Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity Indian Medical PG Practice Questions and MCQs

Question 701: Which of the following is NOT considered a 'date rape drug'?

A. Rohypnol
B. Ketamine
C. Gamma hydroxyl butyrate
D. Propofol (Correct Answer)

Explanation: ***Propofol*** - **Propofol** is an **intravenous anesthetic** and sedative primarily used in medical settings for induction and maintenance of anesthesia or for sedation in critical care. - While it can cause sedation and amnesia, it is not commonly associated with or used as a **'date rape drug'** due to its rapid onset and short duration of action, requiring medical administration. *Rohypnol* - **Rohypnol** (flunitrazepam) is a potent **benzodiazepine** known for its sedative-hypnotic effects and is commonly explicitly referred to as a **'date rape drug'**. - It can cause **amnesia**, muscle relaxation, and impaired judgment, making victims vulnerable and unable to recall events. *Ketamine* - **Ketamine** is a **dissociative anesthetic** that causes a trance-like state, pain relief, sedation, and amnesia, and is also known as a **'date rape drug'**. - At lower doses, it can produce **hallucinations** and a sense of detachment, impairing a person's ability to resist or remember. *Gamma hydroxyl butyrate* - **Gamma-hydroxybutyrate (GHB)** is a **central nervous system depressant** that has been widely implicated as a **'date rape drug'**. - It rapidly induces **sedation**, euphoria, and amnesia, with effects often lasting for several hours.

Question 702: Following are used in treatment of digitalis toxicity except-

A. Fab fragments
B. Lignocaine
C. Hemodialysis (Correct Answer)
D. Potassium

Explanation: ***Hemodialysis***\n - **Digoxin** has a **large volume of distribution (5-7 L/kg)** and is extensively bound to tissue proteins throughout the body.\n - Only a small fraction of digoxin remains in the plasma, making hemodialysis **ineffective** for removing significant amounts of the drug.\n - Hemodialysis is **not recommended** and **not used** as a treatment for digitalis toxicity.\n\n*Fab fragments*\n - **Digoxin-specific antibody fragments** (Digibind/DigiFab) directly bind to and neutralize free digoxin molecules.\n - This is the **gold standard treatment** for severe digitalis toxicity, especially with life-threatening arrhythmias or significant hyperkalemia.\n - Works rapidly to reverse toxic effects by binding digoxin in the serum.\n\n*Lignocaine*\n - **Lignocaine** (lidocaine) is a class IB antiarrhythmic used to treat **ventricular arrhythmias** caused by digitalis toxicity [1].\n - Suppresses ectopic ventricular activity without further depressing AV conduction.\n - Preferred over other antiarrhythmics like phenytoin for digoxin-induced ventricular tachyarrhythmias.\n\n*Potassium*\n - **Context-dependent use**: Potassium is used in digitalis toxicity **only when hypokalemia is present**.\n - **Hypokalemia** increases myocardial sensitivity to digoxin and worsens toxicity, so correction with potassium is therapeutic.\n - **Important contraindication**: Potassium is **contraindicated in acute digoxin overdose with hyperkalemia**, which commonly occurs due to Na-K-ATPase pump inhibition.\n - When appropriately indicated (hypokalemic state), potassium IS used in management of digitalis toxicity.

Question 703: Which of the properties accounts for ethanol's use in ethylene glycol poisoning?

A. Competitive inhibitor of NADPH oxidase
B. Competitive inhibitor of alcohol dehydrogenase (Correct Answer)
C. Competitive inhibitor of aldehyde dehydrogenase
D. Non-competitive inhibitor of aldehyde dehydrogenase

