Opioid Analgesics — MCQs
A farmer with pinpoint pupils, increased secretions and urination. What is the most likely diagnosis?
Which of the following substances is not classified as an opioid?
Which of the following anesthetic drugs is contraindicated in chronic renal failure?
A patient presented with pain in the right lower quadrant of abdomen. He has history of renal stones in right kidney. He was prescribed an opioid which is agonist at kappa receptors and antagonist at mu receptors. The likely drug given was:
All are symptoms of morphine withdrawal except?
What effect does morphine have on muscle tone?
A patient presents with constricted pupils, respiratory depression, and cyanosis. What is the likely poison?
Buprenorphine is a partial agonist at which opioid receptor?
A patient with biliary duct stricture presenting with retching and vomiting was receiving 3mg epidural morphine daily. One day, 12mg of epidural morphine was mistakenly administered. Which of the following is NOT expected to occur with this morphine overdose?
Site of action of epidural analgesia
Opioid Analgesics Indian Medical PG Practice Questions and MCQs
Question 1: A farmer with pinpoint pupils, increased secretions and urination. What is the most likely diagnosis?
- A. Alcohol poisoning
- B. Organophosphate poisoning (Correct Answer)
- C. Opioid poisoning
- D. Atropine poisoning
Explanation: ***Organophosphate poisoning*** - **Pinpoint pupils (miosis)**, **increased secretions** (salivation, lacrimation, bronchial secretions), and **urination** are classic signs of cholinergic crisis caused by organophosphate toxicity [1]. - The patient's profession as a **farmer** increases the likelihood of exposure to pesticides, which often contain organophosphates [1], [2]. *Alcohol poisoning* - While alcohol poisoning can cause CNS depression, it does not typically present with **pinpoint pupils** or **increased secretions** like salivation and urination. - Common signs include **ataxia**, **slurred speech**, **nausea**, and **vomiting**. *Opioid poisoning* - Opioid poisoning also causes **pinpoint pupils** and **CNS depression**, but it typically leads to **decreased secretions** and **urinary retention**, not increased urination [2]. - **Respiratory depression** is a hallmark feature, which is not highlighted here as a primary symptom. *Atropine poisoning* - Atropine is an anticholinergic agent, meaning it would cause the opposite effects of organophosphate poisoning [2]. - Symptoms would include **dilated pupils (mydriasis)**, **dry mouth**, **decreased secretions**, and **urinary retention**.
Question 2: Which of the following substances is not classified as an opioid?
- A. Heroin
- B. Ketamine (Correct Answer)
- C. Methadone
- D. Fentanyl
Explanation: ***Ketamine*** - **Ketamine** is classified as a **dissociative anesthetic** and does not act on opioid receptors. - Its primary mechanism of action involves **N-methyl-D-aspartate (NMDA) receptor antagonism**. *Heroin* - **Heroin** (diacetylmorphine) is a **semisynthetic opioid** derived from morphine [1, 3]. - It rapidly crosses the **blood-brain barrier** and is metabolized to morphine, where it acts as a potent **mu-opioid receptor agonist** [3]. *Methadone* - **Methadone** is a **synthetic opioid** used in the treatment of opioid dependence and chronic pain [1, 2]. - It acts primarily as a **mu-opioid receptor agonist** with a long duration of action [1, 2]. *Fentanyl* - **Fentanyl** is a powerful **synthetic opioid** analgesic, much more potent than morphine [2]. - It selectively binds to and activates **mu-opioid receptors**, producing strong analgesic and sedative effects [2].
Question 3: Which of the following anesthetic drugs is contraindicated in chronic renal failure?
- A. Atracurium
- B. Fentanyl
- C. Pethidine (Correct Answer)
- D. Morphine
Explanation: ***Pethidine*** - **Pethidine** is contraindicated in chronic renal failure due to its active metabolite, **normeperidine**, which is eliminated renally. - Accumulation of **normeperidine** can lead to **central nervous system (CNS) toxicity**, including seizures, tremors, and hyperreflexia. *Atracurium* - **Atracurium** undergoes **Hofmann elimination** and **ester hydrolysis**, which are independent of renal or hepatic function. - This makes it a relatively safe choice for patients with **renal impairment**. *Fentanyl* - **Fentanyl** is primarily metabolized by the liver, with its metabolites being inactive. - While some dose adjustment may be considered in severe renal failure, it is generally **safe** for use in patients with chronic renal impairment as its metabolites are inactive. *Morphine* - **Morphine** is metabolized in the liver to **morphine-3-glucuronide (M3G)** and **morphine-6-glucuronide (M6G)**, both of which are renally excreted. - **M6G** is an active metabolite with potent analgesic effects, and its accumulation in renal failure can cause **prolonged sedation** and **respiratory depression**. While significant caution and dose reduction are needed, it's not strictly contraindicated in the same way pethidine is due to the more neurotoxic nature of normeperidine.
