General Pharmacology — MCQs

General Pharmacology Indian Medical PG Practice Questions and MCQs

Question 571: Which of the following is a long-acting local anesthetic?

A. Dibucaine (Correct Answer)
B. Prilocaine
C. Procaine
D. Lignocaine

Explanation: ***Dibucaine*** - **Dibucaine** is a **long-acting amide local anesthetic** with a duration of action up to 10 hours. - Its high **lipid solubility** contributes to its prolonged effect and greater potency compared to other local anesthetics. *Prilocaine* - **Prilocaine** is considered an **intermediate-duration amide local anesthetic**, with a duration of action typically 1-2 hours. - It carries a risk of **methemoglobinemia** at higher doses, which differentiates it from longer-acting agents. *Procaine* - **Procaine** is a **short-acting ester local anesthetic**, with a duration of action usually less than 1 hour. - It is known for its relatively **high allergenicity** due to its metabolism to para-aminobenzoic acid (PABA). *Lignocaine* - **Lignocaine (Lidocaine)** is an **intermediate-acting amide local anesthetic**, with a duration of action around 1-3 hours. - It is one of the most commonly used local anesthetics, but its duration is not as long as that of dibucaine.

Question 572: A patient undergoing a minor surgical procedure is given lignocaine injection. Assertion: Local anaesthetics act by blocking nerve conduction. Reason: Small fibers and non-myelinated fibers are blocked more easily than large myelinated fibers.

A. Assertion is false, but Reason is true
B. Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion (Correct Answer)
C. Both Assertion and Reason are true, and Reason is the correct explanation for Assertion
D. Assertion is true, but Reason is false

Explanation: ***Both Assertion and Reason are true, and Reason is NOT the correct explanation for Assertion*** - The **Assertion** is true: Local anesthetics (like lignocaine) block nerve conduction by inhibiting **voltage-gated sodium channels**, preventing the depolarization necessary for action potential propagation - The **Reason** is also true: Small diameter and non-myelinated fibers (like C and Aδ pain fibers) are blocked more easily than large myelinated fibers (like Aα motor fibers), which explains the **differential blockade** pattern seen clinically - However, the **Reason does NOT explain WHY** local anesthetics block nerve conduction—it describes **WHICH** nerve fibers are blocked preferentially. The mechanism of blocking conduction is sodium channel inhibition, not fiber size selectivity - The differential sensitivity is a consequence of fiber characteristics (surface area-to-volume ratio, number of nodes of Ranvier), not the explanation for the blocking mechanism itself *Both Assertion and Reason are true, and Reason is the correct explanation for Assertion* - While both statements are individually true, the Reason does not explain the **mechanism** by which local anesthetics block nerve conduction - The Reason addresses fiber **selectivity**, which is a separate pharmacological property from the **mechanism of action** (sodium channel blockade) *Assertion is true, but Reason is false* - The Assertion is demonstrably true—local anesthetics block nerve conduction - The Reason is also true—this is well-established pharmacology: autonomic (small) > sensory (medium) > motor (large) fiber blockade sequence *Assertion is false, but Reason is true* - The Assertion is fundamentally correct and represents the primary pharmacological action of local anesthetics - Blocking nerve conduction is the therapeutic goal of local anesthetic administration

Question 573: From which part of the Papaver somniferum plant does the latex, commonly referred to as 'milk', exude?

A. Leaf of the plant
B. Root of the plant
C. Seeds of the plant
D. Unripe capsule of the plant (Correct Answer)

Explanation: ***Unripe capsule of the plant*** - The **latex** (or 'milk') containing **opioid alkaloids** like morphine and codeine is primarily harvested by incising the **unripe seed capsules** of the *Papaver somniferum* plant. - This milky sap is then collected and dried to produce **crude opium**. *Leaf of the plant* - The leaves of *Papaver somniferum* do not contain significant amounts of the latex and are not the primary source of **opium alkaloids**. - While some **alkaloids** might be present in trace amounts, they are not extracted commercially from the leaves. *Root of the plant* - The roots of the poppy plant are not known to exude latex or to be a significant source of medically relevant **opioid alkaloids**. - Their primary function is absorption of water and nutrients, and anchoring the plant. *Seeds of the plant* - While the dried seeds are used for culinary purposes (poppy seeds), they contain very low levels of **opioid alkaloids** compared to the latex. - The latex is produced within the **capsule** before the seeds fully mature.

Question 574: What is the primary component extracted from the Cannabis Indica plant used in traditional medicine?

