General Pharmacology — MCQs

General Pharmacology Indian Medical PG Practice Questions and MCQs

Question 521: Drug inhibiting granulocyte migration is:-

A. Montelukast
B. Colchicine (Correct Answer)
C. Cromoglycate
D. Felbamate

Explanation: ***Colchicine*** - **Colchicine** inhibits **granulocyte migration** by binding to tubulin, thereby disrupting microtubule assembly and function [2]. - This action is crucial in its use for conditions like **gout**, where it reduces the inflammatory response by preventing neutrophil chemotaxis to crystal deposits [1], [2]. *Montelukast* - **Montelukast** is a **leukotriene receptor antagonist** that primarily reduces bronchoconstriction and inflammation. - While it affects inflammatory pathways, its direct action is not inhibiting granulocyte migration but rather blocking the effects of leukotrienes. *Cromoglycate* - **Cromoglycate** (e.g., cromolyn sodium) is a **mast cell stabilizer** that prevents the release of inflammatory mediators. - Its main mechanism involves preventing mast cell degranulation, not directly inhibiting granulocyte migration. *Felbamate* - **Felbamate** is an **antiepileptic drug** used in the treatment of seizures. - Its mechanism of action involves blocking NMDA receptors and modulating GABAergic transmission; it has no known role in inhibiting granulocyte migration.

Question 522: 'Store in a cool place' is written on a drug label. It means drug should be stored at a temperature of:

A. 0 degree Celsius
B. 2-8 degree Celsius
C. -2 degree Celsius
D. 8-15 degree Celsius (Correct Answer)

Explanation: ***8-15 degree Celsius*** - According to **USP (United States Pharmacopeia)** and **IP (Indian Pharmacopoeia)** guidelines, "store in a **cool place**" specifically refers to a temperature range between **8 and 15 degrees Celsius**. - This is distinct from refrigeration and is suitable for medications that require cooler storage than room temperature but should not be refrigerated. - This temperature range helps maintain the **stability** and **efficacy** of temperature-sensitive medications. *2-8 degree Celsius* - This temperature range defines **"refrigeration"** or storage in a **"cold place"**, not a "cool place." - Refrigeration is indicated by the specific instruction "Store in refrigerator" or "Keep refrigerated" on drug labels. - Many biologics, vaccines, and insulin preparations require refrigeration at this temperature. *0 degree Celsius* - This temperature is the **freezing point of water**, and storing drugs at this temperature could lead to freezing, which can damage the drug's formulation. - Frozen medications may undergo **physical or chemical degradation**, particularly if they are aqueous solutions. - This is not indicated by "cool place" storage instructions. *-2 degree Celsius* - This temperature indicates storing the drug **below freezing**, which is only appropriate for specific **frozen products** with explicit freezing instructions. - **Freezing** can irreversibly alter the drug's structure, potentially affecting its safety and effectiveness. - This is well outside the range for "cool place" storage.

Question 523: G-protein coupled receptor that does not act through opening of potassium channels is:

A. Dopamine D2 receptor
B. Muscarinic M2 receptor
C. Serotonin 5 HT 1 receptor
D. Angiotensin 1 receptor (Correct Answer)

Explanation: ***Angiotensin 1 receptor*** - The **angiotensin 1 receptor (AT1R)** is a **Gq-coupled receptor** that primarily activates the **phospholipase C (PLC)** pathway, leading to increased intracellular **calcium** and **IP3/DAG** signaling. - Its activation mediates vasoconstriction, aldosterone release, and cardiac hypertrophy, none of which involve direct opening of potassium channels. *Dopamine D2 receptor* - **Dopamine D2 receptors** are **Gi/o-coupled receptors** that inhibit adenylyl cyclase and **open potassium channels**, leading to **hyperpolarization** and reduced neuronal excitability. - This action contributes to its **antipsychotic** and **motor control** effects. *Muscarinic M2 receptor* - **Muscarinic M2 receptors** are **Gi/o-coupled receptors** found in the heart that cause **bradycardia** by activating **acetylcholine-gated inwardly rectifying potassium (GIRK) channels**, leading to hyperpolarization. - They also inhibit adenylyl cyclase, reducing cAMP levels and decreasing heart rate and contractility. *Serotonin 5 HT 1 receptor* - **Serotonin 5-HT1 receptors** (e.g., 5-HT1A) are **Gi/o-coupled receptors** that, upon activation, **increase potassium conductance** (hyperpolarization) and inhibit adenylyl cyclase. - This leads to a reduction in neuronal firing and is implicated in the anxiolytic and antidepressant effects of these receptors.

