General Pharmacology — MCQs

General Pharmacology Indian Medical PG Practice Questions and MCQs

Question 251: What is a G-protein coupled receptor?

A. Metabotropic receptor (Correct Answer)
B. Ionic receptor
C. Kinase-linked receptor
D. Nuclear receptor

Explanation: ### Explanation **Correct Option: A. Metabotropic receptor** G-protein coupled receptors (GPCRs) are known as **metabotropic receptors** because their activation initiates a metabolic cascade within the cell. Unlike ion channels that act directly, GPCRs work indirectly through a transducer (G-protein) and a second messenger (e.g., cAMP, IP3/DAG). They are the largest family of cell surface receptors and are characterized by a **7-transmembrane (heptahelical)** structure. **Why other options are incorrect:** * **B. Ionic receptor (Ionotropic):** These are ligand-gated ion channels (e.g., Nicotinic ACh, GABA-A, NMDA). They act very rapidly (milliseconds) by directly opening a pore for ions, without involving G-proteins. * **C. Kinase-linked receptor:** These receptors (e.g., Insulin, Growth Factors) possess intrinsic enzymatic activity or are closely associated with cytosolic kinases (JAK-STAT). They involve protein phosphorylation rather than G-protein signaling. * **D. Nuclear receptor:** These are intracellular receptors (e.g., Steroids, Thyroid hormones) that act as transcription factors to regulate gene expression. They have the slowest onset of action (hours to days). **High-Yield Clinical Pearls for NEET-PG:** * **Structure:** GPCRs are "7-pass" receptors; the N-terminus is extracellular, and the C-terminus is intracellular. * **G-protein types:** * **Gs:** Stimulates Adenylyl Cyclase (e.g., $\beta_1, \beta_2, D_1$). * **Gi:** Inhibits Adenylyl Cyclase (e.g., $\alpha_2, M_2, D_2$). * **Gq:** Activates Phospholipase C $\rightarrow$ IP3/DAG (e.g., $\alpha_1, M_1, M_3$). * **Speed of Action:** Ionotropic (Fastest) > Metabotropic > Kinase-linked > Nuclear (Slowest).

Question 252: A manufacturer labels a drug as containing 500mg of paracetamol, but analysis reveals it contains only 200mg. What type of drug is this?

A. Spurious drug
B. Adulterated drug
C. Unethical drug
D. Misbranded drug (Correct Answer)

Explanation: ### Explanation The correct answer is **Misbranded drug**. This question tests the definitions provided under the **Drugs and Cosmetics Act (1940)**, which is high-yield for NEET-PG. **1. Why Misbranded Drug is correct:** A drug is classified as **misbranded** if its label is misleading, false, or if the actual content does not match the claims made on the label. In this case, the label claims 500mg, but the actual content is 200mg. It also includes drugs that are not labeled in the prescribed manner or those whose labels do not contain necessary warnings. **2. Why other options are incorrect:** * **Spurious drug:** These are "imitations" or substitutes. A drug is spurious if it is manufactured under a name that belongs to another drug, or if it is a product of a fictitious company. It is essentially a "fake" drug intended to deceive the consumer about its origin. * **Adulterated drug:** This refers to the **quality and purity** of the drug. A drug is adulterated if it consists of filthy, putrid, or decomposed substances, or if it is manufactured under unsanitary conditions that may render it injurious to health. * **Unethical drug:** This is not a legal classification under the Drugs and Cosmetics Act. It is a general term sometimes used for drugs marketed or prescribed in violation of medical ethics. **High-Yield Clinical Pearls for NEET-PG:** * **Misbranded:** Think "Labeling/Quantity error." * **Adulterated:** Think "Contamination/Purity issue." * **Spurious:** Think "Identity theft/Fake origin." * **Schedule H:** Drugs that can be sold only against a prescription of a Registered Medical Practitioner. * **Schedule X:** Narcotic and psychotropic drugs requiring special records and double-copy prescriptions.