A. Leaves of Cannabis Indica
B. Flowers of Cannabis Indica (Correct Answer)
C. Resin of Cannabis Indica
D. Stem of Cannabis Indica

Explanation: ***Flowers of Cannabis Indica*** - The **flowers** (also called buds or flowering tops) are the primary component extracted from *Cannabis Indica* for traditional and modern medicinal use. - The female flowers contain the highest concentration of **trichomes**, which produce cannabinoids such as **THC** and **CBD**. - In traditional medicine systems including Ayurveda, the **flowering tops** were the principal medicinal part used. - The flowers are the **primary botanical source** from which all cannabis-based medicines are derived. *Resin of Cannabis Indica* - Resin refers to concentrated **secondary extracts** like hashish or cannabis oil, which are processed products derived from the flowers. - While resin has high cannabinoid content, it is not the primary plant component but rather a concentrated derivative. - Resin is obtained by processing the trichomes from the flowers, making it a downstream product. *Leaves of Cannabis Indica* - While leaves contain some cannabinoids, their concentration is generally much **lower** compared to the flowers. - Leaves are less commonly used as the primary medicinal component due to their significantly lower potency. - They may be used in some traditional preparations but are not the primary component. *Stem of Cannabis Indica* - The stem primarily consists of **fibrous material** and has minimal cannabinoid concentration. - It is not traditionally used as a medicinal component due to its lack of significant active ingredients. - Stems are primarily used for fiber (hemp) rather than medicinal applications.

Question 575: Which of the following vaccines is not freeze-dried?

A. Measles Vaccine
B. Diphtheria, Pertussis, and Tetanus (DPT) Vaccine (Correct Answer)
C. Rubella Vaccine
D. BCG Vaccine

Explanation: ***Diphtheria, Pertussis, and Tetanus (DPT) Vaccine*** - The DPT vaccine is a **liquid vaccine** that contains inactivated toxins and bacterial components, making it stable in liquid form. - It does not require **freeze-drying** because its components are chemically stable and do not degrade significantly in solution. *Measles Vaccine* - The measles vaccine is a **live attenuated vaccine** that needs to be freeze-dried to maintain the viability and stability of the live virus. - Freeze-drying helps preserve the vaccine's potency by removing water, which prevents degradation during storage and transport. *Rubella Vaccine* - Similar to the measles vaccine, the rubella vaccine is a **live attenuated vaccine** and is therefore provided in a freeze-dried form. - This process ensures the long-term stability and efficacy of the viral components, which would otherwise degrade in a liquid state. *BCG Vaccine* - The BCG (Bacillus Calmette-Guérin) vaccine is a **live attenuated bacterial vaccine** used against tuberculosis, and it is also manufactured as a freeze-dried product. - Freeze-drying is essential for maintaining the viability of the live attenuated *Mycobacterium bovis* strain.

Question 576: Which of the following is an example of topical administration producing only local effects (not systemic)?

A. Topical corticosteroid cream (Correct Answer)
B. Sublingual nitroglycerin
C. Transdermal patch
D. Rectal diazepam

Explanation: ***Topical corticosteroid cream*** - When applied to the skin for conditions like dermatitis, topical corticosteroids primarily exert their effects at the site of application, reducing **local inflammation** and itching. - While systemic absorption can occur with potent steroids over large areas, typical use aims for **localized action** without significant systemic effects. *Sublingual nitroglycerin* - This route is designed for **rapid systemic absorption** through the oral mucosa, bypassing first-pass metabolism to quickly treat angina. - The goal is a **widespread vasodilatory effect** throughout the body, not a local one within the mouth. *Transdermal patch* - Transdermal patches, such as those for nicotine or fentanyl, are specifically designed to deliver medication **systemically** through the skin into the bloodstream over a prolonged period. - They provide a **sustained release** and systemic therapeutic effect throughout the body. *Rectal diazepam* - Administered rectally, diazepam is absorbed into the systemic circulation to produce **CNS effects** such as sedation, anxiolysis, or anticonvulsant activity. - Although the administration is local, the intended clinical effect is **systemic** and widespread throughout the body.

Question 577: What is the classification of Lorcaserin?

