Pain Opioids 2

Question 1

The benchmark opioid is _
What component of pain does it mainly affect?
What type of antagonist is it?

Answer 1

• Morphine
• The motivational affective component of pain
• It is not an antagonist. It is an AGONIST at the mu receptor

Question 2

Where in the CNS does morphine mainly function?

Answer 2

Largely in the brain

Question 3

Urinary retention, sedation, euphoria, respiratory depression, and miosis are all side effects of opioids. True or false?

Answer 3

True

Question 4

• True or false: At neutral pH, majority of morphine is in the uncharged state.
• What pharmacokinetic variable is affected by this?

Answer 4

• False. At neutral, approx 80% of morphine is charged.

- Slow absorption across the membrane

Question 5

• Why does morphine have a slow onset of action (3)?

- Approximately for how long (hours) does a single does exert its actions?

Answer 5

• Slow onset because of 1) low lipid solubility, 2) slow entry into brain, also 3) charged at neutral pH
• Approx. 4 hrs, onset of action at 15 mins

Question 6

• What is the chemical moiety added to morphine during its metabolism?
• Where does this addition occur?
• What is the active metabolite (proportion)?
• The inactive metabolite (proportion)?

Answer 6

• Glucuronide (Glucuronidation)
• In Liver
• Active - M-6-glucuronide (5-10%),
• Inactive - M-3-glucuronide (75-85%)

Question 7

What is the half life of morphine?

Answer 7

2 hrs

Question 8

Which is more important consideration for the activity of morphine; liver disease or kidney disease? Why?

Answer 8

• Kidney disease. M-6-glucuronide is excreted by the kidney. If damaged, elevated plasma levels and prolonged drug action
• Unless severe, liver disease has no effect on morphine pharmacokinetics

Question 9

True or false: Opioid Analgesia does not vary much from patient to patient.

Answer 9

False - it is very variable (Pharmacodynamic variability)

Question 10

What are the continuous release and slow release forms of morphine? What are they used for (2)?

Answer 10

• MS contin and Morphine SR

- Chronic pain syndromes, cancer pain

Question 11

How should an IV dose of morphine to altered to achieve the same PO dose? Why?

Answer 11

• 3-5 fold increase

- Reduced bioavailability orally

Question 12

What type of morphine can be administered directly into the spinal cord? What type of spinal cord administration should it be used for acute pain? Chronic pain?

Answer 12

• Morphine, preservative free
• Acute pain - intrathecally or epidurally
• Chronic - intrathecally

Question 13

Among the major morphine side effects, which 2 are generally reduced with spinal administration compared to oral administration?

Answer 13

Sedation

Respiratory depression

Question 14

What is a PCA? What is the advantage?

Answer 14

Patient controlled anesthesia

Allows patient to determine how much opioid they receive by allowing them to admin. small doses

Question 15

How does M-6_glucuronide compare to morphine with regards to potency?

Answer 15

It is 10X more potent than morphine

Question 16

What transporters in the kidney eliminate morphine?

Answer 16

Organic ion transporters

Question 17

[Pick one option] Compared to other opioids, morphine is considered [fast/slow] acting and has a [short/long] duration.

Answer 17

Morphine is slow acting, has long duration

Question 18

Morphine works mainly by ascending or descending inhibition? What fiber type mainly affected? Explain

Answer 18

Descending
C fibers
Binds in brain, blocks the input of more pain through the SPC