Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 741: Which of the following causes teratogenicity?

A. Vitamin E
B. Vitamin D
C. Vitamin A (Correct Answer)
D. Vitamin C

Explanation: ***Vitamin A*** - Excessive intake of **Vitamin A (retinoids)**, particularly during early pregnancy, is a known cause of **teratogenicity**. - It can lead to various birth defects, including **craniofacial abnormalities**, **cardiac defects**, and **central nervous system malformations**. *Vitamin E* - **Vitamin E** is generally considered safe during pregnancy and has no known teratogenic effects at recommended dosages. - It functions as an **antioxidant** and is important for cell protection. *Vitamin D* - While **Vitamin D** is essential for proper fetal development, excessive intake is not typically associated with teratogenicity but can cause **hypercalcemia** in the mother and fetus. - Mild to moderate supplementation is often recommended during pregnancy for bone health. *Vitamin C* - **Vitamin C** is a water-soluble vitamin and is not considered teratogenic, even at higher doses, as excess amounts are readily excreted. - It plays a crucial role in **collagen synthesis** and immune function during pregnancy.

Question 742: Which one of the following antibiotic is not recommended for lactating mothers?

A. Aminoglycoside
B. Quinolones (Correct Answer)
C. Cephalosporins
D. Anti tubercular drugs

Explanation: ***Quinolones*** - **Quinolones** are generally **not recommended** for lactating mothers due to concerns about potential harm to the infant's developing **cartilage** and **joints**. - They have been associated with **arthropathies** and **tendinopathies** in animal studies and young patients, leading to caution in this population. *Aminoglycoside* - **Aminoglycosides** are typically considered **safe** in lactation because they have **poor oral absorption** by the infant, meaning very little drug reaches the infant's systemic circulation. - While they can be excreted into breast milk, the amount absorbed by the infant is usually **negligible**, reducing risk of toxicity. *Cephalosporins* - **Cephalosporins** are generally considered **safe** for lactating mothers as they are excreted into breast milk in **low concentrations** and have a good safety profile for infants. - Potential side effects in the infant are usually minor, such as **diarrhea** or **thrush**, and serious adverse events are rare. *Anti tubercular drugs* - Most **first-line anti-tubercular drugs** (e.g., isoniazid, rifampicin, ethambutol, pyrazinamide) are generally **considered compatible** with breastfeeding. - While they do pass into breast milk, the benefits of treating **maternal tuberculosis** and preventing transmission to the infant usually outweigh the theoretical risks.

Question 743: Ichthyosis is a side effect of -

A. Capreomycin
B. Letrozole
C. Clofazimine (Correct Answer)
D. Cephalosporin

Explanation: ***Clofazamine*** - **Clofazimine** is an antimycobacterial drug used to treat **leprosy**, and one of its characteristic skin-related side effects is **ichthyosis**, presenting as dry, scaly skin. - It accumulates in fatty tissues and the reticuloendothelial system, causing a range of skin pigmentation changes from red-brown to black, often associated with generalized dryness and scaling. *Capreomycin* - **Capreomycin** is an injectable antibiotic primarily used for **multi-drug resistant tuberculosis (MDR-TB)**. - Its main side effects involve **nephrotoxicity** and **ototoxicity**, not ichthyosis. *Letrozole* - **Letrozole** is an **aromatase inhibitor** used in the treatment of **hormone-receptor-positive breast cancer** in postmenopausal women. - Common side effects include **hot flashes**, **arthralgia**, and **fatigue**, but not ichthyosis. *Cephalosporin* - **Cephalosporins** are a class of **beta-lactam antibiotics** widely used for bacterial infections. - While they can cause various side effects like **allergic reactions** (rash, anaphylaxis), **gastrointestinal upset**, and **nephrotoxicity** at high doses, ichthyosis is not a recognized side effect.

Question 744: Drug that is contraindicated in renal failure is:

A. Isoniazid
B. Ethambutol
C. Streptomycin (Correct Answer)
D. Rifampicin

Explanation: ***Streptomycin*** - **Streptomycin** is primarily cleared renally, and its accumulation in **renal failure** can lead to significant **ototoxicity** and **nephrotoxicity**. - Its use in patients with compromised kidney function is contraindicated or requires significant dose reduction and careful monitoring. *Isoniazid* - **Isoniazid** is metabolized mainly by the liver, and only a small portion is excreted unchanged by the kidneys, making it relatively safe in **renal failure** with slight dose adjustments. - While it can cause **hepatotoxicity**, its renal excretion is not a primary concern. *Ethambutol* - Although **Ethambutol** is primarily eliminated renally, its dose can be adjusted in **renal failure** to prevent toxicity, most notably **optic neuritis**. - It is not outright contraindicated, but careful monitoring of renal function and visual acuity is necessary. *Rifampicin* - **Rifampicin** is extensively metabolized by the liver and is largely excreted through bile and feces, with only a small fraction excreted renally. - Therefore, it can be used safely in patients with **renal failure** without significant dose adjustment.

