LEC 7 - Opioid Analgesics Flashcards
Full agonists (8)
Morphine
Methadone
Oxymorphone
Hydromorphone
Fentanyl
Alfentanil
Sufentanil
Carfentanil
Partial agonists (1)
butorphanol
Agonist - Antagonist (2)
Buprenorphine
Nalbuphine
Antagonists (2)
Nalozone
Naltrexone
mu-agonist 5-HT NE reuptake inhibitor (1)
Tramadol
Drugs that inhibit preception (5)
General anesthetics
Opioids
alpha2 agonists
Benzodiazepines
Phenothiazines
Drugs that inhibit transmission (2)
Local anesthetics
Alpha2 agonists
Drugs that inhibit peripheral sensitazation of nociceptors (transduction) (4)
Local anesthetics
Opioids
NSAID’s
Corticosteroids
Drugs that modulate the spinal pathway (7)
Local anesthetics
Opioids
Alpha 2
Tricyclic antidepressants
NMDA antagonits
NSAIDs
Anticonvulsants
What are the opioid receptors linked to?
Gi proteins
What does Gi protein stimulus cause?
decrease cAMP
What effects does opioids have on ion channels?
Close - Presynaptic Ca2+ channels (u + d + K)
Open - postsynaptic K+ channels (u)
What effects does closing the Ca2+ channels have?
Decrease NT release
ACh
NE
Glutamate
5-HT
Substance P
What is the effect of opening post-synaptic K+ channels?
Hyperpolarization
What are the major overall effects of opioids?
INhibition of pain transmitting ascending systems
Stimulating descending pain transmission inhibiting neurons
What are the actions of opioids at the presynaptic terminal?
u/d/k receptors
decrease gCa2+
decrease NT release
What effects does opioids have post-synaptically?
u receptors
Increase gK+ - IPSP
Where in the body are mu receptors found?
Brain
Dorsal horn of spinal cord
What are the effects of mu receptor activation?
Supraspinal + Spinal analgesia
Euphoria
Sedation
Miosis
Respiratory depression
Chemical dependence
Decrease GI motility (ACh effect)
What NT are effected by mu receptors?
ACh
Dopamine
Where in the body are kappa receptors found?
Cerebral cortex
Spinal cord
Brain regions
What is the result of kappa receptor activation?
Spinal + Supraspinal analgesia
Mild sedation
Dysphoria
Miosis
What NT is affected by kappa? What is the result?
Vasopressin
Stops release to induce diuresis
Where are the delta receptors found?
Limbic system
Cerebral cortex
Spinal cord
What occurs with delta receptor activation?
Spinal + Supraspinal analgesia
Cardiovascular depression
What NT is affected by delta receptors?
Dopamine
What are the three endogenous opioids?
Endorphins
Enkephalins
Dynorphins
What levels of analgesia occur with opioid administration?
Brain
Spinal cord
(rarely peripherial)
What receptor has the largest analgesic effects?
Mu
What is the relationship between duration of action and 1/2 life with opioids? Why?
Duration of action normally shorted then 1/2 life
Desensitization + Down regulation of receptors
What CNS occur with opioids at high and low concentrations?
Low - Depression
High - Excitation
What respiratory effects are seen with opioids?
mu receptors = depressants
will see panting due to change in thermoregulatory set point
What is the effect of the respiratory depression seen with opioids?
Increase in arterial CO2 tension
Decreate in arterial O2 tension
Decrease in pH
What are the cardiovascular effects of opiods?
For the most part spare the CV system
Hypotension can occur
What can be seen in dogs with opioid administration that effects heart rate?
Vagal stimulation
Bradycardia
Induce barorecptor response
Why do you see vasodilation with opioid administration?
Histamine release
What are the GI effects of opioid administration?
IM - vomiting dogs
IV decreases this effect
Constipation + decrease gastric emptying
What are the pupilary effects of opioids?
Mioisis
Mydriasis - Cats + Horses
Morphine - Vomit induction in Dogs
Stimulate chemoreceptor trigger zone
Morphine - Uses
Acute pain - dogs, cats, horses
Sedative to reduce pacing + standing procedures - horse
Antitussive - Dogs
Morphine - BA
<20 % - dogs given PO
Due to first pass effect
Morphine - Excretion
Renal
Morphine - Metabolism
Glucuronidation
Morphine - Adverse effects
Hyperexcitability
Hypotension
Cerebral hemorrhage/edema
Abnormal body temp
What animals see hyperthermia with morphine?
Cats
Horses
Ruminants
Why is cerebral hemorrhage + edema a concern with morphine?
Respiration depressed
Arterial CO2 increase
INcrease cerebral blood flow - increased pressure
What animals see hypothermia with morphine?
Rabbits
Dogs
Primates
Tramadol - Mechanism
mu-receptor agonist
inhibits reuptake of serotonin + NE
What contributes to tramadols analgesic effects?
Inhibition of serotonin + NE