Opioid and Opioid Antagonists

Question 1

What is the mechanism of action of all the opioids?

Answer 1

They bind to GI-protein coupled receptors (mu, kappa, and delta), and inhibit adenylyl cyclase.

Impede transmitter release by decreasing calcium influx in pre-synaptic neurons

Impede firing of presynaptic neurons by increasing K efflux

Question 2

What time of pain is not well treated with opioids?

Answer 2

neuropathic pain

Question 3

What is mechanism of action for morphine?

Answer 3

acts at kappa receptors of the dorsal horn and decreases the release of substance P (modulates pain perception of the spinal cord)

Question 4

What are the side effects of Morphine? Remember the mneumonic?

Answer 4

H E C C (k of a) DREAM
H - histamine/hormones
E - emesis
C - Contraction of SM: biliary tract, bladder, ureter
C - Cardio changes at higher doses
D - decreased cough reflex, GI motility, uterine tone, mental function
R - respiratory depression
E - euphoria
A - analgesia
M - miosis

Question 5

What patients is morphine contraindicated in?

Answer 5

patients with head/severe brain injury, patients with bronchial asthma, emphysema, cor pulmonale, liver failure, or bad kidneys, pregnant women and neonates (no gloucoronisyl transferases for 6-9 months)

Question 6

What are the therapeutic uses of morphine?

Answer 6

pain relief very effective, tx diarrhea, relieve cough, tx acute pulmonary edema by relieving dyspnea via vasodilation

Question 7

How is morphine metabolized?

Answer 7

glucoronidated in the liver, excreted in urine.

Question 8

What are the main adverse effects of morphine?

Answer 8

respiratory depression and death, dysphoria, hypotension, ICP elevation, CONSTIPATION

Question 9

What are the withdrawal symptoms from opioids?

Answer 9

“Cold turkey” “Flu like sx”, mydriasis, yawning, cramping, restlessness

Question 10

What are the rare drug effects for morphine with?

Answer 10

MAOIs, TCAs, Phenothiazines

Question 11

What is the hallmark of Meperidine that differs from other opioids?

Answer 11

Causes DILATED Pupils instead of pinpoint pupils

Question 12

What are AE of Meperidine?

Answer 12

anxiety, tremors and muscle twitches. Severe reactions with MAOIs. Do not use in geriatric, patients with impaired kidney function.

Question 13

What is the therapeutic use of methadone?

Answer 13

used to get people off street drugs, controlled w/d from heroine and morphine

Question 14

What is metabolism in Methadone?

Answer 14

metabolized in liver and excreted in feces. VERY lipophilic, repeated dosing can lead to toxicity. Long half life - 24 hours

Question 15

What are the AE of methadone?

Answer 15

Torsades de pointes

Question 16

How does Fentanyl differ from Morphine?

Answer 16

100x analgesic potency so used in anesthesia

Question 17

What are the therapeutic uses of Fentanyl?

Answer 17

cancer patients with breakthrough pain with opioid tolerance, cardiac surgery since MINIMAL effects of heart function

Question 18

What is Sufentanil?

Answer 18

related to Fentanyl, used in transdermal patch like Fentanyl

Question 19

How does oxycodone differ from Morphine?

Answer 19

2x more potent than morphine

Question 20

What is potency of Hydromorphone and what patients is it used in over morphine?

Answer 20

8-10x potency, patients with renal dysfunction

Question 21

What is a common function of hydrocodone?

Answer 21

antitussive

Question 22

What is primary use of codeine and how is it metabolized?

Answer 22

Codeine is used for antitussive effects, metabolized to morphine by p450 system, though 1/3 as potent so less likely to be abused.

Question 23

Which opioid would you give to drug seekers to punish them for drug seeking in the ER?

Answer 23

Pentazocine due to its dysphoric side effects and nightmares, hallucinations, tachycardia, and dizziness.

Question 24

Where does Buprenorphine act and what is it use?

Answer 24

acts on the mu receptor, use is in opiate detox because it has shorter duration of withdrawal

Question 25

What is the benefit to Nalbuphine (opioid)?

Answer 25

doesn’t affect HR or increase BP, but still see respiratory depression, miosis, and constipation.

Question 26

What is the mechanism of Tramadol and what are the SE?

Answer 26

Binds to mu receptor, It has less respiratory depression than morphine but can have anaphylatic reaction, and drug interactions with SSRIs, TCAs, and MAOIs

Question 27

What is the action of Tapentadol?

Answer 27

binds to mu receptor and inhibits Norepi reuptake. Avoid in patients on MAOIs

Question 28

What is action of Naloxone?

Answer 28

reverse coma and respiratory depression in opioid OD with minimal analgesia reversal.

Question 29

What is Naltrexone combined with for rapid detox?

Answer 29

Combined with Clonidine to depress hypertensive response. Can lead to liver damage.