Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Which drug may lead to hemolysis in a child with G6PD deficiency?

Primaquine. ### Explanation **Correct Option: B. Primaquine** **Mechanism of Hemolysis in G6PD Deficiency:** Glucose-6-Phosphate Dehydrogenase (G6PD) is the rate-limiting enzyme in the pentose phosphate pathway, responsible for generating **NADPH**. In RBCs, NADPH is essential to maintain **reduced glutathione**, which neutralizes reactive oxygen species (ROS). **Primaquine** is an oxidizing agent. In G6PD-deficient individuals, the inability to regenerate reduced glutathione leads to the oxidation of hemoglobin into insoluble precipitates called **Heinz bodies**. These damage the RBC membrane, leading to acute hemolytic anemia. This is a classic example of **Pharmacogenetics**. **Analysis of Incorrect Options:** * **A. Penicillin:** While Penicillin can cause immune-mediated hemolytic anemia (Type II Hypersensitivity), it is not an oxidizing agent and does not trigger G6PD-related hemolysis. * **C. Ceftriaxone:** A third-generation cephalosporin that does not possess significant oxidizing potential. * **D. Erythromycin:** A macrolide antibiotic that is safe in G6PD deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Other Trigger Drugs:** Dapsone (highest risk), Nitrofurantoin, Sulfonamides (e.g., Co-trimoxazole), and Ciprofloxacin. * **Non-Drug Triggers:** Fava beans (Favism) and infections (most common cause of hemolysis). * **Peripheral Smear Findings:** Look for **Heinz bodies** (denatured hemoglobin) and **Bite cells** (deformed RBCs after splenic macrophages remove Heinz bodies). * **Inheritance:** G6PD deficiency is an **X-linked recessive** disorder, predominantly affecting males. * **Primaquine Rule:** Always screen for G6PD deficiency before initiating Primaquine for the radical cure of *P. vivax* or *P. ovale*.

Q: Which of the following drugs does NOT cause gynecomastia?

Pyrazinamide. **Explanation:** Gynecomastia (enlargement of male breast tissue) is a high-yield side effect in pharmacology, typically caused by drugs that either decrease testosterone synthesis, block androgen receptors, or increase estrogen levels. **Why Pyrazinamide is the correct answer:** Pyrazinamide is a first-line antitubercular drug. Its primary significant metabolic side effect is **hyperuricemia** (due to inhibition of uric acid excretion), which can precipitate gout. It also carries a risk of hepatotoxicity. However, it has no known effect on the hypothalamic-pituitary-gonadal axis or steroid hormone receptors and, therefore, **does not cause gynecomastia.** **Analysis of Incorrect Options:** * **Cimetidine:** An H2-receptor blocker that causes gynecomastia via two mechanisms: it acts as a mild anti-androgen (blocking androgen receptors) and inhibits the cytochrome P450 enzymes responsible for estradiol metabolism. * **Spironolactone:** A potassium-sparing diuretic and aldosterone antagonist. It is a notorious cause of gynecomastia because it inhibits testosterone synthesis and competes with dihydrotestosterone (DHT) for androgen receptors. (Note: Eplerenone is a more selective alternative that avoids this). * **Ketoconazole:** An antifungal that inhibits the enzyme **17,20-desmolase** (and CYP17), which is essential for steroid synthesis. This leads to decreased testosterone production. **NEET-PG High-Yield Pearls:** To remember the common drugs causing gynecomastia, use the mnemonic **"DISCO"**: * **D**igoxin (estrogenic effect) * **I**soniazid (INH - though rare, it is the TB drug that *can* cause it, unlike Pyrazinamide) * **S**pironolactone * **C**imetidine * **O**estrogens / **K**etoconazole (the 'K' sound) *Other notable mentions: Finasteride, Risperidone (via hyperprolactinemia), and Marijuana.*

Q: Bone marrow aplasia is not seen with which of the following drugs?

