General Pharmacology — MCQs

General Pharmacology Indian Medical PG Practice Questions and MCQs

Question 201: Which of the following conversions is false?

A. 1 qua = 1000 ml
B. 1 teaspoon = 5 ml
C. 1 tablespoon = 15 ml
D. 1 minim = 20 drops (Correct Answer)

Explanation: **Explanation:** In pharmacology, understanding the conversion between the Imperial (Apothecary) system and the Metric system is crucial for accurate dosage calculations. **1. Why Option D is the correct (False) statement:** A **minim** is a very small unit of volume in the apothecary system. In standard medical conversions, **1 minim is approximately equal to 1 drop (0.06 ml)**, not 20 drops. The statement "1 minim = 20 drops" is mathematically incorrect and would lead to a massive overdose if applied clinically. **2. Analysis of Incorrect Options (True Statements):** * **Option A (1 quart = 1000 ml):** In clinical practice, 1 quart is approximately equal to 1 liter (946 ml to be precise, but rounded to 1000 ml for medical exams). * **Option B (1 teaspoon = 5 ml):** This is a standard pharmaceutical conversion used for liquid oral medications (syrups/suspensions). * **Option C (1 tablespoon = 15 ml):** A tablespoon is equivalent to 3 teaspoons, totaling 15 ml. **High-Yield Clinical Pearls for NEET-PG:** * **1 Ounce (oz):** 30 ml (approx.) * **1 Pint:** 500 ml (approx.) * **1 Grain (gr):** 60–65 mg (Crucial for drugs like Aspirin or Phenobarbitone). * **1 Drop (gtt):** 0.06 ml. * **Micro-drip set:** 60 micro-drops = 1 ml. * **Macro-drip set:** 15–20 drops = 1 ml. **Note:** Always distinguish between a "drop" from a standard dropper (0.06 ml) and "drops" in an IV infusion set, as the latter depends on the drip factor of the equipment used.

Question 202: Which of the following statements is wrong?

A. Drugs should be highly lipid soluble to be administered transdermally.
B. Nitrates are given by sublingual route.
C. Intra-arterial injection is a systemic route of drug administration. (Correct Answer)
D. Parenteral route bypasses first-pass metabolism.

Explanation: **Explanation:** The correct answer is **C** because intra-arterial injection is considered a **local (topical)** route of administration, not a systemic one. **1. Why Option C is the correct (wrong statement):** Systemic routes (like oral, IV, or IM) aim to distribute the drug throughout the entire body via the general circulation. In contrast, **intra-arterial injection** is used to deliver a high concentration of a drug to a **specific organ or localized area** (e.g., anticancer drugs for limb malignancies or coronary angiography). Because the drug acts primarily on the target tissue before reaching the general venous circulation, it is classified as a local route. **2. Analysis of other options:** * **Option A:** Correct. For transdermal delivery (patches), drugs must be **highly lipid-soluble** and have low molecular weight to penetrate the stratum corneum of the skin. * **Option B:** Correct. **Nitrates** (like Nitroglycerin) are given sublingually to ensure rapid absorption and to bypass the extensive hepatic first-pass metabolism they would undergo if swallowed. * **Option C:** Correct. The **parenteral route** (IV, IM, SC) delivers drugs directly into the systemic circulation or tissues, bypassing the portal circulation (liver), thus avoiding first-pass metabolism. **NEET-PG High-Yield Pearls:** * **First-pass metabolism** occurs primarily in the liver, but also in the gut wall (e.g., Tyramine, Levodopa). * **Bioavailability** of IV drugs is 100%. * **Intrathecal** (into the CSF) is another example of a local route often confused with systemic routes. * Drugs with high first-pass metabolism: **L**ignocaine, **I**soprenaline, **N**itroglycerin, **P**ropranolol (**LINP**).

Question 203: Which of the following drugs binds to albumin?

