Pain Control and Opioid Analgesics Lecture PDF Flashcards
Analgesic definition and 2 major classes
Drugs that relieve pain without causing loss of consciousness
-Narcotics (act on CNS to inhibit pain impulses) and nonnarcotics (act peripherally to inhibit formation of pain impulse by nociceptive stimuli by inhibiting prostaglandin synthesis)
Function of pain
-protective signal (warns of danger or internal disease)
Types of pain
-Intense sharp stinging
-dull burning aching
(transmitted by different types of neurons)
Somatic pain vs visceral pain
Somatic is well localized to specific local subcutaneous or musculoskeletal tissue while visceral originates in thoracici or abdominal structures and is often poorly localized and referred to somatic structures
Nociceptive (non neuropathic) vs neuropathic pain
Nociceptive occurs with normal conduction of nervous system, neuropathic is where nerves are damaged (often from trauma)
Why is it hard to relax or sleep with pain
The major ascending pain tracts (such as spinothalamic) passes thru the reticular formation stimulating it, the ascension into the limbic structures assigns emotionative suffering along with it
Opioid mech of action
Bind to the same receptors as endorphins and enkephalins that, alongside seratonin and norepi, are released in the descending inhibitory pathway from the brain to exert an inhibitory effect thru inhibition of adenylyl cyclase resulting in decreased cAMP and decreased Ca2+ influx that pushes out neurotransmitters on a spinal interneuron that is receiving a pain signal
A B sensory fibers
Sensory fibers that stimulate the relase of enkephalins from spinal cord neurons that have an inhibitory effect on spinal interneuron receiving pain signal, released upon transcutaneous eleectrical nerve stimulation as well as rubbing or massaging injured tissue
3 receptor classifications that morphine has an effect on
- mu
- kappa
- delta
examples of strong opioid agonists (4)
- fentanyl
- hydromorphone
- methadone
- morphine
Examples of moderate to strong opioid agonists (3)
- codeine
- hydrocodone
- oxycodone
Combo opioid + acetaminophin/aspirin/ibuprofin helps mediate pain through…
….2 separate mechanisms making them very effective to manage pain
Agonist antagonist opioids and example (1)
Produce analgesia when administered alone, can antagonize analgesia caused by a pure agonist
-buprenorphine (suboxone or buprenex)
Dextromethorphan/hydrocodone/codeine drugs class and function
Opioid with minimal analgesic activity but good antitussive activity to be used in anticough meds
Loperamide (imodium) drug class, use, and how do we prevent abuse of it?
- Opioid with minimal analgesic activity
- can be used to treat diarrhea
- prevented from being abused by combo with atropine (lomotil = diphenoxylate + atropine) that gives bad side effects if abused
Example of an opioid antagonist and its function
Naloxone (narcan), used to reverse respiratory and CNS depression caused by opioid agonists
Codeine and poor metabolizers
Refers to how some are genetically inclined to be poor metabolizers of codeine which is biotransformed into morphine to be active but will not have its desired analgesic effect in these patients
Opioids often alter the sensation of pain rather than…
….eliminate it entirely. Patients may still be aware of pain but “don’t care” about it. This is often associated with sense of euphoria and feeling of floating
Drug of choice for dyspnea associated with left ventricular failure or MI pain
Morphine
Opioid side effects (7)
- Respiratory depression (reduce sensitivity of respiratory center neurons to carbon dioxide) (most common cause of death with opioid overdose)
- sedation
- headache
- emesis
- euphoria/dysphoria
- constipation (essential to begin preventative therapy when chronic opioid therapy started)
- miosis (characteristic importance to diagnostic of overdose)
Characteristic triad of opioid overdosage
- coma
- respiratory depression
- pinpoint pupils
Opioid drug interactions (4)
- CNS depressants (alcohold, benzos)
- anticholinergics (intensify constipation)
- hypotensive drugs (drop BP)
- MAOI - contraindicated
Opioid tolerance
With prolonged treatment, some of the effects (especially euphoria, analgesia, sedation and respriatory depression) develop tolerance
Opioid induced hyperalgesia
Controversial condition which patients treated with high doses of opioids experience worsening of pain that cannot be overcome by increasing dose (as in toelrance) cdan be managed by decreasing opioid, reducing dose or changing
physical dependence
Defined as state in which abstinence syndrome will occur if abruptly discontinued, an expected consequence of chronic opioid use
Abstinence syndrome
An unpleasant but rarely dangerous (unlike CNS depressant withdrawal) that occurs 10 hours after last dose causing rhinorrhea, sweating, anorexia, tremor, etc over 10 days, mitigated by gradual withdrawal
Addiction vs abuse
Not the same thing! A case of abuse of a drug even once can kill, while an addiction is a constellation of neurobiologic disease behaviors surrounding use of opioid for purpose other than pain relief
