Opiod agonists and antagonists

Question 1

MOA of opioid analagesics

Answer 1

agonists at opiod receptors, inhibitory signalling
blocks pain transmission and response
raises pain threshold
anti-anxiety effect

Question 2

Receptor subtypes activated by morphine

Answer 2

mu, kappa, delta

Question 3

pharmacokinetics of morphine

Answer 3

Rapid acting, 5-15 min
Maximum effect within 60-90 min
half-life 2.5-3 hrs
lasts 4-5 hrs

Question 4

Standard dose of morphine

Answer 4

10 mg i.m. s.c. , 7 mg for elderly/ children

Question 5

Metabolism of morphine

Answer 5

High level of first pass metabolism
Glucuronic acid conjugation
renal clearance of metabolites, caution with impared liver or renal function

Question 6

Mechanism of respiratory failure in morphine OD

Answer 6

decreased sensitivity to plasma CO2
hypoxic response still intact
tolerance develops with analgesia tolerance

Question 7

“First dose effect of morphine”

Answer 7

nausea and vomiting

Question 8

GI effects of morphine

Answer 8

constipation, little or no tolerance, major problem with chronic use. Naltrexone.

Question 9

Minor side effects of morphine

Answer 9

Miosis
Euphoria, tranquility
Pruritis
Mild CV, orthostatic hypotension

Question 10

Therapeutic use of morphine

Answer 10

moderate to severe pain
primarily in acute pain
chronic pain use is discouraged except in terminal disease
Other: sickle cell crisis, end stage lung cancer and other terminal pain (and COPD)

Question 11

Additional side effects and precautions of morphine (5)

Answer 11

biliary colic, increase urinary tract pressure
allergic reactions
dysphoria, excitement
neonates and aged more sensitive
dependence

Question 12

Drug interactions with morphine (2)

Answer 12

CNS depressants

Ethanol and long release preps

Question 13

Limitations and contraindications or morphine (3)

Answer 13

decreased respiratory reserves
head injuries
pregnancy

Question 14

Advantages of codeine

Answer 14

more orally reliable

effective cough suppressant

Question 15

Disadvantages of codeine

Answer 15

more constipation

Question 16

Therapeutic use of codeine

Answer 16

mild to moderate pain

Question 17

Advantages of methadone

Answer 17

very reliable orally
long half life
full agonist- same effect as morphine

Question 18

Disadvantages of methadone

Answer 18

may prolong Q-T interval
metabolized by CYP 3A4
Also abused like morphine

Question 19

Advantages of fentanyl

Answer 19

full agonist like morphine
potent, short acting
can be used transdermally for chronic pain
lozenge/film/tablet for breakthrough pain
less effect on cardiovascular system

Question 20

Disadvantages of fentanyl

Answer 20

more likely to produce muscle rigidity of chest and abdominal muscles

Question 21

Hydrocodone highlights

Answer 21

similar to codeine, #1 prescription, major abuse problem

Question 22

Oxycodone highlights

Answer 22

more potent than codeine, abuse of timed release formulation

Question 23

Therapeutic use of loperamide

Answer 23

anti-diarrheal agents, full opiod agonists, but do not cross membranes readily

Question 24

Dextromethorphan highlights

Answer 24

chemically similar to opioids, effective cough suppressant, no analgesia, abuse increasing

Question 25

Meperidine highlights

Answer 25

excitatory, at high doses with chronic use due to long lasting metabolite, less effect on GI tract. Can be used IV for infusion related rigors and chills

Question 26

Advantages of mixed agonist-antagonist, partial agonists

Answer 26

ceiling in both respiratory depression and pain analgesia

Question 27

Disadvantages of partial agonists

Answer 27

most have kappa receptor side effects, dysphoria

Question 28

Pentazocine compared to morphine

Answer 28

limited analgesia, resp depression more reliable orally antagonist properties in dependence

Question 29

Therapeutic use of pentazocine

Answer 29

analgesia in moderate to severe pain, not used chronically due to dysphoria

Question 30

Buprenorphine summary

Answer 30

partial agonist at mu receptors- similar effects as morphine antagonist at kappa receptors- no dysphoria may prolong Q-T interval

Question 31

Therapeutic use of buprenorphine

Answer 31

moderate to severe pain | to treat opiod dependence

Question 32

MOA of tramadol

Answer 32

weak mu agonist, inhibits NE and 5HT

Question 33

Therapeutic use of tramadol

Answer 33

can produce dependence, seizures, serotonin syndrome seen. suicide risk, drug interactions. No advantage clinically

Question 34

Naloxone MOA

Answer 34

blocks opiate receptors

Question 35

Therapeutic use of naloxone

Answer 35

used for overdose/high dose treatment | precipitate withdrawal in opiate dependence

Question 36

Diagnosis of opioid overdose

Answer 36

respiratory depression miosis coma

Question 37

Opiod overdose treatment

Answer 37

1. support respiration 2. prevent absorbance if taken orally 3. naloxone IV repeatedly at short intervals