pharm: opioids Flashcards
What kind of analgesics can be given for mild pain?
non opioid +/- adjuvant
What kind of analgesics can be given for moderate pain?
weak opioid +/- non-opioid +/- adjuvant
What kind of analgesics can be given for severe pain?
strong opioid +/- non-opioid +/- adjuvant
List the 3 families of endogenous receptors for opioids.
μ, δ, κ
μ is most targeted
List the 3 families of endogenous peptides for opioids.
endorphins, enkephalins, dynorphins
Where do opioids go in the body?
Opioids are distributed to highly perfused tissues, such as brain, lung, liver, kidneys. Opioids are also stored in fatty tissue
Which cell signalling pathway do opioids act via?
GPCR
What do opioids do in the cell signalling pathway?
- Presynaptic nerve terminals: Close voltage-gated calcium channels
- Postsynaptic nerve terminals: Open potassium channels —> hyperpolarisation
List examples of strong opioid agonists and state their common use.
Morphine, Methadone, Fentanyl, Pethidine.
Used for analgesia.
Major anaesthetic adjuvant and reasons for its use?
Fentanyl. It is short-acting and has a fast onset (high potency)
List examples of moderate opioid agonists, ranking them from most potent to least potent.
Tramadol > Codeine
Cough suppressant/antitussive?
Codeine
Describe the metabolism of codeine.
Codeine is metabolised by CYP enzymes to form morphine.
Describe the metabolism & excretion of morphine.
Morphine is metabolised to form 2 active components:
1. M3G : neuroexcitatory
2. M6G : potent analgesic
Both active compounds are excreted by the kidneys.
Can full agonists and partial agonists be taken together?
No, as it may induce withdrawal symptoms and reduce analgesia.
What are the symptoms of opioid withdrawal?
anxiety, irritability, chills, hot flushes, joint pain, lacrimation, rhinorrhea (runny nose), nausea, vomiting, abdominal cramps, diarrhoea.
How is tolerance to opioids developed?
Exacerbating factors?
Due to upregulation of cAMP, failure of receptor recycling or receptor uncoupling.
Occurs faster when large doses are given over short intervals.
Cross-tolerance often occurs with μ-receptor agonists.
List the side effects of opioids on organs and systems in the body.
Respiratory: respiratory depression
CVS: bradycardia, hypotension
GIT: constipation
Kidney: decreased renal function
Pituitary gland: release of ADH, prolactin and somatotropin affected
In what instances are opioids contraindicated? Why?
- Patients with head injury: respiratory depression → cerebral vasodilation → increased intracranial pressure
- Pregnant women: fetus may develop dependence → withdrawal symptoms
- Patients with emphysema: respiratory depression → acute respiratory failure
- Patients with liver cirrhosis: risk of precipitating hepatic encephalopathy
List some examples of analgesic adjuvants.
Anticonvulsants → neuropathic pain
Calcitonin → for bone pain
Muscle relaxants → for musculoskeletal pain
Anticholinergics → for pain from bowel obstructions
How can opioid overdose be treated? List some examples.
Use opioid antagonists.
Naloxone (IV): short-acting, for emergency use
Naltrexone (oral): long-acting, for maintenance dose
Nalmefene (IV): long-acting
