Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 751: Gout is NOT caused by which of the following?

A. Sulfinpyrazone (Correct Answer)
B. Aspirin
C. Chlorthalidone
D. Pyrazinamide

Explanation: ***Sulfinpyrazone*** - **Sulfinpyrazone** is a **uricosuric agent** [1] that *increases* the excretion of uric acid, thereby *reducing* serum uric acid levels. - This medication is used to *treat* gout by preventing attacks, rather than causing them [3]. *Aspirin* - **Low-dose aspirin** can *inhibit* the renal tubular secretion of uric acid, which can lead to an *increase* in serum uric acid levels and potentially precipitate a gout attack [4]. - High doses of aspirin are uricosuric, meaning they increase uric acid excretion, but the more commonly used low doses tend to cause hyperuricemia. *Chlorthalidone* - **Chlorthalidone** is a **thiazide-like diuretic** that *reduces* uric acid excretion by the kidneys, thus *elevating* serum uric acid levels [2]. - Increased serum uric acid levels can lead to the formation of uric acid crystals and trigger acute gout attacks [5]. *Pyrazinamide* - **Pyrazinamide**, an anti-tuberculosis drug, is well-known to *inhibit* the renal tubular excretion of uric acid. - This inhibition leads to **hyperuricemia** and can consequently cause or exacerbate gout.

Question 752: 'Chemical mumps' is synonymous with

A. Nutritional mumps
B. Epidemic parotitis
C. Iodine mumps (Correct Answer)
D. Nonspecific mumps

Explanation: ***Iodine mumps*** - **Iodine mumps**, or **iodine-induced parotitis**, is a rare adverse effect of exposure to high doses of iodine-containing agents, often after diagnostic procedures using iodinated contrast media [1, 2]. - It presents with **acute, non-suppurative painful swelling** of the salivary glands, resembling infectious mumps. *Epidemic parotitis* - **Epidemic parotitis** is the medical term for **mumps**, an infectious disease caused by the mumps virus. - It is characterized by fever, headache, muscle aches, and most notably, the painful swelling of the **parotid glands**. *Nutritional mumps* - The term **nutritional mumps** is not a recognized medical condition or a synonym for iodine-induced parotitis. - While nutritional deficiencies can impact salivary gland function, they do not typically cause an acute 'mumps-like' presentation. *Nonspecific mumps* - **Nonspecific mumps** is not a standard medical term. - The term 'mumps' usually refers specifically to the viral infection (epidemic parotitis) or refers to the anatomical location of swelling (parotitis) without specifying an etiology.

Question 753: Which of the following produces neuropsychiatric symptoms?

A. Cephalosporin
B. Ethambutol
C. Cyclosporine
D. Cycloserine (Correct Answer)

Explanation: ***Cycloserine*** - **Cycloserine** is an antimicrobial agent that can cause a wide array of neuropsychiatric symptoms, including **headache**, **anxiety**, **depression**, **psychosis**, **seizures**, and **peripheral neuropathy**. - Its mechanism of action involves interfering with cell wall synthesis, but it also crosses the **blood-brain barrier**, leading to central nervous system effects. *Cephalosporin* - While some **cephalosporins** (especially at high doses or in patients with renal impairment) can cause CNS effects like **seizures**, they are not typically associated with a broad range of neuropsychiatric symptoms to the same extent as cycloserine. - The primary side effects of cephalosporins are usually **gastrointestinal disturbances** and **allergic reactions**. *Ethambutol* - **Ethambutol** is known for its ocular toxicity, specifically **optic neuritis**, which can lead to reduced visual acuity and **color blindness**. - It does not typically cause the generalized neuropsychiatric symptoms seen with cycloserine. *Cyclosporine* - **Cyclosporine**, an immunosuppressant, can cause neurological side effects such as **tremor**, **headache**, and **seizures**, and rarely **posterior reversible encephalopathy syndrome (PRES)**. - However, it is not primarily associated with the broad spectrum of psychiatric symptoms like depression or psychosis, unlike cycloserine.

Question 754: Which of the following drug treatment increases thirst and causes dilute diuresis ?

