03 - Opioids and Context Sensitive Half Time Flashcards
Opioid subreceptors and what they do?
Mu - analgesia, resp depression, pruritis, constipation, urinary retention Kappa - analgesia, sedation Delta - constipation, urinary retention Sigma - ?? ?? - constipation, urinary retention
Most opioids bind to which receptor?
Mu
Mechanism of opioids and where their receptors are found
Inhibit release and response of excitatory neurotransmitters in nociceptive neurons
Receptors exist through out CNS and peripheral nerves
Most rapid and complete route of opioid absorption
IV
IM morphine and meperidine takes
20-60 min
Transmucosal absorption of fentanyl takes
10 min
Transdermal absorption of fentanyl takes
14 to 24 min (reservoir in dermis)
Benefits of neuraxial opioid absorption
No sympathectomy, motor blockade, or loss of proprioception
Specific visceral > somatic analgesia
How does neuraxial opioid abs work?
Diffusion to opioid receptors in the spinal cord
The effects of neuraxial abs are less true with __________ due to
Lipid soluble opioids like fentanyl
More systemic absorption
Distribution half life of opioids
5-20 min
First pass uptake of opioids
In the lungs
Which opioids have active metabolites
Morphine and meperidine (Demerol)
The template for opioids
Morphine
Morphine acts on ______ receptors
Mu
Onset and peak of morphine
5 min onset
Peak in 10-40 min
Morphine can decrease MAC by
65%
Redistribution of ________ is age dependent
Morphine
7-8 hours in neonates and 4.5 hours for ages 61-80
Elimination half life of morphine
1.7 - 3.3 hours
Which opioid should be used with caution in renal failure?
Morphine
Meperidine should not be used at all!!
Neuro effects of morphine
Sedation, cognitive impairment, euphoria
Decr CMRO2, CBF, ICP if normocarbia maintained
Miosis and pruritis
Muscle rigidity after large doses
Nausea/vomiting - stimulates CTZ in medulla
Resp effects of morphine
Blunts hypercapnic drive
Hypoventilation
Rousable apnea
Suppresses cough reflex
GI effects of morphine
Decreased motility (constipation), slower gastric emptying Increased common bile duct tone Biliary spasm (sphincter of Oddi)
GU effects of morphine
Urinary retention
CV effects of morphine
Hypotension at higher doses
Can cause brady at high doses
5-10x more potent than morphine
Hydromorphone (Dilaudid)
Length of action for hydromorphone
3-4 hours
How is heroin produced?
Acetylation of morphine
Which receptor is responsible for reducing shivering?
K
Max daily dose of meperidine (Demerol)
600 mg, 1000 mg
Synthetic mu receptor agonist
Fentanyl (sufentanil, alfentanil)