Opioids Flashcards
Opioids
Agonist at opioid receptors (anything that can be displaced by naloxone)
Opiates
Naturally occurring drugs (alkaloids) extracted from opium
Narcosis
Stupor bordering general anesthesia - Used to be induced with opium - Morphine-type drugs are narcotics
Natural (opiates) Opioids
Alkaloids from seed pods of opium (Papaver somniferum) Ex-Morphine
Semisynthetic Opioids
Substitution of chemical radicals in place of hydrogen atoms at hydroxil positions of morphine Ex- “-morphone” Oxymorphone, Hydromorphone, apomorphone
Synthetic Opioids
Completely manufactured in lab Ex- Fentanyl, Carfentanyl, Butorphanol
Opioid receptor types
mu, delta, kappa
Mu opioid receptor - endogenous ligand
B-endorphins - Endomorphins
Mu Opioid receptor- Main effects
Analgesia - Respiratory depression - Euphoria
Delta opioid receptor- endogenous ligand
Enkephalins
What receptors do enkephalins bind to?
Delta opioid receptors
Delta opioid receptor - Main effects
Analgesia Hormonal effects
What type of receptor do B endorphins and endomorphins bind to?
Mu opioid receptor
Kappa Opioid receptor Endogenous ligand
Dynorphin
What opioid receptor does dynorphin bind to?
Kappa opioid receptor
Kappa opioid receptor - Main effects
Analgesia Dysphoria Diuresis
Full U agonists
Activate u-opioid receptors completely
Partial agonists
Activate some opioid receptors, but not completely
Mixed agonist-antagonists
Activate some opioid receptors and block others
Full Antagonists
Block ALL opioid receptors
Opioid Scheduling Schedule II
Most full u agonists
Opioid scheduling Schedule III
Buprenorphine
Opioid scheduling Schedule IV
Butorphanol Tramadol
Opioid Agonists- MoA -Activation of opioid receptors
Reduces adenylate cyclase activity & cAMP synthesis Hyperpolarizes neurons - K+ efflux Reduces neurotransmitter release by decreasing Ca++ influx
Opioid agonists Pharm Effects Overview
Not potent sedative Is neuroleptanalgesic Not much muscle relaxation Excellent analgesia Respiratory depression Antitussive
Opioid agonists Pharm effects at CNS
Behavioral changes Motor activity Thermoregulation Pupil size Antitussive Vomiting
Opioid agonists - @CNS Effect on behavioral change
CNS depression (dogs, monkey, humans) CNS stimulation (cat, horse, ruminant, pig) - Dysphoria
Opioid agonists- @CNS Effect on motor activity
Depression of motor area (dogs) Increased locomotor activity (horses)
Opioid agonists- @CNS Effect on thermoregulation
Hypothermia (dogs, rabbit, monkey) Hyperthermia (cat, ruminant, horse)
Opioid agonists- @CNS Effect on Pupil size
Miosis (dogs) - stimulate oculomotor nucleus to increase parasympathetic tone Mydriasis (cats, horse, sheep) - excitement & increased sympathetic activity
Opioid agonists- @CNS Antitussive effect
Central inhibition of the cough center
Opioid agonists- @CNS Vomiting effect
Related to route of administration (IM>IV) Emetic stimulation of CRTZ Anti-emetic effect on vomiting center
Opioid agonists- Analgesic effect
Supraspinal Spinal Peripheral (?)
Opioid agonists- Respiratory system effects
Small doses - Increased panting (dogs) at Larger doses- depress respiration
Opioid agonists Larger dose, depressed respiration effects
Reducedd sensitivity to PaCO2 Healthy vs. diseased animals Anesthetics Bronchoconstriction (histamine release)
Opioid agonists Cardiovascular system effects Dogs
Dogs- -Bradycardia & vasodilation, maybe reflex tachycardia, vagal stimulation -Cerebral vasodilation (PaCO2)–> Increased intracranial blood pressure
What should be used to treat cardiovascular system effects in dogs due to opioid agonists?
Can treat with anticholinergics if necessary
Opioid agonists GI tract effects
Vomiting Decreased Motility (central & peripheral)
Opioid agonists Effects of decreased GI motility
Delayed gastric emptying Decreased GI secretions Increased intestinal fluid absorption Slowed peristalsis Constipation Sphincter spasm
Opioid agonists Slowed peristalsis description
Contraction of segmental muscles Relaxation of longitudinal muscles
Opioid agonists Urinary tract effects
Decreased micturition (u agonists) Increased micturition (K agonists)
What effect do U agonists have on the urinary tract?
Decreased micturition
What effect do K agonists have on the urinary tract?
Increased micturition
Opioid agonists Describe effects leading to decreased micturition
u- agonists Increased sphincter tone Stimulation of ADH release
Opioid agonists Describe effects leading to increased micturition
K- agonists Inhibition of ADH release
Opioid agonists Other effects
Histamine release (IV morphine, dogs) Immune system modulation Addiction (Schedule II, III, IV)
Opioid agonists Absorption
IM or IV Variable PO absorption (20% morphine, first-pass metabolism) Epidurally, intrathecally CRI Transdermal (fentanyl) Transmucosal (buprenorphine)
Which Opioid agonist is absorbed transdermally?
