Opioids & Analgesics

Question 1

pain transmission: ascending pathway

Answer 1

• spinal and peripheral distribution
• primary afferent nociceptors
• dorsal horn cells

Question 2

pain transmission: descending pathway (inhibitory regulation)

Answer 2

• originates in frontal cortex, amygdala and cingulate cortex
• synapses on PAG then RVA (rostral ventromedial medulla) and then on the dorsal horn cells
• major NTs = 5HT, norepi, glycine, GABA, opioids

Question 3

function of mu receptors

Answer 3

• supraspinal and spinal analgesia
• sedation and inhibition of respiration
• slow GI transit
• modulation of hormones and NT release

Question 4

function of delta receptors

Answer 4

• supraspinal and spinal analgesia

- modulation of hormones and NT release

Question 5

function of kappa receptors

Answer 5

• supraspinal and spinal analgesia
• slow GI transit
• psychomimetic effects

Question 6

all opioid receptors are … (2 things)

Answer 6

• G-protein coupled receptors

- inhibitory

Question 7

codeine

Answer 7

• naturally occurring
• used for mild to moderate pain
• gets metabolized to morpheine in liver
• oxycodone and hyocodone = mild analogs

Question 8

morphine

Answer 8

• gets metabolized in liver to M3G OR M6G

- hydomorphone = more potent derivative

Question 9

methadone

Answer 9

• long half life; used for chronic pain in terminally ill CA pts
• also used for detox
• high risk of respiratory depression and QT prolongation

Question 10

meperidine

Answer 10

• similar effect as morphine but less potent
• metabolites may cause seizures
• causes mydriasis = pupil dilation = different from all other opioids which cause pinpoint pupils

Question 11

fentanyl

Answer 11

• 100x more potent than morphine

- transdermal patch for slow delivery

Question 12

opioid receptor antagonists

Answer 12

• naloxone = high affinity for mu v. kappa

- naltrexone = can be given orally; no preference for mu or kappa; used for alcohol w/drawal, tx of opioid dependence

Question 13

opioid dependence

Answer 13

• psychological: mediated by ventral striatum; interactions b/w opioids and dopaminergic system (nucleus accumbens)
• physical: diaphoresis, insomnia, restlessness, abd cramps, N/V/D

Question 14

opioid tolerance

Answer 14

• mediated in part by NMDA signaling

- mainly cosmetic; rotation therapy can be helpful