Opioid Analgesics and Antagonists Quiz

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Questions and Answers

What is the primary plant source for opioids?

Erythroxylum coca

Digitalis purpurea

Cannabis sativa

Papaver somniferum (correct)

Mu receptors produce the same effects as kappa receptors.

False (B)

Name the three types of opioid receptors.

Mu, Kappa, Delta

The opioid antagonist that has the highest affinity for mu receptors is called __________.

Naloxone Signup and view all the answers

Match the opioid types to their classification:

Morphine = Strong agonist Codeine = Moderate agonist Buprenorphine = Mixed agonist-antagonist Naloxone = Antagonist Signup and view all the answers

Which of the following is NOT a physiological effect produced by opioid activation?

Increased blood pressure (C) Signup and view all the answers

Endogenous peptides such as enkephalins interact with delta receptors.

True (A) Signup and view all the answers

What neurotransmitter is released due to the activation of peripheral nociceptive fibers by opioids?

Substance P Signup and view all the answers

Which of the following neurotransmitters is primarily inhibited by endogenous endorphins or exogenous opioid agonists?

Substance P (A) Signup and view all the answers

Kappa receptors mediate euphoria and have a high liability for dependence.

False (B) Signup and view all the answers

What is the major effect of opioids on the gastrointestinal system?

Constipation Signup and view all the answers

Opioid agonists may cause respiratory ______ as a significant adverse effect.

depression Signup and view all the answers

Match the following drugs with their properties:

Morphine = Used in myocardial infarction Pethidine = Reduces shivering after anesthesia Buprenorphine = Partial agonist at mu receptor Naloxone = Opioid antagonist Signup and view all the answers

Which of the following opioid related actions does not develop tolerance?

Constipation (B) Signup and view all the answers

Alvimopam is an opioid used to treat paralytic ileus.

False (B) Signup and view all the answers

Name one opioid that has anti-cholinergic activity and is relatively safer in biliary colic?

Pethidine Signup and view all the answers

Opioids can stimulate the CTZ and lead to ______ and vomiting.

nausea Signup and view all the answers

Match the following opioid antagonists with their specific uses:

Naloxone = Used to reverse opioid overdose Naltrexone = Used in opioid addiction treatment Methylnaltrexone bromide = Used for opioid-induced constipation Alvimopan = Used for postoperative ileus Signup and view all the answers

Study Notes

Opioid Analgesics and Antagonists

Opioids: Derived from the poppy plant, Papaver somniferum, used for analgesia, euphoria, sedation, cough suppression, and diarrhea relief.

Opioid Receptors

Types: Mu (µ), Kappa (κ), and Delta (∂) receptors.
Mechanism: These are G protein-coupled receptors, inhibiting adenylate cyclase and influencing ion channels (increasing potassium efflux, reducing calcium influx).
Naturally occurring peptides: Endogenous opioid peptides (endorphins, dynorphins, and enkephalins) interact with these receptors, producing analgesic effects. β-endorphin preferentially interacts with µ receptors, enkephalins with ∂ receptors, and dynorphins with κ receptors.
Morphine and Naloxone: Morphine has higher affinity for µ receptors. Naloxone inhibits all opioid receptors, but has strongest action on µ receptors.

Effects of Different Opioid Receptors

µ receptors: Sedation, euphoria, respiratory depression, and physical dependence.
κ receptors: Dysphoria, spinal analgesia, constipation.
∂ receptors: Analgesia, modulation of hormones and neurotransmitter release.

Classification of Opioids

Strong agonists: Morphine, methadone, meperidine
Moderate agonists: Codeine, oxycodone
Weak agonists: Propoxyphene
Mixed agonist-antagonists: Buprenorphine, nalbuphine, pentazocine
Antagonists: Naloxone, naltrexone, nalmefene, methylnaltrexone bromide, Alvimopan.

Opioid Agonists: Mechanism of Action

Pain signal inhibition: Opioid agonists act pre-synaptically to inhibit Substance P release, reducing neurotransmission via changes in ion conductances. This leads to hyperpolarization by increasing potassium conductance and inactivation of calcium channels.
Analgesia: This process halts neurotransmitter release and produces analgesic effects.

Opioid Agonists: Pharmacological Actions

Analgesia: Produces spinal and supraspinal analgesia through µ, κ, and ∂ receptors.
Other effects: Sedation, respiratory depression, cough suppression, nausea/vomiting (via CTZ stimulation), constipation, and decreased heart rate (except pethidine and pentazocine).
Peripheral effects: Intrabiliary pressure increase (contracting biliary smooth muscle), contraindicated in biliary colic, and potentially harmful to asthmatics (due to histamine release).

Opioid Agonists: Clinical Uses

Analgesia: Effective for visceral and dull pain, especially useful in myocardial infarction (Morphine IV) and neuropathic/cancer pain resistant to morphine (Methadone).
Shivering reduction: Pethidine is used after anesthesia.
Biliary colic: Pethidine is a relatively safer option compared to many opioid agents due to it's anticholinergic activity.

Opioid Agonists: Adverse Effects

General: Respiratory depression, nausea, vomiting, constipation, urinary retention, itching, dysphoria.
Tolerance: Develops to most effects, except miosis, constipation, and convulsions.
Dependence: Opioids have high potential for both psychological and physical dependence.
Withdrawal syndrome: Discontinuation can lead to withdrawal symptoms (rhinorrhoea, lacrimation, yawning, chills), which are opposite to the usual opioid effects.

Mixed Agonists-Antagonists

Buprenorphine: Partial µ agonist, κ and ∂ antagonist. Treatment for opioid withdrawal and analgesia.
Nalbuphine & Pentazocine: Kappa agonists, µ antagonists.

Opioid Antagonists

Naloxone, Naltrexone, Nalmefene: Used for opioid overdose reversal.
Methylnaltrexone bromide: Peripheral opioid antagonist, for paralytic ileus treatment.
Alvimopan: Peripheral opioid antagonist, for paralytic ileus.

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Description

Test your knowledge on opioid analgesics and antagonists, focusing on their mechanisms, receptor types, and effects. This quiz covers key concepts related to opioids derived from the poppy plant and their interaction with specific receptors. Discover how different opioids like morphine and naloxone function within the body.