Question 253: All of the following drugs are contraindicated in patients with G-6-PD deficiency, except?

A. Furazolidone
B. Cotrimoxazole
C. Ceftriaxone (Correct Answer)
D. Nalidixic acid

Explanation: **Explanation:** Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is an X-linked recessive disorder where RBCs are unable to regenerate NADPH, making them highly susceptible to oxidative stress. When exposed to certain oxidizing agents, hemoglobin precipitates as **Heinz bodies**, leading to acute hemolysis. **Why Ceftriaxone is the correct answer:** Ceftriaxone is a third-generation cephalosporin. Unlike sulfonamides or certain quinolones, cephalosporins do not possess significant oxidizing potential and do not interfere with the pentose phosphate pathway. Therefore, they are safe to use in G6PD-deficient patients. **Analysis of Incorrect Options:** * **Furazolidone:** This is a nitrofuran derivative. Like Nitrofurantoin, it is a potent oxidizing agent that frequently precipitates hemolytic anemia in G6PD-deficient individuals. * **Cotrimoxazole:** This is a combination of Sulfamethoxazole and Trimethoprim. **Sulfonamides** are classic triggers of hemolysis in G6PD deficiency due to their ability to increase free radical production. * **Nalidixic acid:** This is a first-generation quinolone. Quinolones (including older ones like Nalidixic acid and some newer fluoroquinolones) are known to induce oxidative stress in RBCs and are contraindicated. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for G6PD Triggers:** "**AAA**" – **A**ntimalarials (Primaquine, Pamaquine), **A**ntibiotics (Sulfonamides, Nitrofurantoin, Quinolones), and **A**ntipyretics (high-dose Aspirin, Phenazopyridine). * **Other notable triggers:** Dapsone (highest risk), Rasburicase, Methylene blue, and Fava beans (Favism). * **Safe Alternatives:** Penicillins, Cephalosporins, Aminoglycosides, and Acetaminophen (at therapeutic doses) are generally considered safe.

Question 254: Which of the following statements is true regarding placebo?

A. A placebo is a dummy medication. (Correct Answer)
B. Placebo is an inert material added to a drug for making tablets.
C. Placebos do not produce any effect.
D. All patients respond to placebo.

Explanation: **Explanation:** **1. Why Option A is Correct:** A **placebo** (Latin for "I shall please") is defined as a pharmacologically inactive substance or "dummy medication" given under the guise of effective treatment. The therapeutic effect observed after its administration is known as the **placebo effect**, which is mediated by psychological factors like expectation of relief and the release of endogenous opioids and dopamine in the brain. **2. Why Other Options are Incorrect:** * **Option B:** This describes an **excipient** or **vehicle** (e.g., lactose, starch). While placebos are often made of inert materials, the term "placebo" refers to the intent of the administration (as a control or for psychological benefit), whereas "excipient" refers to the pharmaceutical necessity for formulation. * **Option C:** Placebos **do produce effects** [1]. These can be positive (Placebo effect) or negative (Nocebo effect). They can cause objective physiological changes, such as alterations in heart rate, blood pressure, or gastric secretion. * **Option D:** Not everyone responds to placebos. The response rate is highly variable [1], typically ranging from **20% to 35%**, depending on the condition, the patient’s personality, and the doctor-patient relationship. **High-Yield NEET-PG Pearls:** * **Nocebo Effect:** Refers to the occurrence of adverse effects (e.g., headache, nausea) following the administration of a placebo. * **Clinical Use:** Placebos are primarily used in **double-blind clinical trials** [1], [2] to eliminate bias and distinguish the pharmacodynamic effects of a drug from psychological effects. * **Ethics:** In clinical practice, using placebos without patient consent is generally considered unethical unless used in specific research protocols.

Question 255: A child suffering from acute asthma with intermittent bronchospasm is brought to a hospital ER, and oxygen is administered to establish a Pao2>60 mm Hg. Which of the following statements about the further management of this patient is most accurate?

