Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 1031: Adverse reactions following whole cell pertussis immunization include:

A. Fever
B. Local swelling
C. Excessive cry
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Whole-cell pertussis vaccines** are associated with a range of common, generally self-limiting adverse reactions. - These include systemic effects like **fever** and irritability, often manifested by excessive crying, as well as local reactions at the injection site. *Fever* - **Fever** is a very common systemic adverse reaction following whole-cell pertussis immunization, indicating the body's immune response. - This reaction typically resolves within 24-48 hours. *Excessive cry* - **Excessive crying** (often described as inconsolable crying) for several hours is a known systemic adverse effect of whole-cell pertussis vaccines. - This symptom usually reflects irritability and discomfort experienced by the infant. *Local swelling* - **Local swelling** at the injection site, along with redness and tenderness, is a frequent local adverse reaction to whole-cell pertussis immunization. - These local reactions are generally mild and self-limiting, resolving within a few days.

Question 1032: All of the following drugs are used in acute congestive glaucoma EXCEPT:

A. Mannitol
B. Atropine (Correct Answer)
C. Pilocarpine
D. Acetazolamide

Explanation: ***Atropine*** - **Atropine** is a **muscarinic antagonist** that causes **mydriasis** (pupil dilation). - In acute congestive glaucoma, pupillary dilation can further narrow the **angle of the anterior chamber**, exacerbating the condition and increasing intraocular pressure. *Pilocarpine* - **Pilocarpine** is a **cholinergic agonist** that causes **miosis** (pupil constriction), pulling the iris away from the trabecular meshwork. - This action helps to **open the anterior chamber angle** and facilitate aqueous humor outflow, thus reducing intraocular pressure. *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** that reduces the production of **aqueous humor** by the ciliary body. - This leads to a decrease in intraocular pressure, making it a crucial medication in the management of acute glaucoma. *Mannitol* - **Mannitol** is an **osmotic diuretic** that creates an osmotic gradient, drawing fluid from the eye into the systemic circulation. - This effect rapidly reduces **intraocular volume** and pressure, making it useful in acute glaucoma crises.

Question 1033: Among currently prescribed medications for diabetes mellitus, deaths from lactic acidosis are most commonly associated with which one of the following?

A. Tolbutamide
B. Glipizide
C. Phenformin
D. Metformin (Correct Answer)

Explanation: ***Metformin*** - While generally safe, **lactic acidosis** is a rare but serious complication of metformin, particularly in patients with **renal impairment**, congestive heart failure, or other conditions predisposing to acidosis [1]. - Metformin inhibits **hepatic gluconeogenesis** and increases anaerobic glycolysis, which can lead to lactate accumulation if clearance is compromised [1]. *Tolbutamide* - Tolbutamide is an older **sulfonylurea** medication. - Its primary adverse effect is **hypoglycemia**, not lactic acidosis. *Phenformin* - **Phenformin** is a biguanide like metformin but was withdrawn from most markets due to a significantly higher risk of **lactic acidosis** [2]. - Although it caused frequent deaths from lactic acidosis, it is **no longer a currently prescribed medication** in most countries, making metformin the current agent most commonly associated with this risk. *Glipizide* - Glipizide is a **sulfonylurea** medication. - Its main side effect is **hypoglycemia**, and it does not directly cause lactic acidosis.

Question 1034: Which of the following statements about methyl alcohol poisoning is incorrect?

A. Effects are due to formic acid
B. Metabolic acidosis
C. Blindness
D. Fomepizole competitively inhibits aldehyde dehydrogenase (Correct Answer)

Explanation: ***Fomepizole competitively inhibits aldehyde dehydrogenase*** - **Fomepizole** acts as a competitive inhibitor of **alcohol dehydrogenase**, not aldehyde dehydrogenase. - By inhibiting alcohol dehydrogenase, fomepizole prevents the metabolism of methanol into toxic metabolites like formic acid. *Effects are due to formic acid* - This statement is correct. The primary toxicity of methanol poisoning is due to its metabolism into **formic acid** by alcohol and aldehyde dehydrogenases. - Formic acid is responsible for the **metabolic acidosis** and **ocular toxicity** observed. *Metabolic acidosis* - This statement is correct. Methanol poisoning leads to severe **anion gap metabolic acidosis** due to the accumulation of formic acid. - The acidosis contributes significantly to the overall toxicity and clinical manifestations. *Blindness* - This statement is correct. **Blindness** is a classic and feared complication of methanol poisoning. - **Formic acid** specifically targets the **optic nerve** and retina, leading to **optic neuropathy** and permanent vision loss.

