General Pharmacology — MCQs

General Pharmacology Indian Medical PG Practice Questions and MCQs

Question 541: What is the role of magnesium [Mg] in the Inactivated Polio Vaccine (IPV)?

A. Adjuvant
B. Preservative
C. Antiinfective
D. Stabilizer (Correct Answer)

Explanation: ***Stabilizer*** - Magnesium (Mg) is included in IPV formulations primarily to **maintain the integrity and potency** of the viral antigens. - It helps prevent the **degradation of the inactivated poliovirus** particles, ensuring a consistent immune response upon vaccination. *Adjuvant* - Adjuvants are substances that **enhance the immune response** to an antigen, often by creating a depot effect or stimulating immune cells. - While essential in some vaccines, magnesium's role in IPV is not primarily to boost immunogenicity but to protect the antigen itself. *Preservative* - Preservatives are added to multi-dose vaccine vials to **prevent microbial contamination** after the vial has been opened. - Common preservatives include 2-phenoxyethanol or thimerosal (though less frequently used now), which have antimicrobial properties not shared by magnesium. *Antiinfective* - An antiinfective agent's primary function is to **kill or inhibit the growth of infectious microorganisms**. - Magnesium does not possess significant antiinfective properties at the concentrations used in vaccines and is not intended to treat or prevent infections in this context.

Question 542: Live influenza vaccine is given by which route?

A. Intradermal
B. Subcutaneous
C. Intramuscular
D. Intranasal (Correct Answer)

Explanation: ***Intranasal*** - The **live attenuated influenza vaccine (LAIV)** is specifically designed for **intranasal administration**, allowing it to mimic natural infection in the respiratory tract. - This route promotes a robust **mucosal immune response**, which is crucial for respiratory pathogens. *Intradermal* - **Intradermal vaccines** are typically administered into the dermis, beneath the epidermis. - While some influenza vaccines (e.g., Fluzone Intradermal) exist, the **live influenza vaccine** is not given via this route. *Subcutaneous* - **Subcutaneous injection** delivers the vaccine into the fatty tissue just under the skin. - While some vaccines are given subcutaneously, the **live attenuated influenza vaccine** is not. *Intramuscular* - Most **inactivated influenza vaccines** are administered intramuscularly, depositing the vaccine into muscle tissue. - The **live attenuated influenza vaccine** is not given via this route as it is designed to replicate in the upper respiratory tract.

Question 543: What is the mechanism of action of metyrosine?

A. Phenylethanolamine N-methyltransferase
B. Phenylalanine hydroxylase
C. Tyrosine hydroxylase (Correct Answer)
D. Tyrosinase

Explanation: ***Tyrosine hydroxylase*** - **Metyrosine** acts as a **competitive inhibitor** of **tyrosine hydroxylase**, which is a crucial enzyme in the **catecholamine synthesis pathway**. - By blocking this rate-limiting step, metyrosine reduces the production of **dopamine**, **norepinephrine**, and **epinephrine**. *Phenylethanolamine N-methyltransferase* - This enzyme converts **norepinephrine to epinephrine** and is not the primary target of metyrosine. - While metyrosine indirectly affects downstream products, its direct action is not on this enzyme. *Phenylalanine hydroxylase* - This enzyme converts **phenylalanine to tyrosine** and is associated with conditions like **phenylketonuria**. - It is not involved in the direct synthesis of catecholamines from tyrosine, nor is it the target of metyrosine. *Tyrosinase* - **Tyrosinase** is involved in the synthesis of **melanin**, not catecholamines. - Inhibition of this enzyme would primarily affect pigmentation, which is unrelated to metyrosine's therapeutic use.

Question 544: Rasburicase is a recombinant form of which enzyme?

A. Xanthine oxidase
B. IMP dehydrogenase
C. Adenosine Deaminase
D. Urate Oxidase (Correct Answer)

Explanation: ***Urate Oxidase*** - **Rasburicase** is a recombinant **urate oxidase** enzyme that catalyzes the oxidation of uric acid into allantoin. - This conversion makes uric acid more soluble and easier to excrete, thereby lowering serum uric acid levels, which is crucial in managing or preventing **tumor lysis syndrome** [2]. *Xanthine oxidase* - **Xanthine oxidase** is involved in the catabolism of purines, converting xanthine to uric acid [1]. - **Allopurinol**, a common drug for hyperuricemia, inhibits xanthine oxidase, but rasburicase does not act as an analogue or inhibitor of this enzyme [3], [4]. *IMP dehydrogenase* - **IMP dehydrogenase** is an enzyme involved in the de novo synthesis of guanine nucleotides from inosine monophosphate (IMP). - It is not directly involved in the catabolism of uric acid, and rasburicase has no known functional analogy to it. *Adenosine Deaminase* - **Adenosine deaminase** is an enzyme that catalyzes the deamination of adenosine to inosine. - Its deficiency is associated with a severe combined immunodeficiency (SCID), and it plays no direct role in uric acid metabolism related to rasburicase's action.

