Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Drug which should not be given in renal disease is :

Gentamicin. ***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.

Q: Which drug does not lead to osteoporosis?

Thyroxine. ***Thyroxine*** - While **thyrotoxicosis** (excessive thyroid hormone levels) can accelerate bone turnover and lead to bone loss, appropriate physiological doses of **thyroxine replacement therapy** for hypothyroidism generally *do not* cause osteoporosis. - Maintaining **euthyroid status** with thyroxine replacement is crucial for overall health and does not significantly increase the risk of osteoporosis when monitored correctly. *Alcohol* - **Chronic alcohol abuse** is a significant risk factor for **osteoporosis** due to its toxic effects on osteoblasts, inhibition of calcium absorption, and nutritional deficiencies. - It also leads to increased cortisol levels and often liver disease, further contributing to **bone loss**. *Warfarin* - Long-term use of **warfarin**, an anticoagulant, has been associated with decreased bone mineral density and an increased risk of **osteoporosis**. - This is primarily due to its antagonistic effect on **vitamin K**, which is essential for the gamma-carboxylation of osteocalcin and other bone matrix proteins. *Heparin* - Both unfractionated and to a lesser extent, **low-molecular-weight heparin**, can induce **osteoporosis** with prolonged use, typically after several months. - Heparin's mechanism of action in bone involves stimulating bone resorption, inhibiting osteoblast activity, and potentially increasing the activity of collagenase.

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

Mannitol. ***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.

Q: Increased osmolar gap is not seen in poisoning of:

Paracetamol. ***Paracetamol*** - **Paracetamol (acetaminophen)** poisoning does NOT cause an **increased osmolar gap** because it is not an osmotically active alcohol or small molecule that accumulates significantly in the blood. - Paracetamol toxicity primarily causes **hepatotoxicity** through the formation of the toxic metabolite **NAPQI** (N-acetyl-p-benzoquinone imine), which depletes glutathione stores. - It may cause a **high anion gap metabolic acidosis** in severe cases due to lactic acidosis from hepatic failure, but this does not increase the osmolar gap. *Methanol* - **Methanol** poisoning leads to an **increased osmolar gap** because methanol itself is a small, osmotically active alcohol that accumulates in the blood before it is metabolized. - Its toxic metabolites, **formic acid** and **formaldehyde**, contribute to the characteristic **high anion gap metabolic acidosis** with visual disturbances. *Acetone* - **Acetone** (from isopropanol ingestion) causes an **increased osmolar gap** due to the presence of acetone itself as an osmotically active substance. - Unlike methanol or ethylene glycol, acetone metabolism does not produce highly acidic byproducts, so it typically causes an **increased osmolar gap without a significant anion gap metabolic acidosis** ("osmolar gap without anion gap"). *Ethylene glycol* - **Ethylene glycol** poisoning causes an **increased osmolar gap** due to the parent compound accumulating in the blood. - Its toxic metabolites, particularly **glycolic acid** and **oxalic acid**, lead to a significant **high anion gap metabolic acidosis** with calcium oxalate crystal formation and acute kidney injury.

Q: Hypomagnesemia due to increased excretion by the kidney is caused by all except:

Digitalis. ***Digitalis*** - **Digitalis** (digoxin) is a cardiac glycoside that inhibits the **Na+/K+-ATPase pump**; it is not directly associated with renal magnesium wasting. Instead, its toxicity can be exacerbated by hypomagnesemia, but it does not cause it. - While it affects electrolyte balance intracellularly, it does not primarily lead to increased **urinary excretion of magnesium**. *Aminoglycoside* - **Aminoglycosides** like gentamicin can cause **renal tubular damage**, particularly in the distal tubules. - This damage impairs the kidney's ability to reabsorb magnesium, leading to increased **urinary magnesium excretion** and hypomagnesemia. *Furosemide* - **Furosemide** is a **loop diuretic** that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle. - This inhibition reduces the **transepithelial potential difference**, which in turn reduces the passive reabsorption of magnesium and calcium, leading to increased urinary excretion. *Cisplatin* - **Cisplatin** is a chemotherapeutic agent known to cause **renal tubular toxicity**, particularly affecting the distal convoluted tubule. - This toxicity often results in impaired magnesium reabsorption and consequently increased **urinary magnesium loss**.

