Opioids

Question 1

Opioid general mechanism

Answer 1

• decrease presynaptic Ca+ influx

- decrease postsynaptic K+ effulx (hyperpolarized)

Question 2

opioid presynaptic mechanism

Answer 2

• opioid binds to Ca+ channel - inhibits influx

- > prevents glutamate release into synaptic cleft

Question 3

opioid postsynaptic mechanism

Answer 3

• binding of opioid to K+ channel increases efflux

- hyperpolarized (negative) less excitable

Question 4

Mu opioid receptor

Answer 4

• analgesic effect in CNS

- most common receptor

Question 5

Kappa opioid receptor

Answer 5

-analgesia in spinal cord

Question 6

Delta opioid receptor

Answer 6

-analgesia in periphery

Question 7

Morphine actions

Answer 7

• analgesia
• euphoria
• reduced respiration - neurons less sensitive to CO2
• depressed cough reflex
• increased secretion of ADH

Question 8

Morphine CV actions

Answer 8

• hypotension in large doses
• CO2 retention causes cerebral vessel dilation
• > increases CSF pressure

Question 9

Morphine pharmacokinetics

Answer 9

• onset: 5 - 10 minutes
• half-life: 2 hours (114 minutes)
• poor oral bioavailability

Question 10

Methadone

Answer 10

• longer lasting than morphine
• less euphoric
• absorbed orally

Question 11

Fentanyl

Answer 11

• 100 fold potency of morphine
• uses:
• induction of anesthesia
• postoperative analgesia
• pediatric cardiac surgery

Question 12

Sufentanyl

Answer 12

• 7-10x more potent than fentanyl
• slower onset/faster recovery
• CV effects: bradycardia, decreased SVR

Question 13

Alfentinil

Answer 13

• less potent
• more respiratory effects
• short duration (15 minutes)

Question 14

Remifentanil

Answer 14

• most recently discovered
• similar potency to fentanyl
• shortest half-life (1-20 minutes)