Introduction to Opioids and Their Receptors

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Questions and Answers

Which opioid receptors are primarily involved in the effects of morphine?

Beta (β)

Mu (µ) (correct)

Alpha (α)

Kappa (K)

What physiological effects do opioids have on the central nervous system?

Enhanced motor activity

Respiratory depression (correct)

Increased heart rate

Increased alertness

Which endogenous peptides are mentioned as interacting with opioid receptors?

Histamine and Acetylcholine

Glutamate and GABA

Serotonin and Dopamine

Enkephalin and Endorphin (correct)

What is a significant chronic effect associated with opioid use?

Tolerance Signup and view all the answers

In opioid administration, what is a characteristic effect on the pupils?

Pinpoint constriction Signup and view all the answers

What is the primary role of the nucleus accumbens in opioid use?

Mediating drug-induced reward Signup and view all the answers

What is a potential adverse effect of buprenorphine, a common opioid substitution therapy?

Opioid dependence Signup and view all the answers

What effect do opioids have on the gastrointestinal tract?

Decreased smooth muscle activity Signup and view all the answers

What is a common behavioral effect of morphine that contributes to its abuse potential?

Euphoria Signup and view all the answers

Which of the following is NOT an acute effect of morphine?

Increased anxiety Signup and view all the answers

What physiological effect does morphine have on the gastrointestinal tract?

Decreases motility and increases tone of circular smooth muscle Signup and view all the answers

Which of the following adverse effects can occur with morphine use?

Hypotension and bradycardia at large doses Signup and view all the answers

What is a primary action of morphine on the cardiovascular system?

Causes histamine release leading to urticaria Signup and view all the answers

How does morphine affect respiratory function?

It causes respiratory depression as a side effect Signup and view all the answers

Which effect does morphine NOT develop tolerance to?

Constipation Signup and view all the answers

What is an important consideration when administering morphine to asthmatic patients?

It can trigger histamine release, leading to bronchoconstriction Signup and view all the answers

What are the main pharmacological actions of morphine?

Analgesia, sedation, and euphoria Signup and view all the answers

What effect does morphine have on urinary function?

Increases tone of the sphincter leading to urinary retention Signup and view all the answers

What is the mechanism by which morphine induces vomiting?

It directly stimulates the chemoreceptor trigger zone Signup and view all the answers

Study Notes

Introduction to Opioids

Opium poppy is the source of crude opium
Morphine, a prototypic opioid agonist, was isolated in 1803 by Sertürner

Opioid Receptors

Opioid receptors are abundant in the Central Nervous System (CNS) and Gastrointestinal Tract (GIT)
Mu (μ), Kappa (κ), and Delta (δ) are the main types of opioid receptors
Endogenous peptides like Enkephalin, Endorphin, and Dynorphin bind to these receptors
Exogenously administered opiates also bind to these receptors

Classification of Opioids

Opioids are classified as agonists, mixed agonist-antagonists, and antagonists
Agonists include strong (morphine, methadone, meperidine), moderate (codeine, oxycodone), and weak (propoxyphene) opioids
Antagonists are used to counter opioid overdose and include naloxone and naltrexone
Pethidine is a synthetic opioid

Pharmacological Effects

Acute Effects: Analgesia, sedation, euphoria, respiratory depression, antitussive action, nausea, vomiting, and miosis are observed
Chronic Effects: Tolerance, dependence, and suppression of gonadal hormone secretion are observed
Cardiovascular System: Morphine has minimal effect on blood pressure and heart rate, but large doses can cause hypotension and bradycardia
Respiratory System: Morphine decreases respiration
Gastrointestinal Tract (GIT): Morphine relieves diarrhea and dysentery by reducing motility and increasing intestinal tone. Constipation is also a common side effect

Morphine Specific Effects

Miosis: Pinpoint pupils are characteristic of morphine use, and tolerance does not develop
Emesis: Morphine directly stimulates the chemoreceptor trigger zone, causing vomiting, and tolerance develops to this effect
Euphoria: Morphine produces a powerful sense of well-being, which is a factor in its abuse potential
Depression of cough reflex: Morphine and codeine have antitussive properties

Tolerance

Tolerance develops to most opioid effects, except miosis and constipation
Tolerance is due to pharmacodynamics, where cells adapt to the drug's action
Addicts require progressively higher doses to achieve the same effect

Comparison of Morphine and Pethidine

Morphine is a natural opioid, while Pethidine is synthetic
Oral absorption of Pethidine is better than Morphine
Pethidine has weaker anti-cholinergic action than Morphine
Pethidine is not as effective in pulmonary edema, diarrhoea, or cough as morphine

Antagonist of Morphine

Naloxone and naltrexone are antagonists of morphine
Naloxone is the drug of choice to treat opioid overdose

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Description

This quiz covers the basics of opioids, including their source, classification, and pharmacological effects. Dive into the various opioid receptors and how they interact with different types of opioids. Understanding these concepts is crucial for studying pain management and substance use disorders.