Opioid Pharmacology — MCQs
Pharmacodynamics deals with:-
A female was given morphine sulphate during labour for pain but she developed respiratory distress. Which of the following will be the correct antidote?
Which of the following is a pure opioid antagonist?
Which opioid drug is effectively administered via the transbuccal route?
Which of the following anaesthetic agent lacks analgesic effect? A) N2O B) Thiopentone C) Methohexitone D) Ketamine E) Fentanyl
G-protein coupled receptor that does not act through opening of potassium channels is:
Administration of which of the following will reverse respiratory depression caused by opioids?
Which is NOT a common symptom of opioid withdrawal?
Which of the following statements about Nitrous Oxide (N2O) is true?
Which of the following agents is used for the treatment of post operative shivering?
Opioid Pharmacology Indian Medical PG Practice Questions and MCQs
Question 1: Pharmacodynamics deals with:-
- A. Latency of onset
- B. Mechanism of action of a drug (Correct Answer)
- C. Transport of drug across the biological membranes
- D. Mode of excretion of a drug
Explanation: Detailed study of the **Mechanism of action of a drug** [1][2] - **Pharmacodynamics** describes what the **drug does to the body**, including its **molecular targets** and biochemical effects [3]. - This involves the study of the drug's mechanisms to produce its therapeutic or toxic effects [2]. *Latency of onset* - **Latency of onset** refers to the time it takes for a drug to start producing its effects, which is a pharmacokinetic rather than a pharmacodynamic parameter. - It deals with the drug's absorption and distribution rather than its interaction with the body once it reaches its site of action. *Transport of drug across the biological membranes* - The **transport of drugs across biological membranes** is a key aspect of **pharmacokinetics**, specifically absorption and distribution [1]. - This process determines how much drug reaches its target site, not how it interacts with the target. *Mode of excretion of a drug* - The **mode of excretion** of a drug (e.g., renal, hepatic) falls under **pharmacokinetics**, addressing how the body gets rid of the drug. - This process influences the drug's duration of action and elimination half-life, not its mechanism of action.
Question 2: A female was given morphine sulphate during labour for pain but she developed respiratory distress. Which of the following will be the correct antidote?
- A. Naloxone (Correct Answer)
- B. Epinephrine
- C. Pralidoxime
- D. Atropine
Explanation: ***Naloxone*** - **Naloxone** is a pure opioid antagonist that rapidly reverses the effects of **opioid overdose** [1, 3], including **respiratory depression** [2], by competitively binding to opioid receptors [1]. - Its short half-life may necessitate repeated doses, especially with longer-acting opioids like morphine, to prevent recurrence of respiratory depression [1]. *Epinephrine* - **Epinephrine** is an adrenergic agonist used to treat **anaphylaxis** and severe allergic reactions, as it causes **vasoconstriction** and **bronchodilation**. - It is not an antidote for opioid-induced respiratory depression, which primarily results from central nervous system effects rather than allergic reactions. *Pralidoxime* - **Pralidoxime** is a **cholinesterase reactivator** used to treat poisoning by **organophosphates**, which inhibit acetylcholinesterase, leading to cholinergic crisis. - It works by restoring the function of the enzyme, thereby breaking down excess acetylcholine, and is not indicated for opioid overdose. *Atropine* - **Atropine** is an **anticholinergic agent** that blocks muscarinic acetylcholine receptors, used to treat **bradycardia** and **organophosphate poisoning**. - It would not reverse opioid-induced respiratory depression, as it primarily affects the parasympathetic nervous system and does not antagonize opioid receptor effects.
Question 3: Which of the following is a pure opioid antagonist?
- A. Naloxone (Correct Answer)
- B. Buprenorphine
- C. Pentazocine
- D. Morphine
Explanation: ***Naloxone*** - **Naloxone** is a pure opioid antagonist that rapidly reverses the effects of opioid agonists by competing for opioid receptor binding sites [1,2]. - It has a high affinity for μ-opioid receptors and acts as a competitive antagonist [1], making it clinically useful for treating **opioid overdose**. *Buprenorphine* - **Buprenorphine** is a **partial opioid agonist** at the μ-opioid receptor and an antagonist at the κ-opioid receptor [4]. - It can precipitate withdrawal in opioid-dependent individuals if administered while full agonists are present due to its partial agonistic activity. *Pentazocine* - **Pentazocine** is a **mixed opioid agonist-antagonist**, acting as a partial agonist or antagonist at μ-opioid receptors and an agonist at κ-opioid receptors. - Its effects can vary, including analgesia (kappa agonism) and potential for withdrawal symptoms in opioid-dependent individuals (mu antagonism). *Morphine* - **Morphine** is a potent **full opioid agonist** that primarily acts on μ-opioid receptors, producing analgesia, sedation, and euphoria [3]. - It does not block opioid receptors; instead, it activates them, leading to its therapeutic and adverse effects.