A. Penicillin (Correct Answer)
B. Lidocaine
C. Propranolol
D. Verapamil

Explanation: **Explanation:** The binding of drugs to plasma proteins is a crucial pharmacokinetic parameter. The primary determinant of which protein a drug binds to is its chemical nature (pH). **1. Why Penicillin is Correct:** As a general rule, **acidic drugs** bind primarily to **Albumin**. Penicillin is an acidic drug, and therefore, it binds to albumin in the plasma. Other examples of acidic drugs binding to albumin include Warfarin, NSAIDs, Sulfonamides, and Phenytoin. **2. Why the Other Options are Incorrect:** Options B, C, and D (**Lidocaine, Propranolol, and Verapamil**) are all **basic drugs**. Basic drugs do not bind significantly to albumin; instead, they bind primarily to **$\alpha_1$-Acid Glycoprotein (AAG)** and occasionally to lipoproteins. * **Lidocaine:** A local anesthetic (basic). * **Propranolol:** A beta-blocker (basic). * **Verapamil:** A calcium channel blocker (basic). **3. NEET-PG High-Yield Pearls:** * **Albumin:** Has a high capacity but low affinity for acidic drugs. It possesses four main binding sites (Site I: Warfarin/Azapropazone site; Site II: Diazepam/Ibuprofen site). * **$\alpha_1$-Acid Glycoprotein (AAG):** An acute-phase reactant. Its levels increase during inflammation, surgery, or trauma, which can lead to decreased free (active) fractions of basic drugs like Lidocaine or Quinidine. * **Clinical Significance:** Only the **unbound (free) fraction** of a drug is pharmacologically active, metabolized, and excreted. In conditions like hypoalbuminemia (e.g., Nephrotic syndrome, Cirrhosis), the free fraction of acidic drugs increases, potentially leading to toxicity even with "normal" total drug levels.

Question 204: Rifampicin and ritonavir are examples of which type of drug antagonism?

A. Physical antagonist
B. Chemical antagonist
C. Pharmacokinetic antagonist (Correct Answer)
D. Competitive antagonist

Explanation: ### Explanation **Pharmacokinetic antagonism** occurs when one drug reduces the concentration of another drug at its site of action by interfering with its absorption, distribution, metabolism, or excretion (ADME) [1]. **Why Option C is correct:** Rifampicin is a potent **inducer of Cytochrome P450 enzymes** (specifically CYP3A4). When co-administered with Ritonavir (a protease inhibitor used in HIV treatment), Rifampicin increases the metabolic breakdown of Ritonavir. This leads to significantly decreased plasma levels of Ritonavir, rendering it sub-therapeutic [1]. Because the antagonism occurs via a metabolic pathway rather than at the receptor site, it is classified as pharmacokinetic antagonism. **Why the other options are incorrect:** * **A. Physical Antagonist:** Based on physical properties (e.g., Charcoal adsorbing alkaloids in the gut). * **B. Chemical Antagonist:** Involves a direct chemical reaction between two substances in solution (e.g., Chelating agents like EDTA binding to heavy metals or Antacids neutralizing gastric acid). * **D. Competitive Antagonist:** Occurs when a drug binds to the same receptor site as the agonist, shifting the dose-response curve to the right (e.g., Atropine vs. Acetylcholine). Rifampicin and Ritonavir do not compete for the same receptor. **High-Yield Clinical Pearls for NEET-PG:** * **Rifampicin** is the "classic" enzyme inducer. It reduces the efficacy of **Oral Contraceptive Pills (OCPs)**, Warfarin, and Corticosteroids. * **Ritonavir** is actually a potent **enzyme inhibitor**. In HIV therapy, it is often used in low doses as a "pharmacokinetic booster" for other protease inhibitors (like Lopinavir) to *increase* their plasma levels [1]. * **Pharmacodynamic antagonism** (the opposite concept) occurs at the receptor level (e.g., Beta-blockers vs. Adrenaline).

Question 205: Which skeletal muscle relaxant causes significant release of histamine?

