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