Opioid Analgesics Flashcards
what are the major classes of opioid receptors and where do most opioid analgesics work
- μ, δ and κ.
- most work at the μ receptor
what are opioids action on neurons
- close voltage gated Ca channels on presynaptic nerve terminals –> reduced neurotransmitter release
- open K channels –> hyperpolarizing and inhibiting postsynaptic neurons
opioids reduce the release of large numbers of neurotransmitters. what are the neurotransmitters?
NAGSS
- norepinephrine
- acetylcholine
- glutamate
- serotonin
- substance P
where does the analgesic effects of opioids come from (aka what is the mechanism that leads to analgesia)
- directly inhibits ascending transmission of nociceptive info from spinal cord dorsal horn
- indirectly activates pain inhibitory circuits
receptors that opioids work on in spinal analgesia and the mechanism
- μ, δ and κ.
- inhibits the release of excitatory neurotransmitters substance P and glutamate from these primary afferents
- also inhibits the dorsal horn pain transmission neuron directly
receptors that opioids work on in supraspinal analgesia and mechanism
- μ, δ and κ.
- activation of pain inhibitory descending neurons
mechanism of peripheral analgesia
-stimulation of peripheral μ receptors by opioids decrease sensory neuron activity and release
what are the mixed agonists-antagonists of opioids (what do they agonize and antagonize)
Pentazocine
Butorphanol
Nalbuphine
Buprenorphine - partial μ agonist and κ antagonist
partial agonist/antagonist of μ receptors and are agonists of κ receptors
what are the opioid antagonist and what receptors do they antagonize
antagonize all - μ, δ and κ
naloxone and naltrexone
what are the opioid agonist
Morphine Fentanyl Meperidine Methadone Codeine
might need this box later
thanks
what are the CNS effects of opioids
- analgesia
- euphoria
- sedation and drowsiness
- respiratory depression
- cough suppression
- miosis
- truncal rigidity
- nausea and vomiting
peripheral effects of opioids
- hypotension
- GI effects: constipation
- Biliary Colic
- Decreased renal flow
- Uterus: prolongs labor
- Release of ADH, PRL, Somatotropin and inhibit LH
- Pruritis
how are opioids excreted
turned to metabolites mostly glucuronides then excreted by the kidney
what types of patients should be monitored when given opioids like morphine
those with renal impairment since it is conjugated to a glucuronide then excreted by the kidney
how are opioids like heroin and remifentanil metabolized
they are hydrolyzed by tissue esterases
which opioids causes seizures if in high concentration and what type of patients experience these seizures
normeperidine
patients with decreased renal function since it cannot be excreted hence –> seizures
clinical uses of opioid analgesics
5 As
- Analgesia: pain
- Acute pulmonary edema: relieves dyspnea by reducing cardiac preload and afterload
- Antitussives: relieve cough
- Antidiarrheals
- Anesthesia: sedative, anxiolytic, and analgesic properties
adverse effects of opioids
MAIN ONES: nausea vomiting sedation itching constipation
IN ADDITION:
urinary retention
hypotension
respiratory depression
contraindications/cautions in opioid therapy
- using pure agonists with partial: diminishes effect
- head injury: CO2 retention caused by respiratory depression –> cerebral vasodilation
- pregnancy: fetus becomes dependent and experiences withdrawal postpartum
- impaired pulmonary function: opioids respiratory depressive properties –> acute respiratory failure
- decreased renal function: can’t excrete it so leads to problems associated with high conc
- endocrine disease: adrenal insufficiency or hypothyroidism can have prolong and exacerbated response
drug interactions of opioids
- with sedative hypnotics –> resp depression
- antipsychotics –> increases sedation
- MAOI: meperidine and tramadol –> excitement, muscle rigidity, hyperthermia, unconsciousness
strong opioid agonists
Morphine, Hydromorphine, Oxymorphine Heroin Meperidine Fentanyl Methadone Levorphanol
affinity of morphine towards opioid receptors
high affinity towards μ receptors
lower affinity towards δ and κ
how is heroin hydrolyzed and explain which is more liposoluble and its importance
heroin –> 6-monoacetylmorphine (6-MAM) –> morphine
heroin and 6-MAM are more liposoluble hence enter the brain more readily
