Opiates Flashcards
Effects of opiates
analgesic, antitussive, sedative, gastro-intestinal muscle relaxant
Narcotic
classic term for the opiates and opiate-like drugs; comes from Greek word Narcotikos = to make sleep or to numb.
Heroin is metabolized to morphine in the _____.
Heroin is metabolized to morphine in the brain
Heroin (with two acetyl groups) is a lot more fat soluble that morphine, so it takes a smaller dose.
Fentanyl
a true synthetic opiate that is about 100X as powerful as morphine.
Naloxone/naltrexone
critical drugs, direct antagonists for opiate receptors. Allows blockade of opiate effects (used in EMT cocktail)
Metabolism of opiates:
all opiates are metabolized by liver and excreted by the kidney in urine
Opiate Pharmacodynamics
all opiates are direct agonists that work at a group of receptors in the brain called opiate receptors.
Opiate receptors
all are indirect gating; mediate changes in ion conductances that decrease excitability (K+) or synaptic transmission (Ca2+)
Potassium shunt
Potassium shunt: as sodium goes in, potassium goes out.
3 kinds of opiate receptors
(postsynaptic and presynaptic potassium shunts)
Where do opiates bind?
Brainstem, thalamus, hippocampus
Classic opiate receptor
Mu receptor, most sensitive to morphine and heroin – widespread distribution; underlie euphoric, brain & spinal analgesic, sedative (dorsal horns have a lot of these receptors); GI motility effects
Raphe nuclei:
brain’s main source of serotonin
Delta opiate receptors:
more sensitive to enkephalins, one of the endogenous opiates. Involved in spinal mechanisms of analgesia
Kappa opiate receptors:
most sensitive to dynorphin. Most common in spinal cord and brainstem. Involved in spinal analgesia and sedation – significantly, kappa opiate receptors have analgesic effects without rewarding properties of mu opiates. High in the thalamus, LC, and raphe nucleus.
Nocioceptive neurons, where are they first modulated?
the modulation of pain, but not touch, begins as soon as you hit the CNS at the dorsal root ganglia
Dorsal root ganglia synapse is inhibited by ____
inhibited by 5HT, endogenous opiates, and touch neurons.
Gylcine
in the spinal cord is like GABA in the brain – glycine is the main spinal inhibitor
Opiate tolerance:
develops to most effects; reason why dose must be increased to maintain an analgesic or reinforcing effect of the drug. Generally requires frequent administration, seems to involve enhanced activity of second messengers associated with opiate receptors