A. Chlorpromazine
B. Clozapine
C. Phenobarbitone
D. Lithium (Correct Answer)

Explanation: ***Lithium*** - **Lithium** can cause **nephrogenic diabetes insipidus**, leading to impaired water reabsorption in the kidneys. - This results in increased thirst (polydipsia) and the excretion of a large volume of dilute urine (polyuria). *Chlorpromazine* - **Chlorpromazine** is a typical antipsychotic that can cause **anticholinergic side effects** such as dry mouth, but typically not polyuria or polydipsia directly via renal mechanisms. - It primarily acts on dopamine receptors and can cause **sedation** and **extrapyramidal symptoms**. *Clozapine* - **Clozapine**, an atypical antipsychotic, is associated with a risk of **sialorrhea** (excessive salivation) and **metabolic syndrome**, but not primarily with dilute diuresis. - It is used for refractory schizophrenia but carries risks like **agranulocytosis** and **myocarditis**. *Phenobarbitone* - **Phenobarbitone** is a barbiturate used as an anticonvulsant and sedative, acting on GABA-A receptors. - Its side effects include **sedation** and **respiratory depression**, but it does not typically cause increased thirst or dilute diuresis.

Question 755: SLE like syndrome may be produced by all except:-

A. Sulfonamide
B. Psoralen (Correct Answer)
C. Procainamide
D. Hydralazine

Explanation: ***Psoralen*** - **Psoralen** is a photosensitizing drug used in combination with ultraviolet A (UVA) light (PUVA therapy) for skin conditions like **psoriasis** and **vitiligo** [2]. - While it causes photosensitivity, it is **not associated** with inducing a systemic lupus erythematosus (SLE)-like syndrome. *Sulfonamide* - **Sulfonamides** like sulfamethoxazole are known to cause drug-induced lupus, which can present with symptoms similar to SLE. - They can trigger autoimmune reactions, including the production of **antinuclear antibodies (ANAs)**. *Procainamide* - **Procainamide**, an antiarrhythmic drug, is one of the most common causes of **drug-induced lupus** [1]. - It frequently leads to the development of **anti-histone antibodies**, a hallmark of drug-induced lupus, often without renal or central nervous system involvement [1]. *Hydralazine* - **Hydralazine**, an antihypertensive medication, is also a well-known cause of **drug-induced lupus** [1]. - Like procainamide, it is associated with the production of **anti-histone antibodies** and can lead to a lupus-like syndrome [1].

Question 756: In porphyria all the following drugs are safe Except

A. Propofol
B. Alfentanil
C. Midazolam
D. Pentazocine (Correct Answer)

Explanation: Pentazocine - Pentazocine is known to induce delta-aminolevulinic acid (ALA) synthase activity, leading to increased porphyrin precursor production, making it unsafe in porphyria. - Due to its potential to trigger acute porphyric attacks, it should be avoided in patients with a history of porphyria [2]. Propofol - Propofol is considered a safe anesthetic agent for patients with porphyria as it does not significantly induce ALA synthase or exacerbate symptoms. - Its metabolism does not interfere with the heme biosynthesis pathway, making it a preferred choice for induction and maintenance of anesthesia. Alfentanil - Alfentanil, an opioid analgesic, is generally considered safe in porphyria. - It does not induce hepatic ALA synthase activity, thus avoiding the accumulation of porphyrin precursors. Midazolam - Midazolam, a benzodiazepine, is generally considered safe for use in patients with porphyria [1]. - It does not interact negatively with the heme synthesis pathway and can be used for sedation or as an anxiolytic.

Question 757: Drug which should not be given in renal disease is :

A. Ceftriaxone
B. Doxycycline
C. Nitroprusside
D. Gentamicin (Correct Answer)

Explanation: ***Gentamicin***- **Gentamicin** is an **aminoglycoside antibiotic** known for its **nephrotoxic** properties, meaning it can cause kidney damage [1].- In patients with pre-existing renal disease, the drug can accumulate, leading to increased risk of **acute tubular necrosis** and worsening renal function, making it contraindicated or requiring significant dose adjustment.*Ceftriaxone*- **Ceftriaxone** is a third-generation **cephalosporin antibiotic** that is primarily eliminated via **biliary excretion**, with only a small portion excreted renally.- While dose adjustments may be needed in severe renal impairment, it is generally considered **safe in renal disease** compared to drugs like aminoglycosides.*Doxycycline*- **Doxycycline** is a **tetracycline antibiotic** that is primarily eliminated by non-renal routes, mainly through **fecal excretion**.- It is often favored in patients with **renal impairment** because it does not accumulate to toxic levels in the kidneys.*Nitroprusside*- **Nitroprusside** is a powerful **vasodilator** used in hypertensive emergencies, metabolized to **cyanide**, which then becomes **thiocyanate**.- Thiocyanate is primarily **renally excreted**, and in renal failure, **thiocyanate accumulation** can lead to toxicity, but the absolute contraindication is not as universal as with gentamicin, as careful monitoring can allow its use.