A. Benzodiazepines should be given for sedation.
B. Inhaled steroids are drugs of choice in acute asthma.
C. Frequent high-dose delivery of an inhaled beta2 agonist is indicated. (Correct Answer)
D. Aminophylline is always used if bronchospasm is present.

Explanation: ### Explanation **1. Why Option C is Correct:** The primary goal in managing acute severe asthma is the rapid reversal of airflow obstruction. **Short-acting Beta-2 Agonists (SABA)**, such as Salbutamol, are the first-line treatment. In an emergency setting, they are administered via a metered-dose inhaler (MDI) with a spacer or via nebulization. Frequent, high-dose delivery (e.g., every 20 minutes for the first hour) is necessary to achieve maximal bronchodilation by stimulating $\beta_2$ receptors, which increases intracellular cAMP and leads to smooth muscle relaxation. **2. Why the Other Options are Incorrect:** * **Option A:** Benzodiazepines are **contraindicated** in acute asthma. They cause respiratory depression, which can be fatal in a patient already struggling with ventilation and potential hypercapnia. * **Option B:** While corticosteroids are essential in acute asthma, **systemic steroids** (IV or oral) are preferred over inhaled ones for immediate management. Inhaled steroids are used for long-term maintenance/prophylaxis, not for the rapid reversal of an acute attack. * **Option D:** Aminophylline (a methylxanthine) is no longer a first-line drug. It has a narrow therapeutic index and significant side effects (arrhythmias, seizures). It is only considered as an add-on therapy in patients who do not respond to SABAs, Ipratropium, and systemic steroids. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Acute Attack):** Inhaled SABA (Salbutamol/Albuterol). * **Drug of Choice (Prophylaxis/Chronic Asthma):** Inhaled Corticosteroids (e.g., Fluticasone, Budesonide). * **Ipratropium Bromide:** Often added to SABA in the first hour of a severe attack for synergistic bronchodilation. * **Magnesium Sulfate:** Used intravenously in life-threatening asthma that is unresponsive to initial therapy. * **Side Effects of SABA:** Muscle tremors (most common), tachycardia, and hypokalemia.

Question 256: Phase II in a clinical drug trial is done to assess:

A. Therapeutic efficacy (Correct Answer)
B. Maximal tolerated dose
C. Maximal lethal dose
D. Toxicity

Explanation: **Explanation:** Clinical trials are conducted in four distinct phases to ensure the safety and efficacy of a new drug before and after it reaches the market. **Phase II (Therapeutic Exploration)** is primarily designed to assess **therapeutic efficacy** in a small group of patients (100–300) who actually have the target disease. This phase helps determine the dose range, ceiling effect, and confirms that the drug produces the intended clinical result. **Analysis of Options:** * **Option A (Correct):** Phase II evaluates if the drug works in patients. It is often divided into Phase IIa (pilot studies for efficacy) and Phase IIb (pivotal trials to determine the optimum dose). * **Option B (Incorrect):** The **Maximum Tolerated Dose (MTD)** is determined in **Phase I** (Therapeutic Orphan phase), usually involving healthy volunteers. * **Option C (Incorrect):** The **Lethal Dose (LD50)** is determined during **pre-clinical animal studies**, not in human clinical trials. * **Option D (Incorrect):** While safety is monitored in all phases, the primary screening for **safety and toxicity** occurs in **Phase I**. **High-Yield Clinical Pearls for NEET-PG:** * **Phase I:** Safety, Tolerability, and Pharmacokinetics (Healthy volunteers, except for oncology drugs). * **Phase III:** Therapeutic Confirmation (Large-scale, multicentric, randomized controlled trials). * **Phase IV:** Post-marketing surveillance (Detects rare adverse effects like Phocomelia or Rofecoxib-induced cardiotoxicity). * **Phase 0:** Human microdosing studies to determine PK parameters using AMS (Accelerator Mass Spectrometry).

