Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Predictable and dose-related drug-induced hepatic injury is seen with all of the following EXCEPT:

Isoniazid (INH). Drug-induced liver injury (DILI) is classified into two main types: **Predictable (Intrinsic)** and **Unpredictable (Idiosyncratic).** [1] **1. Why Isoniazid (INH) is the correct answer:** Isoniazid causes **Idiosyncratic (Unpredictable)** hepatotoxicity. This type of injury is not dose-related, has a variable latency period, and cannot be reproduced in animal models. It occurs in a small percentage of patients (approx. 1%) due to individual metabolic variations (e.g., acetylator status) or immune responses [2]. Because it is not dose-dependent, it is the "Except" in this list. **2. Analysis of Incorrect Options (Predictable Hepatotoxins):** * **Acetaminophen (Paracetamol):** The classic example of dose-related toxicity. At high doses, the glutathione pathway is saturated, leading to the accumulation of the toxic metabolite **NAPQI**, causing centrilobular necrosis [3]. * **Carbon Tetrachloride ($CCl_4$):** A potent direct hepatotoxin. It undergoes metabolism to the free radical $CCl_3\cdot$, causing lipid peroxidation and predictable, dose-dependent liver cell death. * **Oral Contraceptive Agents:** These cause predictable, dose-related **cholestasis** (interference with bile excretion) rather than necrosis, but the effect is still considered intrinsic to the drug's pharmacological action on the canalicular membrane. **NEET-PG High-Yield Pearls:** * **Most common cause of DILI (Global):** Acetaminophen [3]. * **Most common cause of Idiosyncratic DILI:** Amoxicillin-Clavulanate. * **INH Monitoring:** Asymptomatic rise in transaminases (up to 3x normal) occurs in 10-20% of patients; the drug is usually continued unless levels exceed 5x normal or the patient becomes symptomatic. * **Halothane:** Another classic example of idiosyncratic (Type II) hepatotoxicity.

Q: All of the following cause hyperglycemia, EXCEPT?

Theophylline. Explanation: The correct answer is Theophylline. In cases of acute toxicity, Theophylline typically causes hypokalemia and hyperglycemia (due to catecholamine release). However, it is not classically categorized as a drug that induces clinical hyperglycemia or diabetes mellitus as a side effect. In fact, among the options provided, it is the least likely to be associated with persistent elevated blood glucose levels. Analysis of Options: * Thiazide Diuretics (A): These are notorious for causing hyperglycemia. They inhibit insulin release from the pancreas (via K+ channel activation) [1] and decrease peripheral glucose utilization, often worsening glycemic control in diabetics. * Diazoxide (B): This drug is a potent K+ATP channel opener in pancreatic beta cells. [2] By keeping these channels open, it hyperpolarizes the cell and inhibits insulin secretion. [2] It is clinically used to treat hypoglycemia in conditions like insulinoma. * Pentamidine (D): This is a high-yield "double-edged sword" for NEET-PG. It is initially cytotoxic to pancreatic beta cells. This causes an initial massive release of insulin (leading to hypoglycemia), followed by permanent beta-cell destruction, resulting in insulin-dependent diabetes mellitus (hyperglycemia). Clinical Pearls for NEET-PG: * Drugs causing Hyperglycemia: Steroids, Thiazides, Diazoxide, Protease Inhibitors, Phenytoin, Beta-blockers, and Niacin. * Pentamidine Paradox: Remember the sequence: Acute Hypoglycemia → Chronic Hyperglycemia. * Theophylline Toxicity: Focus on the triad of Seizures, Arrhythmias, and Hypokalemia. While hyperglycemia can occur in acute overdose, it is not a standard metabolic side effect of the drug.

Q: A patient receives a toxic dose of lignocaine intravenously. Which of the following is the patient likely to exhibit?

Seizures and coma. ### Explanation **Correct Answer: D. Seizures and coma** Local anesthetic (LA) toxicity, particularly with Lignocaine, primarily affects the **Central Nervous System (CNS)** and the **Cardiovascular System (CVS)**. **Pathophysiology:** Lignocaine toxicity follows a predictable progression based on plasma concentration. Initially, LAs selectively inhibit **inhibitory cortical pathways** (GABAergic neurons). This leaves excitatory pathways unopposed, leading to signs of CNS excitation such as restlessness, tremors, and **tonic-clonic seizures**. As plasma levels rise further, both inhibitory and excitatory pathways are depressed, resulting in generalized CNS depression, **coma**, and respiratory arrest. **Analysis of Incorrect Options:** * **A & B (Salivation, Mydriasis, Diarrhea):** These are autonomic symptoms (cholinergic or adrenergic). Lignocaine toxicity does not typically present with these; instead, early signs include circumoral numbness, metallic taste, and tinnitus. * **C (Respiratory paralysis):** While respiratory arrest can occur in the terminal stages of toxicity due to medullary depression, it is preceded by CNS excitation (seizures). Seizures and coma are the classic hallmark sequence of systemic toxicity (LAST). **High-Yield Clinical Pearls for NEET-PG:** 1. **Sequence of Toxicity:** CNS symptoms (Seizures → Coma) usually appear *before* CVS symptoms (Arrhythmias → Cardiac arrest), except with Bupivacaine, which is highly cardiotoxic. 2. **Treatment of Choice:** **Intravenous Lipid Emulsion (20% Intralipid)** is the specific antidote for Local Anesthetic Systemic Toxicity (LAST). 3. **Seizure Management:** Benzodiazepines (e.g., Midazolam) are the first-line agents to control LA-induced seizures. 4. **Maximum Dose of Lignocaine:** 3 mg/kg (plain) and 7 mg/kg (with Adrenaline).

