Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 831: Which of the following is the drug of choice for the treatment of neuroleptic malignant syndrome?

A. Haloperidol
B. Dantrolene (Correct Answer)
C. Chlorpromazine
D. Lorazepam

Explanation: ***Dantrolene*** - **Dantrolene** is a **direct-acting skeletal muscle relaxant** that works by inhibiting calcium release from the sarcoplasmic reticulum, thus reducing muscle rigidity and hyperthermia. - Among the given options, it is the **most appropriate choice** for treating **neuroleptic malignant syndrome (NMS)**, particularly when severe muscle rigidity and hyperthermia are present. - **Note:** In clinical practice, **bromocriptine** (a dopamine agonist) is often considered first-line pharmacotherapy as it reverses the underlying dopamine blockade. Dantrolene is typically used as **adjunctive therapy** or when bromocriptine is unavailable, though it remains highly effective for the hypermetabolic muscle crisis. *Haloperidol* - **Haloperidol** is a typical **antipsychotic** that blocks dopamine D2 receptors and is one of the drugs most commonly implicated in **causing NMS**, not treating it. - Administering haloperidol would exacerbate the underlying dopamine blockade pathology and significantly worsen the patient's condition. *Chlorpromazine* - **Chlorpromazine** is another typical **antipsychotic** that causes significant dopamine blockade and is also associated with precipitating NMS. - Its use would worsen NMS symptoms rather than treat them, as continued antipsychotic administration perpetuates the syndrome. *Lorazepam* - **Lorazepam** is a **benzodiazepine** that can help manage agitation, anxiety, and muscle spasms in NMS as **supportive care**. - While useful as an **adjunctive treatment**, it does not address the core pathophysiology of dopamine blockade or the massive muscle contraction and hyperthermia characteristic of NMS. - It plays a supportive role but is not the primary pharmacological intervention.

Question 832: A 30-year-old woman with rheumatoid arthritis who is on methotrexate therapy presents with shortness of breath. What is the most likely explanation for this patient's respiratory symptoms?

A. Hepatotoxicity
B. Pulmonary fibrosis (Correct Answer)
C. Nephrotoxicity
D. Gastrointestinal bleeding

Explanation: ***Pulmonary fibrosis*** - Methotrexate can cause **interstitial lung disease**, including **pulmonary fibrosis**, which manifests as shortness of breath and cough due to inflammation and scarring of lung tissue. - Rheumatoid arthritis itself can also lead to **interstitial lung disease**, making patients on methotrexate particularly susceptible to respiratory complications. *Hepatotoxicity* - Methotrexate can cause **liver damage**, leading to elevated liver enzymes and, rarely, cirrhosis, but this would not directly cause **shortness of breath**. - While significant liver dysfunction can impact overall health, respiratory symptoms are not a primary and direct manifestation of isolated hepatotoxicity. *Nephrotoxicity* - Methotrexate is primarily cleared by the kidneys, and high doses can cause **kidney damage** leading to acute kidney injury, but this would not cause **shortness of breath**. - Renal impairment might complicate methotrexate elimination, but direct respiratory symptoms are not a typical presentation of nephrotoxicity. *Gastrointestinal bleeding* - Methotrexate can cause gastrointestinal side effects such as nausea, vomiting, and mucositis, and rarely, gastrointestinal ulceration and bleeding, but this would not primarily present as **shortness of breath**. - While severe anemia from significant GI bleeding could cause dyspnea, it is not the most direct or common respiratory complication from methotrexate therapy in this context.

Question 833: What is the primary purpose of Phase III clinical trials for a new antihypertensive drug?

A. Determine the drug's safety profile
B. Evaluate the drug's efficacy and monitor side effects (Correct Answer)
C. Assess pharmacokinetics and pharmacodynamics
D. Test the drug in a small group of healthy volunteers

Explanation: **Evaluate the drug's efficacy and monitor side effects** - **Phase III trials** are designed to confirm the drug's effectiveness and safety in a large patient population, comparing it to standard treatments or placebo. - This phase aims to gather comprehensive data on **efficacy** and identify **rare or long-term side effects** that may not have been observed in earlier phases. *Determine the drug's safety profile* - While safety is continuously monitored throughout all phases, the primary focus on detailed **safety profiling** for rare adverse events often takes place during **Phase III** due to the larger sample size. - However, initial assessment of **basic safety and tolerability** is performed in **Phase I and II**. *Assess pharmacokinetics and pharmacodynamics* - **Pharmacokinetics (PK)**, which describes how the body affects the drug (absorption, distribution, metabolism, excretion), and **pharmacodynamics (PD)**, which describes how the drug affects the body, are primarily assessed in **Phase I** trials. - This early assessment helps determine optimal dosing and administration routes. *Test the drug in a small group of healthy volunteers* - This description best fits **Phase I clinical trials**, where a new drug is initially tested in a small group of **healthy volunteers** to assess its safety, dosage, and pharmacokinetics. - The goal is to determine if the drug is safe enough for further testing in patients.