Q: Carbonic anhydrase inhibitor should not be given in:

Sulfonamide hypersensitivity. ***Sulfonamide hypersensitivity*** - Carbonic anhydrase inhibitors (CAIs) are **sulfonamide derivatives**, so they are absolutely contraindicated in patients with a history of **sulfonamide allergy**. - Administration to such patients can lead to severe **hypersensitivity reactions**, including rash, fever, and even anaphylaxis. *Epilepsy* - **Acetazolamide**, a carbonic anhydrase inhibitor, can be used as an **adjunct therapy for certain types of epilepsy**, such as absence seizures. - It works by reducing neuronal excitability through its effects on pH, thus it is not contraindicated but rather sometimes indicated. *High altitude sickness* - Carbonic anhydrase inhibitors like **acetazolamide** are commonly used to **prevent and treat high altitude cerebral and pulmonary edema** by inducing metabolic acidosis and stimulating respiration. - This is a recognized therapeutic indication, not a contraindication. *Glaucoma* - CAIs are a **primary treatment for glaucoma** (both open-angle and angle-closure) because they reduce the production of aqueous humor, thereby lowering intraocular pressure. - They are used both systemically and topically for this purpose, making it an indication, not a contraindication.

Q: All of the following are causes of drug-induced lupus, except:

Clofibrate. ***Clofibrate*** - Clofibrate is a **fibric acid derivative** (fibrate) used to treat hyperlipidemia and is not known to cause drug-induced lupus. - Its primary mechanism of action involves activating **PPAR-alpha**, leading to decreased triglyceride levels and increased HDL production. *Penicillamine* - Penicillamine is a known cause of **drug-induced lupus**, often leading to symptoms mimicking systemic lupus erythematosus. - It is a chelating agent used to treat conditions like **Wilson's disease** and severe rheumatoid arthritis. *Hydralazine* - Hydralazine is a classic and frequent cause of **drug-induced lupus**, particularly at higher doses. - It is an **antihypertensive medication** that acts as a direct vasodilator. *Chlorpromazine* - Chlorpromazine, an antipsychotic medication, can induce a **lupus-like syndrome** in some susceptible individuals. - It is a **phenothiazine derivative** primarily used to treat schizophrenia and other psychotic disorders.

Q: A 6-year-old boy is admitted to the ward with drowsiness, dull deep tendon reflexes and seizures. On examination the child has a line on gums and there is a history of constipation. Which will be most appropriate drug that should be used for this child?

DMSA. ***DMSA*** - The child's symptoms of **drowsiness**, **dull deep tendon reflexes**, **seizures**, a **gingival line**, and **constipation** are classic signs of **lead poisoning**. - **DMSA (dimercaptosuccinic acid)** is a chelating agent that is generally considered the **first-line treatment** for pediatric lead poisoning due to its oral administration, good safety profile, and efficacy in reducing lead levels. *Penicillamine* - While penicillamine is a chelating agent, it is **less commonly used** for lead poisoning in children due to a higher incidence of **side effects** compared to DMSA. - Its use is often reserved for patients who cannot tolerate other chelating agents or in specific situations. *EDTA* - **EDTA (ethylenediaminetetraacetic acid)** is a powerful chelator often used for severe lead poisoning, but it is typically administered **intravenously** or **intramuscularly**. - It is often combined with BAL to prevent redistribution of lead to the brain and is not usually the first choice for chronic, less severe lead poisoning in an ambulatory setting. *BAL* - **BAL (British Anti-Lewisite)**, or **dimercaprol**, is an oil-based intramuscular injection and is usually reserved for **severe lead encephalopathy**. - It has a high incidence of **adverse effects** and should not be used as monotherapy for lead poisoning due to the risk of redistributing lead to the brain; it is typically administered with EDTA for very high lead levels.

Q: Antidote for acetaminophen poisoning is?