Question 524: All of the following statements about insulin Afrezza are true except:

A. Inhalational preparation of insulin
B. Requires multiple inhalations per administration
C. Used in combination with short acting insulin (Correct Answer)
D. Not a substitute for long-acting injectable insulin

Explanation: ***Used in combination with short acting insulin*** - Insulin Afrezza is a **rapid-acting inhaled insulin** that is typically used *before meals* as a prandial insulin. - It is used **in combination with a long-acting (basal) insulin**, not short-acting insulin, to manage blood glucose levels. - Afrezza itself IS a rapid-acting insulin, so combining it with another short-acting insulin would be redundant. *Inhalational preparation of insulin* - Afrezza is an **inhaled insulin preparation**, delivered via a small, hand-held inhaler device. - This delivery method offers a **needle-free alternative** for mealtime insulin administration. *Requires multiple inhalations per administration* - Each dose of Afrezza often requires **multiple inhalations** to deliver the prescribed insulin unitage, depending on the cartridge size (4, 8, or 12 units). - This can be perceived as less convenient than a single injection for some patients. *Not a substitute for long-acting injectable insulin* - Afrezza is an **alternative to rapid-acting injectable insulin** for mealtime glucose control. - However, patients still require **long-acting basal insulin** (such as insulin glargine or detemir), which is usually administered via injection, to manage blood glucose between meals and overnight. - Afrezza does NOT replace the need for basal insulin therapy.

Question 525: What is the mechanism of action of acetazolamide in the treatment of glaucoma?

A. Increases aqueous humor production
B. Increases intraocular pressure
C. Decreases aqueous outflow
D. Decreases aqueous production (Correct Answer)

Explanation: ***Decreases aqueous production*** - **Acetazolamide** is a **carbonic anhydrase inhibitor** that acts on the **ciliary body** to reduce the formation of **bicarbonate ions** [2]. - This reduction in bicarbonate ions subsequently decreases the amount of fluid and solutes entering the **posterior chamber**, thereby lowering **aqueous humor production** and **intraocular pressure (IOP)** [2]. *Increases aqueous humor production* - This is incorrect; acetazolamide's therapeutic effect in glaucoma is specifically to **decrease** aqueous humor production [2]. - Increased aqueous humor production would lead to an **increase** in intraocular pressure, worsening glaucoma [1]. *Increases intraocular pressure* - This is incorrect; the primary goal of acetazolamide in glaucoma treatment is to **lower intraocular pressure**, not increase it [2]. - An increase in IOP is detrimental in glaucoma, leading to optic nerve damage [1]. *Decreases aqueous outflow* - This is incorrect; acetazolamide does not primarily affect the outflow pathways (e.g., **trabecular meshwork** or **uveoscleral outflow**) [1]. - A decrease in aqueous outflow would lead to an **increase in IOP**, which is contrary to the drug's intended action [1].

Question 526: Which of the following is the primary neurotransmitter involved in nausea and vomiting associated with chemotherapy?

A. Dopamine
B. Acetylcholine
C. GABA
D. Serotonin (Correct Answer)

Explanation: ***Serotonin*** - **Serotonin (5-HT)**, particularly acting on **5-HT3 receptors**, is a major neurotransmitter mediating chemotherapy-induced nausea and vomiting (CINV). - Chemotherapeutic agents can damage **enterochromaffin cells** in the gastrointestinal tract, leading to the release of serotonin, which then stimulates vagal afferents and the **chemoreceptor trigger zone (CTZ)**. *Dopamine* - **Dopamine (D2 receptors)** plays a role in nausea and vomiting, particularly in the **chemoreceptor trigger zone (CTZ)**. - While dopamine antagonists can be used as antiemetics, **serotonin** is considered the primary neurotransmitter in CINV due to the direct impact of chemotherapy on serotonin release. *Acetylcholine* - **Acetylcholine** is involved in motion sickness and is targeted by **anticholinergic antiemetics (e.g., scopolamine)**. - Its primary role in CINV is less significant compared to serotonin, which has a more direct link to the mechanisms of chemotherapy. *GABA* - **GABA (gamma-aminobutyric acid)** is the main inhibitory neurotransmitter in the brain and can reduce anxiety and modulate vomiting. - While **benzodiazepines**, which enhance GABAergic activity, are used as adjuncts in CINV to reduce **anticipatory nausea** and anxiety, GABA itself is not the primary mediator of the emetic response to chemotherapy.

Question 527: A patient with cyanosis and methemoglobinemia is treated with methylene blue. What is the mechanism of action of this drug?

A. Acts as an oxygen transporter
B. Reduces methemoglobin to hemoglobin (Correct Answer)
C. Inhibits cytochrome c oxidase
D. Oxidizes ferrous iron to ferric iron in hemoglobin

Explanation: ***Reduces methemoglobin to hemoglobin*** - Methylene blue acts as an **electron acceptor** for **NADPH-methemoglobin reductase**, facilitating the reduction of ferric iron (Fe3+) in methemoglobin back to its functional ferrous state (Fe2+) in hemoglobin. - This process restores the **oxygen-carrying capacity** of hemoglobin, alleviating the symptoms of methemoglobinemia. *Acts as an oxygen transporter* - Methylene blue does not directly transport oxygen; its role is to **restore the ability of hemoglobin** to bind oxygen. - Oxygen transport is the primary function of **hemoglobin**, which is compromised in methemoglobinemia. *Oxidizes ferrous iron to ferric iron in hemoglobin* - This is the opposite of methylene blue's therapeutic effect; **oxidation of ferrous iron (Fe2+) to ferric iron (Fe3+)** is precisely what causes methemoglobinemia. - Methylene blue's mechanism involves **reducing ferric iron** back to ferrous iron. *Inhibits cytochrome c oxidase* - Inhibition of **cytochrome c oxidase** is the mechanism of action for certain toxins like **cyanide**, leading to cellular hypoxia. - Methylene blue does not primarily act on the electron transport chain in this manner for the treatment of methemoglobinemia.