Q: Patisiran was approved by FDA recently for which condition?

Neuropathy of amyloidosis. **Explanation:** **Patisiran** is a groundbreaking medication that represents the first-ever FDA-approved drug (2018) utilizing **RNA interference (RNAi)** technology [2]. **Why Option D is correct:** Patisiran is specifically indicated for the treatment of polyneuropathy caused by **Hereditary Transthyretin-mediated (hATTR) Amyloidosis**. In this condition, mutations in the TTR gene lead to the accumulation of misfolded amyloid proteins in peripheral nerves. Patisiran consists of a **small interfering RNA (siRNA)** formulated in lipid nanoparticles [2]. It works by binding to and degrading the messenger RNA (mRNA) responsible for producing the transthyretin (TTR) protein in the liver, thereby reducing amyloid deposits in tissues and improving neurological symptoms. **Why other options are incorrect:** * **A. Filariasis:** This is a parasitic infection treated with anthelmintics like Diethylcarbamazine (DEC) or Ivermectin. * **B. Peripheral Neuropathy:** This is a broad clinical symptom, not a specific disease entity. Patisiran is only indicated for the specific amyloid-related subtype. [3] * **C. Neuropathy of diabetes:** The most common cause of neuropathy, usually managed with glycemic control and symptomatic drugs like Pregabalin, Duloxetine, or Amitriptyline. [1] **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** RNA interference (gene silencing) [2]. * **Route:** Intravenous infusion. * **Related Drug:** **Inotersen** is another drug for hATTR, but it is an *antisense oligonucleotide* (ASO), not an siRNA [2]. * **Side Effects:** Infusion-related reactions and Vitamin A deficiency (as TTR normally transports Vitamin A; supplementation is required).

Q: Which drug is contraindicated in patients allergic to sulphonamides?

Zonisamide. **Explanation:** The correct answer is **Zonisamide**. **Mechanism and Concept:** Sulphonamide allergy is a common clinical concern due to potential cross-reactivity between drugs containing a sulfonamide ($-SO_2NH_2$) moiety. **Zonisamide**, an antiepileptic drug used for focal seizures, is chemically classified as a sulfonamide. Therefore, it is contraindicated in patients with a known hypersensitivity to sulfonamides, as it can trigger severe allergic reactions, including Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN). **Analysis of Options:** * **Brizolamide (Option A):** While Brinzolamide is a carbonic anhydrase inhibitor and *is* a sulfonamide derivative, the question asks for the most definitive contraindication among the choices provided. However, in many clinical contexts, Zonisamide is more strictly highlighted in pharmacology textbooks regarding this specific contraindication. (Note: Brinzolamide is also technically contraindicated, but Zonisamide is a classic high-yield "non-antimicrobial sulfonamide" in NEET-PG). * **Brimonidine (Option B):** This is an alpha-2 adrenergic agonist used in glaucoma. It does not contain a sulfonamide group and is safe to use. * **Bimatoprost (Option D):** This is a prostaglandin analogue (PGF2α) used for glaucoma and eyelash hypotrichosis. It has no structural relation to sulfonamides. **High-Yield Clinical Pearls for NEET-PG:** * **Non-antimicrobial Sulfonamides:** Remember the mnemonic "Common Sulfonamides" – **C**elecoxib, **A**cetazolamide/Brinzolamide, **S**ulfonylureas (Glipizide), **T**hiazide diuretics, **L**oop diuretics (Furosemide), and **Z**onisamide. * **Cross-reactivity:** While the risk of cross-reactivity between sulfonamide antibiotics and non-antibiotics is debated, for exam purposes, they are considered contraindicated. * **Dermatological Emergency:** Always monitor for rashes when starting Zonisamide, as it can cause life-threatening SJS.

Q: Fomepizole is used as an antidote in poisoning by which of the following substances?

