Opioid and Non-Opioid Analgesics Flashcards
Which analgesics effect transduction?
Which analgesics target transmission?
Which analgesics target modulation?
Which analgesics target perception?
The most important site of pain modulation is:
the substantia nigra in the dorsal horn
Pain signals are transmitted on a three-neuron pathway:
First-order neuron: Periphery to dorsal horn
Second-order neuron: dorsal horn to thalamus
Third-order neuron: thalamus to cerebral cortex
Pain is inhibited when:
- spinal neurons release GABA and Glycine
- The descending pathway releases NE, serotonin, and endorphins
What happens when an opioid binds to its receptor?
- Adenylate cyclase activity is decreased
- cAMP is decreased
- Ca conductance is decreased
- K conductance is increased (hyperpolarizes the membrane)
In the brain, where are opioid receptors located?
Periaqueductal gray
locus coeruleus
Rostral Ventral Medulla
In the spinal cord, where are opioid receptors located?
Afferent neurons in the dorsal horn
In the periphery, where are opioid receptors located?
Sensory neurons and immune cells
What are the cardiovascular effects of opioid administration?
Just bradycardia
The only exception is demerol, because of its atropine-like ring
What are the neurological effects of opioids?
What are the cardiovascular effects of opioids?
What are the GI effects of opioids?
How do opioids impact thermoregulation?
They reset the hypothalamic set point, resulting in decreased body temperature
What are the immunologic effects of opioids?
Histamine release (morphine, demerol, codeine)
Inhibition of cellular and humoral function
Suppression of natural killer cell function
Tolerance develops to nearly all the side effects of opioids EXCEPT:
miosis and constipation. Those are neve attenuated
Rank the opioids in order of potency
When does heroin withdrawal begin?
Onset 6-18 hrs
Peak 36-72 hours
Duration 7-10 days
Which opioids undergo hepatic biotransformation?
All of them except remifentanil
Which opioids have active metabolites?
Morphine
Demerol
Maybe hydromorphone
Morphine is conjugated into:
Morphine-3-gluconuride
Morphine-6-gluconuride
Compared to morphine, is M-6-G more or less water soluble?
It is more water soluble, meaning it is less likely to cross the BBB
Why are renal patients more prone to complications from morphine?
M-6-G accumulates in quantities large enough to cross the BBB
Morphine is ______ in the liver
conjugated
Demerol is ______ in the liver
demethylated
What metabolite is produced from demerol?
Normeperidine, which is about 50% as potent as meperidine
What are the side effects of normeperidine?
Myoclonus
Seizures
Remifentanil is metabolized by:
tissue esterases and erythrocytes
NOT PSEUDOchE
Remifentanil is always dosed using:
LBW
Which opioid is associated with anticholinergic side effects?
Demerol
It has an atropine-like ring
Which opioid receptors does demerol stimulate?
mu and kappa
Meperidine is the only opioid that ______
reduces shivering
Meperidine should never be given to patients taking:
MAOIs
Can cause serotonin syndrome
What is the benefit of alfentanil?
It has a rapid onset
Why does alfentanil have a rapid onset?
It has a pKa of 6.5 and it’s a weak base. This means it exists almost entirely in a non-ionized, lipid-soluble form, which makes it easier for it to cross the BBB
Alfentanil is useful for:
blunting SNS response to brief, intense stimulation like intubation or a retrobulbar block
Which drugs can be used to attenuate hyperalgesia from Remifentanil?
Ketamine and Mag
Which opioid receptors does remifentanil agonize?
Mu
Can remifentanil be used in neuraxial anesthesia?
NO! it contains glycine, which can cause skeletal muscle weakness
Methadone reduces pain through three mechanisms:
- Mu receptor agonism
- NMDA antagonism
- MAO reuptake inhibition
How does methadone impact ECGs?
It can prolong the QT
What is the best treatment for muscle stiffness d/t opioid administration?
Paralysis and intubation
Name three partial opioid agonists
Buprenorphine
Nalbuphine
Butorphanol
Which partial agonist can be administered nasally?
Butorphanol
Which partial agonist can be administered transdermally?
Buprenorphine
Name two partial agonists that provide BETTER analgesia than morphine
Buprenorphine
Butorphanol
What is the dose for naloxone?
20-40 mcg at a time
What is the duration of naloxone?
30-45 min
What are the side effects of naloxone in the dependent patient?
Tachycardia
Pulmonary Edema
Cardiac dysrhythmias
Sudden death
What is methylnaltrexone?
Its an opioid antagonist that cannot cross the BBB. It can relieve systemic symptoms of opioid use
Which opioid antagonist does NOT reverse respiratory depression?
Relistor, because it does not cross the BBB
Which opioid inhibits nerve conduction?
Meperedine, because it’s also structurally similar to LAs
