pharm: opioids

Question 1

What kind of analgesics can be given for mild pain?

Answer 1

non opioid +/- adjuvant

Question 2

What kind of analgesics can be given for moderate pain?

Answer 2

weak opioid +/- non-opioid +/- adjuvant

Question 3

What kind of analgesics can be given for severe pain?

Answer 3

strong opioid +/- non-opioid +/- adjuvant

Question 4

List the 3 families of endogenous receptors for opioids.

Answer 4

μ, δ, κ

μ is most targeted

Question 5

List the 3 families of endogenous peptides for opioids.

Answer 5

endorphins, enkephalins, dynorphins

Question 6

Where do opioids go in the body?

Answer 6

Opioids are distributed to highly perfused tissues, such as brain, lung, liver, kidneys. Opioids are also stored in fatty tissue

Question 7

Which cell signalling pathway do opioids act via?

Answer 7

GPCR

Question 8

What do opioids do in the cell signalling pathway?

Answer 8

1. Presynaptic nerve terminals: Close voltage-gated calcium channels
2. Postsynaptic nerve terminals: Open potassium channels —> hyperpolarisation

Question 9

List examples of strong opioid agonists and state their common use.

Answer 9

Morphine, Methadone, Fentanyl, Pethidine.
Used for analgesia.

Question 10

Major anaesthetic adjuvant and reasons for its use?

Answer 10

Fentanyl. It is short-acting and has a fast onset (high potency)

Question 11

List examples of moderate opioid agonists, ranking them from most potent to least potent.

Answer 11

Tramadol > Codeine

Question 12

Cough suppressant/antitussive?

Answer 12

Codeine

Question 13

Describe the metabolism of codeine.

Answer 13

Codeine is metabolised by CYP enzymes to form morphine.

Question 14

Describe the metabolism & excretion of morphine.

Answer 14

Morphine is metabolised to form 2 active components:
1. M3G : neuroexcitatory
2. M6G : potent analgesic

Both active compounds are excreted by the kidneys.

Question 15

Can full agonists and partial agonists be taken together?

Answer 15

No, as it may induce withdrawal symptoms and reduce analgesia.

Question 16

What are the symptoms of opioid withdrawal?

Answer 16

anxiety, irritability, chills, hot flushes, joint pain, lacrimation, rhinorrhea (runny nose), nausea, vomiting, abdominal cramps, diarrhoea.

Question 17

How is tolerance to opioids developed?
Exacerbating factors?

Answer 17

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.

Question 18

List the side effects of opioids on organs and systems in the body.

Answer 18

Respiratory: respiratory depression
CVS: bradycardia, hypotension
GIT: constipation
Kidney: decreased renal function
Pituitary gland: release of ADH, prolactin and somatotropin affected

Question 19

In what instances are opioids contraindicated? Why?

Answer 19

1. Patients with head injury: respiratory depression → cerebral vasodilation → increased intracranial pressure
2. Pregnant women: fetus may develop dependence → withdrawal symptoms
3. Patients with emphysema: respiratory depression → acute respiratory failure
4. Patients with liver cirrhosis: risk of precipitating hepatic encephalopathy

Question 20

List some examples of analgesic adjuvants.

Answer 20

Anticonvulsants → neuropathic pain
Calcitonin → for bone pain
Muscle relaxants → for musculoskeletal pain
Anticholinergics → for pain from bowel obstructions

Question 21

How can opioid overdose be treated? List some examples.

Answer 21

Use opioid antagonists.

Naloxone (IV): short-acting, for emergency use
Naltrexone (oral): long-acting, for maintenance dose
Nalmefene (IV): long-acting