Levodopa. **Explanation:** Bone marrow aplasia (aplastic anemia) is a serious condition characterized by the pancytopenia of peripheral blood and a hypocellular bone marrow. In the context of pharmacology, it is often a result of drug-induced myelosuppression. **Why Levodopa is the Correct Answer:** **Levodopa** is a precursor of dopamine used in the treatment of Parkinson’s disease [1]. Its primary side effects are gastrointestinal (nausea, vomiting), cardiovascular (arrhythmias, orthostatic hypotension), and neurological (dyskinesias, hallucinations) [1], [2]. It is **not** associated with bone marrow suppression or aplastic anemia [1]. **Analysis of Incorrect Options:** * **Azathioprine:** This is a potent immunosuppressant (prodrug of 6-mercaptopurine). Its primary dose-limiting toxicity is **bone marrow suppression**, leading to leukopenia and occasionally full aplasia, especially in patients with Thiopurine Methyltransferase (TPMT) deficiency. * **Furosemide:** While primarily a loop diuretic, sulfonamide-derived drugs like Furosemide can rarely cause idiosyncratic bone marrow suppression and blood dyscrasias. * **Chloramphenicol:** This is a classic "high-yield" cause of bone marrow aplasia. It causes two types of toxicity: a dose-dependent, reversible suppression and a rare, **dose-independent, irreversible aplastic anemia** which can be fatal. **NEET-PG High-Yield Pearls:** 1. **Chloramphenicol** is the most notorious drug associated with idiosyncratic aplastic anemia. 2. **Gold salts, Phenylbutazone, and Carbamazepine** are other frequent culprits of drug-induced aplastic anemia. 3. **TPMT testing** is recommended before starting Azathioprine to prevent life-threatening myelosuppression. 4. **Gray Baby Syndrome** is another specific toxicity of Chloramphenicol due to deficient glucuronidation in neonates.

Q: Which of the following statements regarding aspirin toxicity is true?

Tinnitus is an early symptom.. **Explanation:** **1. Why Option A is Correct:** Tinnitus (ringing in the ears) is a classic, early, and sensitive indicator of salicylate toxicity (salicylism). It occurs due to the inhibition of cyclooxygenase (COX) and the subsequent alteration of ion transport in the stria vascularis of the cochlea, alongside increased pressure in the labyrinth. In clinical practice, the onset of tinnitus often serves as a warning sign to reduce the dose of aspirin. **2. Analysis of Incorrect Options:** * **Option B:** While 10–30 g is a significant amount, it is actually the **lethal dose** for adults, not just the threshold for poisoning. Mild toxicity (salicylism) can occur at much lower therapeutic doses if taken chronically. * **Option C:** While hyperthermia and tachypnea do occur, they are typically seen in **moderate to severe toxicity**. Tachypnea results from direct stimulation of the respiratory center, and hyperthermia results from the uncoupling of oxidative phosphorylation. Tinnitus precedes these systemic metabolic derangements. * **Option D:** Aspirin causes a **qualitative platelet defect** (by irreversibly inhibiting COX-1 and thromboxane A2 synthesis), leading to an increased bleeding time. It does not typically cause a decrease in platelet count (thrombocytopenia). **High-Yield Clinical Pearls for NEET-PG:** * **Acid-Base Balance:** Aspirin toxicity causes a unique **mixed acid-base disturbance**: Respiratory Alkalosis (early, due to hyperventilation) + Metabolic Acidosis (later, due to accumulation of organic acids). * **Management:** Treatment involves **Urinary Alkalinization** (using IV Sodium Bicarbonate) to enhance the excretion of salicylates (ion trapping). * **Done Nomogram:** Used to estimate the severity of toxicity based on serum salicylate levels (though clinical correlation is preferred).

Q: Which of the following drugs does NOT cause cholestasis with inflammation of bile ducts?