Question 745: Nowadays radium is not used in the Rx of cancer because:

A. It is a very unstable element
B. It decays into daughter Radon which is a constant hazard (Correct Answer)
C. It decays faster and needs frequent replacement
D. It has a very long half life

Explanation: ***It decays into daughter Radon which is a constant hazard*** - Radium-226 decays into **Radon-222**, a radioactive gas that can leak from sealed sources or medical devices. - This **gaseous daughter product** poses a significant radiation hazard to patients and medical staff, necessitating extensive safety precautions. *It is a very unstable element* - While radium is a **radioactive element** and thus unstable, its inherent instability alone isn't the primary reason for its disuse in cancer therapy. - The specific hazard comes from **what it decays into**, not just the act of decay itself. *It decays faster and needs frequent replacement* - Radium-226 has a **half-life of 1600 years**, meaning it decays very slowly and would not require frequent replacement. - This long half-life is actually a characteristic that makes its daughter product, Radon-222, a persistent issue rather than a rapid decay being the problem. *It has a very long half life* - A long half-life (e.g., 1600 years for Radium-226) means the radioactive material persists for a very long time, leading to a **prolonged source of radiation**. - While this is true, the primary concern in its historical therapeutic use was the **radioactive gaseous daughter product**, Radon, which accumulates and poses an ongoing hazard.

Question 746: Which Benzodiazepine decreases post-operative nausea & vomiting:-

A. Midazolam (Correct Answer)
B. Diazepam
C. Lorazepam
D. All of the options

Explanation: ***Midazolam*** - **Midazolam** is a commonly used benzodiazepine in anesthesia that has been shown to have **antiemetic properties** and can decrease the incidence of **postoperative nausea and vomiting (PONV)**. - Its mechanism may involve its sedative and anxiolytic effects, indirectly reducing the triggers for nausea. *Diazepam* - While **diazepam** is a benzodiazepine with sedative and anxiolytic effects, it is not primarily known for reducing PONV. - Its longer duration of action compared to midazolam can also contribute to unwanted **postoperative sedation**. *Lorazepam* - **Lorazepam** is another benzodiazepine used for anxiolysis and sedation but is not a primary agent for the prevention of PONV. - Like diazepam, its prolonged effects can lead to **delayed recovery** and drowsiness, which may not be desirable in the postoperative period. *All of the options* - While all listed drugs are benzodiazepines, only **midazolam** is consistently recognized and utilized for its ability to reduce PONV in the perioperative setting. - The other benzodiazepines do not demonstrate the same consistent benefit in PONV reduction and may have other side effects that limit their utility for this specific purpose.

Question 747: Pseudotumor Cerebri in Infants is seen with?

A. Aminoglycosides
B. Tetracyclines (Correct Answer)
C. Macrolides
D. NSAIDs

Explanation: ***Tetracyclines***- **Tetracyclines**, particularly in infants, are a known cause of **pseudotumor cerebri**, also known as **idiopathic intracranial hypertension (IIH)**. - This condition involves increased **intracranial pressure (ICP)**, leading to symptoms like **headache**, **visual disturbances**, and **papilledema**. *Aminoglycosides*- **Aminoglycosides** are primarily associated with **ototoxicity** (hearing loss) and **nephrotoxicity** (kidney damage) [1]. - They are not typically linked to the development of **pseudotumor cerebri**. *NSAIDS*- **NSAIDs** (Nonsteroidal Anti-inflammatory Drugs) are more commonly associated with **gastrointestinal ulcers** and **renal impairment**. - While they can have neurological side effects in some cases, **pseudotumor cerebri** is not a characteristic or common adverse effect. *Macrolides*- **Macrolides** like erythromycin or azithromycin are generally well-tolerated and are primarily associated with **gastrointestinal upset** and **QT prolongation**. - There is no significant evidence linking **macrolide use** to the development of **pseudotumor cerebri**.

