria
condition in which no urine is produced
dysphoria
feeling of discomfort or unpleasantness
emesis
vomiting
endogenous
naturally occurring within the body
endorphins
neuropeptides produced within the CNS that interact with opioid receptors to produce analgesia
expectorant
substance that causes the removal (expulsion) of mucous secretions from the respiratory system
hyperalgesia
an abnormally painful response to a stimulus
neuropathic pain
- pain resulting from a damaged nervous system or damaged nerve cells
- abnormal signals or nerves damaged by entrapment, infection, amputation, or diabetes
nociceptor
- specialized peripheral nerve cells sensitive to tissue injury that transmit pain signals to the brain for interpretation of pain
- or free nerve endings, respond to tissue injury and painful stimuli. Nociceptors are located in the skin, muscle, joints, bones, and viscera, and transmit pain signals to the brain for interpretation of pain
nonopioid analgesic
formerly known as nonnarcotic analgesics, such as NSAIDs and COX-2 inhibitors
NSAIDs
nonsteroidal anti-inflammatory drugs’ nonopioid analgesics that relieve pain without producing physical dependence
oliguria
condition in which very small amounts of urine are produced
opiate
drug derived from opium and producing the same pharmacological effects as opium
opioid
- drug that produces the same pharmacological effects as opium and its family of drugs or neuropeptides (enkephalin, endorphin) produced by the body
- Any molecule that acts on the opioid receptors - Drugs that were extracted from opium (opiates) or synthetic chemicals that produced the same pharmacological effects as opium
opioid analgesic
- chemically related to morphine or opium and sued to relieve pain
- Centrally acting analgesics - affect the CNS at any dose
- Tolerance develops to all opioids.
- Physical dependence results from long-term daily use.
- Federally restricted (controlled) substances because of the high potential for abuse
opioid antagonist
a drug that attaches to opioid receptors and displaces the opioid analgesic or opioid neuropeptide
peripheral nerve
part of the nervous system that is outside the central nervous system (the brain or spinal cord) usually near the surface of the tissue fivers or skin
phlem
secretion from the respiratory tract’ usually called mucus
physical dependence
condition in which the body requires a substance (drug) not normally found in the body in order to avoid symptoms associated with withdrawal, or the abstinence syndrome
referred pain
origin of the pain is in a different location than where the individual feels pain
spasmogenic
causing a muscle to contract intermittently, resulting in a state of spasms
synthetic drug
drug produced by a chemical process outside the body
tolerance
ability of the body to alter its response (to adapt) to drug effects so the the effects are minimized over time
Pain
Protective signal
Warn of imminent danger or presence of internal disease
Part of the normal healing process (inflammation)
What are 2 major classes of Analgesic’s?
Opioid analgesics
Non-opioid analgesics
Nociceptive Pain
-Occurs due to the proper functioning of neural equipment (nerve cells, nerve endings, spinal cord, and brain)
- Elements that cause the sensation of pain
- Local irritation that stimulates the peripheral nerves
- Recognition of pain within the CNS
Pathways for Pain Recognition
If the originating signal is transmitted through :
A-delta fibers - pain is sharp
C fibers - pain is dull and achy
Characteristics of Pain
- Pain duration can either be acute or chronic.
- Acute – usually associated with an injury and goes away when healed
- Chronic - persists for weeks, months, or years even with analgesic therapy
- Peripheral sensitization can lead patients to perceive normal stimuli as painful
- Inadequate control of pain can delay the healing process
Types of Pain managment
- Opioid analgesics
- Nonopioid analgesics – NSAIDS, acetaminophen, and COX-2 inhibitors
Clinical Indications of Opioids
-Analgesia, sedation, cough, and diarrhea suppression
- Opioids are considered first-line therapy for:
- Pain associated with procedures (bone marrow transplant)
- Pain due to trauma or cancer (burns)
- Visceral pain (appendicitis)
- Opioids are drug of choice in treating acute postoperative pain due to no increased risk of bleeding (as with NSAIDS)
- Used to relieve acute or chronic pain
- Also used pre-operatively to decrease apprehension to aid in induction of anesthesia
- Suppress cough and treat diarrhea
Sources of Opioids
-Naturally occurring opiates
Morphine and codeine
Hydrocodone, hydromorphone, oxycodone, and oxymorphone
-Synthetic chemicals
Fentanyl
Sites and Mechanism of Opioid Action
- Endogenous analgetic peptides
- Opioid analgesics act selectively within the CNS to reduce the reaction to pain.
- Do not impair the functions of the peripheral nerves; patients respond as though they can tolerate the pain
- Include endorphin, enkephlin, dynorphin, nociceptin, and nocistatin – our body’s built in pain relief
- Opioid analgesics act selectively within the CNS to reduce the reaction to pain.
-Opioid receptors (G-protein receptors)
Mu - Mu1 and mu2
Kappa
Delta
- Each of the endogenous opioid peptides have a preference for one of the opioid receptors.
- May interact with multiple receptors
How do opioids work?
Opioids bind to their G-protein (mu) receptors, resulting in the closure of presynaptic neurons. This prevents the flow of calcium ions into the cell and facilitates the release of neurotransmitters such as acetylcholine, Substance P, catecholamines, and glutamate. Glutamate is an excitatory neurotransmitter that sends the pain signal along the nerve. So pain transmission is prevented by opioids by inhibiting the release of glutamate.