Astemizole. **Explanation:** Drug-induced liver injury (DILI) can manifest as hepatocellular necrosis, steatosis, or cholestasis. **Cholestatic jaundice** is characterized by the impairment of bile flow, which can occur with or without inflammation of the bile ducts (vanishing bile duct syndrome). **Why Astemizole is the correct answer:** Astemizole is a second-generation H1-antihistamine. While it was notorious for causing **QT interval prolongation** and *Torsades de Pointes* (leading to its withdrawal from many markets), it is not associated with cholestatic liver injury or bile duct inflammation. **Analysis of Incorrect Options:** * **Erythromycin:** Specifically the **estolate salt**, is a classic cause of cholestatic hepatitis. It typically presents with right upper quadrant pain and jaundice, mimicking acute cholecystitis. * **Amoxicillin-Clavulanic Acid:** This is one of the most common causes of drug-induced cholestatic liver injury worldwide. The injury is primarily attributed to the **clavulanic acid** component and often presents several weeks after stopping the therapy. * **Trimethoprim-Sulphamethoxazole (TMP-SMX):** Sulfonamides are well-known triggers for idiosyncratic liver injury, frequently presenting as mixed hepatocellular-cholestatic patterns with ductal involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Pure Cholestasis (without inflammation):** Classically caused by **Anabolic steroids** and **Oral Contraceptive Pills (OCPs)**. * **Cholestatic Hepatitis (with inflammation):** Associated with **Erythromycin, Chlorpromazine,** and **Amoxicillin-Clavulanic acid**. * **Astemizole & Terfenadine:** High-yield for their **cardiotoxicity** (prolonged QT) when co-administered with CYP3A4 inhibitors like Ketoconazole or Macrolides.

Q: Which one of the following is ineffective in acute iron toxicity?

BAL. **Explanation:** Acute iron toxicity is a medical emergency characterized by gastrointestinal hemorrhage, metabolic acidosis, and multi-organ failure. The management focuses on preventing absorption and enhancing elimination through specific chelation. **Why BAL is the correct answer:** **BAL (British Anti-Lewisite/Dimercaprol)** is ineffective and contraindicated in iron toxicity. Dimercaprol forms a complex with iron that is **nephrotoxic**. It is primarily used for heavy metals like arsenic, mercury, and lead. Using it for iron poisoning can exacerbate renal damage rather than resolve the toxicity. **Analysis of Incorrect Options:** * **Desferrioxamine:** This is the **specific antidote of choice** for acute iron toxicity. It is administered parenterally and binds free iron to form ferrioxamine, which is excreted in the urine (often turning it a "vin-rose" color). * **Whole Bowel Irrigation (WBI):** Since iron tablets are radiopaque and do not bind to activated charcoal, WBI using Polyethylene Glycol (PEG) is the preferred method to mechanically flush unabsorbed tablets from the GI tract. * **Deferasirox:** This is an **oral iron chelator**. While primarily used for chronic iron overload (e.g., Thalassemia), it is pharmacologically active against iron, unlike BAL. However, Desferrioxamine remains the gold standard for *acute* cases. **High-Yield Clinical Pearls for NEET-PG:** 1. **Activated Charcoal:** Does **not** bind iron; it is useless in pure iron poisoning. 2. **Vin-Rose Urine:** A classic sign during Desferrioxamine therapy indicating the excretion of the iron-chelate complex. 3. **Abdominal X-ray:** Useful in diagnosis because iron tablets are radiopaque. 4. **Toxicity Stages:** Remember the "latent period" (Stage 2) where the patient appears to improve before crashing into hepatic failure and shock.

Q: Warfarin embryopathy manifests characteristically as?