Question 4: Which opioid drug is effectively administered via the transbuccal route?
- A. Sulfentanil
- B. Remifentanil
- C. Fentanyl (Correct Answer)
- D. Alfentanil
Explanation: ***Fentanyl*** - **Fentanyl** is a potent, **lipophilic opioid** that is well-absorbed through mucous membranes, making it suitable for **transbuccal administration**. - Its high potency and rapid onset of action when administered transbuccally make it useful for breakthrough pain or rapid analgesia. *Sulfentanil* - While also a potent opioid, **sulfentanil** is primarily used intravenously for anesthesia and is not commonly formulated or administered via the transbuccal route. - Its chemical properties and pharmacokinetic profile do not lend themselves as readily to transbuccal absorption compared to fentanyl for practical clinical use. *Remifentanil* - **Remifentanil** is an **ultra-short-acting opioid** metabolized by plasma esterases, making it ideal for continuous intravenous infusions where rapid offset is desired. - Its rapid metabolism and specific pharmacokinetic properties make it unsuitable for transbuccal extended release or sustained absorption. *Alfentanil* - **Alfentanil** is a short-acting opioid predominantly used intravenously for induction and maintenance of anesthesia. - Although it has a rapid onset, it is not optimized or commonly utilized for transbuccal administration due to its lower lipophilicity and different absorption characteristics compared to fentanyl.
Question 5: Which of the following anaesthetic agent lacks analgesic effect? A) N2O B) Thiopentone C) Methohexitone D) Ketamine E) Fentanyl
- A. N2O
- B. Methohexitone
- C. Ketamine
- D. Fentanyl
- E. Thiopentone (Correct Answer)
Explanation: ***Thiopentone*** - Thiopentone is a **barbiturate** anesthetic primarily used for inducing anesthesia. - It provides significant **hypnosis** and sedation but lacks intrinsic **analgesic properties**, meaning it does not relieve pain. *N2O* - **Nitrous oxide** (N2O) is an inhalation anesthetic that provides good **analgesia** at sub-anesthetic concentrations. - It is often used as an adjunct to other anesthetic agents to enhance pain relief during procedures. *Methohexitone* - Methohexitone is another **barbiturate** similar to thiopentone, used for induction of anesthesia. - While it provides rapid **hypnosis**, it also lacks significant **analgesic effects**. *Ketamine* - Ketamine is a **dissociative anesthetic** known for its potent **analgesic properties**. - It works by blocking **NMDA receptors**, providing pain relief even at sub-anesthetic doses. *Fentanyl* - Fentanyl is a powerful **opioid analgesic** that is commonly used in anesthesia for its strong pain-relieving effects. - It acts on **opioid receptors** in the central nervous system to reduce pain perception.
Question 6: G-protein coupled receptor that does not act through opening of potassium channels is:
- A. Dopamine D2 receptor
- B. Muscarinic M2 receptor
- C. Serotonin 5 HT 1 receptor
- D. Angiotensin 1 receptor (Correct Answer)
Explanation: ***Angiotensin 1 receptor*** - The **angiotensin 1 receptor (AT1R)** is a **Gq-coupled receptor** that primarily activates the **phospholipase C (PLC)** pathway, leading to increased intracellular **calcium** and **IP3/DAG** signaling. - Its activation mediates vasoconstriction, aldosterone release, and cardiac hypertrophy, none of which involve direct opening of potassium channels. *Dopamine D2 receptor* - **Dopamine D2 receptors** are **Gi/o-coupled receptors** that inhibit adenylyl cyclase and **open potassium channels**, leading to **hyperpolarization** and reduced neuronal excitability. - This action contributes to its **antipsychotic** and **motor control** effects. *Muscarinic M2 receptor* - **Muscarinic M2 receptors** are **Gi/o-coupled receptors** found in the heart that cause **bradycardia** by activating **acetylcholine-gated inwardly rectifying potassium (GIRK) channels**, leading to hyperpolarization. - They also inhibit adenylyl cyclase, reducing cAMP levels and decreasing heart rate and contractility. *Serotonin 5 HT 1 receptor* - **Serotonin 5-HT1 receptors** (e.g., 5-HT1A) are **Gi/o-coupled receptors** that, upon activation, **increase potassium conductance** (hyperpolarization) and inhibit adenylyl cyclase. - This leads to a reduction in neuronal firing and is implicated in the anxiolytic and antidepressant effects of these receptors.
Question 7: Administration of which of the following will reverse respiratory depression caused by opioids?