Question 257: What does the suffix "&;xi&;" represent in a monoclonal antibody?

A. Name
B. Chimeric (Correct Answer)
C. Tumour targeted for
D. None of the above

Explanation: The nomenclature of monoclonal antibodies (mAbs) follows a specific international convention where the **infix** (the syllable before the suffix "-mab") indicates the source of the antibody. ### Explanation of the Correct Answer The suffix **"-xi-"** stands for **Chimeric**. A chimeric antibody is genetically engineered to contain approximately **65-75% human** protein and **25-35% murine (mouse)** protein. Specifically, the constant regions are human, while the variable (antigen-binding) regions are mouse-derived. * **Example:** **Ri-tu-xi-mab** (used in Non-Hodgkin Lymphoma). ### Why Other Options are Wrong * **A. Name:** The prefix of a monoclonal antibody (e.g., "Ri-" in Rituximab) is distinct and randomly chosen by the manufacturer to provide a unique name; it does not represent the "-xi-" component. * **C. Tumour targeted for:** The target of the drug is represented by a different infix placed *before* the source infix. For example, **"-tu-"** stands for tumor, **"-li-"** for immune system, and **"-ci-"** for cardiovascular. In "Rituximab," "-tu-" indicates it targets a tumor. ### NEET-PG High-Yield Pearls: Source Infixes To excel in pharmacology questions regarding mAbs, memorize this hierarchy of humanization: 1. **-omab:** 100% Murine (Mouse) — High immunogenicity (e.g., Muromonab). 2. **-ximab:** Chimeric (Mixed) — ~75% Human (e.g., Infliximab). 3. **-zumab:** Humanized — ~95% Human; only the complementarity-determining regions are murine (e.g., Trastuzumab). 4. **-umab:** 100% Fully Human — Lowest immunogenicity (e.g., Adalimumab). **Mnemonic:** **X**i = Mi**X**ed (Chimeric).

Question 258: What is the second messenger that mediates the action of nitric oxide?

A. cAMP
B. cGMP (Correct Answer)
C. PDE4
D. PPE4

Explanation: **Explanation:** **Nitric Oxide (NO)**, also known as Endothelium-Derived Relaxing Factor (EDRF), is a potent vasodilator. The correct answer is **cGMP** because of the following mechanism: 1. NO is synthesized in endothelial cells and diffuses into adjacent vascular smooth muscle cells. 2. It activates the enzyme **Soluble Guanylyl Cyclase (sGC)**. 3. This enzyme converts GTP into **cyclic Guanosine Monophosphate (cGMP)**. 4. Elevated cGMP activates Protein Kinase G (PKG), leading to dephosphorylation of myosin light chains and sequestration of calcium, resulting in **smooth muscle relaxation**. **Analysis of Incorrect Options:** * **A. cAMP:** This is the second messenger for drugs like Beta-agonists and Prostacyclin ($PGI_2$). While it also causes vasodilation, it utilizes the Adenylyl Cyclase pathway, not the NO pathway. * **C & D. PDE4 and PPE4:** Phosphodiesterases (PDEs) are enzymes that *break down* second messengers rather than acting as them. PDE4 specifically degrades cAMP in inflammatory cells; PDE5 is the enzyme responsible for degrading cGMP in the corpus cavernosum and vasculature. **High-Yield Clinical Pearls for NEET-PG:** * **Drug Link:** Sildenafil (Viagra) works by inhibiting **PDE5**, thereby preventing the breakdown of cGMP and prolonging the vasodilatory effects of NO. * **Nitrates:** Drugs like Nitroglycerin act as "NO donors" to relieve angina via this cGMP pathway. * **Other cGMP activators:** Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP) also use cGMP, but they activate *membrane-bound* (particulate) guanylyl cyclase, whereas NO activates *soluble* guanylyl cyclase.

Question 259: Which of the following is NOT a Category X drug?