A. Pancuronium
B. Atracurium
C. Gallamine
D. D-tubocurarine (Correct Answer)

Explanation: ### Explanation **Correct Option: D. D-tubocurarine** D-tubocurarine is a prototype non-depolarizing neuromuscular blocker (benzylisoquinoline class). It is notorious for causing **significant histamine release** from mast cells. This occurs through a direct non-immunologic mechanism. The systemic release of histamine leads to clinical manifestations such as **hypotension, bronchospasm, flushing, and excessive salivary/bronchial secretions**. Due to these side effects and the availability of safer alternatives, its clinical use is now obsolete. **Analysis of Incorrect Options:** * **A. Pancuronium:** An aminosteroid muscle relaxant. It does not cause histamine release but is known for its **vagolytic effect**, which causes tachycardia and hypertension. * **B. Atracurium:** While it can cause some histamine release (especially at high doses), it is significantly less potent in this regard than D-tubocurarine. Its primary clinical highlight is metabolism via **Hofmann elimination**, making it safe in liver and kidney failure. * **C. Gallamine:** An older synthetic agent that lacks significant histamine-releasing properties but, like pancuronium, has strong antimuscarinic (vagolytic) effects leading to tachycardia. **High-Yield Clinical Pearls for NEET-PG:** * **Histamine Releasers:** D-tubocurarine (Maximum) > Atracurium > Mivacurium. * **Safest in Renal/Hepatic Failure:** Atracurium and Cisatracurium (due to Hofmann elimination). * **Drug of Choice for Rapid Sequence Induction:** Succinylcholine (fastest onset, shortest duration). * **Vagolytic Agents:** Pancuronium and Gallamine (cause tachycardia). * **Cisatracurium:** An isomer of atracurium that is more potent and produces **negligible histamine release**, making it the preferred benzylisoquinoline in clinical practice.

Question 206: Effects mediated by H1 histamine receptor include?

A. Inhibition of gastric acid secretion
B. Induction of hepatic cytochrome P450 enzyme
C. Maintenance of a wakeful state (Correct Answer)
D. Vasoconstriction of arterioles

Explanation: **Explanation:** Histamine is a biogenic amine that acts through four types of G-protein coupled receptors ($H_1$ to $H_4$). Understanding the distribution and function of these receptors is high-yield for NEET-PG. **Why Option C is Correct:** $H_1$ receptors are widely distributed in the Central Nervous System (CNS), particularly in the tuberomammillary nucleus of the hypothalamus. Histaminergic neurons play a crucial role in the **maintenance of wakefulness and alertness**. This explains why first-generation antihistamines (like Diphenhydramine), which cross the blood-brain barrier and block central $H_1$ receptors, cause significant sedation. **Analysis of Incorrect Options:** * **Option A:** Gastric acid secretion is mediated by **$H_2$ receptors** located on the parietal cells of the stomach. $H_1$ receptors have no role in acid secretion. * **Option B:** Histamine does not induce hepatic enzymes. In fact, Cimetidine (an $H_2$ blocker) is a well-known **inhibitor** of the Cytochrome P450 system. * **Option C:** Activation of $H_1$ receptors typically causes **vasodilation** of arterioles (via nitric oxide release) and increased capillary permeability, leading to the "triple response." Vasoconstriction is not a primary effect of $H_1$ activation. **Clinical Pearls for NEET-PG:** 1. **$H_1$ Receptor Coupling:** It is a **$G_q$** protein-coupled receptor (activates the PLC-IP3/DAG pathway). 2. **Smooth Muscle:** $H_1$ stimulation causes bronchoconstriction and contraction of intestinal smooth muscle. 3. **Inverse Agonism:** Most "antihistamines" used clinically are technically inverse agonists rather than simple competitive antagonists. 4. **Second-Generation Antihistamines:** Drugs like Cetirizine and Loratadine are non-sedating because they have poor CNS penetration and high affinity for peripheral $H_1$ receptors.

Question 207: Which of the following statements about prostaglandins is true?

A. Prostaglandins are precursors to arachidonic acid.
B. Prostaglandins release arachidonic acid from membranes through the action of phospholipase A.
C. Prostaglandins were first observed to cause uterine contraction and lowering of blood pressure. (Correct Answer)
D. Although found in many organs, prostaglandins are synthesized only in the prostate and seminal vesicles.