Fentanyl
Which Opioid agonists is absorbed transmucosally?
Buprenorphine (remember Cat after surgery)
Opioid agonists Distribution
Well-distributed Plasma protein binding differences Solubility differences
Opioid agonists Metabolism
Hepatic (morphine) vs. non-hepatic (remifentanil)
Opioid agonists Hepatic metabolism
Morphine Conjugation with glucaronic acid Conjugation with sulfuric acid (cats)
Opioid agonists Hepatic metabolism Conjugation with glucaronic acid process
Morphine–> Morphine-3-glucuronide & morphine-6-glucuronide (active metabolites - analgesic)
Opioid agonists Hepatic metabolism Conjugation with sulfuric acid
In cats Morphine–> Morphine-3-Sulphate
Opioid agonists Non-hepatic metabolism
Remifentanil Tissue (muscle, intestine) and plasma esterases
Opioid agonists Elimination
Mainly as metabolites Some as free drug Mainly renal (80%) some fecal (20%) Enterohepatic recirculation (ex etorphine)
Which Opioid agonists goes through enterohepatic recirculation?
Etorphine
Opioid agonists Treatment Uses
Analgesia Preanesthetic Neuroleptanalgesia Antitussive Emesis Antidiarrheal
Opioid agonists Analgesia
Morphine is prototype Before, during, after surgery Spinal analgesia Colic in horses (butorphanol infusion)
What Opioid agonist is used for treatment of colic in horses?
Butorphanol infusion
Opioid agonists Neuroleptanalgesia Drugs used
Combo of sedative & opioid Phenothiazine, benzodiazepine, alpha-2-agonist
Opioid agonists Neuroleptanalgesia Effect
Synergistic effect, deep sedation, borders general anesthesia
Opioid agonists Antitussive
Butorphanol (approved), hydrocodone, codeine, tramadol
What effect do butorphanol, hydrocodone, codeine and tramadol share?
Antitussive. Anti-coughing
Opioid agonists Emesis
Morphine IV in dogs Apomorphine (conjunctival mucosa)
Opioid agonists Antidiarrheal
Loperamide Diphenoxylate
Opioid agonists Loperamide
“Immodium” -Does not cross BBB -Caution with MDR-1 mutants
Opioid agonists Diphenoxylate
Tincture of opium (paregoric)
Opioid agonists Caution with these conditions
Epilepsy Tetanus Strychnine poisoning Head injury (could increase ICP) Severe cardiovascular or respiratory condition **Ceiling effect**
Opioid agonists Reason for caution when have severe cardiovascular or respiratory condition
Potential depression of cough reflex Changes in myocardial blood flow Chest injury? Balance pain vs. respiratory suppression
Opioid agonists As pain meds
Cause of pain should always be diagnosed & treated
Opioid agonists Tolerance & dependence
Less of an issue in veterinary patients
Opioid agonists Antagonist use
Use to revert toxic effects
Opioid agonists Comments/Cautions
May need O2 supplement Vets can be killed by potent opioids! (etorphine, carfentanil)
Opioid agonists Interactions
Sedatives NSAIDS MAO inhibitors Tricyclic antidepressants Serotonin re-uptake inhibitors
Opioid agonists Interactions Sedatives
Synergy to induce neuroleptanalgesia
Opioid agonists Interactions w/NSAIDS
Ex- Aspirin, acetaminophen, ibuprofen -“dose sparing” effect
Opioid agonists Interactions w/MAO inhibitors
Ex- Selegiline, amitraz -Hallucinations in people, serotonin syndrome with tramadol
Selegiline & amitraz are examples of ___?
MAO inhibitors
Aspirin, acetominophen, ibuprofen are examples of ___?
NSAIDS
Opioid agonists Interactions w/ Tricyclic antidepressants
Ex. Amitriptyline Additive CNS depression
Amitriptyline is an example of what type of drug?
Tricyclic antidepressant
Opioid agonists Interactions with serotonin re-uptake inhibitors
Ex. Fluoxetine Serotonin syndrome with pentazocine, tramadol
Fluoxetine is an example of what type of drug?
Serotonin re-uptake inhibitor
What opioid agonists does fluoxetine react with to cause serotonin syndrome?
Pentazocine Tramadol
Describe serotonin syndrome?