Explanation: ***Competitive inhibitor of alcohol dehydrogenase*** - **Ethanol** acts as a **competitive inhibitor** of **alcohol dehydrogenase (ADH)**, the enzyme responsible for metabolizing ethylene glycol into toxic metabolites. - By competing for ADH, ethanol prevents the formation of toxic compounds like **glycolic acid** and **oxalic acid**, which cause the severe acidosis and organ damage seen in ethylene glycol poisoning. *Competitive inhibitor of NADPH oxidase* - **NADPH oxidase** is an enzyme complex primarily involved in the production of **reactive oxygen species** during the respiratory burst in phagocytes, related to immune function. - This enzyme is not directly involved in the metabolism of ethylene glycol, so inhibiting it would not be a treatment for ethylene glycol poisoning. *Competitive inhibitor of aldehyde dehydrogenase* - **Aldehyde dehydrogenase (ALDH)** is an enzyme that metabolizes **acetaldehyde** (a product of ethanol metabolism) and other aldehydes, converting them into carboxylic acids. - While ALDH is involved in alcohol metabolism, it is not the primary enzyme responsible for the initial metabolism of ethylene glycol into its toxic byproducts, which is the target for treatment. *Non-competitive inhibitor of aldehyde dehydrogenase* - Non-competitive inhibition of **aldehyde dehydrogenase (ALDH)** would primarily affect the metabolism of other aldehydes, including those produced from ethanol breakdown, leading to an accumulation of aldehydes (e.g., acetaldehyde). - This mechanism would not prevent the initial formation of toxic metabolites from ethylene glycol, which is the goal of therapy in ethylene glycol poisoning.

Question 704: Which one of the following drugs cannot cause Pseudotumor Cerebri ?

A. Nitrofurantoin
B. Metformin (Correct Answer)
C. Tetracycline
D. Nalidixic acid

Explanation: ***Metformin*** - **Metformin** is an oral hypoglycemic agent used for **type 2 diabetes** and is not associated with pseudotumor cerebri. - There is no known mechanism by which metformin would increase **intracranial pressure**. *Nitrofurantoin* - **Nitrofurantoin**, an antibiotic used for urinary tract infections, has been rarely implicated in drug-induced **pseudotumor cerebri**. - It works by interfering with **bacterial enzyme systems**, not typically affecting host intracranial fluid dynamics directly, but can cause idiosyncratic reactions. *Tetracycline* - **Tetracycline-class antibiotics** are well-known causes of **pseudotumor cerebri** (idiopathic intracranial hypertension). - This effect is thought to be dose-dependent and related to interference with **cerebrospinal fluid (CSF) absorption** or production. *Nalidixic acid* - **Nalidixic acid**, a quinolone antibiotic, is also recognized as a cause of **pseudotumor cerebri**, particularly in children. - Its mechanism is not fully understood but is believed to involve disturbances in **CSF dynamics**.

Question 705: Which of the following topical agents boosts cell-mediated immunity in burns?

A. Cerium nitrate (Correct Answer)
B. Povidone iodine
C. Mafenide acetate
D. Silver nitrate

Explanation: Cerium nitrate - **Cerium nitrate** is notable for its ability to **stabilize complement activation** and reduce inflammatory responses in burn wounds. [1] - By modulating the immune response, it helps to **restore cell-mediated immunity**, which is often compromised in severe burns. Povidone iodine - **Povidone iodine** is a broad-spectrum **antiseptic** used for disinfection due to its strong oxidative properties against bacteria, viruses, and fungi. - It does not specifically boost **cell-mediated immunity** but rather exerts its effect through direct antimicrobial action. Mafenide acetate - **Mafenide acetate** is a potent **antibacterial agent** used topically for burns, particularly effective against Gram-negative bacteria like *Pseudomonas aeruginosa*. - Its primary function is to **penetrate eschar** and prevent infection; it does not directly enhance cell-mediated immunity. Silver nitrate - **Silver nitrate** is an antiseptic that precipitates proteins and is used to prevent bacterial growth in burn wounds. [2] - While effective in controlling infection, it does **not have immunomodulatory properties** that boost cell-mediated immunity.

Question 706: What is the shortest needle length commonly used in insulin pens according to current clinical guidelines, in mm?