A. Warfarin
B. Methotrexate
C. Alprazolam (Correct Answer)
D. Simvastatin

Explanation: **Explanation:** The US FDA Pregnancy Categories (A, B, C, D, and X) classify drugs based on their safety profile during pregnancy. **Category X** drugs are strictly contraindicated because studies in animals or humans have demonstrated fetal abnormalities, and the risks clearly outweigh any possible benefits. **Why Alprazolam is the correct answer:** Alprazolam is classified as **Category D**. While there is evidence of human fetal risk (potential for cleft lip/palate or neonatal withdrawal), the potential benefits from use in pregnant women may be acceptable in certain life-threatening or severe situations where safer drugs cannot be used or are ineffective. **Analysis of Incorrect Options (Category X Drugs):** * **Warfarin:** A potent teratogen causing "Fetal Warfarin Syndrome" (nasal hypoplasia, stippled epiphyses). Heparin (LMWH) is the preferred anticoagulant in pregnancy. * **Methotrexate:** A folate antagonist that causes "Fetal Methotrexate Syndrome" (skull defects, limb malformations, and CNS anomalies). It is used as an abortifacient in ectopic pregnancies. * **Simvastatin:** Statins are Category X because cholesterol is essential for fetal development (steroid synthesis and cell membranes). However, recent updates suggest individual assessment, but for exam purposes, they remain classic Category X examples. **High-Yield Clinical Pearls for NEET-PG:** * **Other Category X Drugs:** Thalidomide (Phocomelia), Isotretinoin (craniofacial/CNS defects), Misoprostol, and Diethylstilbestrol (clear cell vaginal adenocarcinoma). * **ACE Inhibitors/ARBs:** These are **Category D** (cause fetal renal dysgenesis and oligohydramnios), often confused with Category X. * **Phenytoin/Valproate:** Also **Category D**, causing Fetal Hydantoin Syndrome and Neural Tube Defects, respectively. * **Note:** The FDA has phased out the A-B-C-D-X system for the "Pregnancy and Lactation Labeling Rule" (PLLR), but NEET-PG frequently tests the traditional letter categories.

Question 260: Alkalinization of urine is done for which type of drugs?

A. Weak acid drugs (Correct Answer)
B. Weak basic drugs
C. Strong acidic drugs
D. Strong basic drugs

Explanation: **Explanation:** The principle underlying this question is the **pH Partition Hypothesis** and the concept of **Ion Trapping**. 1. **Why Option A is Correct:** Drugs are better absorbed in their unionized (lipid-soluble) form and excreted in their ionized (water-soluble) form. **Weakly acidic drugs** (e.g., Aspirin, Barbiturates) remain unionized in an acidic environment but become **ionized (charged)** in an alkaline environment. By alkalinizing the urine (using Sodium Bicarbonate), these weak acids lose a proton, become ionized, and lose their lipid solubility. Consequently, they cannot be reabsorbed across the renal tubular membrane back into the blood and are "trapped" in the urine for excretion. 2. **Why Other Options are Incorrect:** * **Weak Basic Drugs (B):** These require **acidification of urine** (using Ammonium Chloride or Vitamin C) to become ionized and excreted. Alkalinizing the urine would keep them unionized, increasing their reabsorption. * **Strong Acids/Bases (C & D):** Strong electrolytes remain almost completely ionized regardless of physiological pH changes. Their excretion is not significantly manipulated by simple urinary pH adjustment. **NEET-PG High-Yield Pearls:** * **Alkalinization of urine:** Used for poisoning with **Salicylates (Aspirin)** and **Phenobarbitone**. * **Acidification of urine:** Historically used for **Amphetamine**, **Quinine**, and **Strychnine** poisoning (though clinically less common now due to risks of metabolic acidosis). * **Mnemonic:** "Like dissolves in Like" (Acid in Acid = Reabsorbed; Acid in Base = Excreted). * **Agent used for Alkalinization:** IV Sodium Bicarbonate ($NaHCO_3$).

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