Question 1035: Drugs that can be used to manage complications of Kernicterus include

A. Barbiturates (Correct Answer)
B. Phenytoin
C. Chlorpromazine
D. Benzodiazepines

Explanation: ***Barbiturates*** - **Phenobarbital** is the **first-line antiepileptic drug for neonatal seizures**, including those caused by kernicterus complications. - It has a well-established **safety profile in neonates** and is the standard of care for managing seizures in bilirubin encephalopathy. - Additionally, phenobarbital acts as a **hepatic enzyme inducer**, which can help reduce serum bilirubin levels when used preventively, though its primary role here is managing the neurological sequelae (seizures). - Most effective for controlling the epileptic complications that arise from permanent neurological damage in kernicterus. *Phenytoin* - While phenytoin is an antiepileptic drug, it is **generally avoided in neonates** due to poor efficacy in neonatal seizures and significant side effects. - **Not first-line** for kernicterus-related seizures and is not recommended in modern neonatal guidelines. - Has unpredictable pharmacokinetics in newborns and potential for toxicity. *Benzodiazepines* - Benzodiazepines (e.g., **diazepam, lorazepam, midazolam**) can be used as **second-line agents** for acute seizure management in neonates. - Useful for stopping acute seizure activity but not typically used as primary long-term management for kernicterus complications. - May be combined with phenobarbital in refractory cases. *Chlorpromazine* - Chlorpromazine is an **antipsychotic drug** with no role in managing kernicterus complications such as seizures. - Could potentially **worsen neurological outcomes** and has significant sedative and extrapyramidal side effects. - Not indicated in neonatal neurological emergencies.

Question 1036: Azathioprine is used as a treatment for which specific condition?

A. Autoimmune diseases (Correct Answer)
B. Gout
C. HIV infection
D. Cancer

Explanation: ***Autoimmune diseases*** - **Azathioprine** is a **purine analogue** that acts as an **immunosuppressant**, making it effective in managing various autoimmune conditions by reducing the immune response. - It is specifically used in diseases like **rheumatoid arthritis** [1], lupus, Crohn's disease, and in **organ transplantation** to prevent rejection [1]. *Gout* - **Gout** is an inflammatory arthritis caused by the deposition of **urate crystals** in the joints. - Treatment typically involves **NSAIDs**, **colchicine**, and **allopurinol** (to lower uric acid), not immunosuppressants like azathioprine. *HIV infection* - **HIV infection** is a viral disease that attacks the immune system, requiring **antiretroviral therapy (ART)** to control viral replication. - Azathioprine is not used for HIV treatment as it would further suppress an already compromised immune system. *Cancer* - While some **cytotoxic agents** are used in cancer therapy, azathioprine is primarily an immunosuppressant and its role in cancer treatment is limited. - **Chemotherapy** for cancer involves agents specifically designed to target and kill rapidly dividing cancer cells through various mechanisms.

Question 1037: Which of the following is likely to cause bull's-eye retinopathy?

A. Chloroquine (Correct Answer)
B. Isoniazid (INH)
C. Ethambutol
D. Corticosteroids

Explanation: ***Chloroquine*** - **Chloroquine** and **hydroxychloroquine** are known to cause a dose-dependent retinopathy, often described as "**bull's-eye maculopathy**." - This toxicity manifests as pigmentary changes in the **macula**, leading to visual field defects, especially paracentral scotomas. *Isoniazid (INH)* - Isoniazid is primarily associated with **peripheral neuropathy** and **hepatotoxicity**. - It does not typically cause bull's-eye retinopathy. *Ethambutol* - Ethambutol is known to cause **optic neuritis** and **red-green color blindness** due to optic nerve damage. - While it affects vision, it does not lead to bull's-eye retinopathy. *Corticosteroids* - Long-term use of corticosteroids can lead to **posterior subcapsular cataracts** and **glaucoma**. - They are not associated with bull's-eye retinopathy.

Question 1038: Etomidate is not used for long-term infusion because?