Explanation: ### Explanation **Correct Option: C** Prostaglandins (PGs) were discovered in the 1930s when scientists (notably Kurzrok, Lieb, and later Ulf von Euler) observed that human semen contained substances capable of causing **strong contraction or relaxation of the uterine muscle** and **potent vasodilation**, leading to a lowering of blood pressure. This historical context is a classic "fact-based" high-yield point in general pharmacology. **Analysis of Incorrect Options:** * **Option A:** This is reversed. **Arachidonic acid is the precursor** to prostaglandins. It is a 20-carbon polyunsaturated fatty acid (eicosanoid precursor). * **Option B:** Prostaglandins do not release arachidonic acid. Instead, **Phospholipase A₂** acts on membrane phospholipids to release arachidonic acid, which is then converted into PGs by the **Cyclooxygenase (COX)** enzyme. * **Option D:** While the name "prostaglandin" originates from the belief that they were secreted solely by the prostate gland, we now know they are **ubiquitous**. They are synthesized in virtually all nucleated cells in the body (except RBCs) and act as local hormones (autacoids). **High-Yield Clinical Pearls for NEET-PG:** * **Rate-limiting step:** The release of arachidonic acid from the cell membrane by **Phospholipase A₂** (inhibited by Corticosteroids). * **Key Enzyme:** **COX-1** is constitutive (housekeeping), while **COX-2** is inducible (inflammatory). * **PGE2:** Known for cervical ripening, maintaining the Patency of Ductus Arteriosus (PDA), and causing fever. * **PGI2 (Prostacyclin):** Produced by vascular endothelium; acts as a potent vasodilator and inhibitor of platelet aggregation. * **TXA2 (Thromboxane):** Produced by platelets; acts as a potent vasoconstrictor and inducer of platelet aggregation.

Question 208: Which drugs should be avoided in G-6-PD deficiency?

A. Nalidixic acid
B. Dapsone
C. Sulfamethoxazole
D. All of the above (Correct Answer)

Explanation: Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is an X-linked recessive enzymatic disorder where red blood cells (RBCs) lack the ability to regenerate **reduced glutathione**. Glutathione is essential for neutralizing reactive oxygen species (ROS); without it, oxidative stress leads to hemoglobin denaturation (forming **Heinz bodies**) and subsequent hemolysis [1]. **Why "All of the Above" is correct:** Certain drugs act as oxidizing agents that increase the production of free radicals within RBCs. In G6PD-deficient individuals, these drugs trigger acute hemolytic anemia [1]. * **Nalidixic acid:** A quinolone antibiotic known to cause oxidative stress. * **Dapsone:** A sulfone used in leprosy; it is one of the most potent triggers of hemolysis in G6PD deficiency [2]. * **Sulfamethoxazole:** A sulfonamide antibiotic that frequently induces hemolytic crises in these patients. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Mnemonic for G6PD triggers (AAA):** **A**ntimalarials (Primaquine, Chloroquine), **A**ntibiotics (Sulfonamides, Nitrofurantoin, Fluoroquinolones), and **A**ntipyretics (high-dose Aspirin). * **Primaquine** is the most classic "textbook" trigger mentioned in exams. * **Rasburicase** (used for tumor lysis syndrome) is strictly contraindicated in G6PD deficiency. * **Diagnosis:** Peripheral smear during a crisis shows **"Bite cells"** (degluticytes) and **"Blister cells"** resulting from splenic macrophages removing Heinz bodies. * **Note:** Avoid testing G6PD enzyme levels during an acute hemolytic episode, as younger RBCs (reticulocytes) have higher enzyme levels and can yield a **false-normal** result.

Question 209: At pharmacological doses, unavoidable unwanted effects are called what?