Question 834: Pegloticase is used for the treatment of which of the following?

A. Reactive Arthritis
B. CPPD
C. Chronic tophaceous gout (Correct Answer)
D. Refractory Rheumatoid arthritis

Explanation: ***Chronic tophaceous gout*** - Pegloticase is a **recombinant pegylated uricase** that metabolizes **uric acid** into allantoin, which is readily excreted by the kidneys. - It is specifically indicated for refractory chronic tophaceous gout when other therapies have failed. *Reactive Arthritis* - This condition is an **autoimmune response** to an infection elsewhere in the body, presenting with aseptic arthritis. - Treatment focuses on managing symptoms with **NSAIDs** and occasionally immune suppressants, not uric acid-lowering agents. *CPPD* - Also known as **pseudogout**, this condition is caused by the deposition of **calcium pyrophosphate dihydrate crystals** in joints. - Treatment involves **NSAIDs**, colchicine, or corticosteroids to manage acute flares, not uric acid-targeted therapies. *Refractory Rheumatoid arthritis* - Rheumatoid arthritis is a chronic inflammatory autoimmune disease primarily affecting the joints. - Treatment involves **DMARDs** (disease-modifying antirheumatic drugs) and biological agents, which target inflammation and immune response, not uric acid.

Question 835: What is the drug of choice for smoking cessation?

A. Acamprosate
B. Varenicline (Correct Answer)
C. Thalidomide
D. Tryptophan

Explanation: ***Varenicline*** - **Varenicline** is a **partial agonist** at the **α4β2 nicotinic acetylcholine receptor**, reducing cravings and withdrawal symptoms while blocking the pleasurable effects of nicotine [1]. - It is often considered the **first-line pharmacological treatment** for smoking cessation due to its superior efficacy compared to other monotherapies. *Acamprosate* - **Acamprosate** is primarily used to maintain **abstinence from alcohol** in patients with alcohol dependence. - Its mechanism involves modulating **glutamatergic activity**, primarily at **NMDA receptors**, which is not directly relevant to nicotine addiction. *Thalidomide* - **Thalidomide** is an **immunomodulatory** and **anti-angiogenic drug** used in conditions like **multiple myeloma** and **leprosy**. - It has no role or approved indication for **smoking cessation**. *Tryptophan* - **Tryptophan** is an **amino acid** that serves as a precursor to **serotonin**, a neurotransmitter involved in mood regulation. - While sometimes explored for mood or sleep issues, it is **not indicated** or effective as a primary treatment for **smoking cessation**.

Question 836: Which of the following agents is associated with maximum histamine release?

A. Pancuronium
B. Rocuronium
C. Cisatracurium
D. d-Tubocurarine (Correct Answer)

Explanation: ***d-Tubocurarine*** - This **non-depolarizing neuromuscular blocker** is known for its significant potential to cause **histamine release** [2], [3], [4]. - Histamine release can lead to undesirable side effects such as **hypotension**, **tachycardia**, and **bronchospasm** [2], [3]. *Cisatracurium* - Cisatracurium is a **benzylisoquinolinium neuromuscular blocker** that is known for its minimal to no histamine release. - Its degradation through **Hofmann elimination** contributes to its favorable cardiovascular profile. *Pancuronium* - Pancuronium is an **aminosteroid neuromuscular blocker** that has a low incidence of histamine release [1]. - It can cause a **vagolytic effect**, leading to an increase in heart rate [2], [3]. *Rocuronium* - Rocuronium is another **aminosteroid neuromuscular blocker** that is associated with very minimal histamine release [2]. - It is often favored in situations where a **rapid onset** is required, such as in rapid sequence intubation.

Question 837: What is the LNG content of Mirena?