Excitation Sweating Rigidity Coma Seizures
Opioid agonists Classifications - u agonist
Morphine Natural opioid Prototypical analgesic Analgesia Preanesthetic Histamine release
U agonist analgesia time chart
Analgesia onset 15 mins Peak 30-45min Duration up to 4h (IM) or 24h (IT)
U agonist - Morphine histamine release
After IV injection (dogs) Give slowly or another route
u agonist - Hydrocodone
Semisynthetic opioid 6x more potent than morphine Sometimes orally to dogs Antitussive (mainly) Analgesic (sometimes)
Hydrocodone human formulation
May contain other drugs -Homotropine -Be aware with human pharmacies
U agonist- Hydromorphine
Semisynthetic opioid Greater lipid solubility Greater potency (8x) than morphine Analgesia Preanesthetic Less histamine release than morphine Less expensive than oxymorphone
Hydrocodone orally to dogs
F= 34-44% Demethylated to hydromorphone
Hydromorphone Analgesia timetable
Onset 5-10min Peak 20-30min Duration similar to morphine 2hr IV 4h IM
U agonist - Oxymorphone
Semisynthetic 10x potency of morphine More lipophilic Analgesic Preanesthetic
Oxymorphone Species uses:
FDA approved for dogs & cats Off-label in horses & pigs
Oxymorphone compared to hydromorphone
Less emesis & histamine release than hydromorphone
U agonist - Methadone
Synthetic opioid NMDA receptor antagonist Serotonin & NE reuptake inhibition Analgesia & potency like morphine
Methadone - species uses
Dogs Cats Horses (excitement) More in Europe than N. Am
U agonist- Fentanyl
Synthetic 100x more lipophilic and potent analgesia than morphine Use before, during, after anesthesia
Fentanyl analgesia time
Onset 1 min Peak 2.5-10min Duration 30 min
Fentanyl - Approved species
Approved in dogs in combination with droperidol
Fentanyl- Administration
IV CRI (after loading IV dose) Transdermal
Fentanyl transdermal patches
Lag time to therapeutic effect (12-24 hrs- dogs, 6-12hr cats) Therapeutic concentrations for 72hr-dogs, 120hr-cats Therapeutic concentrations for 2-12hr after patche removal (accumulation in skin)
Fentanyl transdermal patch DONT CUT IT
Different sizes with different doses Cover part of patch if necessary
How should a Fentanyl patch be disposed of?
**Patch must be flushed for disposal**
How can dysphoria from the Fentanyl patch be controlled?
Acepromazine
U agonist - Carfentanil
Synthetic 10,000x more potent analgesic than morphine -Moose, elk, deer, zoo animals
Carfentanil antagonists
Naloxene Naltrexone Diprenorphine (M50/50)
U agonist - Etorphine M99!!
Synthetic U, K, gamma agonist! ~4000x more potent than morphine -Zoo & wildlife -Dart immobilization (IM)
Etorphine antagonists
Naloxone Diprenorphine (M50/50)
Partial agonist activity
*Picture*
U agonist activity
*Picture*
Partial agonist - Buprenorphine
Semisynthetic u & K antagonist 25x more potent than morphine Neuroleptanalgesia
Buprenorphine analgesic time chart
Slow onset 45 min Long duration 8hr (4hr, dog) Slow diffustion in and out of CNS Ceiling effect
What drugs help buprenorphine cause neuroleptanalgesia
Acepromazine Xylazine
What is needed to reverse respiratory depression from Buprenorphine?
High dose naloxone (or even doxapram)
Agonist- antagonist activity
*Picture*
Agonist/antagonist- Butorphanol
Synthetic K agonist Synthetic u agonist/antagonist 1-7x potency of morphine IV, IM, SC, PO
How can Butorphanol be administered?
IV IM SC PO
Butorphanol analgesic timechart
3hr cat 90 min dogs 30 min horse Visceral not somatic pain Ceiling effect
Pure antagonists
Naloxone Naltrexone/ Diprenorphine (M50/50) Methylnaltrexone (human med)
What are full/pure antagonists used for?
Reverse effects of opioids -Overdose -Opioid-induced respiratory depression
What type of drugs are naloxene, naltrexone/diprenorphine, and methylnaltrexone?
Full/Pure opioid antagonists
Full antagonist - Naloxone
Competitive receptor antagonist (u>K = gamma) Approved in dogs Reverse opioid effects Reverse hypovolemic shock in dogs
Naloxone administration
IV IM SC
Naloxene reversal of canine hypovolemic shock
B-endorphins reduce sympathetic vasoconstrictor response, directly induce venodilation
Naloxene timechart
Rapid onset (few mins) short duration (1-2hr)
Full antagonist - Natrexone
Competitive receptor antagonist (u=K=gamma) Reversal of carfentanil in moose & elk 1/4 of dose IV and remaining 3/4 SC
Full antagonist Diprenorphine (M50/50)
Competitive receptor antagonist (u=k=gamma) Reversal of etorphine in wild & exotics Also reverse carfentanil
Full antagonist - Methylnaltrexone
“Relistor” Human med Doesnt cross BBB Reverse peripheral effects (constipation) without reversing analgesic effects
Other Opioids
Tramadol Apomorphine
Tramadol
Multimodal, central-acting analgesic Oral administration Treat moderate pain or cough in dogs/cats May lower seizure treshold in epileptic patients
Tramadol as analgesic
Multimodal, central-acting Weak u-opioid agonist Serotonin reuptake inhibitor NE reuptake inhibitor M1 receptor antagonist
Apomorphine
Originally, morphine decomposition product Now completely synthesized Vomiting in dogs Poisoning treatment
Apomorphine as vomiting inducer
Low doses and concentrations D2-like family receptor agaonist in CRTZ and vomiting center SC, onto conjunctiva, IV, IM High doses- antiemetic effects (activate central u-opioid receptors?)