A. Anti-anxiety
B. Anti-smoking
C. Anti-helminthic
D. Anti-obesity (Correct Answer)

Explanation: ***Anti-obesity*** - Lorcaserin is a selective **serotonin 5-HT₂C receptor agonist** that works by promoting satiety and reducing food intake. - It is prescribed as a long-term treatment for **weight management** in adults who are obese or overweight with at least one weight-related comorbidity. *Anti-anxiety* - Anti-anxiety medications, such as **benzodiazepines** or **SSRIs**, primarily target neurotransmitters like GABA or serotonin 5-HT₁A receptors to reduce anxiety symptoms. - Lorcaserin's primary mechanism of action is distinct, focusing on the 5-HT₂C receptor for appetite regulation, not anxiety. *Anti-smoking* - Anti-smoking medications, like **varenicline** or **bupropion**, are designed to reduce nicotine cravings and withdrawal symptoms. - Their mechanisms often involve nicotinic acetylcholine receptors or dopamine and norepinephrine reuptake inhibition, which differs from lorcaserin's action. *Anti-helminthic* - Anti-helminthic drugs are used to treat **parasitic worm infections** by paralyzing or killing the worms. - Common examples include **albendazole** or **mebendazole**, which have no relation to appetite control or obesity treatment.

Question 578: Which of the following pairs are considered physiological antagonists in pharmacology?

A. Adrenaline and Isoprenaline
B. Isoprenaline and Propranolol
C. Histamine and Adrenaline (Correct Answer)
D. All of the options

Explanation: ***Histamine and Adrenaline*** - **Physiological antagonism** occurs when two drugs produce opposite effects by acting on different receptors or pathways. - **Histamine** causes bronchoconstriction and vasodilation, while **adrenaline** causes bronchodilation and vasoconstriction, counteracting each other's effects through different mechanisms. *Adrenaline and Isoprenaline* - Both **adrenaline** and **isoprenaline** are **adrenergic agonists** that produce similar physiological effects, primarily through beta-adrenergic receptor activation. - They are not physiological antagonists but rather have **synergistic** or similar pharmacological actions. *Isoprenaline and Propranolol* - **Isoprenaline** is a **beta-adrenergic agonist**, while **propranolol** is a **beta-adrenergic antagonist**. - This is an example of **pharmacological antagonism (receptor antagonism)**, where one drug blocks the effect of another at the same receptor site, rather than physiological antagonism.

Question 579: Which of the following is not a common side effect of clonidine?

A. Xerostomia
B. Sedation
C. Diarrhea (Correct Answer)
D. Impotency

Explanation: ***Diarrhea*** - **Clonidine** commonly causes **constipation**, not diarrhea, due to its **alpha-2 adrenergic agonist** effects, which decrease gastrointestinal motility. - Diarrhea is not typically associated with clonidine's mechanism of action or adverse effect profile. *Xerostomia* - **Xerostomia** (dry mouth) is a very common side effect of **clonidine** occurring in up to 40% of patients. - This results from **alpha-2 agonist** activity that reduces sympathetic stimulation of salivary gland secretions. - This symptom can significantly impact patient compliance and quality of life. *Sedation* - **Sedation** is a frequent side effect of **clonidine**, particularly when initiating treatment or increasing dosage, because it acts as an **alpha-2 agonist** in the central nervous system, reducing sympathetic outflow and promoting drowsiness. - Patients are often advised to avoid driving or operating heavy machinery until they know how the medication affects them. *Impotency* - **Impotency** or **erectile dysfunction** is a recognized and common sexual side effect of **clonidine**, which can interfere with quality of life and adherence to treatment for hypertension. - This effect is related to the drug's impact on the autonomic nervous system and vascular tone through central alpha-2 agonism.

Question 580: Which of the following is a PGE1 analogue used in medical treatments?

A. Carboprost
B. Alprostadil (Correct Answer)
C. Epoprostenol
D. Dinoprostone

Explanation: ***Alprostadil*** - **Alprostadil** is a synthetic **prostaglandin E1 (PGE1)** analogue. - It is used in neonates to maintain the **patency of the patent ductus arteriosus** and in adults for the treatment of **erectile dysfunction**. *Carboprost* - **Carboprost** is a synthetic analogue of **prostaglandin F2 alpha (PGF2α)**. - It is primarily used to manage **postpartum hemorrhage** due to its potent uterotonic effects. *Epoprostenol* - **Epoprostenol** is a synthetic analogue of **prostacyclin (PGI2)**. - It is known for its potent **vasodilatory** and **antiplatelet** properties, making it useful in treating **pulmonary arterial hypertension**. *Dinoprostone* - **Dinoprostone** is a synthetic form of **prostaglandin E2 (PGE2)**. - It is used to **induce labor** or **cervical ripening** due to its role in uterine contractions and cervical dilation.

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