A. Side effects (Correct Answer)
B. Idiosyncratic reaction
C. Toxicity
D. Pharmacogenetics

Explanation: ### Explanation **1. Why "Side Effects" is the correct answer:** Side effects are defined as **unavoidable, unwanted, but predictable** pharmacological effects that occur at **therapeutic (normal) doses**. They are an extension of the drug's mechanism of action. Because the drug targets receptors that may be present in multiple tissues, these effects occur alongside the intended therapeutic effect. For example, Atropine is used for its antispasmodic effect, but it inevitably causes dryness of the mouth due to its systemic anticholinergic action. **2. Why the other options are incorrect:** * **Idiosyncratic reaction:** These are **unpredictable**, genetically determined abnormal reactions to a drug (e.g., hemolysis in G6PD deficiency after taking Primaquine). Unlike side effects, they do not occur in everyone and are not related to the dose-response curve. * **Toxicity:** This refers to harmful effects occurring due to **excessive dosage** or prolonged use (overdosage). While side effects occur at pharmacological doses, toxicity occurs when the drug concentration exceeds the therapeutic window. * **Pharmacogenetics:** This is the **study** of how genetic variations influence an individual’s response to drugs. It is a field of study, not a type of adverse drug reaction itself. **3. High-Yield Clinical Pearls for NEET-PG:** * **Side Effect vs. Toxic Effect:** Side effects are seen at therapeutic doses; toxic effects are seen at high doses. * **Adverse Drug Reaction (ADR):** Any noxious and unintended response to a drug occurring at doses used for prophylaxis, diagnosis, or therapy. * **Secondary Effects:** These are indirect consequences of the primary action of a drug (e.g., Vitamin B deficiency or oral thrush occurring after prolonged use of broad-spectrum antibiotics). * **Type A vs. Type B Reactions:** Side effects are **Type A (Augmented)** reactions (predictable/dose-dependent), whereas Idiosyncrasy and Allergy are **Type B (Bizarre)** reactions (unpredictable/dose-independent).

Question 210: Which of the following local anaesthetics raises blood pressure instead of tending to cause a fall?

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

Explanation: **Explanation:** **Cocaine** is the correct answer because it is the only local anaesthetic (LA) that possesses significant **sympathomimetic** properties. While most LAs are vasodilators and can cause a fall in blood pressure (hypotension) due to direct myocardial depression and smooth muscle relaxation, cocaine inhibits the reuptake of norepinephrine (NET) at sympathetic nerve endings. This leads to an accumulation of catecholamines in the synaptic cleft, resulting in potent vasoconstriction, tachycardia, and a subsequent **rise in blood pressure (hypertension).** **Analysis of Incorrect Options:** * **Lignocaine (Lidocaine):** The most widely used LA; it causes vasodilation and is also used as a Class IB antiarrhythmic. In systemic toxicity, it typically causes hypotension. * **Procaine:** An ester-linked LA known for its short duration and significant vasodilatory effects. * **Dibucaine (Cinchocaine):** A potent, long-acting amide LA. Like most others in its class, it does not possess vasoconstrictive properties and tends to lower BP in toxic doses. **High-Yield Clinical Pearls for NEET-PG:** * **Vasoconstriction:** Cocaine is the only naturally occurring LA and the only one that causes vasoconstriction. All other LAs (except perhaps Mepivacaine/Ropivacaine which have minimal effects) are vasodilators. * **Adrenaline Addition:** Because most LAs are vasodilators, they are often combined with Adrenaline (1:200,000) to prolong duration of action and reduce systemic toxicity. * **Contraindication:** Never use Adrenaline with LAs for "end-artery" areas (fingers, toes, tip of nose, penis) to avoid gangrene. * **Cardiotoxicity:** Bupivacaine is the most cardiotoxic LA; Intralipid (lipid emulsion) is the antidote for systemic LA toxicity.

Practice by Chapter

Pharmacokinetics: Absorption and Distribution

Practice Questions

Pharmacokinetics: Metabolism and Excretion

Practice Questions

Pharmacodynamics and Receptor Theory

Practice Questions

Drug-Receptor Interactions and Dose-Response

Practice Questions

Pharmacogenetics and Personalized Medicine

Practice Questions

Adverse Drug Reactions and Toxicity

Practice Questions

Drug Interactions

Practice Questions

Drug Development and Regulation

Practice Questions

Pediatric and Geriatric Pharmacology

Practice Questions

Placental Transfer and Lactation

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free