Pain Pathways and Opioids Flashcards
(39 cards)
1
Q
pain
A
- an unpleasant sensory and emotional experience associated with actual or potential tissue damage
- subjective, unique to each individual (genetic)
- physical and emotional components
- requires a functional CNS
- involves multiple brain areas (no single pain center)
2
Q
pain pathway
A
nociceptors
- transduction (sensory afferents)
- transmission
- modulation (spinal cord)
- projection (spinothalamic tracts)
- perception
brain
3
Q
classification of pain
A
- categorized according to duration as well as anatomical location or site of origin
- acute vs. chronic
- neuropathic, visceral, somatic
4
Q
acute pain
A
- short-term pain often with an easily identificable cause
- acute pain is the body’s warning of tissue damage or disease
5
Q
chronic pain
A
- pain that persists longer than the normal course of time associated with a particular type of injury
- may be constant or intermittent but it has often outlived any useful purpose, does not help the body to prevent injury
- often more difficult to treat than acute pain
6
Q
nociception
A
- ability to perceive or sense pain
- opiates produce “anti-nociception”
7
Q
analgesia
A
- loss of sensitivity to pain without loss of consciousness
- opiates: ‘narcotic analgesics’
- other drugs classified as non-narcotic analgesics (NSAIDs)
8
Q
hyperalgesia
A
- increased response to painful stimuli
9
Q
allodynia
A
- pain caused by a stimulus that would not normally provoke pain
10
Q
signs of pain
A
- behavioral signs
- physiological changes
11
Q
behavioral signs of pain
A
- can be very species dependent
- vocalization
- protective postures
- mood changes (aggression)
- self-mutilation
- loss of appetite
- shallow/rapid breathing
12
Q
physiological changes with pain
A
- species dependent
- general CV activation (increased sympathetic activity)
- increased stress response (activation of HPA axi)
- hyperglycemia (increased glycogenolysis and increased lipolysis)
- reduced GI activity (ileus)
- reduced immune function (diminished wound healing)
13
Q
therapeutic uses of opiod drugs
A
- analgesic
- anti-tussive
- adjunct to general anesthesia
- emetic
- neuroleptanalgesic
- immobilization/restraint
= CNS!
14
Q
problems with treating pain
A
- difficult to assess pain in animals
- specific behavior for each species
- training personal and use validated scales
- time and efficiency
- subjective assessment
15
Q
multidimensional pain scales
A
- accounts for:
- pain intensity
- sensory and affective qualities of pain
- incorporate sensitive and specific components (behavior, grimace scale)
- Glasglow Composite (GCMPS)
- SF-GCMPS
- University of Melbourne Pain Scale (UMPS)
- categories: physiologic parameters and behavioral responses
16
Q
approaches to alleviate pain
A
- prevention
- acupuncture (may activate endogenous pathways for pain suppression)
- analgesics
17
Q
types of analgesics
A
- drugs that block formation, release or actions of substances that stimulate sensory nerve endings -transduction (NSAIDs)
- drugs that block impulse transmission in sensory nerves (local anesthetics)
- drugs that block or modulate tranmission in spinal/supraspinal pathways or alter the central perception of pain (opioids)
18
Q
sites of analgesic drug action
A
- peripheral-nociceptors (NSAIDs)
- nerve block-sensory afferents (locals)
- epidural injection-spinal cord (opioids)
- CNS action-brain (alpha-2’s)
19
Q
opioid
A
- all drugs, natural and synthetic, that have morphine-like properties
- opioid agonists and antagonists
20
Q
opiate
A
- morphine-like drugs that are exratcted or derived from the opium poppy
- morphine and codeine
21
Q
drug classifications and control
A
- nearly all opioids are controlled
- class I, II, III, IV and V
- I- no approved medical uses with very high abuse potential in humans
- must have DEA license to purchase or presribe
- must keep records of purchase and use
- must store durgs in locked area with limited access
22
Q
opioid receptors
A
- mu (µ) = OP3 (MOP-µ)
- kappa (k) = OP2 (KOP-k)
- delta (∂) = OP1 (DOP-∂)
