General Pharmacology Practice Questions

Q: Maximum first-pass metabolism is observed with which route of drug administration?

Oral. **Explanation:** **1. Why Oral is Correct:** The oral route is associated with the maximum first-pass metabolism because drugs absorbed from the gastrointestinal tract (stomach and intestines) enter the **portal circulation** via the portal vein. This carries the drug directly to the **liver**—the primary site of drug metabolism—before it reaches the systemic circulation. Consequently, a significant fraction of the drug may be inactivated by hepatic enzymes (like Cytochrome P450) or excreted in bile, reducing its overall bioavailability. **2. Why Other Options are Incorrect:** * **Sublingual:** Drugs are absorbed directly through the oral mucosa into the superior vena cava, bypassing the portal circulation and the liver entirely. This results in rapid action and high bioavailability. * **Subcutaneous:** Absorption occurs via local capillaries into the systemic venous drainage, bypassing the gastrointestinal tract and the initial trip through the liver. * **Rectal:** This route has **partial** first-pass metabolism. The lower rectum drains into the systemic circulation (internal iliac veins), while the upper rectum drains into the portal system (superior rectal vein). Roughly 50% of the drug bypasses the liver. **Clinical Pearls for NEET-PG:** * **Definition:** First-pass metabolism (pre-systemic elimination) is the metabolism of a drug during its passage from the site of absorption to the systemic circulation. * **High First-Pass Drugs:** Nitroglycerin (hence given sublingually), Propranolol, Lidocaine, Morphine, and Salbutamol. * **Bioavailability:** Drugs with high first-pass metabolism have low oral bioavailability ($F$). * **Other Sites:** While the liver is the primary site, first-pass metabolism can also occur in the gut wall (e.g., Tyramine, Levodopa) and lungs.

Q: Prescription drugs are included in which schedule of the Drugs and Cosmetic Act?

Schedule H. The **Drugs and Cosmetics Act (1940)** and Rules (1945) classify drugs into various schedules to regulate their manufacture, sale, and distribution in India. **Correct Option: Schedule H** Schedule H contains the list of **prescription drugs**. These drugs are required to be sold by retail only upon the prescription of a Registered Medical Practitioner (RMP). The drug container must display the symbol **'Rx'** on the top left corner and a warning stating that it is dangerous to take the preparation except under medical supervision. **Analysis of Incorrect Options:** * **Schedule C:** Deals with **Biological and Special Products** (e.g., Sera, Vaccines, Insulin, and Antibiotics for parenteral use). These have specific requirements for import, manufacture, and sale. * **Schedule P:** Specifies the **Life period (Expiry date)** and storage conditions for various drugs. For example, it dictates how long a particular antibiotic or vaccine remains potent. * **Schedule X:** Includes **Psychotropic substances** and Narcotic drugs (e.g., Ketamine, Amphetamines). These require a special license for sale, and the pharmacist must preserve a copy of the prescription for two years. They are marked with the symbol **'NRx'**. **High-Yield Clinical Pearls for NEET-PG:** * **Schedule H1:** A sub-category introduced to curb the misuse of antibiotics and anti-TB drugs. It requires the pharmacist to maintain a separate register with patient and prescriber details. * **Schedule G:** Drugs to be taken under **medical supervision** (e.g., Metformin, Antihistamines), marked with a cautionary label but not necessarily requiring a formal prescription for every refill like Schedule H. * **Schedule Y:** Requirements and guidelines for **Clinical Trials**.

Q: Pseudocholinesterase acts on which of the following substances?

Mivacurium. **Explanation:** The question tests your knowledge of drug metabolism via specific esterases. **Mivacurium**, a short-acting non-depolarizing neuromuscular blocker, is primarily metabolized by **Pseudocholinesterase** (also known as Butyrylcholinesterase or Plasma Cholinesterase). This is clinically significant because patients with a genetic deficiency of this enzyme (atypical pseudocholinesterase) will experience prolonged muscle paralysis and apnea after receiving Mivacurium or Succinylcholine. **Analysis of Incorrect Options:** * **Esmolol:** This ultra-short-acting beta-blocker is metabolized by **Red Blood Cell (RBC) esterases**, not plasma pseudocholinesterase. * **Atracurium:** It undergoes degradation via **Hofmann elimination** (a spontaneous non-enzymatic chemical process dependent on pH and temperature) and, to a lesser extent, hydrolysis by non-specific esterases. * **Remifentanil:** This opioid is metabolized by **non-specific tissue and plasma esterases**, allowing for its rapid offset regardless of pseudocholinesterase levels. **High-Yield Clinical Pearls for NEET-PG:** * **Pseudocholinesterase substrates:** Succinylcholine, Mivacurium, Cocaine, and Procaine. * **RBC Esterase substrates:** Esmolol. * **Hofmann Elimination:** Characteristic of Atracurium and Cisatracurium; safe in renal and hepatic failure. * **Dibucaine Number:** Used to screen for pseudocholinesterase deficiency. A low number (<20) indicates an abnormal enzyme and high risk for prolonged apnea.

Q: Botulinum toxin mimics which class of drugs?

