Clinical Pharmacology and Drug Toxicity — MCQs

Vasanthi, a 45-year-old woman, was brought to the casualty with persistent neck deviation to the right side and abnormal movements, one day after being prescribed haloperidol 5 mg three times daily from the psychiatry OPD. She also had a recent altercation with her husband. Which of the following is the most likely cause of her symptoms?

Q1056

Which electrolyte component is present in Oral Rehydration Solution (ORS) at a concentration of 75 mmol/litre?

Q1057

Cisapride was withdrawn from the market due to?

Q1058

SLE-like reactions are caused by?

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

Question 1051: At which phase of a drug trial is permission from the DCGI required?

A. Phase 1 (Correct Answer)
B. Phase 2
C. Phase 3
D. Phase 4

Explanation: ***Phase 1*** - **Permission from the Drugs Controller General of India (DCGI)** is **first required** to initiate **Phase 1 clinical trials** in India. - This permission is obtained through submission of an **Investigational New Drug (IND)** application to DCGI. - Phase 1 trials involve the **first-in-human** studies to assess **safety, tolerability, pharmacokinetics**, and **pharmacodynamics** in a small group of healthy volunteers or patients. - **No clinical trial can begin in India without DCGI approval**, making Phase 1 the critical regulatory checkpoint for initial permission. *Phase 2* - While Phase 2 trials also require DCGI oversight and approval to proceed from Phase 1, the question asks when permission is **required**, which is at the **initial entry point** (Phase 1). - Phase 2 focuses on evaluating **efficacy** and further assessing **safety** in a larger group of patients with the target disease. *Phase 3* - Phase 3 trials involve large-scale studies to confirm **efficacy**, monitor **adverse reactions**, and compare with standard treatments. - These trials proceed under the original DCGI approval framework established at Phase 1, with continued regulatory oversight. *Phase 4* - Phase 4 trials are **post-marketing surveillance** studies conducted after the drug has received marketing approval. - These are conducted under different regulatory guidelines for pharmacovigilance and long-term safety monitoring.

Question 1052: Which of the following is not a known side effect of dantrolene?

A. Hypertension (Correct Answer)
B. Muscle weakness
C. Phlebitis
D. Respiratory insufficiency

Explanation: Hypertension- Hypertension is not a known side effect of dantrolene; in fact, dantrolene typically causes hypotension rather than elevated blood pressure.- The drug's muscle relaxant properties and effects on calcium regulation can lead to decreased peripheral vascular resistance and cardiovascular depression.- Cardiovascular side effects of dantrolene include hypotension and bradycardia, not hypertension.Muscle weakness- Dantrolene acts by inhibiting calcium release from the sarcoplasmic reticulum, directly interfering with muscle contraction.- This mechanism of action leads to generalized muscle weakness, which is one of the most common side effects, especially at higher doses.Phlebitis- Intravenous dantrolene commonly causes local irritation and inflammation of the vein (phlebitis/thrombophlebitis).- This occurs because the IV preparation is highly alkaline (pH ~9.5) and can cause venous irritation, particularly when administered through peripheral veins.Respiratory insufficiency- Due to its muscle relaxant properties, dantrolene can affect respiratory muscles, potentially leading to respiratory depression or insufficiency.- This risk is higher in patients with pre-existing respiratory conditions or when dantrolene is used with other CNS/respiratory depressants.

Question 1053: In which of the following conditions is morphine use LEAST contraindicated?