Question 545: Tocilizumab acts as an antagonist at which receptor?

A. IL-1
B. IL-2
C. IL-6 (Correct Answer)
D. TNF-alpha

Explanation: ***Correct: IL-6*** - **Tocilizumab** is a **monoclonal antibody** that specifically targets the **IL-6 receptor**, blocking the binding of **interleukin-6 (IL-6)** and inhibiting its pro-inflammatory effects. - This mechanism makes it effective in treating inflammatory conditions like **rheumatoid arthritis**, **giant cell arteritis**, and **cytokine release syndrome**. *Incorrect: IL-1* - **IL-1 antagonists**, such as **anakinra**, target the **IL-1 receptor** to block the inflammatory actions of **interleukin-1**. - These are typically used for conditions like **rheumatoid arthritis** and **cryopyrin-associated periodic syndromes (CAPS)**, distinct from tocilizumab's mechanism. *Incorrect: IL-2* - **IL-2 receptor antagonists**, such as **basiliximab** and **daclizumab**, are primarily used to prevent **organ transplant rejection** by inhibiting **T-cell activation**. - Their mechanism is different from **tocilizumab**, which targets a different cytokine pathway. *Incorrect: TNF-alpha* - **TNF-alpha inhibitors**, like **adalimumab** or **infliximab**, block the activity of **tumor necrosis factor-alpha**, a key cytokine in inflammation. - These agents are widely used for diseases such as **rheumatoid arthritis**, **psoriasis**, and **Crohn's disease**, but they operate on a different pathway than tocilizumab.

Question 546: Advantage of glycopyrrolate over atropine is?

A. It is a natural alkaloid
B. Can be used in OPC poisoning
C. Is more potent
D. It lacks central nervous system penetration (Correct Answer)

Explanation: ***It lacks central nervous system penetration.*** - **Glycopyrrolate** is a **quaternary ammonium compound** and is highly ionized, which prevents it from crossing the **blood-brain barrier**. - This characteristic significantly reduces the risk of **CNS side effects** such as sedation, confusion, or delirium, which are commonly associated with **atropine**. *It is a natural alkaloid* - **Atropine** is a **natural alkaloid** derived from plants like *Atropa belladonna*, whereas **glycopyrrolate** is a synthetic compound. - Being a natural alkaloid does not confer an advantage in terms of selective action or side effect profile. *Can be used in OPC poisoning* - Both **atropine** and **glycopyrrolate** can be used in the treatment of **organophosphate poisoning (OPC)** due to their anticholinergic properties. - However, **atropine** is generally preferred in acute OPC poisoning for its ability to reverse both peripheral and central muscarinic effects. *Is more potent* - While both are **antimuscarinic agents**, their potency can vary depending on the specific receptor subtype or clinical effect. - Glycopyrrolate is often cited for its potent **antisialagogue** (reducing saliva) effect, but atropine is more potent at blocking cardiac vagal effects.

Question 547: Which of the following conditions is treated with botulinum toxin?

A. Blepharospasm
B. Axillary hyperhidrosis
C. Cervical dystonia
D. All of the options (Correct Answer)

Explanation: **All of the options** - **Botulinum toxin** is widely used in medicine to treat various conditions characterized by **muscle overactivity** or excessive glandular secretion. - Its mechanism of action involves blocking the release of **acetylcholine** at neuromuscular junctions or nerve endings, leading to muscle paralysis or reduced glandular activity. *Axillary hyperhidrosis* - **Botulinum toxin** is an effective treatment for **severe primary axillary hyperhidrosis**, which is characterized by excessive sweating in the armpits. - It works by blocking the release of **acetylcholine** from sympathetic nerves that stimulate sweat glands, thereby reducing sweat production. *Blepharospasm* - **Blepharospasm** is a focal dystonia characterized by **involuntary twitching or sustained contractions** of the muscles around the eyes, leading to forceful eyelid closure. - **Botulinum toxin injections** into the orbicularis oculi muscle weaken the excessive muscle contractions, providing symptomatic relief. *Cervical dystonia* - **Cervical dystonia** (also known as spasmodic torticollis) involves **involuntary contractions of neck and shoulder muscles**, causing the head to twist or turn abnormally. - **Botulinum toxin injections** into the affected neck muscles help relax them, reducing pain and abnormal posturing.