A. 6
B. 4 (Correct Answer)
C. 5
D. 8

Explanation: ***4 mm*** - Current clinical guidelines recommend **4 mm needles** as the shortest available for insulin pens to reduce pain and minimize the risk of intramuscular injection. - This length is suitable for injecting into the subcutaneous tissue in most adults, even without pinching the skin. *6 mm* - While 6 mm needles are still used, they are longer than the shortest recommended and may increase the risk of an **intramuscular injection**, especially in leaner individuals. - Injecting insulin into the muscle can lead to **unpredictable absorption rates** and hypoglycemia. *5 mm* - A 5 mm needle is also commonly used, but it is not the shortest length according to current clinical guidelines which emphasize the use of **4 mm needles** for optimal patient comfort and safety. - It still carries a slightly higher risk of intramuscular injection compared to a 4 mm needle, particularly without a **skin-fold**. *8 mm* - An 8 mm needle is significantly longer and is generally not recommended for routine insulin pen injections due to the high risk of **intramuscular injection**. - This length is typically reserved for patients with a very thick subcutaneous fat layer or specific medical indications, but even then, shorter needles are often preferred.

Question 707: An elderly male on ventilator has received atracurium infusion for 3 days. He now develops epileptic fits. Probable cause for his epilepsy is:

A. Ventilator failure
B. Accumulation of Atracurium
C. Accumulation of Laudanosine (Correct Answer)
D. Allergy to drug

Explanation: Accumulation of Laudanosine\n - Atracurium is metabolized in the body via Hofmann elimination and ester hydrolysis into laudanosine and other inactive metabolites.\n - Laudanosine is a tertiary amine that can cross the blood-brain barrier and, at high concentrations, is a CNS stimulant, potentially inducing seizures.\n\nVentilator failure\n - Ventilator failure would lead to respiratory distress and potentially hypoxia, which can cause seizures, but it's not a direct pharmacological effect of atracurium or its metabolites.\n - The question implies a drug-related cause due to prolonged atracurium infusion, making ventilator failure less likely as the probable cause for drug-induced epilepsy.\n\nAccumulation of Atracurium\n - While prolonged infusion of atracurium means continuous drug administration, atracurium itself does not typically accumulate to toxic levels in the same way as its metabolites, especially in patients with normal organ function, due to its organ-independent elimination.\n - Atracurium is a neuromuscular blocker and its accumulation would primarily lead to prolonged paralysis, not directly to epileptic fits.\n\nAllergy to drug\n - An allergic reaction to a drug typically manifests as rash, anaphylaxis, or bronchospasm, not primarily as epileptic fits, unless severe anaphylaxis leads to cerebral hypoperfusion and secondary seizure.\n - While possible, it is not the most common or direct cause of seizures associated with atracurium administration.

Question 708: Polyvalent snake vaccines contain immunoglobulins against all, except

A. Naja naja
B. Bungarus caeruleus
C. Ophiophagus hannah (Correct Answer)
D. Daboia russelii

Explanation: ***Ophiophagus hannah*** - Polyvalent snake vaccines (antivenoms) in many regions, particularly India, are designed to neutralize venoms from the "Big Four" snakes: **Naja naja (cobra), Bungarus caeruleus (common krait), Daboia russelii (Russell's viper), and Echis carinatus (saw-scaled viper)**. - *Ophiophagus hannah* (king cobra) is not typically included in these polyvalent antivenoms due to its comparatively rare biting incidence and the distinct nature of its venom, requiring a specific **monovalent antivenom** if available. *Naja naja* - This is one of the "Big Four" snakes in India, and its venom, predominantly **neurotoxic**, is specifically targeted by many polyvalent antivenoms. - Antivenom production protocols ensure inclusion of antibodies against *Naja naja* venom to provide broad protection against common snakebites. *Bungarus caeruleus* - Known as the common krait, its highly potent **neurotoxic venom** is a significant component addressed by polyvalent snake antivenoms. - Bites from *Bungarus caeruleus* often lead to severe paralysis and are a primary target for neutralization by standard antivenoms. *Daboia russelii* - Russell's viper is another of the "Big Four" and contributes a predominantly **hemotoxic and cytotoxic venom** to the array of toxins covered by polyvalent antivenoms. - Antibodies against *Daboia russelii* venom are crucial in polyvalent antivenoms to counter its effects such as coagulopathy and tissue damage.