Opioids bind to the postsynaptic mu receptors and open potassium ion channels resulting in the movement of potassium ions out of the cell, which produces a hyperpolarized state. The nerve cannot respond to pain signals, further interrupting the transmission to the brain. Opioids interact with their receptors at different CNS levels
Nonanalgesic opioid effects on the cardiovascular system
- Opioids do not depress cardiac function.
- Help relieve pain during myocardial infarction
- Bradycardia and hypotension may occur
Nonanalgesic opioid effects on the CNS system
- Mood – decrease mental alertness
- Nausea and vomiting
- Respiratory depression
- Miosis
Distribution of Opioid Receptors/side effects
- Widely distributed outside the CNS
- Endogenous peptides
- Modify pain perception and mood
- Regulate cardiovascular, respiratory, and endocrine function
-Side effects
Sedation, euphoria, dysphoria, miosis, constipation, urinary retention, and respiratory depression
Gastrointestinal Tract
Nonanalgesic Opioid effects On smooth muscles
Intermittent muscle contractions or spasms – peristalsis is inhibited
Constipation – parasympathetic stimulation is inhibited by analgesics
Bile Duct
Nonanalgesic Opioid effects On smooth muscles
Spasms in common bile duct, causing increased pressure in the gall bladder which usually leads to intense pain, but the opioid will eliminate the pain
Bronchial tissue
Nonanalgesic Opioid effects On smooth muscles
Spasmogenic action on bronchial smooth muscle
Constriction of bronchioles by release of histamine – making it more difficult to breathe
Antidiuretic effect
Nonanalgesic Opioid effects On smooth muscles
Decreased urination and urine formation by stimulating secretion of antidiuretic hormone
Spasmogenic activity of ureters and sphincter muscles inhibits urine from passing from bladder
Routes and Schedule of Opioid administration
Opioids are available in oral and parenteral preparations.
Administered on a repeated schedule to avoid intense pain
Oral formulations should never be chewed
-If unable to swallow, capsules can be prescribed and opened up and placed on applesauce and swallowed
Factors determining selection and dosage levels
- Intensity and type of pain
- Acute or chronic
- Cancer, MI,postsurgery
Tolerance and physical dependence levels
Opioid Delivery system
Patient controlled analgesia (PCA)
- Dosing is often under patient control.
- Allows the use of the lowest effective dose of opioid before the intensity becomes unbearable – patient feels they have control over the pain
-Nasal spray, lozenges, and patches
Opioid Disposition
Drugs are absorbed in the intestines
Metabolized by the hepatic drug microsomal metabolizing system to produce analgesia
Several opioids are metabolized to products that produce analgesia -duration of analgesic activity
Excreted through the kidneys
Tubular reabsorption of opioids increases:
- Concentration of drug in the blood
- Risk of developing drug toxicity
Adverse Effects of Opioids
Mental confusion Somnolence Nausea and vomiting Dry mouth Constipation Urinary retention Respiratory or cardiovascular depression Opioid-induced histamine release produces hypotension and allergic reactions
What is a black box warning?
Special cautionary warnings that emphasize the level of abuse liability is highest among the opioids
What are some cautions and contraindications when it comes to opioids?
Opioids should not be given in place of nonopioid analgesics.
Opioids should not be used in patients with:
- Acute bronchial asthma, heavy pulmonary secretions, or respiratory depression
- Convulsive disorders, biliary obstruction, or head injuries
Use of opioids during pregnancy should be minimized. Pregnancy Category C or NR
Opioid specific drug interactions
Opioid analgesics potentiate the effects of CNS depressants.
Meperidine and dextromethorphan should not be given with MAO inhibitors.
Rifampin and phenytoin cause withdrawal symptoms when administered with methadone.
Mixing parenteral solutions may result in drug inactivation.
Opioid Tolerance
Develops due to changes in the opioid receptors (desensitization and/or fewer opioid receptors available)
Tolerance to sedation, drowsiness, or respiratory depression is a beneficial response.
Analgesic tolerance is not beneficial to the patient.
Cross-tolerance is relative to the patient’s condition and the specific opioid.
Opioid Physical Dependence
Develops with the chronic use of opioids
Treatment - Controlled gradual tapering of the medication
Opioid Addiction
Complex interaction of factors that leads to lack of control over drug use
Onset of withdrawal should be avoided.
Opioid Treatment
Methadone - Does not produce severe withdrawal symptoms
Levomethadyl acetate - Used to manage opiate addiction
Buprenorphine - Blocks the attachment of opioids to receptors
Drugs that attach to Opioid receptors
Displace the analgesic and rapidly reverse respiratory depression
Pure - Competitive blocking drugs (naloxone)
- Occupy the mu, delta, and kappa opioid receptors but has no agonist activity (stimulation)
- Inhibits the analgesic from attaching to the receptors but does not produce any pharmacological action of its own
Partial
- Produce respiratory depression in normal individuals
- Reverse respiratory depression in case of acute opioid poisoning
Naloxone - Preferred drug for the treatment of acute opioid poisoning
Antagonist treatment of constipation
-Methylnaltrexone bromide