Question 4: A patient presented with pain in the right lower quadrant of abdomen. He has history of renal stones in right kidney. He was prescribed an opioid which is agonist at kappa receptors and antagonist at mu receptors. The likely drug given was:
- A. Pentazocine (Correct Answer)
- B. Tramadol
- C. Buprenorphine
- D. Fentanyl
Explanation: ***Pentazocine*** - **Pentazocine** is a **mixed agonist-antagonist opioid analgesic** that acts as an **agonist at kappa opioid receptors** and a **weak antagonist or partial agonist at mu opioid receptors**. - This unique receptor profile makes it the drug described in the question. - It is effective for **moderate to severe pain** including **renal colic** (pain from renal stones), while having a **lower abuse potential** and **ceiling effect on respiratory depression** compared to pure mu agonists. *Tramadol* - **Tramadol** is a synthetic opioid that acts primarily as a **weak mu-opioid receptor agonist** and also inhibits the reuptake of **norepinephrine** and **serotonin**. - It does **not** have significant kappa receptor agonism or mu receptor antagonism. - Does not fit the description given in the question. *Buprenorphine* - **Buprenorphine** is a **partial agonist at mu opioid receptors** and an **antagonist at kappa opioid receptors**. - This receptor activity profile is the **opposite** of what is described in the question (which asks for kappa agonist, mu antagonist). *Fentanyl* - **Fentanyl** is a highly potent **pure mu-opioid receptor agonist**. - It has **no significant kappa receptor agonism** or mu receptor antagonism. - Does not match the pharmacological profile described in the question.
Question 5: All are symptoms of morphine withdrawal except?
- A. Yawning
- B. Lacrimation
- C. Mydriasis
- D. Fall in BP (Correct Answer)
Explanation: ***Fall in BP*** - **Hypotension (fall in BP)** is **not** typically a symptom of opioid withdrawal; rather, **hypertension** can occur due to sympathetic overdrive. - Opioid withdrawal symptoms are primarily characterized by **hyperactivity** and increased sympathetic nervous system activity. *Mydriasis* - **Mydriasis (dilated pupils)** is a classic symptom of opioid withdrawal, resulting from reduced parasympathetic tone and increased sympathetic activity. - In contrast, opioid intoxication causes **miosis (pinpoint pupils)**. *Yawning* - **Yawning** is a very common and early symptom of opioid withdrawal, often accompanied by feelings of fatigue and restlessness. - It reflects generalized **autonomic dysregulation** during withdrawal. *Lacrimation* - **Lacrimation (tearing)** is another prominent autonomic symptom of opioid withdrawal. - This, along with rhinorrhea, contributes to the **"flu-like" symptoms** experienced during withdrawal.
Question 6: What effect does morphine have on muscle tone?
- A. Increased muscle tone (Correct Answer)
- B. Respiratory stimulation
- C. Decreased muscle tone
- D. Mydriasis
Explanation: ***Increased muscle tone*** - Morphine **increases skeletal muscle tone** and can cause muscle rigidity, particularly with rapid IV administration (truncal rigidity). - It significantly increases **smooth muscle tone** in various organs including the sphincter of Oddi (causing biliary colic), bladder sphincter (causing urinary retention), and GI tract (causing constipation). - This increased tone in sphincters and smooth muscle is a well-documented effect mediated through **opioid receptor activation**. *Bradycardia (not increased heart rate)* - Morphine typically causes **bradycardia** (decreased heart rate) due to vagal stimulation and central effects, not tachycardia. - Increased heart rate would be atypical and not a primary pharmacological effect of morphine. *Miosis (not mydriasis)* - Morphine characteristically causes **miosis** (pinpoint pupils) due to stimulation of the Edinger-Westphal nucleus of the oculomotor nerve. - Mydriasis (dilated pupils) is seen with anticholinergics or sympathomimetics, not opioids. *Respiratory depression (not stimulation)* - Morphine causes **respiratory depression**, not stimulation, by reducing the responsiveness of brainstem respiratory centers to CO2. - This is one of the most dangerous adverse effects and the primary cause of death in opioid overdose.
Question 7: A patient presents with constricted pupils, respiratory depression, and cyanosis. What is the likely poison?
