Pharmacotherapy for Substance Use Disorders — MCQs
Which of the following drugs is used for smoking cessation?
Which of the following is a pure opioid antagonist?
Which opioid drug is effectively administered via the transbuccal route?
Which of the following drugs is given for detoxification of alcohol in chronic alcoholics?
Which of these is the best for management of methanol poisoning?
Opioid antagonist that can be given orally –
Plasma cholinesterase levels are affected by various conditions. Which of the following conditions does not typically reduce plasma cholinesterase levels?
A patient with known cirrhosis presents with jaundice and abdominal distention. Ultrasound reveals ascites and splenomegaly. What is the most likely cause of his ascites?
Diagnose the underlying medical disorder based on the ECG changes.
A 20-year-old chronic alcoholic presents with severe hematemesis. USG shows distension of portal vein and the liver appears hyperechoic. Pantoprazole has been initiated. What is the next step in management?
Pharmacotherapy for Substance Use Disorders Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following drugs is used for smoking cessation?
- A. Gabapentin
- B. Acamprosate
- C. Nalmefene
- D. Varenicline (Correct Answer)
Explanation: ***Varenicline*** - **Varenicline** is a **partial agonist** at the **α4β2 nicotinic acetylcholine receptor**, reducing cravings and withdrawal symptoms while decreasing the rewarding effects of nicotine [2]. - It is a first-line pharmacotherapy for **smoking cessation**, often initiated a week before the target quit date. *Gabapentin* - **Gabapentin** is primarily an **anticonvulsant** and is also used to treat **neuropathic pain**. - It is not indicated for **smoking cessation** and acts by modulating **GABAergic neurotransmission**, unrelated to nicotine dependence. *Acamprosate* - **Acamprosate** is used to maintain **abstinence from alcohol** in patients with alcohol dependence. - Its mechanism involves restoring the balance between **excitation and inhibition** in the brain, which is not directly applicable to nicotine dependence. *Nalmefene* - **Nalmefene** is an **opioid system modulator** used for reducing **alcohol consumption** in adults with alcohol dependence [1]. - It acts as an **opioid receptor antagonist**, a mechanism distinct from the neurotransmitter systems involved in nicotine addiction [1].
Question 2: 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 3: 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 4: Which of the following drugs is given for detoxification of alcohol in chronic alcoholics?
- A. Haloperidol
- B. Naltrexone
- C. Chlordiazepoxide (Correct Answer)
- D. Buprenorphine
Explanation: ***Correct Option: Chlordiazepoxide*** - **Chlordiazepoxide** is a **benzodiazepine** commonly used for acute alcohol withdrawal syndrome due to its long half-life and efficacy in reducing withdrawal symptoms. - It helps prevent **seizures** and **delirium tremens** by acting on GABA receptors, reducing neuronal hyperexcitability. *Incorrect Option: Haloperidol* - **Haloperidol** is an **antipsychotic** medication primarily used to manage acute psychosis, agitation, or delirium. - It does not directly address alcohol withdrawal symptoms and can potentially lower the **seizure threshold**, which is risky in alcohol withdrawal. *Incorrect Option: Naltrexone* - **Naltrexone** is an **opioid antagonist** used to reduce alcohol cravings and prevent relapse in individuals who have achieved abstinence. - It is not used for acute detoxification or withdrawal management, as it does not alleviate acute symptoms. *Incorrect Option: Buprenorphine* - **Buprenorphine** is a **partial opioid agonist** used primarily in the treatment of opioid use disorder. - It has no role in the detoxification or management of alcohol withdrawal syndrome.
Question 5: Which of these is the best for management of methanol poisoning?
