Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 841: What type of venom is primarily produced by sea snakes?

A. Neurotoxic (Correct Answer)
B. All types of venom
C. Hemotoxic
D. Musculotoxic

Explanation: ***Neurotoxic***- Sea snake venom is **primarily neurotoxic**, containing potent **postsynaptic neurotoxins** that block acetylcholine receptors at the neuromuscular junction [1].- The **neurotoxic component is the predominant and most immediately life-threatening** aspect, causing **descending paralysis, ptosis, respiratory failure**, and death if untreated [1].- While myotoxicity is also present, the **initial clinical presentation and main cause of mortality** is neurotoxic paralysis.*All types of venom*- While sea snake venom contains multiple components, it is **not a general combination of all venom types**.- It lacks significant **hemotoxic, cytotoxic, or cardiotoxic effects** that characterize other snake families.- The venom is specifically adapted for rapid neuromuscular paralysis of fish prey.*Hemotoxic*- **Hemotoxic venom** primarily affects blood and blood vessels, causing **coagulopathy, hemorrhage**, and tissue necrosis, commonly seen in **viper venoms**.- Sea snake venom does **not cause significant coagulation defects or bleeding** as the primary mechanism.- This is not the characteristic feature of sea snake envenomation.*Musculotoxic*- While sea snake venom **does contain myotoxins** that can cause **rhabdomyolysis and myoglobinuria**, this occurs **secondary to the neurotoxic effects** and develops over hours.- The term "**primarily produced**" refers to the **dominant and most dangerous component** - the neurotoxins that cause immediate paralysis and respiratory arrest.- Clinically, **neurotoxicity determines the acute management** (ventilatory support and antivenom), making it the primary concern despite coexisting myotoxicity.

Question 842: For which of the following medications is the Z-track technique recommended for administration?

A. Injection Iron Dextran (Correct Answer)
B. Injection Hydroxyzine hydrochloride
C. Injection Depomedroxyprogesterone
D. Injection Erythromycin

Explanation: ***Injection Iron Dextran*** - The **Z-track technique** is the **classical and primary indication** for iron dextran injections to prevent **permanent skin staining (tattooing)** and tissue irritation at the injection site. - This method seals the medication deep within the muscle, preventing leakage into subcutaneous tissue that causes characteristic brown discoloration. - Iron dextran is the **most emphasized example** in medical education for Z-track administration. *Injection Hydroxyzine hydrochloride* - While Z-track technique **can be used** for hydroxyzine due to its tissue-irritating properties, it is not the **primary or classical indication** taught in medical education. - Hydroxyzine requires deep IM injection and can cause local irritation, but does not produce the **permanent skin staining** that makes iron dextran the definitive Z-track indication. - The key differentiator is the **severity and permanence of tissue complications**. *Injection Depomedroxyprogesterone* - This is a long-acting contraceptive administered intramuscularly, usually into the **deltoid** or **gluteal muscle**. - Standard deep IM technique is used; **Z-track method** is not routinely required as it doesn't cause significant skin staining or severe local tissue damage. *Injection Erythromycin* - Intramuscular erythromycin is rarely used due to significant pain at the injection site and is not a medication for which the **Z-track technique** is primarily indicated. - If given intramuscularly, general IM injection guidelines would be followed rather than the specialized Z-track method.

Question 843: The percentage of atropine present in atropine drops as cycloplegic is:

A. 1% (Correct Answer)
B. 4%
C. 2%
D. 0.5%

Explanation: ***1%*** - A **1% solution of atropine** is the standard concentration used as a cycloplegic agent for ophthalmic purposes. - This concentration is effective in causing **ciliary muscle paralysis** and pupillary dilation (mydriasis) for examination and treatment. *0.5%* - A **0.5% solution** of atropine is generally too weak to achieve a full and reliable cycloplegic effect in most clinical scenarios. - While it may cause some dilation, it often does not provide adequate **ciliary muscle paralysis** for comprehensive cycloplegic refraction. *4%* - A **4% solution** of atropine is an unusually high concentration for ophthalmic use and carries a significantly increased risk of systemic and local side effects. - Such a high concentration is not typically used as a cycloplegic due to the potential for severe adverse reactions like **tachycardia**, **dry mouth**, and **flushing**. *2%* - While a **2% solution** is stronger than the commonly used 1%, it is not the standard concentration and may lead to a higher incidence of side effects without a significant increase in cycloplegic efficacy. - The standard and most widely accepted concentration for atropine as a cycloplegic is **1%**, balancing efficacy and safety.