A. 52 mg (Correct Answer)
B. 20 mg
C. 13.5 mg
D. 39 mg

Explanation: ***52 mg*** - Mirena is a **levonorgestrel-releasing intrauterine system (IUS)** that contains 52 mg of **levonorgestrel (LNG)**. - This specific dosage ensures effective contraception for up to 8 years by continuously releasing a small amount of LNG. *20 mg* - This dosage refers to **Kyleena**, another levonorgestrel IUS that contains 19.5 mg (approximately 20 mg) of LNG. - Kyleena is effective for up to 5 years and is a smaller-sized IUS option. *13.5 mg* - This dosage is associated with the IUS **Skyla**, which contains 13.5 mg of levonorgestrel for a shorter duration of use (up to 3 years). - Different IUS devices are designed with varying **LNG content** to suit different clinical needs and durations. *39 mg* - This is not a standard **LNG content** for currently available IUS devices. - The main levonorgestrel IUS options contain 52 mg (Mirena, Liletta), 19.5 mg (Kyleena), or 13.5 mg (Skyla).

Question 838: Which of the following is not an absolute contraindication for the use of methylergometrine?

A. Eclampsia
B. Heart disease
C. After delivery of first baby in twin pregnancy
D. Rh incompatibility (Correct Answer)

Explanation: ***Rh incompatibility*** - **Rh incompatibility** is a condition related to blood type issues between mother and fetus, and it does not directly contraindicate the use of methylergometrine. - Methylergometrine's primary action is on uterine contractility and vasoconstriction, not directly affecting Rh immune responses. *Eclampsia* - **Eclampsia** is characterized by seizures in a pregnant woman with preeclampsia, often associated with severe hypertension. - Methylergometrine can exacerbate **hypertension** and therefore poses a significant risk for patients with eclampsia due to the potential for stroke or severe hypertensive crisis. *Heart disease* - **Heart disease**, especially conditions like **coronary artery disease** or **valvular heart disease**, is a contraindication due to methylergometrine's vasoconstrictive effects. - The drug can increase **blood pressure** and **cardiac afterload**, potentially leading to myocardial ischemia or heart failure exacerbation. *After delivery of first baby in twin pregnancy* - Administering methylergometrine after the delivery of the first twin but before the second is delivered can cause **strong uterine contractions**. - These contractions could **prematurely separate the placenta** of the second twin or lead to **fetal distress**, posing a significant risk to the undelivered twin.

Question 839: Penicillamine use in pregnancy is associated with this fetal complication?

A. Connective tissue abnormalities (Correct Answer)
B. Urinary system malformations
C. Thymic developmental disorders
D. Skeletal growth abnormalities

Explanation: Connective tissue abnormalities - Penicillamine is a **chelation agent** that can interfere with **collagen synthesis** and cross-linking due to its effect on copper and zinc metabolism. - This interference can lead to disorders resembling **Ehlers-Danlos syndrome**, causing **skin fragility** and **joint hypermobility** in the fetus. *Urinary system malformations* - While various medications can cause fetal urinary tract malformations, **penicillamine is not primarily associated** with this type of complication. - **ACE inhibitors**, for instance, are known to cause renal anomalies [1], [2]. *Thymic developmental disorders* - Penicillamine is not known to directly cause **thymic developmental disorders** leading to immunodeficiency. - Some drugs, like **phenytoin**, have been linked to **thymic hypoplasia** in specific syndromes. *Skeletal growth abnormalities* - Although penicillamine can affect copper, which is essential for bone health, its primary teratogenic effect is not typically seen as **gross skeletal growth abnormalities**. - **Thalidomide**, for example, is notorious for causing distinctive limb reduction defects [2].

Question 840: What is the sodium (Na+) content in Ringer's lactate solution in mEq/L?

A. 154
B. 12
C. 130 (Correct Answer)
D. 144

Explanation: ***130*** - **Ringer's lactate** solution typically contains **sodium (Na+) at 130 mEq/L**. - This concentration is designed to be **isotonic** with plasma while providing important electrolytes and a metabolic precursor to bicarbonate. *154* - This concentration of sodium is characteristic of **0.9% normal saline**, not Ringer's lactate. - While both are isotonic, their electrolyte profiles and uses differ significantly. *12* - A sodium concentration of **12 mEq/L** is extremely low and not found in standard intravenous fluids like Ringer's lactate. - This level is far below physiological concentrations and would be associated with severe **hyponatremia**. *144* - While **144 mEq/L** is closer to the plasma sodium concentration, it is not the standard sodium content for Ringer's lactate solution. - Some specialized solutions might have this, but standard Ringer's lactate has a lower sodium content to allow for the presence of other cations.

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