- A. Opium (Correct Answer)
- B. Anticholinergic
- C. Cyanide Poisoning
- D. Arsenic Poisoning
Explanation: ***Opium*** - **Opioid toxicity** classically presents with the triad of **miosis** (constricted pupils), **respiratory depression**, and **CNS depression**, which aligns with the patient's symptoms. - **Cyanosis** is a direct consequence of severe respiratory depression leading to hypoxemia. *Anticholinergic* - Anticholinergic toxidrome typically presents with **dilated pupils (mydriasis)**, **dry skin and mucous membranes**, and **tachycardia**, which are opposite to the patient's presentation. - Respiratory depression is not a primary feature of anticholinergic poisoning; rather, patients may exhibit agitation or delirium. *Cyanide Poisoning* - Cyanide poisoning primarily affects cellular respiration, leading to a rapid onset of symptoms like **headache**, **confusion**, **tachycardia**, and **metabolic acidosis**. - While it can cause respiratory distress, **pupils are typically normal or dilated**, and the characteristic smell of bitter almonds may be present. *Arsenic Poisoning* - Acute arsenic poisoning manifests with severe **gastrointestinal symptoms** (nausea, vomiting, diarrhea), **cardiovascular collapse**, and **neurological symptoms** like altered mental status. - It does not typically cause constricted pupils or primary respiratory depression as seen in this case.
Question 8: Buprenorphine is a partial agonist at which opioid receptor?
- A. Mu (Correct Answer)
- B. Kappa
- C. Delta
- D. ORL-1
Explanation: ***Mu*** - Buprenorphine primarily acts as a **partial agonist** at the **mu opioid receptor**, providing analgesic effects with a ceiling effect on respiratory depression. - Its partial agonism at the mu receptor contributes to its lower potential for respiratory depression and overdose compared to full mu agonists. *Kappa* - While buprenorphine has some antagonist activity at the kappa receptor, its primary therapeutic action is not at this receptor. - **Kappa receptor agonists** like pentazocine can produce dysphoria and psychotomimetic effects. *Delta* - The delta opioid receptor is involved in analgesia and emotional responses, but buprenorphine has very low affinity and activity at this receptor. - **Delta receptor agonists** are not widely used clinically due to limited efficacy and side effects. *ORL-1* - The ORL-1 (Opioid Receptor-like 1) receptor, also known as the nociceptin receptor, is distinct from classical opioid receptors. - Buprenorphine has **no significant activity** at the ORL-1 receptor, which primarily mediates pain, anxiety, and learning.
Question 9: A patient with biliary duct stricture presenting with retching and vomiting was receiving 3mg epidural morphine daily. One day, 12mg of epidural morphine was mistakenly administered. Which of the following is NOT expected to occur with this morphine overdose?
- A. Overstimulation of respiratory centre
- B. Urinary retention (Correct Answer)
- C. Itching
- D. Increase vomiting
Explanation: ***Urinary retention*** - **Morphine** is known to cause **urinary retention** by increasing the tone of the urinary sphincter and detrusor muscle, leading to difficulty in urination or inability to empty the bladder. - This effect would be **expected** with an overdose of epidural morphine, not *unexpected*. *Overstimulation of respiratory centre* - **Opioid overdose** typically leads to **respiratory depression** due to direct effects on the brainstem respiratory centers, decreasing respiratory rate and tidal volume. - An **overstimulation** of the respiratory center is therefore not an expected finding. *Itching* - **Itching (pruritus)** is a common side effect of **epidural opioids**, including morphine, often due to histamine release or interaction with opioid receptors in the spinal cord. - This would be an **expected** symptom following a morphine overdose. *Increase vomiting* - **Opioids** can stimulate the **chemoreceptor trigger zone** in the brain, leading to **nausea and vomiting**. - An overdose would likely **exacerbate** this effect, leading to increased vomiting.
Question 10: Site of action of epidural analgesia
- A. Anterior horn
- B. Substantia gelatinosa (Correct Answer)
- C. Ventral horn
- D. Sensory nerve endings
Explanation: ***Substantia gelatinosa*** - Epidural analgesia primarily acts on the **substantia gelatinosa** (Rexed lamina II) within the **dorsal horn** of the spinal cord. - This area is crucial for processing and modulating **pain signals**, which are inhibited by local anesthetics and opioids administered epidurally. *Anterior horn* - The **anterior horn** (ventral horn) primarily contains **motor neurons** responsible for skeletal muscle control. - While local anesthetics can block motor fibers if they diffuse sufficiently, the primary target for analgesia is sensory. *Ventral horn* - The **ventral horn** is synonymous with the **anterior horn** and is mainly involved in **motor function**. - Its role is not directly related to the primary analgesic effect of epidural medications on pain transmission. *Sensory nerve endings* - **Sensory nerve endings** are located in the periphery, such as the skin, muscles, and organs. - Epidural analgesia acts within the **spinal canal** and does not directly target peripheral sensory nerve endings.
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