Question 844: What is the major side effect of Rubidomycin?

A. Hepatotoxicity
B. Nephrotoxicity
C. Ototoxicity
D. Cardiotoxicity (Correct Answer)

Explanation: ***Cardiotoxicity*** - **Rubidomycin** (also known as **daunorubicin**) is an **anthracycline antibiotic** chemotherapy drug, which is well-known for its dose-dependent **cardiotoxic effects**. - This can manifest as acute arrhythmias or delayed, irreversible **dilated cardiomyopathy** leading to heart failure. *Nephrotoxicity* - While some chemotherapy agents are nephrotoxic, **daunorubicin** is not primarily associated with significant kidney damage. - **Cisplatin** and **carboplatin** are examples of chemotherapy drugs more commonly linked to nephrotoxicity. *Hepatotoxicity* - Liver damage can occur with many drugs, but **daunorubicin**'s hepatic side effects are generally less severe and less common than its cardiac effects. - Drugs like **methotrexate** and **6-mercaptopurine** are more frequently associated with dose-limiting hepatotoxicity. *Ototoxicity* - **Ototoxicity**, causing hearing loss or tinnitus, is a known side effect of certain drugs like **cisplatin** and **aminoglycoside antibiotics**. - It is not a primary or significant side effect of **rubidomycin**.

Question 845: Which T cell surface molecule's co-stimulatory function is blocked by Abatacept?

A. CD11
B. CD20
C. CD22
D. CD28 (Correct Answer)

Explanation: ***CD28*** - **Abatacept** is a fusion protein that binds to **CD80** and **CD86** on antigen-presenting cells (APCs). - This binding prevents the interaction of **CD80/CD86** with **CD28** on T cells, thereby blocking the critical co-stimulatory signal required for full T-cell activation [1]. *CD11* - **CD11** is part of the **integrin** family (e.g., CD11b/CD18, known as Mac-1 or CR3) and is involved in cell adhesion and migration, primarily on myeloid cells. - It does not directly participate in the **T-cell co-stimulation pathway** targeted by abatacept. *CD20* - **CD20** is a B-cell specific surface molecule that is the target of **rituximab**, a monoclonal antibody used in various lymphomas and autoimmune diseases. - It is not expressed on T cells and therefore not involved in **T-cell co-stimulation** blocked by abatacept. *CD22* - **CD22** is a **B-cell co-receptor** molecule involved in B-cell activation and signaling, acting as a negative regulator. - It does not play a direct role in the **co-stimulatory signals** between APCs and T cells that are modulated by abatacept.

Question 846: What is a known side effect of clofazimine?

A. Reddish black skin discoloration (Correct Answer)
B. Hemolytic anaemia
C. Flu like syndrome
D. Axillary freckling

Explanation: ***Reddish black skin discoloration*** - **Clofazimine** is known to cause a dose-dependent and reversible **reddish-brown to black discoloration** of the skin, conjunctiva, and bodily secretions [1]. - This skin discoloration is a common and characteristic side effect associated with the drug's accumulation in fatty tissues and macrophages. *Hemolytic anaemia* - **Hemolytic anemia** is more commonly associated with drugs like **dapsone**, especially in patients with G6PD deficiency, or rifampicin in rare cases [1], [2]. - It is not a typical or well-known side effect of clofazimine. *Flu like syndrome* - **Flu-like syndrome** is a classic side effect associated with **rifampicin**, another drug used in the treatment of leprosy [2]. - This adverse effect is not characteristic of clofazimine. *Axillary freckling* - **Axillary freckling** (Crowe's sign) is a cutaneous manifestation associated with **neurofibromatosis type 1 (NF1)**. - It is a genetic condition and not a side effect of any medication.

Question 847: Which of the following causes retinal pigmentation?