A. Causes adrenal suppression (Correct Answer)
B. May cause vasodilation
C. Can lead to bradycardia
D. May cause increased intracranial pressure

Explanation: ***Causes adrenal suppression*** - Etomidate is a **GABA-A agonist** that inhibits the enzyme **11-beta-hydroxylase**, crucial for cortisol synthesis in the adrenal cortex. - This inhibition leads to a dose-dependent and prolonged **adrenal suppression**, making it unsuitable for long-term infusions due to the risk of **adrenal insufficiency** and increased mortality. *May cause vasodilation* - Etomidate is known for its **hemodynamic stability**, causing minimal changes in **heart rate** or **blood pressure**, rather than vasodilation. - It generally maintains **cardiac output** and **systemic vascular resistance**, which is why it's often favored in patients with cardiovascular instability for induction. *Can lead to bradycardia* - Etomidate typically has **minimal effects on heart rate** and sympathetic nervous system activity. - It does not commonly cause **bradycardia** and is often used in patients where myocardial depression or significant heart rate changes are undesirable. *May cause increased intracranial pressure* - Etomidate is known to **reduce cerebral blood flow (CBF)** and **cerebral metabolic rate of oxygen (CMRO2)**. - This action usually leads to a **reduction, not an increase, in intracranial pressure (ICP)**, making it a suitable choice for induction in patients with neurological concerns.

Question 1039: Which of the following drugs was classified as Category X (highest teratogenic risk) in the former FDA pregnancy risk classification system?

A. Isotretinoin (Correct Answer)
B. Penicillin
C. Thiopental
D. Acetylsalicylic acid

Explanation: ***Isotretinoin*** - **Isotretinoin** is a powerful teratogen with **high risk of causing severe birth defects** including craniofacial, cardiac, thymic, and CNS malformations if taken during pregnancy. - Under the former FDA classification (discontinued 2015), it was Category X due to its significant teratogenic potential. - Requires strict contraception programs (iPLEDGE in US, pregnancy prevention programs globally) for all patients of childbearing potential. - **Absolute contraindication in pregnancy.** *Penicillin* - **Penicillin** was classified as Pregnancy Category B under the former system. - Generally considered **safe for use during pregnancy** when indicated for bacterial infections. - No evidence of teratogenic effects in human studies. - Widely used throughout pregnancy for appropriate indications. *Thiopental* - **Thiopental** was classified as Pregnancy Category C under the former system. - Used cautiously during pregnancy, typically only when **potential benefits outweigh risks**, primarily in situations requiring general anesthesia. - Short-term use for induction of anesthesia is generally considered acceptable when medically necessary. *Acetylsalicylic acid (Aspirin)* - **Aspirin** was Category C in first/second trimesters and Category D in third trimester under the former system. - **High doses and chronic use** carry risks including premature closure of **ductus arteriosus**, impaired platelet function, and increased bleeding risk. - Low-dose aspirin (75-150 mg) is now commonly used for prevention of preeclampsia in high-risk pregnancies. - Third trimester use of full doses should be avoided due to fetal and maternal bleeding complications.

Question 1040: Which of the following statements about clinical trials is true?

A. Post-marketing surveillance is done in Phase 3
B. Safety and non-toxicity is evaluated in Phase 2
C. Randomized controlled trial in patients is done in Phase 3 (Correct Answer)
D. Unit of study in Phase 1 is Patients

Explanation: ***Randomized controlled trial in patients is done in Phase 3*** - **Phase 3 trials** involve large groups of patients to confirm the drug's effectiveness, monitor side effects, and compare it to standard treatments. - These trials are typically **randomized, controlled**, and often multicenter, providing robust data for regulatory approval. *Post-marketing surveillance is done in Phase 3* - **Post-marketing surveillance** (Phase 4) occurs after a drug has been approved and is available to the general public. - Its purpose is to monitor for long-term or rare side effects not detected in earlier, smaller trials. *Safety and non-toxicity is evaluated in Phase 2* - While safety is monitored in all phases, **Phase 1 trials** are primarily focused on assessing the **safety, dosage, and pharmacokinetics** of a new drug in a small group of healthy volunteers. - **Phase 2 trials** primarily evaluate the drug's **effectiveness** and further assess safety in a larger group of patients with the target disease. *Unit of study in Phase 1 is Patients* - The primary unit of study in **Phase 1 trials** is typically a small group of **healthy volunteers** (20-100 individuals) to determine the drug's safety, dosage, and pharmacokinetic profile. - Patients are included in later phases (Phase 2 and 3) once initial safety in healthy individuals has been established.

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