BIOMED 10/24a Pharmacology Flashcards
sources of opiods
opium poppy
endogenous substances like opiods: endorphins, enkephalins, dynorphins
opioid receptors
- µ (mu)- analgesia, euphoria, resp. depression, addiction (most and best pain relief)
- k (kappa)- analgesia, euphoria, sedation (moderate affinity, not same as mu, cause hallucinations and warped perception)
- ∂ (delta)- analgesia, sedation
what do opiods when with?
ine
what are classifications of opiods?
- Strong agonists: fully bind to mu
□ Used to treat severe pain, morphine, meperidine - Mild-to-moderate agonists: partially bind to mu, may bind to kappa or delta
□ Codeine, oxycodone - Mixed agonist-antagonists:
□ Nalbulphine (bind to kappa and partially block the mu), buprenorphine (partially binds mus but blocks kappa) - Antagonists: bind and don’t allow opioids to bind, use with overdose
□ Used to treat opioid overdose and addiction, naloxone
opioid mechanisms of action
- spinal effects
- brain effects
- peripheral effects
spinal effects of opioids
inhibition of nociceptive pathways
- Presynaptic: decrease release of substance P
- Postsynaptic: hyperpolarization
brain effects of opioids
influence descending pain pathways, norepinephrine and serotonin, which inhibit pain pathways
- Descending pathways
- Affect mostly interneurons
- Altered perception of the pain
peripheral effects of opioids
decrease excitability of sensory neurons
-Nociceptors decrease excitability
after pain comes from the ___, it is relayed by ___ to ____ of spinal cord and at each junction there are two main occurances
periphery
afferent nerves
dorsal horn
when pain enters the spinal cord, what happens at the junction when there are opioids present?
- Front end: presynaptic, opioid binds to receptors on sensory nerve and calcium cannot enter -> pain substances (substance P and glutamate) aren’t released because they release with calcium channels opening
- Post synaptic: creates opening of potassium channels such that potassium moves out and yields hyperpolarization (too negative) and goes farther away from threshold and AP is not relayed to the next portion inward (decrease awareness to CNS)
what are clinical considerations of opioid treatment for pain management
- treatment is for moderate to severe pain that is consistent
- alter perception of pain rather than eliminating painful sensations
- route of admin
- dosing schedule
what is the difference between oral and parenteral administration of drugs
oral - is taken by mouth and is subject to the first pass effect
parenteral - is taken by IV and goes straight to the target tissue
different dosing schedules of opioids
- patient-controlled analgesia: patient can re-adminster at the end of the effective dose
- fentanyl and other delivery vehicles (more localized) - delivery via patch, injection, and avoid respiratory depression
best dosing schedule of opioids?
IV - constantly matching the effect of the drug with the clearance of the drug
what are adverse effects and rehab concerns of opiods?
- Sedation - narcosis (sleep)
- Patients will be nodding off and falling asleep most often - Mood changes - dysphoria
- Can become combative (acutely) - Confusion
- respiratory depression
- most severe - orthostatic hypotension
- GI effects
- decrease GI motility
- can get some nausea and vomiting - addiction, tolerance, dependence
adverse effects of opioids that cause addiction, tolerance, and physical dependence
- Addiction
- Complex interaction of factors that leads to lack of control over drug use, onset of withdrawal should be avoided. - Tolerance
- The need to progressively increase the dosage of a drug to achieve a therapeutic effect when the drug is used for prolonged periods
- Receptor downregulation and desensitization, G protein uncoupling - Physical dependence
- Onset of withdrawal symptoms when drug is abruptly removed
what is the treatment of opioid addiction?
- Methadone: strong opioid agonist, similar in potency and efficacy to morphine
- Mild withdrawal
- Low success rate - Buprenorphine: mixed agonist-antagonist which partially stimulates mu receptors while acting as strong antagonist at kappa receptors
- Naloxone (Narcan) nasal spray – antagonist to all receptors but has high affinity for mu
- Bumping off opioids from mu receptors and binding with them so opioids can’t bind
what type of drug is meperidine?
Strong agonist, associated with great pain relief but also problems
when should therapist schedule treatment session so that meperidine is reaching peak effects (effective dose is every 4 hrs)
1 hr after administration
what precautions should PT take into place when with a patient who is on meperidine?
-Orthostatic hypotension (BP in lying, then at 45o, then 90o)
>Bring reclinable wheelchair or stretcher
-Cognizance of respiratory rate
NSAID primary use
in the treatment of mild to moderate pain