A. Ischemic heart disease patients (Correct Answer)
B. Bronchial asthma patients
C. Elderly male patients
D. Biliary colic patients

Explanation: ***Ischemic heart disease patients*** - Morphine is often used in **acute myocardial infarction** to reduce pain and anxiety, which can decrease cardiac workload. - It causes **venodilation**, reducing preload and myocardial oxygen demand, which is beneficial in ischemia. *Bronchial asthma patients* - Morphine can induce **histamine release**, which can cause bronchospasm and exacerbate asthma symptoms. - Patients with **reactive airway disease** are at higher risk for respiratory depression and adverse effects from opioids. *Elderly male patients* - Elderly men may experience increased **urinary retention** due to prostatic hypertrophy, which morphine can worsen by increasing sphincter tone. - They are also more susceptible to morphine's side effects like **respiratory depression** and **constipation** due to altered metabolism and excretion. *Biliary colic patients* - Morphine can cause **spasm of the Sphincter of Oddi**, leading to increased pressure in the bile duct and exacerbating biliary pain. - While it relieves pain, this specific side effect makes it less ideal compared to other pain medications for biliary colic.

Question 1054: Bleomycin toxicity affects which type of cells?

A. Type I pneumocytes
B. Type II pneumocytes (Correct Answer)
C. Endothelial cells
D. Pulmonary macrophages

Explanation: ***Type II pneumocytes*** - **Bleomycin** primarily causes lung toxicity by damaging **Type II pneumocytes**, leading to fibrosis. - These cells are more vulnerable due to their **lower concentrations of bleomycin hydrolase**, an enzyme that inactivates the drug. *Type I pneumocytes* - While **Type I pneumocytes** line most of the alveolar surface, they are less directly affected by bleomycin in the initial stages of toxicity compared to Type II cells. - Damage to Type I pneumocytes usually follows more severe and widespread lung injury. *Endothelial cells* - **Endothelial cells** play a role in vascular permeability and inflammation but are not the primary target of bleomycin toxicity in the lung. - Bleomycin's direct toxic effect is on the **alveolar epithelial cells**. *Pulmonary macrophages* - **Pulmonary macrophages** are immune cells involved in clearing debris and pathogens, and while they participate in the inflammatory response to bleomycin-induced lung injury, they are not the direct cellular target of the drug. - Their role is largely secondary to initial damage to **Type II pneumocytes**.

Question 1055: Vasanthi, a 45-year-old woman, was brought to the casualty with persistent neck deviation to the right side and abnormal movements, one day after being prescribed haloperidol 5 mg three times daily from the psychiatry OPD. She also had a recent altercation with her husband. Which of the following is the most likely cause of her symptoms?

A. Conversion disorder
B. Acute psychotic episode
C. Cerebrovascular accident
D. Acute drug dystonia due to haloperidol (Correct Answer)

Explanation: ***Acute drug dystonia due to haloperidol*** - The sudden onset of **persistent neck deviation** (torticollis) and **abnormal movements** one day after starting **haloperidol**, a dopamine receptor blocker, is highly characteristic of an **acute dystonic reaction** [1]. - **Haloperidol** is a **first-generation antipsychotic** known for its increased risk of **extrapyramidal symptoms**, including dystonia [1]. *Conversion disorder* - Conversion disorder involves neurological symptoms that are **incompatible with known neurological or medical conditions** and are often preceded by psychological stressors. - While she had a recent altercation, the clear temporal relationship with a known **dopamine-blocking drug** makes drug-induced dystonia more likely than a functional neurological disorder. *Acute psychotic episode* - An acute psychotic episode is primarily characterized by **delusions, hallucinations, disorganized speech, or behavior**, not focal neurological symptoms like a persistent neck deviation. - Although the symptoms followed a psychiatric consultation, the specific presentation points away from a primary psychotic exacerbation. *Cerebrovascular accident* - A **cerebrovascular accident (stroke)** would typically present with **unilateral weakness, numbness, speech difficulties, or vision changes**, depending on the affected brain region. - The sudden onset of isolated neck deviation and generalized abnormal movements is not typical for a stroke, especially in someone starting haloperidol.

Question 1056: Which electrolyte component is present in Oral Rehydration Solution (ORS) at a concentration of 75 mmol/litre?