Methanol. **Explanation:** **Correct Answer: B. Methanol** Fomepizole is a potent competitive inhibitor of the enzyme **Alcohol Dehydrogenase (ADH)** [1]. In methanol poisoning, the toxicity is not caused by the methanol itself, but by its metabolite, **formic acid**, which causes metabolic acidosis and retinal damage (blindness) [1]. By inhibiting ADH, Fomepizole prevents the conversion of methanol into formaldehyde and subsequently formic acid, allowing the parent compound to be excreted harmlessly by the kidneys. It is also the antidote of choice for **Ethylene glycol** poisoning [1]. **Incorrect Options:** * **A. Organophosphorus compounds:** These are treated with **Atropine** (muscarinic antagonist) and **Pralidoxime/PAM** (cholinesterase reactivator) [2]. * **C. Aluminium phosphide:** There is no specific antidote for "Celphos" poisoning. Management is primarily supportive (gastric lavage with KMnO4 and coconut oil, magnesium sulfate). * **D. Copper:** Wilson’s disease or acute copper toxicity is treated with chelating agents like **D-Penicillamine** or Trientine. **High-Yield Clinical Pearls for NEET-PG:** * **Fomepizole vs. Ethanol:** While both inhibit ADH, Fomepizole is preferred over ethanol because it does not cause CNS depression or hypoglycemia and does not require constant blood level monitoring. * **Methanol Triad:** CNS depression, severe metabolic acidosis (high anion gap), and visual disturbances ("snowfield vision") [1]. * **Indication:** Fomepizole is indicated when the plasma methanol concentration is >20 mg/dL or if there is a documented osmolar gap with metabolic acidosis.

Q: Which of the following is NOT a treatment given for acute severe digitalis toxicity?

Potassium. In digitalis toxicity, the management strategy depends heavily on whether the toxicity is **acute** or **chronic**, and the patient's current serum potassium levels. ### Why Potassium is the Correct Answer In **acute severe digitalis toxicity**, the inhibition of the Na+/K+ ATPase pump is so profound that potassium cannot enter the cells, leading to **hyperkalemia**. Administering supplemental potassium in a patient who is already hyperkalemic is contraindicated as it can precipitate fatal cardiac arrest. While potassium is used to treat digitalis-induced arrhythmias in *chronic* toxicity (where diuretics often cause hypokalemia), it is **NOT** given in acute severe cases where potassium levels are already high. ### Explanation of Other Options * **Digibind (Digoxin Immune Fab):** This is the **specific antidote** and the first-line treatment for severe life-threatening toxicity. It binds to digoxin molecules, making them pharmacologically inactive. * **Lignocaine (Lidocaine):** This is the **drug of choice** for treating digitalis-induced ventricular arrhythmias. It suppresses ventricular irritability without significantly worsening AV block. ### NEET-PG High-Yield Pearls * **Most common arrhythmia:** Ventricular Bigeminy. * **Most characteristic arrhythmia:** Atrial Tachycardia with AV block. * **Electrolyte triggers:** Hypokalemia, hypomagnesemia, and hypercalcemia predispose a patient to toxicity. * **ECG finding:** "Reverse Tick" sign or "Sagging" ST-segment depression. * **Contraindication:** DC cardioversion is avoided in digitalis toxicity as it may precipitate ventricular fibrillation.

Q: Which of the following drugs does NOT cause interstitial lung disease?

Alpha methyldopa. **Explanation:** **Interstitial Lung Disease (ILD)**, or drug-induced pulmonary fibrosis, is a serious adverse effect associated with several classes of drugs. Understanding which drugs target the lungs is crucial for NEET-PG. **Why Alpha-methyldopa is the correct answer:** Alpha-methyldopa is a centrally acting antihypertensive primarily known for causing **Coombs-positive hemolytic anemia** and **drug-induced hepatitis/lupus** [1]. It is not associated with pulmonary fibrosis or interstitial lung disease. **Analysis of Incorrect Options:** * **Phenytoin:** This antiepileptic is a known cause of hypersensitivity pneumonitis and can lead to interstitial lung changes, alongside other side effects like gingival hyperplasia and hirsutism. * **Sulfonamides:** These can cause pulmonary eosinophilia (Löffler's syndrome) and hypersensitivity-mediated interstitial pneumonitis. * **Busulfan:** An alkylating agent notorious for causing **"Busulfan Lung"** (progressive pulmonary fibrosis). It is one of the classic "high-yield" causes of ILD in oncology. **High-Yield Clinical Pearls for NEET-PG:** To remember the common causes of drug-induced pulmonary fibrosis, use the mnemonic **"BAM-P"**: 1. **B**leomycin (Most common chemotherapy cause; dose-dependent) 2. **A**miodarone (Contains iodine; causes "foamy macrophages" in alveoli) 3. **M**ethotrexate (Causes hypersensitivity pneumonitis) 4. **P**henytoin/Nitrofurantoin (Nitrofurantoin is a very common cause in elderly patients treated for UTIs). **Key Fact:** Unlike most drugs, **Steroids** are the treatment of choice for drug-induced ILD once the offending agent is discontinued [2].