Anticholinergics. **Explanation:**1. Why Anticholinergics is the correct answer:Botulinum toxin (produced by *Clostridium botulinum*) acts by cleaving **SNARE proteins** (specifically SNAP-25, synaptobrevin, or syntaxin) at the presynaptic nerve terminal. This prevents the fusion of synaptic vesicles with the presynaptic membrane, thereby **inhibiting the release of Acetylcholine (ACh)** into the synaptic cleft [1]. Since it blocks cholinergic transmission at both the neuromuscular junction (NMJ) and autonomic ganglia/parasympathetic endings, it results in effects similar to **Anticholinergics** (e.g., muscle paralysis, dry mouth, and blurred vision) [2, 3].2. Why other options are incorrect:* **Cholinergics:** These drugs (e.g., Pilocarpine, Neostigmine) enhance or mimic ACh action. Botulinum toxin does the opposite by preventing ACh release.* **Adrenergics:** These drugs act on the sympathetic nervous system (Norepinephrine/Epinephrine). Botulinum toxin specifically targets cholinergic vesicles.* **Antiadrenergics:** These drugs (e.g., Beta-blockers) inhibit sympathetic activity. While Botulinum toxin is an inhibitor, its site of action is the cholinergic system, not the adrenergic system.3. NEET-PG High-Yield Pearls:* **Mechanism:** Irreversible inhibition of ACh release (Presynaptic blockade).* **Clinical Uses:** Strabismus, Blepharospasm, Achalasia Cardia, Spasticity, Hyperhidrosis, and Cosmetic (Botox) for wrinkles.* **Antidote for Botulism:** Equine Botulinum Antitoxin (Heptavalent).* **Comparison:** **Black Widow Spider Venom (Latrotoxin)** does the opposite—it causes massive explosive release of ACh, leading to muscle spasms.

Q: What is the effect of a drug in the body called?

Pharmacodynamics. **Explanation:** The correct answer is **Pharmacodynamics**. **1. Why Pharmacodynamics is correct:** Pharmacodynamics is defined as **"what the drug does to the body."** [1], [2] It focuses on the biochemical and physiological effects of drugs and their mechanisms of action. This includes drug-receptor interactions, dose-response relationships, and the sequence of events leading to a pharmacological effect (e.g., adrenaline causing bronchodilation via $\beta_2$ receptors). **2. Why the other options are incorrect:** * **Pharmacokinetics:** This is **"what the body does to the drug."** [3] It involves the processes of **ADME**: Absorption, Distribution, Metabolism, and Excretion. It deals with drug concentration over time rather than the biological effect. * **Pharmacotherapeutics:** This is the clinical application of pharmacodynamic and pharmacokinetic knowledge for the prevention, diagnosis, and treatment of diseases. It focuses on the "use" of drugs in a clinical setting. * **Pharmacogenetics:** This is the study of how genetic variations influence an individual’s response to drugs (e.g., G6PD deficiency leading to hemolysis after taking Primaquine). **3. NEET-PG High-Yield Pearls:** * **Mnemonic:** Pharmacody**n**amics = **D**rug does to body; Pharmaco**k**inetics = Body does to **k**ompound (drug). * **Key Concept:** Receptors, ion channels, and enzymes are the primary targets of pharmacodynamics. * **High-Yield Fact:** The **Therapeutic Index** ($LD_{50}/ED_{50}$) is a major pharmacodynamic parameter used to measure drug safety. * **Clinical Correlation:** Understanding pharmacodynamics helps in predicting drug-drug interactions at the receptor level (e.g., competitive antagonism).

Question 1

Maximum first-pass metabolism is observed with which route of drug administration?

Accepted Answer

Oral

Answer

Subcutaneous

Answer

Rectal

Answer

Sublingual

Question 2

Prescription drugs are included in which schedule of the Drugs and Cosmetic Act?

Accepted Answer

Schedule H

Answer

Schedule C

Answer

Schedule P

Answer

Schedule X

Question 3

Pseudocholinesterase acts on which of the following substances?

Accepted Answer

Mivacurium

Answer

Esmolol

Answer

Atracurium

Answer

Remifentanil

Question 4

Botulinum toxin mimics which class of drugs?

Accepted Answer

Anticholinergics

Answer

Cholinergics

Answer

Adrenergics

Answer

Antiadrenergics

Question 5

What is the definition of a competitive antagonist?

Accepted Answer

Binds to the same receptor site and progressively inhibits the agonist response.

Answer

Interacts with receptors and produces a submaximal effect.

Answer

Binds to non-specific sites on the tissue.

Answer

Binds to one receptor subtype as an agonist and to another as an antagonist.

Question 6

Pharmacogenetics is associated with which of the following?

Accepted Answer

Individual variations in drug response due to gene variability

Answer

Environmental influence on drug response

Answer

Individual variability in oral absorption

Answer

Different mechanisms of drug action in different individuals

Question 7

Which of the following is NOT a second-generation antihistamine?

Accepted Answer

Cyclizine

Answer

Fexofenadine

Answer

Loratadine

Answer

Atorvastatin

Question 8

Which of the following statements regarding histamine is FALSE?

Accepted Answer

It tends to constrict larger blood vessels.

Answer

It can be used as a positive control injection during allergy skin testing.

Answer

In the dermis, it evokes pain and sometimes itching.

Answer

Bronchospasm is induced by histamine by blockage of H2 receptors.

Question 9

What is the effect of a drug in the body called?

Accepted Answer

Pharmacodynamics

Answer

Pharmacokinetics

Answer

Pharmacotherapeutics

Answer

Pharmacogenetics

Question 10

Phase IV of clinical trials is conducted:

Accepted Answer

Post-marketing surveillance

Answer

To find safety and toxicity

Answer

To compare with existing drugs

Answer

Pre-marketing surveillance

General Pharmacology — MCQs

General Pharmacology — MCQs

On this page

Practice by Chapter

Want unlimited practice?