A. Potassium
B. Glucose
C. Chloride
D. Sodium (Correct Answer)

Explanation: ***Sodium*** - The **WHO-recommended** ORS formulation contains **sodium** at a concentration of **75 mmol/L**. This concentration is crucial for optimizing water and electrolyte absorption through the **sodium-glucose co-transport mechanism** [1] in the small intestine. [2] - Adequate sodium replacement is vital to correct **hyponatremia** and prevent further dehydration, especially in individuals with **acute diarrheal diseases**. *Potassium* - While ORS does contain potassium, its concentration is typically **20 mmol/L**, not 75 mmol/L. This is to replenish losses and prevent **hypokalemia**, which can worsen with diarrhea. [2] - Excessive potassium could be harmful, especially in individuals with impaired renal function. *Glucose* - Glucose is present at a concentration of **75 mmol/L**, but it is a sugar, not an electrolyte. It's essential for co-transporting sodium and water into enterocytes. [1] - While crucial for ORS efficacy, glucose itself directly contributes to osmolality and absorption, but is not an electrolyte. *Chloride* - Chloride is also present in ORS for maintaining **electroneutrality** and is absorbed along with sodium. [2] - The typical concentration of chloride in WHO ORS is **65 mmol/L**, not 75 mmol/L.

Question 1057: Cisapride was withdrawn from the market due to?

A. QT Prolongation (Correct Answer)
B. Hepatotoxicity
C. Nephrotoxicity
D. PR interval prolongation

Explanation: ***QT Prolongation*** - Cisapride was withdrawn from the market primarily due to its association with **dose-dependent QT interval prolongation**, which increased the risk of serious ventricular arrhythmias. - This **QT prolongation** could lead to potentially fatal **Torsades de Pointes**, a polymorphic ventricular tachycardia. *PR interval prolongation* - While some medications can affect the PR interval, **cisapride's primary cardiac concern** was specifically related to the QT interval, not the PR interval. - PR interval changes generally indicate issues with **AV nodal conduction**, a different mechanism than that affected by cisapride. *Hepatotoxicity* - Although drug-induced liver injury is a known adverse effect for many medications, **hepatotoxicity was not the primary reason** for cisapride's withdrawal. - The most significant and life-threatening adverse effect was its impact on cardiac repolarization. *Nephrotoxicity* - **Nephrotoxicity (kidney damage)** was not identified as a major or significant adverse effect associated with cisapride that led to its market withdrawal. - The drug's safety profile concerns were focused on its cardiovascular effects.

Question 1058: SLE-like reactions are caused by?

A. Hydralazine (Correct Answer)
B. Rifampicin
C. Furosemide
D. Paracetamol

Explanation: ***Hydralazine*** - **Hydralazine**, an antihypertensive, is a well-known cause of **drug-induced lupus erythematosus (DILE)**, characterized by symptoms mimicking systemic lupus erythematosus (SLE) [1]. - DILE often presents with **arthralgia, myalgia, fever, serositis**, and the presence of **anti-histone antibodies** [1]. - **Hydralazine** is the **second most common cause of DILE** (after procainamide), with higher risk in slow acetylators. - Other drugs causing DILE include procainamide, isoniazid, quinidine, minocycline, and phenytoin [1]. *Rifampicin* - **Rifampicin** is an antibiotic primarily used for tuberculosis and is known for causing **hepatotoxicity**, **red-orange discoloration of body fluids**, and **gastrointestinal disturbances**. - It does not typically induce an SLE-like reaction. *Furosemide* - **Furosemide** is a **loop diuretic** used to treat edema and hypertension, primarily causing **electrolyte imbalances** (e.g., hypokalemia, hyponatremia) and **ototoxicity** at high doses [2]. - It is not associated with drug-induced lupus erythematosus. *Paracetamol* - **Paracetamol (acetaminophen)** is an analgesic and antipyretic, and its main adverse effect is **hepatotoxicity** when taken in overdose [3]. - It is not known to cause SLE-like reactions.

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