BIOM 3090 Lecture Notes - Lecture 21: Chemoreceptor Trigger Zone, Opioid Overdose, Biliary Colic
9 Jun 2018
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Opioids – Physiological effects
1) CNS:
o Most provide about 4-6 h of analgesia + sedation (not sleep)
o Sedation is most likely in primates and dogs, excitement id likely in
most other species (cat, horse, ruminants, pig, etc.,) → can be intense
(sham rage)
2) Cardiovascular
o Usually little effect on CVS at the dosages normally administered
o Unlike most opioids, morphine may cause histamine release →
vasodilation → hypotension
3) Respiratory
o Dose-dependent depression
o Intense effect when combined with general anesthetic
o Death from overdose is due to respiratory arrest
o Use naloxone to reverse
o Opioids suppress the cough reflex
4) Gastrointestinal
o Increase segmentation but reduce propulsion in large bowel → stool
becomes dehydrated → constipation
o Bile duct sphincter constriction → increase in gall bladder pressure →
biliary colic
o Nausea & vomiting (chemoreceptor trigger zone MOR stimulation)
5) Urinary bladder
o Sphincter tone increased, detrusor muscle tone increased → urgency
to urinate, but difficult
Opioids – Uses
- Full mu agonists (e.g. fentanyl, morphine) are used to treat moderate to
severe pain
- When combined with a sedative, opioids can cause profound sedation → may
be beneficial prior to surgery
- Antitussive (usually codeine is used for this purpose)
- Fentanyl:
o Full mu agonist
o For profound pain relief
o Potency 100x morphine
o Overdose → seizures
o Constipating, but may defecate first (after admin.)
o Commonly administered as a transdermal patch
o Patch releases a small amount (e.g. 50 micrograms) of drug per hour
▪ Pyrexia may dramatically increase blood flow o the skin and
absorption of drug → may be fatal
▪ Ensure children and pets do not eat the patch – abuse
associated deaths on the rise for past several years
Opioids – Chemical immobilization
- Carfentanyl
find more resources at oneclass.com
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Document Summary
Full mu agonists (e. g. fentanyl, morphine) are used to treat moderate to severe pain. When combined with a sedative, opioids can cause profound sedation may be beneficial prior to surgery. Antitussive (usually codeine is used for this purpose) Carfentanyl: analgesic potency ~ 10 000x that of morphine. Etorphine (m-99: analgesic potency ~ 3 000x that or morphine, used for wildlife (capture of bear, moose, etc. , & in zoos, renders large animals ataxic within seconds (e. g. ~ 5mg. 50/50(cid:499)(cid:524) to be used at the end of the procedure. Certain less addictive opioids are used for over-the-counter anti-diarrheal medications. Two most important examples are: loperamide (imodium, diphenoxylate (lomotil) Both reduce propulsive gut motility (in large bowel) and gut secretions; also constrict anal sphincter: stool remains in large colon longer, more water reabsorbed from stool, potent constipating effect. Bind and block most opioid receptors (competitive inhibitor)
