Terms in this set (26)
What is an opioid?
What are opiates?
• DRUGS WITH MORPHINE-LIKE PROPERTIES
• OPIATES: DRUG DERIVATIVE OF OPIUM (EX.
What is the mechanism of action?
main thing they do is produce analgesia
primary afferent nerve synapses on secondary afferent nerve in spinal cord
decreases flow of calcium on primary afferent which blocks signal to release NT
on secondary afferent blocks K being pumped out to hyper polarize nerve
basically hyper polarize nerve to dampen pain
What do opioids inhibit (mechanism of action)?
What does the effect depend on ?
analgesic effects depend on
1) doseage and efficacy
3) stimulus intensity, character and duration
What are opioid classes based on ?
What are the 4 main opioid receptors?
• Μ - MU
• Δ - DELTA
• Κ - KAPPA
• N/OFQ - NOCICEPTIN / ORPHANIN FQ
What are the subtypes of MU opioids?
What type of analgesia ect does each class provide?
• CLASSIFICATION AS MU1, MU2, MU3
• SUPRASPINAL AND SPINAL ANALGESIA
• MU1 - ANALGESIA
• MU2 - BRADYCARDIA, HYPOVENTILATION,
• OTHER SUBTYPES - UNCLEAR
What suptypes of kappa receptors are there?
What effects do they have?
What are they difficult to distinguish from?
What is the benefit?
If you have severe pain do you want kappa or mu receptors?
Do detla receptors have good or poor analgesia?
What is the distribution of opioid receptors?
EACH RECEPTOR HAS UNIQUE DISTRIBUTION
• DIFFERENT RECEPTOR DISTRIBUTION IN EACH SPECIES
• OPIOID RECEPTORS LOCATED:
• SUPRASPINALLY (BRAIN, BRAINSTEM)
• SPINAL CORD
• DORSAL HORN (PRE OR POST SYNAPTIC), SUBSTANTIA GELATINOSA (PRE-SYNAPTIC, PREVENT SUBSTANCE P RELEASE)
• PERIPHERALLY (SENSORY, SYMPATHETIC
NEURONS, PULMONARY, LEUKOCYTES)
What do mu agonists do?
What happens when you increase dose?
stimulate mu receptors
increased analgesia with increased dose
What does partial mu agonist do?
What does it compete with?
binds mu receptor but elicits
competes with full agonist
What receptors do opioid antagonist bind?
What do they do?
- high affinities for opioid receptors
- displace opioid agonist from Mu and kappa receptors
when you use this they get their pain back as it kicks off the agonist
What do kappa agonist and mu antagonist do?
bind and cause effect at kappa receptor
occupies mu receptor but does NOT give effect
maintains analgesia effects
Are they weak acids or bases?
Lipid soluable or not?
How much does it bind protein?
What is the onset and duration?
- weak base
- high lipid soluability
- more rapid onset
- some protein binding = unbound is diffusible
- onset and durations depends on lipid soluability and protein binding
How can you administer opioids?
• IV - 100% BIOAVAILABILITY, RAPID
• IM, SC
• BUCCAL MUCOSAL, RECTAL, INHALED, OCULAR
How are opioids metabolized?
how are they excreted?
What is the exception ?
excreted by kidneys
exception is remifentanil has significant pulmonary metabolism
How can opioids be given for analgesia?
What is used for moderate-severe pain?
What is used for mild-moderate pain?
What is used for mild pain?
• CAN BE GIVEN SYSTEMICALLY OR EPIDURALLY
• FULL MU AGONISTS FOR MODERATE-SEVERE PAIN
• PARTIAL MU AGONISTS FOR MILD-MODERATE PAIN
• MU ANTAGONISTS-KAPPA AGONISTS FOR MILD PAIN
Is opioid alone sufficient for neuropathic or chronic pain?
Is opioid used for premed?
yes - some animals become dysphoric when opioids are used alone (esp cats and horses)
can cause - euphoria, dysforia or neuroexcitiation
What is the benefit of premeding with opioid?
need less anesthetic
What are the CNS side effects?
↓ CEREBRAL METABOLIC RATE
• NEUROEXCITATION MAY CAUSE REGIONAL INCREASE
• ≈ ∕ ↑CEREBRAL BLOOD FLOW
• DEPENDS ON DRUGS BEING USED
• ≈ INTRACRANIAL PRESSURE
• DEPENDS ON SURGICAL PROCEDURE
• MONITOR VENTILATION
• SAFE FOR CASES WITH ELEVATED INTRACRANIAL PRESSURE
• IF VENTILATION IS MONITORED & CONTROLLED IF NEEDED
What are the respiratory side effects?
INCREASE TOLERANCE ET INTUBATION
• RESPIRATORY DEPRESSION
• DIRECT EFFECTS ON RESPIRATORY CENTERS
• EFFECTS ON CHEMORECEPTOR CENTERS
• DECREASE HYPOXIC VENTILATORY DRIVE
DECREASE C02 VENTILATORY DRIVE
• PANTING - THERMOREGULATORY
What are the cardiovascular side effects?
1) minimal cardiovascular effects
- medullary vagal stimulation
- tachycardial - meperidine, metabolite similar to atropine
3) histamine release --> hypotension
IV morphine and meperidine
What are the urinary side effects?
1) Mu receptor activated renal effects
- ADH release
- atrial natriuretic peptide release
- net effect still some anti-diuresis
2) kappa receptor activation diuresis
- inhibition of ADH
3) urinary retention
- decreased detrusor contractility (fentenyl and buprenorphine)
- decreased sensation of urge (all opioids)
- esp if epidural admin
What are GI side effects?
cerenia will 100% stop and prevent opioid vomiting
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