General Pharmacology Practice Questions

Q: Which of the following conversions is false?

1 minim = 20 drops. **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.

Q: Which of the following drugs binds to albumin?

Penicillin. **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.

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

Pharmacokinetic antagonist. ### 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).

Q: Which skeletal muscle relaxant causes significant release of histamine?

D-tubocurarine. ### 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.

Q: Effects mediated by H1 histamine receptor include?

Maintenance of a wakeful state. **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.

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

All of the above. 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.

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

Cocaine. **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.

Question 1

Which of the following conversions is false?

Accepted Answer

1 minim = 20 drops

Answer

1 qua = 1000 ml

Answer

1 teaspoon = 5 ml

Answer

1 tablespoon = 15 ml

Question 2

Which of the following statements is wrong?

Accepted Answer

Intra-arterial injection is a systemic route of drug administration.

Answer

Drugs should be highly lipid soluble to be administered transdermally.

Answer

Nitrates are given by sublingual route.

Answer

Parenteral route bypasses first-pass metabolism.

Question 3

Which of the following drugs binds to albumin?

Accepted Answer

Penicillin

Answer

Lidocaine

Answer

Propranolol

Answer

Verapamil

Question 4

Rifampicin and ritonavir are examples of which type of drug antagonism?

Accepted Answer

Pharmacokinetic antagonist

Answer

Physical antagonist

Answer

Chemical antagonist

Answer

Competitive antagonist

Question 5

Which skeletal muscle relaxant causes significant release of histamine?

Accepted Answer

D-tubocurarine

Answer

Pancuronium

Answer

Atracurium

Answer

Gallamine

Question 6

Effects mediated by H1 histamine receptor include?

Accepted Answer

Maintenance of a wakeful state

Answer

Inhibition of gastric acid secretion

Answer

Induction of hepatic cytochrome P450 enzyme

Answer

Vasoconstriction of arterioles

Question 7

Which of the following statements about prostaglandins is true?

Accepted Answer

Prostaglandins were first observed to cause uterine contraction and lowering of blood pressure.

Answer

Prostaglandins are precursors to arachidonic acid.

Answer

Prostaglandins release arachidonic acid from membranes through the action of phospholipase A.

Answer

Although found in many organs, prostaglandins are synthesized only in the prostate and seminal vesicles.

Question 8

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

Accepted Answer

All of the above

Answer

Nalidixic acid

Answer

Dapsone

Answer

Sulfamethoxazole

Question 9

At pharmacological doses, unavoidable unwanted effects are called what?

Accepted Answer

Side effects

Answer

Idiosyncratic reaction

Answer

Toxicity

Answer

Pharmacogenetics

Question 10

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

Accepted Answer

Cocaine

Answer

Dibucaine

Answer

Lignocaine

Answer

Procaine

General Pharmacology — MCQs

General Pharmacology — MCQs

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