Question 548: Which of the following compounds is most commonly used as an antacid in pharmaceutical formulations?

A. Potassium chlorate
B. Sodium bicarbonate (Correct Answer)
C. Potassium nitrate
D. Nitroglycerin

Explanation: ***Sodium bicarbonate*** - It readily reacts with **hydrochloric acid** in the stomach to produce water, carbon dioxide, and sodium chloride, effectively neutralizing stomach acid. - Its **rapid onset of action** makes it a popular choice for immediate relief from heartburn and indigestion. *Potassium chlorate* - This compound is primarily known for its use in **explosives** and as an **oxidizing agent**, not as an antacid. - Its ingestion can be **toxic**, causing methemoglobinemia and renal damage. *Potassium nitrate* - It is often used as a component in **toothpaste for sensitive teeth** to reduce pain, and in fertilizers, but not as an antacid. - It does not possess the necessary chemical properties to effectively neutralize stomach acid. *Nitroglycerin* - This compound is a potent **vasodilator** used primarily to treat angina (chest pain) by relaxing blood vessels. - It has **no antacid properties** and can cause significant side effects like hypotension and headaches.

Question 549: What is the active principle of the plant Calotropis?

A. Calotropin (Correct Answer)
B. Emodin
C. Ricin
D. Plumbagin

Explanation: ***Calotropin*** - **Calotropin** is the primary **cardiac glycoside** found in the latex of the *Calotropis* plant, responsible for its toxic and medicinal properties. - This compound exerts its effects by inhibiting the **Na+/K+-ATPase pump**, leading to increased intracellular calcium and potentially cardiotoxicity. *Plumbagin* - **Plumbagin** is a **naphthoquinone** derivative found in plants like *Plumbago zeylanica*, known for its antimicrobial and anticancer activities. - It is not associated with *Calotropis* and has a different chemical structure and mechanism of action compared to cardiac glycosides. *Ricin* - **Ricin** is a highly potent **protein toxin** derived from the seeds of the **castor bean plant** (*Ricinus communis*). - Its mechanism involves inhibiting protein synthesis, which is distinct from the cardiac glycoside action of *Calotropis*. *Emodin* - **Emodin** is an **anthraquinone** derivative commonly found in plants such as **rhubarb** and **aloe**, known for its laxative and anti-inflammatory properties. - It is structurally and functionally different from the cardiac glycosides found in *Calotropis*.

Question 550: Which drug acts primarily as a selective 5HT4 receptor agonist?

A. Loxiglumide
B. Renzapride (Correct Answer)
C. Atractiloside
D. Metoclopramide

Explanation: ***Renzapride*** - **Renzapride** is a **selective 5-HT4 receptor agonist** used to stimulate gut motility, particularly in conditions like chronic constipation. - It enhances the release of acetylcholine in the enteric nervous system, promoting **gastrointestinal motility**. - Unlike metoclopramide, renzapride's **primary mechanism** is 5-HT4 receptor agonism. *Loxiglumide* - **Loxiglumide** is an antagonist of the **cholecystokinin-A (CCK-A) receptor**, not the 5-HT4 receptor. - It is used experimentally to inhibit the effects of CCK, such as gallbladder contraction and pancreatic enzyme secretion. *Atractiloside* - **Atractiloside** is a plant toxin that interferes with mitochondrial function by inhibiting the **adenine nucleotide translocase (ANT)**. - It is not a pharmacological agent targeting serotonin receptors, but rather a mitochondrial poison. *Metoclopramide* - **Metoclopramide** primarily acts as a **D2 dopamine receptor antagonist**, which is its main mechanism for prokinetic effects. - While it has **some 5-HT4 agonistic activity**, this is a **secondary mechanism**, and its primary action is dopamine antagonism. - It is also a **5-HT3 antagonist** at higher doses, making it a mixed-mechanism drug rather than a selective 5-HT4 agonist like renzapride.

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