Drugs for Pain: Opiod Analgesics Flashcards
define pain. describe nociceptors and role of a and c fiber neurons in pain transmission.
pain is defined as: “an unpleasant sensory and emotional experience associated with actual and potential tissue drainage”
nociceptors are sensory receptors that are activated by noxious insults to peripheral tissues. They have free nerve endings to transmit the pain stimuli into action potentials that are transmitted by a dorsal root ganglion into the spinal cord and up to the brain.
A fiber neurons are myelinated and have a great conduction velocity, transmitting impulses at 6 to 30 m/second. Pain conducted by A fibers is called fast pain and is elicited by mechanical or thermal stimuli.
C fiber neurons are the smallest of all peripheral nerve fibers and they transmit pain at a rate of 0.5/2.0 m/second. C-fiber pain is often described as slow-wave pain because it is slower in it’s onset and longer in duration. It is incited by chemical stimuli or by persistent mechanical or thermal stimulin. C fibers are responsible for central sensitization to chronic pain.
describe steps in pain transmission. (from Porth)
- Pain begins as a message received by nerve endings, such as found in a burnt finger.
- the release of substance P, bradykinin, and prostaglandins sensitize the nerve endings, which helps to transmit the pain from the site of injury towards the brain.
- The pain signal then travels as an electrochemical impulse along the length of the nerve to the dorsal horn on the spinal cord.
- the spinal cord sends the message to the thalamus and then to the cortex.
- pain relief starts with signals from the brain that descend by way of the spinal cord.
- chemicals such as endorphin s are released in the dorsal horn to diminish the pain message.
what types of drugs pass through the blood-brain barrier?
drugs that pass through the blood brain barrier are opioids.
list important responses to the activation of Mu receptors, a class of opioid receptors.
analgesia, respiratory depression, sedation, euphoria, physical dependence, decreased GI motility.
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differentiate the action of opioid antagonist and opioid agonists.
OPIOID AGONISTS:
activate mu receptors and kappa receptors. by doing so they can produce analgesia, euphoria, sedation, respiratory depression, physical dependence and other side effects.
example drug: CODEINE
OPIOID ANTAGONISTS:
act as antagonists at mu and kappa receptors. they don’t produce analgesia or any of the other effects caused by opioid agonists. Their principle use is reversal of respiratory and CNS depression caused by overdose with opioid agonists
example drug: NARCAN
morphine: therapeutic uses, MOA adverse effects nursing implications
therapeutic use: relief of moderate to severe pain
MOA: relieve pain by mimicking the actions of endogenous opioid peptides, primarily at mu receptors.
adverse effects: respiratory depression, constipation, orthostatic hypotension, urinary retention, cough suppression, BILIARY COLIC , emesis, elevation of intracranial pressure, euphoria/dysphoria, sedation, miosis, birth defects, neurotoxicity.
adverse effects of prolonged use: hormonal changes, altered immune function. not sure if clinically relevant.
nursing implications: warn patients not to increase the dosage without consulting the prescriber, against abrupt discontinuation of treatment, about respiratory depression–call hcp if respiratory distress occurs, about drowsiness–potential side effect, inform about symptoms of hypotension and tell them to minimize it by changing positions slowly, encourage patients to void every four hours and to cough at regular intervals. warn patients against the use of alcohol and other depressants.
fentanyl: therapeutic use MOA adverse effects nursing implications
therapeutic use for fentanyl: used to treat pain (regular and breakthrough, used if someone becomes tolerant to other pain medications.
MOA: Fentanyl selectively binds to and activates the mu-receptor in the central nervous system (CNS) thereby mimicking the effects of endogenous opiates.
adverse effects: respiratory depression, sedation, constipation, urinary retention, nausea. respiratory depression is the greatest concern.
nursing implications: warn patients not to increase the dosage without consulting the prescriber, against abrupt discontinuation of treatment, about respiratory depression–call hcp if respiratory distress occurs, about drowsiness–potential side effect, inform about symptoms of hypotension and tell them to minimize it by changing positions slowly, encourage patients to void every four hours and to cough at regular intervals. warn patients against the use of alcohol and other depressants. ALSO warn patients using fentanyl patches to avoid exposing the patch to direct heat because doing so can accelerate fentanyl release.
Meperidine: therapeutic use: mechanisms of action: adverse effects: nursing implications:
therapeutic use: moderate to severe pain, although pain is declining. Best for use in patients who can’t take other opioids and for patients with drug-induced rigors or post anesthesia shivering.
mechanisms of action: selectively binds to and activates the mu-receptor in the central nervous system (CNS) thereby mimicking the effects of endogenous opiates.
adverse effects: excitation, delirium, hyperpyrexia and convulsions.
nursing implications: warn patients not to increase the dosage without consulting the prescriber, against abrupt discontinuation of treatment, about respiratory depression–call hcp if respiratory distress occurs, about drowsiness–potential side effect, inform about symptoms of hypotension and tell them to minimize it by changing positions slowly, encourage patients to void every four hours and to cough at regular intervals. warn patients against the use of alcohol and other depressants.
