Opioid Analgesics Flashcards
In terms of neurotransmitters, endogenous opioids such as kephalin and endorphins are unique chemically: they are ______________.
pentapeptides–not small molecules like acetylcholine
What is the “opioid motif”?
Tyr-Gly-Gly-Phe-X
Endogenous opioids only affect nearby targets. Why?
Because they are rapidly broken down by peptidases
Endorphans can act as neurohormones. Why can they do so and enkephalin can’t?
Because endorphins are larger–roughly 30 amino acids–and aren’t broken down as quickly.
What two categories of endogenous opioids are least understood?
Dynorphins and endomorphins
Nociceptin does not bind to _____________.
opioid receptors
What type of G-protein are opioid receptors?
Gi/Go
So far there are no drugs that are selective for the delta-opioid receptor. Why would it be desirable to have a drug that did so?
Because the delta receptors do not induce respiratory depression
At what two sites do opioids inhibit pain?
At the first synapse of the pain pathway (in the posteromarginal nucleus of the dorsal horn) which prevents pain signals from ascending, and at the PAG.
Opioids do not cause ___________, like local anesthetics do; and they do not cause __________, like general anesthetic.
block of all sensation; unconsciousness
Opiates are not able to treat __________ pain very well.
neuropathic
What opiate causes hallucinations?
Salvinorin A
Respiratory depression is present even at ________ doses.
normal analgesic
Opiates are contraindicated in cases of ______________.
head injury or respiratory dysfunction (because of their ability to suppress respiratory function); the only exception to the no-pulm disorder rule is with pulmonary edema (the reason is not understood)
What is the weird relationship between opiates and vomiting?
They cause vomiting at low doses but suppress it at high doses.
What descriptive category is dextromethorphan in?
Non-analgesic antitussive.
It still has abuse potential because it blocks NMDA receptors (like ketamine).
What is the brandname of loperamide?
Imodium
What opiate does not induce histamine release?
Fentanyl
Opiate-induced histamine release usually manifests as ______________.
itching, hives, or asthma exacerbation
The main cardiovascular effect of opiates is _________.
indirect because of histamine-induced vasodilation (resulting in hypotension)
While some opioids are readily absorbed from the GI tract (like codeine and methadone), they work better __________.
intravenously (because of first pass metabolism)
Pharmacokinetically, how are morphine and heroin different?
They have the same efficacy, but heroin has greater potency.
10% of Caucasians have a deficiency of CYP2D6 and thus codeine is __________.
less effective, because metabolism activates it
Percocet is ____________.
oxycodone and tylenol
The brand name of meperidine is __________. What is its main advantage?
Demerol; fast on, fast off
Fentanyl, aside from not having as much histamine release, is great because ____________.
it is fast acting and wears off quickly (1 hr vs. 6 hrs for morphine)
What is the main clinical difference between naloxone and naltrexone?
Naltrexone is orally available while naloxone is not.
Tolerance usually takes _____________.
at least 3 weeks
Tolerance is at the __________ level.
receptor level (this is important, because any drug that stimulates mu-opioid receptors will develop cross-tolerance)
What is the difference between physical and psychological dependence?
Physical dependence is needing the drug to maintain a normal physiologic state (i.e., avoiding withdrawal symptoms), while psychological dependence is the continued craving of a drug.
What can be used to treat withdrawal symptoms without stimulating mu receptors?
Clonidine (suppressing sympathetic outflow)
All endogenous opioids are derived from _______________.
proopiomelanocortin (POMC)
What drug stimulates kappa-opioid receptors?
Pentazocine (spinal analgesia)
Inhibitory interneurons (in the spinal cord) are activated by ______________.
serotonin secreted from cells that originate in the PAG and descend to the level of the posteromarginal nucleus in the dorsal horn)
Opioids can induce constriction of the sphincter of Oddi. Where is that?
The biliary tract
Opioids have been known to inhibit the __________ reflex.
baroreceptor (hypovolemia)
Which antagonist can reverse the effect of endogenous opioids?
Naltrexone
The major metabolic path of morphine is through ____________.
glucuronidation in the liver
The drug ____________ is not absorbed from the GI tract but can act locally to block constipation.
alvimopam (similar to naloxone)