N-Acetyl cysteine. ***N-Acetyl cysteine*** - **N-acetyl cysteine (NAC)** is the specific antidote for acetaminophen (paracetamol) poisoning, acting by replenishing hepatic **glutathione stores**. - **Glutathione** is crucial for detoxifying the toxic metabolite **N-acetyl-p-benzoquinone imine (NAPQI)**, preventing liver damage. *Penicillamine* - **Penicillamine** is a chelating agent used primarily in conditions like **Wilson's disease** (copper toxicity) and **rheumatoid arthritis**. - It has no role in the treatment or detoxification of **acetaminophen poisoning**. *Glycolamine* - **Glycolamine** is not a recognized pharmaceutical antidote for any specific poisoning. - This compound is not therapeutically relevant in toxicology scenarios, particularly for **acetaminophen overdose**. *Fomipezole* - **Fomepizole** is an antidote used for poisoning by **methanol** and **ethylene glycol**, not acetaminophen. - It works by inhibiting **alcohol dehydrogenase**, preventing the formation of toxic metabolites from these alcohols.

Q: Dicobalt EDTA is used as an antidote for which poisoning?

Cyanide. Cyanide - **Dicobalt EDTA** acts as a **chelating agent** that specifically binds to cyanide ions, forming a stable, non-toxic complex that can be excreted from the body. - This binding prevents cyanide from inhibiting **cytochrome c oxidase** in the mitochondria, thus restoring cellular respiration. *Mushroom* - Treatment for mushroom poisoning is highly dependent on the **species of mushroom** and the toxins involved, and typically involves **supportive care**, activated charcoal, and specific antidotes like **silymarin** or **N-acetylcysteine** for certain types of Amanita poisoning. - Dicobalt EDTA is not indicated for any known form of mushroom toxicity. *Lead* - **Lead poisoning** is treated with **chelating agents** such as **EDTA (calcium disodium EDTA)**, **dimercaprol (BAL)**, or **succimer (DMSA)**, which bind to lead and promote its excretion [1], [2]. - Dicobalt EDTA is specifically formulated for cyanide and would not be effective or safe for lead poisoning due to its cobalt content. *Mercury* - **Mercury poisoning** is typically treated with **chelating agents** like **dimercaprol (BAL)**, **succimer (DMSA)**, or **D-penicillamine**, which help remove mercury from the body [3]. - Dicobalt EDTA does not have affinity for mercury and can be harmful if used for mercury poisoning.

Question 1

Drug which should not be given in renal disease is :

Accepted Answer

Gentamicin

Answer

Ceftriaxone

Answer

Doxycycline

Answer

Nitroprusside

Question 2

Which drug does not lead to osteoporosis?

Accepted Answer

Thyroxine

Answer

Alcohol

Answer

Warfarin

Answer

Heparin

Question 3

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

Accepted Answer

Mannitol

Answer

Acetazolamide

Answer

Thiazide

Answer

Furosemide

Question 4

Increased osmolar gap is not seen in poisoning of:

Accepted Answer

Paracetamol

Answer

Methanol

Answer

Acetone

Answer

Ethylene glycol

Question 5

Hypomagnesemia due to increased excretion by the kidney is caused by all except:

Accepted Answer

Digitalis

Answer

Aminoglycoside

Answer

Furosemide

Answer

Cisplatin

Question 6

Carbonic anhydrase inhibitor should not be given in:

Accepted Answer

Sulfonamide hypersensitivity

Answer

Epilepsy

Answer

High altitude sickness

Answer

Glaucoma

Question 7

All of the following are causes of drug-induced lupus, except:

Accepted Answer

Clofibrate

Answer

Penicillamine

Answer

Hydralazine

Answer

Chlorpromazine

Question 8

A 6-year-old boy is admitted to the ward with drowsiness, dull deep tendon reflexes and seizures. On examination the child has a line on gums and there is a history of constipation. Which will be most appropriate drug that should be used for this child?

Accepted Answer

DMSA

Answer

EDTA

Answer

BAL

Answer

Penicillamine

Question 9

Antidote for acetaminophen poisoning is?

Accepted Answer

N-Acetyl cysteine

Answer

Penicillamine

Answer

Glycolamine

Answer

Fomepizole

Question 10

Dicobalt EDTA is used as an antidote for which poisoning?

Accepted Answer

Cyanide

Answer

Mushroom

Answer

Lead

Answer

Mercury

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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