Chondrodysplasia punctata. **Explanation:** Warfarin is a vitamin K antagonist that crosses the placenta and is highly teratogenic, especially when administered during the **first trimester (6th to 9th week of gestation)**. **Why Chondrodysplasia Punctata is Correct:** Warfarin interferes with the γ-carboxylation of osteocalcin and other bone proteins. This leads to **Chondrodysplasia punctata**, characterized by "stippled epiphyses" (punctate calcifications) seen on X-ray. Other classic features of Warfarin Embryopathy include **nasal hypoplasia** (depressed nasal bridge), limb hypoplasia, and low birth weight. **Analysis of Incorrect Options:** * **B. Dysplastic hips:** While skeletal issues occur, developmental dysplasia of the hip is not a specific feature of warfarin toxicity; it is more commonly associated with breech presentation or oligohydramnios. * **C. Auditory sensorineural hearing loss:** This is a classic feature of **Aminoglycoside** (e.g., Streptomycin) toxicity during pregnancy, not warfarin. * **D. Gastrointestinal atresias:** These are more commonly associated with vascular disruptions or chromosomal anomalies (e.g., Duodenal atresia in Down Syndrome) rather than warfarin exposure. **NEET-PG High-Yield Pearls:** * **Safe Alternative:** Heparin (both UFH and LMWH) does **not** cross the placenta and is the anticoagulant of choice during pregnancy. * **CNS Effects:** Exposure in the 2nd and 3rd trimesters can lead to CNS anomalies like microcephaly, optic atrophy, and hydrocephalus due to fetal hemorrhage. * **Fetal Hydantoin Syndrome:** Contrast this with Phenytoin toxicity, which presents with cleft lip/palate and digital hypoplasia.

Question 1

Which drug may lead to hemolysis in a child with G6PD deficiency?

Accepted Answer

Primaquine

Answer

Penicillin

Answer

Ceftriaxone

Answer

Erythromycin

Question 2

Which instructions should be included in the teaching care plan for a patient with cystitis receiving phenazopyridine?

Accepted Answer

Instruct the patient to stop taking phenazopyridine after painful urination is relieved.

Answer

Inform the patient that the urine will turn orange-red.

Answer

Instruct the patient to take phenazopyridine just before urination to relieve pain.

Answer

Advise the patient to discontinue prescribed antibiotics once painful urination is relieved.

Question 3

Forced alkaline diuresis cannot be done in which poisoning?

Accepted Answer

Alcohol

Answer

Barbiturates

Answer

Salicylates

Answer

Methotrexate

Question 4

Which of the following drugs does NOT cause gynecomastia?

Accepted Answer

Pyrazinamide

Answer

Cimetidine

Answer

Spironolactone

Answer

Ketoconazole

Question 5

Bone marrow aplasia is not seen with which of the following drugs?

Accepted Answer

Levodopa

Answer

Azathioprine

Answer

Furosemide

Answer

Chloramphenicol

Question 6

Which of the following statements regarding aspirin toxicity is true?

Accepted Answer

Tinnitus is an early symptom.

Answer

A dose of 10-30 g can cause poisoning.

Answer

Hyperthermia and tachypnea are early complications.

Answer

Aspirin causes thrombocytopenic purpura.

Question 7

Which of the following drugs does NOT cause cholestasis with inflammation of bile ducts?

Accepted Answer

Astemizole

Answer

Erythromycin

Answer

Amoxicillin clavulanic acid

Answer

Trimethoprim sulphamethoxazole

Question 8

Which one of the following is ineffective in acute iron toxicity?

Accepted Answer

BAL

Answer

Desferrioxamine

Answer

Whole bowel irrigation

Answer

Deferasirox

Question 9

Warfarin embryopathy manifests characteristically as?

Accepted Answer

Chondrodysplasia punctata

Answer

Dysplastic hips

Answer

Auditory sensineuronal hearing loss

Answer

Gastrointestinal atresias

Question 10

Which of the following antihistamines is free of arrhythmogenic potential?

Accepted Answer

Loratadine

Answer

Terfenadine

Answer

Fexofenadine

Answer

Ebastine

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

On this page

Practice by Chapter

Want unlimited practice?