Methadone therapeutic use mechanism of action adverse effects nursing implications
therapeutic use: relieve pain and treat opioid addiction
mechanism of action: selectively binds to and activates the mu-receptor in the central nervous system (CNS) thereby mimicking the effects of endogenous opiates.
adverse effects: respiratory depression, fatal dysrhythmias, Torsades de pointes, sedation, etc.
nursing implications:
warn against taking more medicine than prescribed, and avoid other CNS depressants (benzos, alcohol and other opioids). Also watch drugs that inhibit CYP3A4 metabolism (because methadone levels can be raised) should be used with care–Clarithromycin, azole antifungal drugs, and HIV protease inhibitors.
Codeine: therapeutic use: mechanism of action: adverse effects: nursing implications:
therapeutic use: relief of mild to moderate pain
mechanism of action: Codeine binds to mu-opioid receptors, which are involved in the transmission of pain throughout the body and central nervous system The analgesic properties of codeine are thought to arise from its conversion to Morphine, although the exact mechanism of analgesic action is unknown at this time
adverse effects: dose-limiting, but toxicity can develop in babies whose mothers are taking Codeine d/t it getting in the breast milk.
nursing implications: teach moms about signs of codeine toxicity in babies: excessive sleepiness, breathing difficulties, poor feeding–seek medical attention if these develop. warn patients not to increase the dosage without consulting the prescriber, against abrupt discontinuation of treatment, about respiratory depression–call hcp if respiratory distress occurs, about drowsiness–potential side effect, inform about symptoms of hypotension and tell them to minimize it by changing positions slowly, encourage patients to void every four hours and to cough at regular intervals. warn patients against the use of alcohol and other depressants.
Oxycodone: therapeutic use mechanism of action adverse effects nursing implications
therapeutic use: relief of mild to moderate pain
extended release for moderate to severe
mechanism of action: selectively binds to and activates the mu-receptor in the central nervous system (CNS) thereby mimicking the effects of endogenous opiates.
adverse effects: drowsiness, headache, dizziness, tiredness; or. constipation, stomach pain, nausea, vomiting, respiratory depression, etc.
nursing implications: swallow OxyContin tablets whole, 80mg formation for all patients who are already opioid tolerant. prescribe appropriately and use as prescribed to combat abuse potential.
general opioids: warn patients not to increase the dosage without consulting the prescriber, against abrupt discontinuation of treatment, about respiratory depression–call hcp if respiratory distress occurs, about drowsiness–potential side effect, inform about symptoms of hypotension and tell them to minimize it by changing positions slowly, encourage patients to void every four hours and to cough at regular intervals. warn patients against the use of alcohol and other depressants.
Hydrocodone therapeutic use mechanism of action adverse effects nursing implications
therapeutic use: relieve pain and suppress cough
mechanism of action: Hydrocodone inhibits pain signaling in both the spinal cord and brain–mu receptors
adverse effects: common: stomach pain, dry mouth, tiredness, headache, back pain, muscle tightening, difficult, frequent, or painful urination, ringing in the ears, difficulty falling asleep or staying asleep, foot, leg, or ankle swelling, uncontrollable shaking of a part of the body
adverse effects: severe: chest pain, agitation, hallucinations (seeing things or hearing voices that do not exist), fever, sweating, confusion, fast heartbeat, shivering, severe muscle stiffness or twitching, loss of coordination, nausea, vomiting, or diarrhea
nausea, vomiting, loss of appetite, weakness, or dizziness
inability to get or keep an erection, irregular menstruation, decreased sexual desire, swelling of your eyes, face, lips, tongue, or throat, hoarseness, changes in heartbeat, hives, itching
difficulty swallowing or breathing
nursing implications: complete dosage as prescribed, same as other opioids–no alcohol or other CNS depressants, orthostatic hypotension, drowsiness, void/cough at regular intervals.
Tramadol therapeutic use mechanism of action adverse effects nursing implications
therapeutic use: moderate to moderately severe pain
mechanism of action: an analog of codeine that relives pain in part by blocking uptake of norepi and serotonin, and part by weak activation of mu receptors.
adverse effects: rare. sedation, dizziness, headache, dry mouth, constipation. However, avoid giving this drug to patients with epileptic hx, as seizures have happened.
nursing implications:
no giving with benzos or alcohol (CNS depression)
avoid giving this drug to patients with epileptic hx (seizure potential)
no combining with a monoamine oxidase inhibitor (hypertensive crisis)
monitor with TCAs, SSRIs, MAOIs, Triptans (serotonin syndrome)
SUICIDE RISK (Do NOT give to suicidal pt, pt. taking sedatives or antidepressants, or patients prone to excessive alcohol use.
Naloxone (Narcan) therapeutic use: mechanism of action: adverse effects: nursing implications:
therapeutic use: reversal of opioid overdose, reversal of postoperative opioid effects, reversal of neonatal respiratory depression.
mechanism of action: competitive antagonist at opioid receptors (blocks opioid actions)
adverse effects: None listed in Lehne….???
nursing implications: titrate dosage carefully. In opioid addicts excessive doses can precipitate withdrawal. In postoperative patients, excessive doses can unmask pain by reversing opioid-mediated analgesia.
what pain relivers are best for postop?
opioid analgesics, such as
tramadol, oxycodone, fentanyl, methadone, dextromethorphan, meperidine, codeine, and buprenorphine.