Question 528: Which of the following is NOT a synthetic pyrethroid compound?

A. DDT (Correct Answer)
B. Permethrin
C. Cypermethrin
D. Prallethrin

Explanation: ***DDT*** - **DDT** (dichlorodiphenyltrichloroethane) is a **chlorinated hydrocarbon insecticide**, not a synthetic pyrethroid. - It was widely used in the past but is now banned in many countries due to its **environmental persistence** and toxicity. *Permethrin* - **Permethrin** is a common **synthetic pyrethroid** used as an insecticide and acaricide, often found in mosquito nets and topical treatments for lice. - It works by disrupting the nervous system of insects, leading to **paralysis and death**. *Prallethrin* - **Prallethrin** is a **synthetic pyrethroid** commonly used in indoor insecticide products, such as mosquito coils and mats. - It is effective against various flying insects and has a **rapid knockdown effect**. *Cypermethrin* - **Cypermethrin** is a **synthetic pyrethroid** widely used in agriculture, public health, and pest control. - It is known for its effectiveness against a broad spectrum of insect pests and its **photostability**.

Question 529: A 50-year-old male with hyperlipidemia is prescribed a statin. What is the primary mechanism of action of statins?

A. Inhibition of HMG-CoA reductase (Correct Answer)
B. Inhibition of cholesterol absorption
C. Stimulation of lipoprotein lipase
D. Inhibition of bile acid reabsorption

Explanation: ***Inhibition of HMG-CoA reductase*** - Statins primarily act by inhibiting **3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase**, a key enzyme in the cholesterol synthesis pathway in the liver. - This inhibition leads to a decrease in **hepatic cholesterol production**, which in turn upregulates LDL receptors on liver cells, increasing the clearance of LDL from the blood. *Inhibition of cholesterol absorption* - This mechanism is characteristic of drugs like **ezetimibe**, which specifically block the **Niemann-Pick C1-like 1 (NPC1L1)** protein in the small intestine. - While it lowers cholesterol, it is not the primary action of statins. *Stimulation of lipoprotein lipase* - **Lipoprotein lipase (LPL)** activity primarily enhances the clearance of **triglyceride-rich lipoproteins** from the circulation. - Fibrates, for example, increase LPL activity, whereas statins exert their main effect through cholesterol synthesis inhibition. *Inhibition of bile acid reabsorption* - This mechanism is associated with **bile acid sequestrants** (e.g., cholestyramine), which bind to bile acids in the intestine, preventing their reabsorption and increasing their fecal excretion. - This forces the liver to use more cholesterol to synthesize new bile acids, thereby lowering serum cholesterol, but it is not a statin's mechanism.

Question 530: A patient is given epinephrine to treat anaphylaxis. Which second messenger system is primarily activated by epinephrine in this situation?

A. cAMP (Correct Answer)
B. cGMP
C. IP3/DAG
D. Calcium ions

Explanation: ***cAMP*** - Epinephrine primarily acts on **β-adrenergic receptors**, which are G-protein coupled receptors. - Activation of β-adrenergic receptors leads to the stimulation of **adenylyl cyclase**, which converts ATP to **cyclic AMP (cAMP)**, initiating a cascade of intracellular events. *cGMP* - **cGMP** is primarily associated with the activation of **guanylyl cyclases**, which are often stimulated by nitric oxide or natriuretic peptides. - It plays a significant role in **vascular smooth muscle relaxation** and visual transduction, not the primary anaphylactic response to epinephrine. *IP3/DAG* - The **inositol triphosphate (IP3)** and **diacylglycerol (DAG)** pathway is activated by Gq-protein coupled receptors, leading to the mobilization of intracellular calcium and activation of protein kinase C. - While epinephrine can activate **α1-adrenergic receptors** which use this pathway, the predominant life-saving effects in anaphylaxis (bronchodilation, vasoconstriction, cardiac stimulation) are mediated by β-receptors via cAMP. *Calcium ions* - Although **calcium ions** act as a universal second messenger, their increase in the context of epinephrine's primary action in anaphylaxis is often a consequence of other second messenger pathways, such as **IP3/DAG** or direct effects on voltage-gated channels. - **cAMP** is the direct and primary second messenger system activated by the major therapeutic targets of epinephrine during anaphylaxis.

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