Q: The disulfiram-alcohol reaction occurs due to the inhibition of which enzyme?

Aldehyde dehydrogenase. ### Explanation **Correct Answer: D. Aldehyde dehydrogenase** The metabolism of ethanol primarily occurs in the liver via a two-step oxidative process: 1. **Ethanol** is converted to **Acetaldehyde** by the enzyme *Alcohol Dehydrogenase*. 2. **Acetaldehyde** is then converted to **Acetic acid** (acetate) by the enzyme **Aldehyde Dehydrogenase (ALDH)**. **Disulfiram** works by irreversibly inhibiting **Aldehyde Dehydrogenase**. When a patient taking disulfiram consumes alcohol, acetaldehyde cannot be converted to acetate. This leads to a 5-10 fold accumulation of acetaldehyde in the blood, resulting in the **Disulfiram-Ethanol Reaction (DER)**. Symptoms include flushing, throbbing headache, nausea, vomiting, palpitations, tachycardia, and hypotension. **Analysis of Incorrect Options:** * **A & C (Reductases):** Ethanol metabolism is an **oxidative** process (loss of hydrogen), not a reductive one. Reductases are not the primary enzymes involved in this pathway. * **B (Alcohol dehydrogenase):** This enzyme catalyzes the first step. If this were inhibited (e.g., by **Fomepizole**), acetaldehyde would not form, and the unpleasant disulfiram-like reaction would not occur. Fomepizole is instead used to treat methanol and ethylene glycol poisoning. **High-Yield Clinical Pearls for NEET-PG:** * **Drugs causing Disulfiram-like reactions:** Metronidazole (most common), Cefoperazone, Cefotetan, Procarbazine, Sulfonylureas (1st Gen), and Griseofulvin. * **Acamprosate:** Used for maintaining abstinence (NMDA antagonist); unlike disulfiram, it does not cause a reaction if alcohol is consumed. * **Fomepizole:** Inhibits Alcohol Dehydrogenase; used in Methanol poisoning to prevent the formation of toxic Formaldehyde.

Question 1

Predictable and dose-related drug-induced hepatic injury is seen with all of the following EXCEPT:

Accepted Answer

Isoniazid (INH)

Answer

Carbon tetrachloride

Answer

Acetaminophen

Answer

Oral contraceptive agent

Question 2

All of the following cause hyperglycemia, EXCEPT?

Accepted Answer

Theophylline

Answer

Thiazide

Answer

Diazoxide

Answer

Pentamidine

Question 3

A patient receives a toxic dose of lignocaine intravenously. Which of the following is the patient likely to exhibit?

Accepted Answer

Seizures and coma

Answer

Excessive salivation

Answer

Mydriasis and diarrhea

Answer

Respiratory paralysis

Question 4

Patisiran was approved by FDA recently for which condition?

Accepted Answer

Neuropathy of amyloidosis

Answer

Filariasis

Answer

Peripheral Neuropathy

Answer

Neuropathy of diabetes

Question 5

Which drug is contraindicated in patients allergic to sulphonamides?

Accepted Answer

Zonisamide

Answer

Brizolamide

Answer

Brimonidine

Answer

Bimatoprost

Question 6

Which of the following patients is most likely to be treated with intravenous glucagon?

Accepted Answer

An old man with severe bradycardia and hypotension resulting from ingestion of an overdose of atenolol

Answer

A young man who took cocaine and has a blood pressure of 190/110 mm Hg

Answer

A middle-aged man with type II diabetes who has not taken his regular dose of glipizide for the last 4 days

Answer

An old woman with lactic acidosis as a complication of severe infection and shock

Question 7

Fomepizole is used as an antidote in poisoning by which of the following substances?

Accepted Answer

Methanol

Answer

Organophosphorus compounds

Answer

Aluminium phosphide

Answer

Copper

Question 8

Which of the following is NOT a treatment given for acute severe digitalis toxicity?

Accepted Answer

Potassium

Answer

Digibind

Answer

Lignocaine

Answer

None of these

Question 9

Which of the following drugs does NOT cause interstitial lung disease?

Accepted Answer

Alpha methyldopa

Answer

Phenytoin sodium

Answer

Sulfonamide

Answer

Busulfan

Question 10

The disulfiram-alcohol reaction occurs due to the inhibition of which enzyme?

Accepted Answer

Aldehyde dehydrogenase

Answer

Alcohol reductase

Answer

Alcohol dehydrogenase

Answer

Aldehyde reductase

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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