Most pain experts state that addiction is uncommon in patients who have…
…no history fo substance abuse or addiction
Pseudoaddiction
Drug seeking behaviors that occur when pain is undertreated and may mimic addictive behavior, however once controlled patient uses medication as prescribed without addiction
Fentanyl potency
High miligram potency about 100x that of morphine
Meperedine (demerol) drug class and function
Short term opioid, used for treatment of severe acute pain, short half life and highly irritating but sometimes used for drug induced rigors and shivering analgesia post anesthesic patient
Methadone 2 functions
- PO treatment for chronic nociceptive pain
- drug abuse treatment programs for opioid addiction
Oxycodone (percocet) drug class and potency
Semi synthetic derivative of morphine 9.5 more potent than codeine and 1.5x more potent than PO morphine
hydrocodone function
analgesic activity equivalent to codeine, PO only to relieve pain and suppress cough Most widely prescribed drug in the US,
Tapentadol (nucynta) drug class and function
Weak opioid agonist and norepi reuptake inhibitor indicated for acute or chronic management of severe pain acting by 2 mechanisms and causing less constipation
Buprenorphine (buprenex, subutex, suboxone)
Used as analgesic and to treat opioid addiction, significant tolerance has not been observed, dependence can occur but abstinence syndrome delayed
naloxone (narcan) mech of action
Structural morphine analog that binds to and blocks actions of opioids at their opioid receptors, can reverse most effects including analgesia and resp. depression. In absence of opioids, has no effect - will precipitate immediate withdrawal in someone physically dependent upon opioids
Naltrexone (vivitrol) function
Pure opioid antagonist used for alcohol and opioid abuse by preventing euphoria (but can precipitate withdrawal and has no effect on craving)
tramadol (ultram) drug class and function
Non opioid central acting agent, PO agent for treatment of moderate to severe pain
clonidine (duraclon) drug class and function
Non opioid central acting agent, functions to manage HTN and relieve severe pain often in combo with an opioid
Pain assessment
Physical and neurological exams can hep characterize and identify source of pain as well as wong baker face pain rating scale
assessment barriers to pain analysis (3)
- fear of opioids
- want to be stoic
- fear of admitting pain signifying dz progression
Unlike most other types of severe pain, neuropathic pain responds better to…
….adjuvants such as antidepressants and anticonvulsants
Ladder of pain management
- nonopioid first
- then opioid +non opioid adjuvant
- strong opioid agonist
Aspirin and acetominophen together have an equal pain relief as…
…an opioid acetaminophen combo
Patient controlled analgesia (PCA pump)
Method of IV administration that allows patient to administer preset amounts of analgesic such as morphine via syringe pump interfaced with a timing device, allows for more constant maintenance around therapeutic range
Chronic noncancer pain treatment
Rarely eliminated in absence of anestheia, goal is to reduce pain and associated symptoms, nondrug interventions can have major impact on maintaining wellbeing
Chrnoic cancer pain
Most common symptom of cancer, frequenlty undertreated, can be managed with PO meds
Opioid rotation
Transitioning of a patient from one to another because opioids have different effects profies so goal is to helpminimize adverse effects while maintaining good analgesia, performed in morphine equvialent daily dose (MEDD_
Opioid should not be the ___ treatment for most pain conditions
1st
Higher opioid doses are associated with risks for these 3 things
- motor vehicle injury
- opioid use disorder
- overdose
Adjuvants (conalgesic) for pain management
-used to complement the effets of opioids often used in treatment of neuropathic pain), pain releief is limited and less predictable and often develops slowly, likely work by inhibiting conduction of pain impuses in CNS
Gabapentin (neurontin) drug class, function, and side effects(4)
Inhibits Ca2+ channel activity effective in reducing pain in postherpetic neuralgia and diabetic neuropathy, common side effects include -drowsiness, ataxia, swollen legs, weight gain
Pregablin (lyrica) drug class and function
Ca2+ channel activity inhibitor, usually sees analgesia within frst 3 days,
Carbamezapine (tegretol) drug class, function, ADR’s (3)
Na+ channel blocker used to treat neuropathic pain and only drug approved for trigem neuralgia - is not apporved for treatment of pain, ADR’s include dizziness, double vision, ataxia
Tricyclic antidepressants mechanism and function in postherpatic neuralgia, diabetic nephropathy, etc.
-inhibit reuptake of NE and serotonin as well as mild opioid action in the receptor sites
Drugs recommended for postherpetic (2)neuralgia and side effects(3)
- SNRI such as duloxetine and milnacipran
- dizziness, constipation, liver injury
Example of local anesthetics/aniarrhythmics (2)
- lidocane (local)
- mexiletine
Diclofenac function
Topical solution approved for treatment of osteoarthritis or musculoskeletal pain