A. Quinine
B. Chloroquine (Correct Answer)
C. Mefloquine
D. Atovaquone

Explanation: ***Chloroquine*** - Chloroquine can cause **retinal toxicity**, leading to **pigmentary changes** and potentially irreversible vision loss, particularly with prolonged use or high doses. - The characteristic finding is often described as **"bull's eye maculopathy,"** a central area of depigmentation surrounded by a ring of hyperpigmentation in the macula. *Quinine* - Quinine is known for causing **cinchonism**, which includes symptoms like **tinnitus**, headache, and blurred vision, but not typically retinal pigmentation. - While it can cause **visual disturbances**, these are usually related to **optic nerve toxicity** or vascular changes, not direct pigmentary retinopathy. *Mefloquine* - Mefloquine is associated with **neuropsychiatric side effects**, such as vivid dreams, anxiety, depression, and hallucinations, but not retinal pigmentation. - Its adverse ocular effects are less common than with chloroquine and do not typically involve permanent pigmentary changes to the retina. *Atovaquone* - Atovaquone is generally well-tolerated with common side effects including gastrointestinal upset, headache, and rash. - It is **not known to cause retinal pigmentation** or significant ocular toxicity.

Question 848: Nux vomica seeds contain 2 alkaloids, strychnine and which other alkaloid?

A. Hyoscine
B. Hyoscyamine
C. Atropine
D. Brucine (Correct Answer)

Explanation: ***Brucine*** - **Nux vomica seeds** (Strychnos nux-vomica) are known to contain two primary alkaloids: **strychnine** and **brucine**. - **Brucine** is structurally similar to strychnine but is generally less toxic and contributes to the bitter taste of the seeds. *Hyoscine* - **Hyoscine** (scopolamine) is an alkaloid found in plants like **deadly nightshade** (Atropa belladonna) and **Datura**. - It is known for its **anticholinergic** properties and is not a primary alkaloid of Nux vomica. *Hyoscyamine* - **Hyoscyamine** is another **tropane alkaloid** found in plants such as **henbane** (Hyoscyamus niger) and **deadly nightshade**. - It also exhibits **anticholinergic** effects and is not associated with Nux vomica seeds. *Atropine* - **Atropine** is a well-known **tropane alkaloid** found in plants of the **Solanaceae family**, like **Atropa belladonna**. - It is used as a potent **anticholinergic** agent and is not a constituent of Nux vomica.

Question 849: What is the approximate incidence of hepatotoxicity in patients receiving HAART?

A. 10% (Correct Answer)
B. 20%
C. 30%
D. 40%

Explanation: ***10%*** - The incidence of **hepatotoxicity** among patients on **HAART** (Highly Active Antiretroviral Therapy) is estimated to be around 10%. - This adverse effect can range from mild, asymptomatic enzyme elevations to **severe liver injury**. *20%* - While hepatotoxicity is a known complication of HAART, an incidence of 20% is generally considered higher than the average reported rates in most studies. - Higher rates might be encountered in specific high-risk populations, such as those with pre-existing liver disease or co-infection with viral hepatitis, but not as a general approximation. *30%* - An incidence of 30% for HAART-induced hepatotoxicity is significantly higher than typically observed and would suggest a higher level of risk than is generally presented in clinical literature. - Such high rates are usually associated with specific, older regimens or very vulnerable patient groups. *40%* - An incidence of 40% is exceptionally high for HAART-induced hepatotoxicity and would indicate a severe and frequent adverse reaction, which is not characteristic of modern HAART regimens. - This figure is not representative of the general incidence in patients receiving contemporary antiretroviral therapy.

Question 850: Which drug is associated with a defect in the ability to discriminate between blue and green colors?

A. Alprostadil
B. Sildenafil (Correct Answer)
C. Chloroquine
D. Quinidine

Explanation: ***Sildenafil*** - **Sildenafil** is a **PDE5 inhibitor** that can cause temporary visual disturbances, including difficulty distinguishing between **blue and green colors**. - This effect is due to its non-selective inhibition of **PDE6** in the retina, which plays a role in **color vision**. *Alprostadil* - **Alprostadil** is a **prostaglandin E1 analog** used to treat erectile dysfunction or maintain patency of the ductus arteriosus. - Its side effects primarily include **penile pain**, **priapism**, or **flushing**, and it is not associated with color vision defects. *Quinidine* - **Quinidine** is an **antiarrhythmic drug** that can cause "cinchonism," characterized by **tinnitus**, **headache**, and **visual disturbances**. - While it can cause visual blurring or photophobia, it is not specifically linked to the inability to discriminate between blue and green colors. *Chloroquine* - **Chloroquine** is an **antimalarial** and **immunomodulatory drug** that can cause irreversible **retinal toxicity** with long-term use. - This toxicity can lead to **central or pericentral scotomas** and general loss of visual acuity, but not specifically blue-green color discrimination issues.

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