- A. Fomepizole (Correct Answer)
- B. Naltrexone
- C. Disulfiram
- D. Acamprosate
Explanation: ***Fomepizole*** - **Fomepizole** is a competitive inhibitor of **alcohol dehydrogenase**, the enzyme responsible for metabolizing methanol into toxic metabolites like formic acid. - By inhibiting this enzyme, it prevents the formation of these toxic metabolites, thereby reducing organ damage and metabolic acidosis in methanol poisoning. *Naltrexone* - **Naltrexone** is an **opioid receptor antagonist** used in the treatment of alcohol and opioid dependence. - It does not have any direct action on the metabolism of methanol or its toxic byproducts. *Disulfiram* - **Disulfiram** inhibits **aldehyde dehydrogenase**, leading to an unpleasant reaction when alcohol is consumed (flushing, nausea, vomiting). - It is used for alcohol cessation and has no role in the management of methanol poisoning. *Acamprosate* - **Acamprosate** is a medication used to reduce alcohol cravings in individuals recovering from alcohol dependence, possibly by modulating **glutamate neurotransmission**. - It does not directly affect the metabolism of methanol or mitigate its toxic effects.
Question 6: Opioid antagonist that can be given orally –
- A. Naltrexone (Correct Answer)
- B. Pentazocine
- C. Naloxone
- D. Nalbuphine
Explanation: ***Naltrexone*** - **Naltrexone** is an opioid antagonist used for treating **opioid dependence** and alcohol dependence. - It has good oral bioavailability and is administered orally, typically as a daily dose. *Pentazocine* - **Pentazocine** is an opioid agonist-antagonist, primarily acting as an **agonist** at kappa opioid receptors and a weak antagonist or partial agonist at mu opioid receptors. - It is not a pure opioid antagonist and thus cannot reverse opioid effects effectively. *Naloxone* - **Naloxone** is a pure opioid antagonist primarily used to reverse **acute opioid overdose** due to its rapid onset and short duration of action. - While it can be given orally, it has very **low oral bioavailability** due to extensive first-pass metabolism, making it unsuitable for chronic oral administration. *Nalbuphine* - **Nalbuphine** is an opioid agonist-antagonist, similar to pentazocine, acting as an **agonist** at kappa opioid receptors and an antagonist at mu opioid receptors. - It is typically administered parenterally for pain relief and is not used as an oral opioid antagonist.
Question 7: Plasma cholinesterase levels are affected by various conditions. Which of the following conditions does not typically reduce plasma cholinesterase levels?
- A. Pregnancy
- B. Liver disease
- C. Malnutrition
- D. Chronic renal failure (Correct Answer)
Explanation: ***Chronic renal failure*** - While chronic renal failure can cause various metabolic derangements, it does not typically lead to a significant **reduction in plasma cholinesterase levels**. - Plasma cholinesterase is primarily synthesized in the liver, and its levels are more directly impacted by conditions affecting **liver function** or **protein synthesis** [1]. *Pregnancy* - **Plasma cholinesterase levels** are known to decrease during normal pregnancy, particularly in the third trimester. - This reduction is thought to be due to **hormonal changes** and possibly increased plasma volume. *Liver disease* - Since plasma cholinesterase is synthesized in the **liver**, severe **liver disease** (e.g., cirrhosis, acute hepatitis) significantly impairs its production [1]. - This leads to a marked **reduction in circulating enzyme levels**, which can affect drug metabolism [1]. *Malnutrition* - **Severe malnutrition**, especially protein-calorie malnutrition, can lead to decreased synthesis of many proteins, including plasma cholinesterase. - This is because the body lacks the necessary **amino acids** for enzyme production.
Question 8: A patient with known cirrhosis presents with jaundice and abdominal distention. Ultrasound reveals ascites and splenomegaly. What is the most likely cause of his ascites?