- A. Naloxone (Correct Answer)
- B. Kappa receptor blocker
- C. Delta receptor blocker
- D. Adrenergic receptor stimulator
Explanation: ***Naloxone*** - **Naloxone** is a pure **opioid receptor antagonist** that rapidly reverses all effects of opioid overdose, including respiratory depression - It has high affinity for **mu-opioid receptors**, which mediate both respiratory depression and analgesia - Naloxone is the **gold standard antidote** for opioid overdose and life-threatening respiratory depression - It reverses opioid effects within 1-2 minutes when given intravenously *Kappa receptor blocker* - **Kappa receptors** primarily mediate dysphoria, sedation, and some analgesia - The life-threatening **respiratory depression** from opioid overdose is primarily mediated by **mu receptors**, not kappa receptors - Selective kappa blockade would not effectively reverse mu-opioid induced respiratory depression *Delta receptor blocker* - **Delta opioid receptors** are primarily involved in modulating pain perception and emotional responses - They have minimal direct involvement in **respiratory depression** compared to mu receptors - Blocking delta receptors would not effectively counteract respiratory depression induced by **mu-opioid agonists** like morphine, fentanyl, or heroin *Adrenergic receptor stimulator* - **Adrenergic stimulators** (e.g., epinephrine) act on the sympathetic nervous system and may cause bronchodilation - They do not reverse the **central mechanism** of opioid-induced respiratory depression, which occurs at the brainstem respiratory centers via opioid receptors - While they might provide some cardiovascular support, they do not address the underlying **CNS depression** and are not appropriate antidotes for opioid toxicity
Question 8: Which is NOT a common symptom of opioid withdrawal?
- A. Seizures (Correct Answer)
- B. Yawning
- C. Insomnia
- D. Diarrhea
Explanation: ***Seizures*** - Seizures are **not typical** of opioid withdrawal; they are more characteristic of withdrawal from substances like **alcohol** or **benzodiazepines**. - Opioid withdrawal symptoms are primarily **autonomic** and **flu-like**, not neurological in the sense of causing seizures. *Yawning* - **Frequent yawning** is a common and early **autonomic symptom** of opioid withdrawal, indicating central nervous system overactivity. - It is often accompanied by other signs of hyperarousal and discomfort. *Insomnia* - **Insomnia** (difficulty sleeping) is a very common and distressing symptom during opioid withdrawal due to heightened central nervous system activity and generalized discomfort. - Patients often experience **restlessness** and an inability to achieve restful sleep. *Diarrhea* - **Diarrhea** is a prominent gastrointestinal symptom of opioid withdrawal, resulting from the cessation of opioid-induced slowing of gut motility. - This symptom reflects the **autonomic hyperactivity** caused by opioid cessation.
Question 9: Which of the following statements about Nitrous Oxide (N2O) is true?
- A. Least potent inhalational anesthetic (Correct Answer)
- B. Lighter than air
- C. Effective muscle relaxant
- D. Does not cause diffusion hypoxia
Explanation: **Least potent inhalational anesthetic** - Nitrous oxide has a **high Minimum Alveolar Concentration (MAC)** of approximately 104%, making it the least potent of the commonly used inhalational anesthetics. - Its high MAC means a very high concentration is required to achieve surgical anesthesia, which is why it is typically used as an adjunct to more potent agents. *Lighter than air* - The molecular weight of nitrous oxide (N2O) is 44, which is **heavier than air** (average molecular weight approximately 29 g/mol). - Its density is greater than air, meaning it would tend to sink rather than rise. *Effective muscle relaxant* - Nitrous oxide provides **minimal to no skeletal muscle relaxation** benefits. - If muscle relaxation is required, a neuromuscular blocking agent must be administered separately. *Does not cause diffusion hypoxia* - Nitrous oxide rapidly diffuses out of the blood into the alveoli during emergence, diluting the oxygen and carbon dioxide there. - This rapid diffusion can lead to **diffusion hypoxia** (also known as the "second gas effect"), necessitating the administration of 100% oxygen during recovery to prevent this complication.
Question 10: Which of the following agents is used for the treatment of post operative shivering?
- A. Atropine
- B. Thiopentone
- C. Pethidine (Correct Answer)
- D. Suxamethonium
Explanation: ***Pethidine*** - **Pethidine (meperidine)** is a **synthetic opioid** known for its **mu-receptor agonism** and weak anticholinergic properties, making it effective in treating **post-operative shivering**. - Its mechanism in reducing shivering is thought to involve modulation of the **thermoregulatory center** in the hypothalamus. *Atropine* - **Atropine** is an **anticholinergic drug** that primarily blocks muscarinic acetylcholine receptors, leading to effects like increased heart rate and decreased secretions. - It does not directly act on the thermoregulatory centers or muscle activity responsible for shivering. *Thiopentone* - **Thiopentone** is a **barbiturate** used as an intravenous anesthetic, primarily for induction of anesthesia. - While it has CNS depressant effects, it is not indicated or effective for the specific treatment of post-operative shivering. *Suxamethonium* - **Suxamethonium (succinylcholine)** is a **depolarizing neuromuscular blocker** used to induce muscle paralysis, typically for intubation. - It would prevent shivering by paralyzing skeletal muscles, but this is a dangerous and inappropriate treatment for shivering due to its profound respiratory depressant effects.
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