Question 748: Which one of the following increases the potassium level in the body –

A. Suxamethonium (Correct Answer)
B. Pancuronium
C. E–tubocurarine
D. Gallamine

Explanation: ***Suxamethonium*** - **Suxamethonium** (succinylcholine) is a depolarizing neuromuscular blocker that causes a transient, dose-dependent release of potassium from muscle cells, leading to a rise in serum potassium levels. - This effect is due to its action on **nicotinic acetylcholine receptors**, which causes prolonged depolarization and opening of ion channels, allowing potassium to efflux from the cells. *Pancuronium* - **Pancuronium** is a non-depolarizing neuromuscular blocker that acts by competitively binding to nicotinic acetylcholine receptors without causing depolarization. - It does not cause a significant release of potassium from muscle cells and is not associated with hyperkalemia. *E–tubocurarine* - **Tubocurarine** is a non-depolarizing neuromuscular blocker that works by competing with acetylcholine for binding to nicotinic receptors at the neuromuscular junction. - It does not directly cause potassium release from cells and is not associated with an increase in serum potassium levels. *Gallamine* - **Gallamine** is a non-depolarizing neuromuscular blocker with a similar mechanism of action to pancuronium and tubocurarine. - It works by competitively antagonizing acetylcholine at the neuromuscular junction and does not cause clinically significant hyperkalemia.

Question 749: Renal stones are seen as a complication by using the following drug:

A. Zonisamide (Correct Answer)
B. Oxcarbazepine
C. Phenytoin
D. Tiagabine

Explanation: ***Zonisamide*** - **Zonisamide** is a sulfonamide derivative that can inhibit **carbonic anhydrase**, leading to metabolic acidosis and increased urinary calcium excretion, which promotes the formation of **kidney stones**. - Patients on zonisamide should be monitored for **renal stone formation** and advised to maintain adequate hydration. *Oxcarbazepine* - **Oxcarbazepine** is an antiepileptic drug known for causing **hyponatremia** and, less commonly, dermatological reactions such as rash. - It is not typically associated with a significant risk of **renal stone formation**. *Phenytoin* - **Phenytoin** is an older antiepileptic drug commonly associated with side effects such as **gingival hyperplasia**, hirsutism, and folate deficiency. - While it has various side effects, **nephrolithiasis** (kidney stones) is not a common or recognized complication. *Tiagabine* - **Tiagabine** is an antiepileptic drug that works by inhibiting GABA reuptake. Its main side effects include dizziness, weakness, and somnolence. - There is no significant evidence to suggest that **tiagabine** causes **renal stone formation**.

Question 750: Which of these drugs can be a cause of rhabdomyolysis?

A. Statins
B. All of these (Correct Answer)
C. Antidepressants
D. Salicylates

Explanation: ***All of these*** - **Statins**, **salicylates**, and **antidepressants** (especially selective serotonin reuptake inhibitors or tricyclic antidepressants in overdose) have all been linked to cases of rhabdomyolysis. - The risk of rhabdomyolysis can increase significantly in the presence of **polypharmacy**, certain genetic predispositions, or concurrent medical conditions. **Statins (HMG-CoA reductase inhibitors)** - Well-known for their potential to cause **myopathy** and, in more severe cases, **rhabdomyolysis**, due to their effects on muscle cell integrity. - The risk is **dose-dependent** and can be exacerbated by interactions with other drugs that inhibit statin metabolism (e.g., fibrates, azole antifungals, macrolides). - Most commonly reported drug class associated with rhabdomyolysis. **Antidepressants** - Certain **antidepressants**, particularly in overdose or when combined with other serotonergic agents (leading to **serotonin syndrome**), can induce rhabdomyolysis. - **Tricyclic antidepressants (TCAs)** and **selective serotonin reuptake inhibitors (SSRIs)** have been implicated, either directly or indirectly through complications like seizures or hyperthermia. - Risk is higher in overdose situations or with drug-drug interactions. **Salicylates** - **Salicylates**, especially in cases of **acute or chronic toxicity** (e.g., **aspirin overdose**), can directly cause muscle damage leading to rhabdomyolysis. - Mechanisms involved may include uncoupling of oxidative phosphorylation, leading to **hyperthermia** and direct cellular toxicity within muscle tissue. - Less common than statins but well-documented in toxicity cases.

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Principles of Clinical Pharmacology

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Drug-Induced Liver Injury

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