Question 758: All of the following can aggravate Myasthenia gravis except :

A. Aminoglycoside
B. d–Tubocurarine
C. Azathioprine (Correct Answer)
D. Tetracycline

Explanation: ***Azathioprine*** - **Azathioprine** is an **immunosuppressant** used to *treat* Myasthenia Gravis, meaning it *alleviates* symptoms rather than aggravating them. - It works by suppressing the immune system, thereby reducing the production of **acetylcholine receptor antibodies** that cause muscle weakness in Myasthenia Gravis. *Aminoglycoside* - **Aminoglycosides** can worsen Myasthenia Gravis by blocking **acetylcholine release** from nerve terminals and by stabilizing the **postsynaptic membrane**, further impairing neuromuscular transmission. - This effect is due to their structural similarities to **magnesium**, which can interfere with calcium-dependent acetylcholine release. *d–Tubocurarine* - **d-Tubocurarine** is a **non-depolarizing neuromuscular blocker** that acts by competing with **acetylcholine** for binding to its receptors on the muscle endplate. - Patients with Myasthenia Gravis have fewer functional acetylcholine receptors, making them highly susceptible to the effects of **neuromuscular blockers** and easily aggravated by them. *Tetracycline* - **Tetracyclines** can exacerbate Myasthenia Gravis by inhibiting **presynaptic acetylcholine release** and hindering the actions of **acetylcholine** on the postsynaptic membrane. - While less potent than aminoglycosides, they can still significantly worsen **muscle weakness** in affected individuals.

Question 759: In a patient on cisplatin therapy, which of the following diuretics would be preferred?

A. Acetazolamide
B. Thiazide
C. Mannitol (Correct Answer)
D. Furosemide

Explanation: ***Mannitol*** - Cisplatin is a highly **nephrotoxic** drug, and mannitol is often co-administered to induce a potent osmotic diuresis, which helps to flush out the drug and its metabolites through the kidney tubules. - This **osmotic diuretic** effect increases urine flow and minimizes the contact time of cisplatin with renal tubular cells, thereby reducing the risk and severity of **acute tubular necrosis (ATN)**. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor** primarily used for glaucoma, altitude sickness, and metabolic alkalosis. - It is not typically used to mitigate cisplatin-induced nephrotoxicity, and its mechanism does not directly address the primary toxic effects of cisplatin on renal tubules. *Thiazide* - Thiazide diuretics (e.g., hydrochlorothiazide) work by inhibiting the **sodium-chloride cotransporter** in the distal convoluted tubule. - While they promote diuresis, their effect is generally less potent than loop diuretics or osmotic diuretics, and they do not provide the same protective osmotic effect against cisplatin nephrotoxicity. *Furosemide* - Furosemide is a **loop diuretic** that acts on the thick ascending limb of the loop of Henle, producing significant diuresis. - While it can increase urine output, it does not offer the same **renal protective benefits** as mannitol against cisplatin toxicity and can potentially exacerbate electrolyte imbalances, especially **hypokalemia**, which is a concern with cisplatin.

Question 760: Red man syndrome occurs with :

A. Polymyxin
B. Teicoplanin
C. Clindamycin
D. Vancomycin (Correct Answer)

Explanation: ***Vancomycin*** - **Red man syndrome** is a common adverse reaction to **vancomycin**, characterized by flushing, erythema, and pruritus, primarily affecting the upper body. - It results from the **rapid infusion of vancomycin**, leading to **non-immunologically mediated histamine release** from mast cells and basophils. *Polymyxin* - Polymyxins, such as **colistin**, are associated with toxicities like **nephrotoxicity** and **neurotoxicity**, not red man syndrome. - Their mechanism of action involves disrupting bacterial cell membranes, which differs significantly from vancomycin's effects. *Teicoplanin* - **Teicoplanin** is structurally similar to vancomycin but is **less frequently associated with red man syndrome** due to its slower infusion rate and lower histamine-releasing potential. - While it can cause some cutaneous reactions, they are typically less severe and less common than with vancomycin. *Clindamycin* - **Clindamycin** is an antibiotic known for causing **gastrointestinal side effects**, including **Clostridium difficile-associated diarrhea (CDAD)**, and skin rashes, but not red man syndrome. - Its mechanism of action involves inhibiting bacterial protein synthesis by binding to the 50S ribosomal subunit.

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