Question 709: Succinylcholine causes hyperkalemia in patients with -

A. Major trauma with crush injury
B. Burns
C. All of the options (Correct Answer)
D. Prolonged immobilization

Explanation: ***All of the options*** - **Succinylcholine** can cause dangerous **hyperkalemia** due to upregulation of **extrajunctional acetylcholine receptors** on muscle cell membranes, leading to exaggerated potassium efflux upon depolarization [1]. - This occurs in conditions causing **muscle denervation** or **prolonged disuse** [1], [2]. *Major trauma with crush injury* - Patients with **severe trauma** involving **crush injuries** or extensive muscle damage develop receptor upregulation within 24-48 hours [1]. - The trauma causes muscle **denervation** and damage, leading to proliferation of acetylcholine receptors across the muscle membrane [1]. - Risk persists for weeks to months after injury. *Burns* - Patients with **major burns** (typically >10% total body surface area) develop marked upregulation of **extrajunctional acetylcholine receptors** in damaged and regenerating muscle tissue [1], [2]. - Risk begins **24-48 hours post-burn** and can persist for **months to years**. - This is one of the **most well-established contraindications** to succinylcholine use [2]. *Prolonged immobilization* - **Extended bed rest**, **ICU immobilization**, or **prolonged casting** leads to disuse-induced upregulation of acetylcholine receptors. - Risk typically develops after **5-7 days** of immobilization and persists throughout the immobilization period [2]. - Includes patients with paraplegia, quadriplegia, or prolonged mechanical ventilation [2].

Question 710: Efalizumab disrupts the interaction between which of the following adhesion molecules?

A. LFA-3 and ICAM-3
B. LFA-1 and ICAM-1 (Correct Answer)
C. LFA-3 and CD2
D. LFA-3 and ICAM-1

Explanation: **LFA-1 and ICAM-1** - **Efalizumab** (now withdrawn) was a monoclonal antibody that targeted the **CD11a subunit of LFA-1**. - By binding to **LFA-1** on T-cells, efalizumab prevented its interaction with **ICAM-1** on endothelial cells and antigen-presenting cells, thereby inhibiting T-cell activation and migration. *LFA-3 and ICAM-3* - This interaction primarily involves **T-cell co-stimulation** (CD2 with LFA-3) and **adhesion** (ICAM-3 with LFA-1, though less prominent than ICAM-1). - Efalizumab's mechanism of action directly targeted **LFA-1/ICAM-1**, not this specific pair. *LFA-3 and CD2* - **CD2** on T-cells interacts with **LFA-3 (CD58)** on antigen-presenting cells, providing a **co-stimulatory signal** for T-cell activation. - While important for immune responses, this specific interaction was not the primary target of efalizumab. *LFA-3 and ICAM-1* - **LFA-3** (CD58) is a ligand for **CD2**, and **ICAM-1** is a ligand for **LFA-1**. They do not directly interact with each other in a functionally significant way that would be targeted by efalizumab. - Efalizumab targeted the **LFA-1/ICAM-1** pathway, not a combination involving LFA-3 with ICAM-1.

Practice by Chapter

Principles of Clinical Pharmacology

Practice Questions

Therapeutic Drug Monitoring

Practice Questions

Drug Toxicity and Overdose

Practice Questions

Antidotes and Their Applications

Practice Questions

Management of Drug Poisoning

Practice Questions

Drug-Induced Liver Injury

Practice Questions

Drug-Induced Kidney Injury

Practice Questions

Drug-Induced Blood Dyscrasias

Practice Questions

Drug-Induced QT Prolongation

Practice Questions

Pharmacovigilance

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free