- A. Portal hypertension (Correct Answer)
- B. Peritoneal carcinomatosis
- C. Nephrotic syndrome
- D. Congestive heart failure
Explanation: ***Portal hypertension*** - In cirrhosis, **fibrosis** and **regenerative nodules** increase resistance to blood flow through the liver, leading to **portal hypertension** [1]. - This increased pressure in the portal venous system, combined with **splanchnic vasodilation** and **renal sodium retention**, drives the transudation of fluid into the peritoneal cavity, forming ascites [1]. *Peritoneal carcinomatosis* - This would typically result in **exudative ascites**, often with a high protein content and positive cytology for malignant cells [1]. - While it can cause abdominal distention, it is not directly linked to the pathology of **cirrhosis** and **splenomegaly** as the primary cause of ascites in this context. *Nephrotic syndrome* - Characterized by **massive proteinuria**, **hypoalbuminemia**, and **generalized edema**, including ascites. - While it causes fluid retention, the clinical picture of **jaundice** and **splenomegaly** strongly points to liver pathology rather than primary renal disease [1]. *Congestive heart failure* - Can cause **dependent edema** and ascites due to elevated systemic venous pressures, but typically presents with other signs like **dyspnea**, orthopnea, and pulmonary edema [1]. - The patient's history of **cirrhosis** and the presence of **splenomegaly** make portal hypertension a significantly more likely cause of ascites [1].
Question 9: Diagnose the underlying medical disorder based on the ECG changes.
- A. ECG changes due to hypokalemia
- B. ECG changes due to hypercalcemia
- C. ECG changes due to hypocalcemia (Correct Answer)
- D. ECG changes due to hyperkalemia
Explanation: ***ECG changes due to hypocalcemia*** - **Hypocalcemia** characteristically causes a **prolonged QT interval** on the ECG due to delayed repolarization of ventricular myocytes. - This prolongation is primarily due to the lengthening of the **ST segment**, while the T wave itself is usually unchanged. *ECG changes due to hypokalemia* - **Hypokalemia** typically presents with prominent **U waves**, T wave flattening or inversion, and sometimes ST segment depression. - While it can also prolong the QT interval, the primary distinguishing feature is the presence of U waves, which are not mentioned as the main finding. *ECG changes due to hypercalcemia* - **Hypercalcemia** is associated with a **shortened QT interval** on the ECG due to accelerated repolarization. - It can also cause a shortened ST segment and widened QRS complex in severe cases. *ECG changes due to hyperkalemia* - **Hyperkalemia** classically manifests as tall, **peaked T waves**, followed by a prolonged PR interval, widened QRS complex, and eventual sine wave pattern as it worsens. - These changes are distinctly different from the prolonged QT interval seen in hypocalcemia.
Question 10: A 20-year-old chronic alcoholic presents with severe hematemesis. USG shows distension of portal vein and the liver appears hyperechoic. Pantoprazole has been initiated. What is the next step in management?
- A. Administer IV fluids and electrolytes to stabilize hemodynamics
- B. Perform an endoscopy to identify and treat varices (Correct Answer)
- C. Order a liver biopsy to assess for fibrosis
- D. Initiate a course of broad-spectrum antibiotics
Explanation: **Perform an endoscopy to identify and treat varices** - Severe **hematemesis** in a chronic alcoholic with signs of **portal hypertension** (distended portal vein, hyperechoic liver) strongly suggests bleeding esophageal varices [1]. - **Endoscopy** is crucial for both diagnosing the source of bleeding and providing immediate therapeutic intervention, such as **variceal band ligation** or **sclerotherapy** [1]. *Administer IV fluids and electrolytes to stabilize hemodynamics* - While **hemodynamic stabilization with IV fluids** is an immediate and critical step in managing severe GI bleeding, it is not the *next step in definitive management* after pantoprazole initiation, which aims to address the *cause* of the bleeding. - This is an initial supportive measure, but addressing the source of hemorrhage is paramount once stabilization begins [1]. *Order a liver biopsy to assess for fibrosis* - A **liver biopsy** is primarily used for diagnosing the underlying cause and severity of liver disease, such as **cirrhosis** and **fibrosis**. - It is not an urgent procedure in the context of acute, severe hematemesis and would delay critical interventions to stop the bleeding. *Initiate a course of broad-spectrum antibiotics* - **Antibiotics** are indeed utilized in patients with cirrhosis and upper GI bleeding to prevent **spontaneous bacterial peritonitis** and other infections, often administered *after* hemodynamic stabilization and initial endoscopic management. - However, stopping the active bleeding is the immediate priority before initiating prophylactic antibiotics.
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