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Pain Management
What is Pain?
29
Pharmacology
Graduate
07/06/2010

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Cards

Term
What is Pain?
Definition
It is described as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Term
What specialized receptors perceive pain and where?
Definition

*Dorsal horn by A-delta and C-fibers

*Dorsal horn contains complex circuitry of neurons

*6 Laminae (Rexed's)

*Substantia Gelatinosa (Lamina II)

*Interneurons or 2nd neurons

 

Term
Where is the first and second neurons in the pain pathway located?
Definition

*1st is located in the spinal ganglia or ganglia of CNs

*2nd is located in dorsal horn or the rhombencephalon

Term
What effect does pain have on perfusion?
Definition
*Direct activation of autonomic sympathetic neurons by the processing of nociceptive information of the segmental spinal level can lead to immediate changes in the perfusion of defined areas.
Term
Where are the high concentrations of opioid receptors in the spinal cord?
Definition

*In the dorsal horn in the periaqueductal gray area

*Greatest abundance is substantia gelatinosa

Term
Where do opioid receptors have the highest affinity for opioids but do not have the greatest number?
Definition
*Pulmonary vasculature 
Term
What is the endogenous pathway for pain?
Definition
Periaquaductal gray matter-->Nucleus raphe magnus--> substantia gelatinosa-->APs stimulate enkephalin release OR exogenous given ligands-->Decreases APs to lateral spinothalamic tract
Term
What is the exogenous pathway for pain?
Definition
*AP stimulate enkephalin neurons-->enkephalin released or exogenous given-->decreases action potentials to lateral spinothalamic tract.
Term
How do opioids effect presynaptic receptors?
Definition
*Presynaptic receptors inhibit th release of substance P, glutamate and other neurotransmitters and postsynaptic receptros decrease the evoked excitatory postsynaptic potential (EPSP).
Term
Where are first order and second order receptors found?
Definition

*First order found outside of the cell

*second order found on the inside of the cell

Term
What are the natural ligands for opioid receptors?
Definition

*Enkephalins

*Endorphins

*Dynorphins

Term
What are the most clinically relevant pharmacodynamic measures?
Definition

*Potency

*Speed of Onset

*Duration of Action

Term
What is used as the benchmark analgesic opioid?
Definition
Morphine
Term
List Phenylpiperidines
Definition

*Fentanyl

*Sulfentanyl

*Alfentanil

*Remifentanil

*Methadone

Term
What are important pharmacologic characteristics?
Definition

*Metaboism

*Bioavailability 

*Protein binding

*Lipid solubility

Term
What do all opioid receptors have common?
Definition
They all are G-protein coupled receptors
Term
What are the MOA when G-protein coupled opioid receptors are activated?
Definition

*Potassium ion channels open causing hyperpolarization and decreased neuronal firing 

*Reduction of calcium ion influx and subsequent neurotransmitter release

*Glutamine and substance P release is inhibited

Term
Why can muscle rigidity result with opioid use?
Definition
*Inhibition of dopamine release and GABA pathways in the striatum and substantia nigra.
Term
How can muscle rigidity be treated
Definition
With a partial antagonist such as Nubain or Stadol.  Allows delta and kappa receptors to have opioid agonist on board but removes Mu agonist only.
Term
What nerve fibers and neurotransmitters are associated with acute pain?
Definition

*A-delta nerve fibers 

*Glutamate

Term
What nerve fibers and neurotransmitter are associated with chronic pain?
Definition

*Unmyelinated C fibers at the dorsal roots and free nerve endings

*Substance P

Term
What does substance P do to vessels?
Definition
It increases vasodilation and permeability
Term
Describe Superficial somatic pain, where receptors are located, and what to use for treatment
Definition

*Superficial Somatic pain is characterized by sharp, throbbing, pricking and is well localized

*Nociceptive receptors in skin, sub Q tissue, mucous membranes

*Treat with opioids

Term
Describe deep somatic pain, location of receptors and treatment
Definition

*Deep somatic pain is characterised by dull, aching, quality more diffuse

*Arises from muscle, tendon, joints, and bones

*NSAIDS such as Torodol, good drug

Term
What is radicular pain caused by?
Definition
*Irritation of nerve roots ie disc herniation
Term
What is radiculopathy?
Definition
*Weakness, numbness, tingling or loss of reflexes in the distribution of the nerve.
Term
What does neuropathic pain result from?
Definition

*Injury to the nervous system either central or peripheral.

*Occurs after trauma and many disease

Term
What is the first line therapy in cancer pain treatment?
Definition
*Opioids
Term
Why does cancer pain arise?
Definition

*Arises when a tumor presses on bone, nerves, or body organs.

*Tumor cells lie between capillary and nerve causing inflammation when the chemo destroys the cells.

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