- most are stimulated by morphine (agonist) and blocked by naloxone (antagonist)
- marked species variation with respect to tissue localization and responses to drugs
23
Q
pharmacological actions of opioids
A
- diverse and drug-specific actions with marked species-dependent effects
- in general, opioids depress CNS, GI and CV systems
24
Q
CNS actions of opioids
A
- analgesia
- sedation
- ventilatory depression
- nausea & emesis
- cough suppression (anti-tussive)
- pupillary effect
25
analgesic action of opioids
* selective reduction and/or alteration of pain sensation w/o loss of consciousness
* **spinal cord-modulation**
* decrease substance P release from sensory afferents
* decrease post-synaptic actions of substance P
* **supraspinal level-perception**
* decrease affective response to pain
* decrease fear/anxiety associated with pain
26
sedative action of opioids
* variable degree based on species, age and demeanor
* additive depression with other CNS depressants
* reduces overall anesthetic requirement in most animals
27
ventilatory depressive actions of opioids
* **depress PCO2 sensitivity of brainstem respiratory center neurons**
* reversible with naloxone
28
nausea and emesis actions of opioids
* caused by **stimulation of brainstem CTZ**
* apomorphine is extremely effective
* reduced by phenothiazines and other dopamine antagonists
* **anti-emetic after first dose-effect of vomiting center**
29
pupillary effect of opioids
* species differences
* dogs, rabbits, humans -\> **miosis**
* cats, horses, sheep, primates -\> **mydriasis**
* birds -\> no change
30
GI actions of opioids
* opioids **inhibit most GI activity**
* constipation and GI stasis
* GI effects involve local as well as CNS actions
* **decrease peristalsis and secretions**
* **increase segmental contractions**
31
CV actions of opioids
* **decrease HR and BP** if there is an increase in **histamine release**
* reversed by **anti-cholinergic agents**
32
codeine
* **morphine derivative**
* **µ-agonist**
* 1/10th potency of morphine as analgesic
* indications: **orally active antitussive** and **mild analgesic**
* long term admin may produce **constipation**
* metabolized in **liver**, and excreted in urine
33
morphine
* **µ-agonist**
* **natural** alkaloid from opium poppy seed
* **moderate lipid solubility** with intermediate ability to penetrate BBB (ideal for epidural)
* relative **high 'first-pass' metabolism**
* metabolized via **glucuronic conjugation** (cats)
* **active metabolites**
* excreted by kidneys
34
fentanyl
* **µ-agonist**
* potent **synthetic** opioid agonist
* **good analgesic** in dogs, cats and horses
* **less CV impact** than morphine (**less histamine** release)
* **fairly short half life** (rapid liver metabolism)
* CRI
35
buprenorphine
* **partial µ-agonist**
* ****binds strongly to µ-receptor and requires higher doses of naloxone to reverse
* **mild to moderate analgesic**
* give SC, IM or IV
* **sublingual** (only in cats!)
* very **slow onset of analgesic** effect (over 30 min) but **long duration of action** (6-12 hours)
36
butorphanol
* **opioid k-agonist/µ-antagonist**
* less side effects than µ-agonists, but causes less analgesia
* mild analgesic in dogs, cats
* less CV and respiratory depression
* **effective anti-tussive** in dogs and cats
* good analgesic in horses and ruminants
* can be used to reverse µ-agonist side effects
37
meperidine
* **µ-agonist**
* **mild analgesia**
* most commonly used as **pre-anesthetic**
* **good sedative** in young and geriatric patients
* **less excitatory effects** in cats and horses
* similar structure to atropine
* **only opioid to cause increase in HR**
38
naloxone
* potent synthetic **opioid-antagonist**
* relatively **short half-life** compared to most opioids
* smaller doses, but frequent
* **reversal agent or treatment of opioid intoxication**
39
neuroleptanalgesia
* drug-induced condition in which the animal is unresponsive to sensory stimuli and shows no response to pain but is NOT completely unconscious
* produced by combo of a neuroleptic agent such as phenothiazines and alpha-2 agonists
