Module 9 Flashcards
Breakthrough pain
episodic bursts of intense pain that “breaks through” the pain control of the medication regime
Ceiling effect
a phenomenon of certain drugs that limits the ability to produce a further effect above a particular dosage level
endogenous analgesia
system nerve signals that relieve pain by suppressing the transmission fo pain signals from peripheral nerves; can be activated by nerve signals entering the brain or by morphine-like drugs
Endorphins
morphine-like neuropeptides that interact with neuroreceptors to inhibit the transmission of pain signals while also producing a sense of euphoria
Enkephalins
morphine-like neuropeptides that interrupt the transmission of pain signals at the spinal cord level by modulation pain, perception, mood, behavior, and neuroendocrine regulation
nociceptors
nerve endings that selectively respond to painful stimuli and send pain signals to the brain and spinal cord
opiod-naive
patients who do not meet opiod-tolerant criteria and have not had at least 60 mg of morphine or an equianalgesic dose of another opioid for a week or longer
opioid-tolerant
patient has been taking at least 60 mg of morphine or an equianalgesic dose of another opioid for a week or longer
patient-controlled
analgesia any method used by patients to administer their own pain medication, typically used to indicate administration through a controlled intravenous pump
Opioid Epidemic
The United States is in the midst of an opioid epidemic.
Much of the early use and abuse of the drugs resulted from the mistaken belief that opioids were not addictive.
The number of deaths from accidental overdose of opioids—both prescription and nonprescription—has eclipsed that of every other drug combined and is now the leading cause of accidental death in the United States.
Ascending pain pathway
Signals from the nociceptors in peripheral tissues are transmitted to the spinal cord and then to the thalamus and cerebral cortex in the brain. The signal is carried to the spinal cord by two types of nerve cells: A-delta fibers and C fibers
A Delta fibers
A-delta fibers, which are myelinated and found mainly in skin and muscle, transmit fast, sharp, well-localized pain signals. Tissue damage resulting from acute injury often produces an initial sharp pain transmitted by A-delta fibers, followed by sensation transmitted by C fibers.
C fibers
C fibers, which are unmyelinated and found in muscle, abdominal viscera, and periosteum, conduct the pain signal slowly and produce a poorly localized, dull, or burning type of pain. After the initial sharp pain transmitted by A-delta fibers following acute tissue injury, a dull ache or burning sensation is transmitted by C fibers. C fibers release substance P and other chemicals at synapses in the spinal cord to transmit pain.
Dorsal horn of the spinal cord
the control center or relay station for information from the A-delta and C nerve fibers, for local modulation of the pain impulse, and for descending influences from higher centers in the central nervous system. Here, nociceptive nerve fibers synapse with nonnociceptive nerve fibers (neurons that carry information other than pain signals).
Thalamus function
a relay station for incoming sensory stimuli, including pain. Perception of pain is a primitive awareness in the thalamus, and sensation is not well localized.
From the thalamus, pain messages are relayed to the cerebral cortex, where they are perceived more specifically and analyzed to determine actions needed.
Descending pathway (inhibitory)
This descending pathway is part of the CNS endogenous analgesia system
Relieves pain by suppressing transmission of pain received from peripheral nerves
Descending pathways release serotonin and norepinephrine to the dorsal horn to:
Inhibit transmission of pain signals (release of substance P)
Stimulate opioid interneurons
Opioid interneurons
stimulated by the release of norepinephrine and serotonin, release morphine-like neuropeptides which include:
* Enkephalins
* Endorphins
* Dynorphins
Morphine-like neuropeptides
work to inhibit the first order presynaptic neuron from releasing substance P, as well as inhibit the postsynaptic neuron, thereby decreasing the pain signal
Morphine-like neuropeptides can also stimulate receptors in the CNS to elicit euphoria. This release can be triggered by excitement, stress, and aerobic exercise among other things.
Opioid Agonists
Prototype: morphine
others: codeine, fentanyl, hydrocodone, oxycodone
MOA of opioids
Relieve moderate to severe pain by inhibiting pain signal transmission from periphery to brain
Opioid pharmacokinetics
Well-absorbed with PO, IM, sub-Q, IV administration
Metabolized in the liver, metabolites excreted in urine
Contraindications of opioids
Existing respiratory depression
* Chronic lung disease
* Liver or kidney disease
* Depression of GI activity.
* Diarrhea caused by toxic poisons.
* Caution with GU/GI surgery, acute abdomen, ulcerative colitis (GI depressive effects of narcotics).
* Caution with head trauma, alcoholics, cerebral vascular disease, delirium tremens (exacerbated by CNS effects of narcotics).
* No Meperidine (Demerol) for patients with kidney failure.
Widespread pharmacologic effects of opioids
- CNS effects: analgesia, CNS depression, decreased mental and physical activity, respiratory depression, N/V, pupil constriction
- GI effects: Nausea & Vomiting, slow motility, constipation, bowel and biliary spasm
- GU : Urinary Retention, hesitancy, loss of libido
- Opioid Overdose Triad: coma, miosis, and respiratory depression
Black box warning present with all opioid analgesics
Black Box Warning present with all opioid analgesics because of potentially fatal adverse effects and risk of drug abuse; analgesics with warnings include
* Fentanyl, hydromorphone, methadone, oxycodone, and oxymorphone
* Highest potential for abuse
* Highest risk of fatal overdoses because of respiratory depression
