CLASS 3 - PAIN + ANALGESICS Flashcards
What is a prototype drug?
One specific drug that best represents the classification of drugs. Other drugs in the classifcation are compared to the prototype bc it sets the standard for that classification of drugs.
What is a prodrug? Give an example.
A prodrug is a precursor drug that must undergo conversion in the liver to the active form. Ex - codeine is converted to morphine in the liver.
What is an opioid?
Opioid is a general term that is defined as any drug that has actions similar to morphine.
Define opiate.
The term opiate applies only to compounds present in opium.
What is nociception?
Nociception is the activation of the primary afferent nociceptors (PAN) w free nerve endings that respond to noxious (tissue-damaging) stimuli.
Describe the function of nociceptors. What happens if nociceptive stimuli are blocked?
Nociceptors function primarily to sense and transmit pain signals + promote the pain response. If nociceptive stimuli are blocked, pain is not perceived.
Identify 6 chemicals that activate PAN.
Bradykinin, Prostaglandin, Arachidonic acid, Serotonin, Substance P, and Histamine.
Identify the 4 Physiological Dimensions of Pain
Transduction, Transmission, Perception, and Modulation.
Describe the process of Transduction. Where does it occur?
Transduction - conversion of a noxious stimulus to a neuronal action potential.
Occurs at the level of the peripipheral free nerve endings (PANS).
Noxious stimuli cause cell damage with the release of sensitizing chemicals (prostaglandin, bradykinin, serotonin, substance p, histamine) which activate nociceptors and lead to the generation of APs.
What drugs are used to influence transduction? How do they do this?
NSAIDs block the action of COX enzymes which produce prostaglandin.
Local anesthetics, antiseizure drugs, and corticosteroids also block prostaglandin production.
What is transmission? Describe this process.
Transmission is the mvmt of pain impulses from the site of transduction to the brain.
The AP continues from the site of injury along peripheral nerve fibrers (A + C) to the spinal cord. From there, it undergoes processing in the dorsal horn and is then transmitted to the thalamus + cortex.
Identify the differences between A + C fibers in terms of pain sensation, acute or chronic pain, and myelination.
A FIBERS
pain sensation: pricking, sharp, well localized pain + short in duration.
acute pain.
myelinated.
C FIBERS
dull, aching, burning pain, slow onset
chronic
unmyelinated
Identify the 2 drugs used to influence the process of transmission. How do they work?
OPIOIDS - block the release of substance P
CANNABINOIDS - inhibit mast cell degranulation and response of nociceptive neurons
What is referred pain?
Referred pain occurs when the location of pain is referred from its origin to another site.
Describe the process of referred pain in terms of dorsal horn processing.
Once the nociceptive signal arrives in the CNS, it is processed within the dorsal horn of the spinal cord. This processing includes the release of neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on nearby cell bodies and dendrites of cells that may be located elsewhere in the dorsal horn.
Describe the process of referred pain in terms of Wide Dynamic Range Neurons.
The dorsal horn of the spinal cord contains specialized cells called wide dynamic range neurons.
These neurons receive input from noxious stimuli carried by A and C fiber afferent pathways, and non-noxious stimuli from A fibers. These stimuli come from distant areas, providing a neural explanation for referred pain.
Inputs from both nociceptive fibers and A fibers converge on the wide dynamic range neuron, and when the message is transmitted to the brain, pain in the originating area of the body becomes poorly localized.
Describe perception.
Perception is the recognition of, definition of, and response to pain by the individual experiencing it. It is the conscious experience of pain.
In the brain, nociceptive input is perceived as ____.
pain.
Identify 3 drugs used to influence the perception of pain. How do they do this?
OPIOIDS: decrease the conscious experience of pain
NSAIDs: inhibit COX action
ADJUVANTS (ex - antidepressants): depends on the adjuvant
What is modulation?
Modulation involves the activation of descending pathways that exert inhibitory or facilitatory effects on the pathways that exert inhibitory or facilitatory effects on the transmission of pain.
ex - neurons in the brain stem descend to the spinal cord and release substances that inhibit nociceptive impulses.
Which drugs are used to influence modulation? How do they do this?
Tricyclic antidepressants - interfere w reuptake of serotonin + norepinephrine
Identify the 4 sources of pain
Somatic, visceral, neuropathic, and referred pain
What causes nociceptive pain? What is it responsive to?
Nociceptive pain is caused by damage to somatic or visceral tissue. It is the processing of noxious stimuli by an intact nervous system. Responsive to analgesics such as opioids and NSAIDS, or physical modalities.
What are some causes of nociceptive pain?
surgical incision, broken bone, arthritis, etc.
What are the 2 types of nociceptive pain?
Somatic + Visceral Pain.
Describe somatic pain.
Somatic pain is an aching or throbbing sensation. It is well localized and arises form bones, joints, muscles, or CT.
Describe visceral pain.
Visceral pain results from stimuli such as tumor involvement or obstruction. Arises from internal organs such as the intestines and bladder.
What is neuropathic pain? What does it responsive to?
Neuropathic pain is caused by damage to nerve cells or changes in spinal cord processing. It is an abnormal processing of sensory input as a result of injury to the PNS or CNS. Feels like burning, shooting, or stabbing.
Neuropathic pain is difficult to treat, but mgmt includes opioids, antiseizure drugs, and antidepressants.
What are the 2 types of neuropathic pain?
Centrally generated + peripherally generated
Describe Centrally Generated Pain.
Centrally generated pain is an injury to the CNS or PNS; disregulation of the ANS.