General Pharmacology Practice Questions

Q: Which of the following is NOT used in erectile dysfunction?

Phenylephrine. **Explanation:** The management of erectile dysfunction (ED) involves enhancing vasodilation and blood flow to the corpora cavernosa. **Phenylephrine** is the correct answer because it is a selective **alpha-1 (α1) agonist**, which causes potent vasoconstriction. In the context of male reproductive health, phenylephrine is actually the drug of choice for treating **priapism** (a prolonged, painful erection) by inducing detumescence through smooth muscle contraction. **Analysis of Options:** * **Vardenafil (Option B):** A selective **PDE-5 inhibitor** (like Sildenafil). It prevents the breakdown of cGMP, leading to smooth muscle relaxation and increased blood flow, making it a first-line oral treatment for ED. * **Alprostadil (Option D):** This is a synthetic **Prostaglandin E1 (PGE1)** analogue. It increases cAMP levels to cause vasodilation. It is administered via intracavernosal injection or intraurethral pellets for ED. * **PGE-2 (Option A):** While PGE1 (Alprostadil) is more commonly used, Prostaglandin E2 also possesses vasodilatory properties and has been utilized in various formulations for ED, though it is less common than PGE1. **High-Yield Clinical Pearls for NEET-PG:** 1. **Priapism Treatment:** Phenylephrine is preferred over adrenaline for priapism because it lacks β-activity, minimizing the risk of cardiac arrhythmias. 2. **PDE-5 Inhibitor Contraindication:** Never co-administer nitrates with PDE-5 inhibitors (e.g., Vardenafil) as it can lead to life-threatening hypotension. 3. **Alprostadil:** It is the drug of choice for maintaining a **Patent Ductus Arteriosus (PDA)** in neonates with cyanotic heart disease.

Q: Which of the following drugs can result in the teratogenic effect shown in the diagram if given during pregnancy?

Retinoic acid. **Explanation:** **Retinoic Acid (Vitamin A derivative)** is a potent teratogen. When administered during the first trimester of pregnancy, it interferes with the migration and differentiation of **cranial neural crest cells**. This leads to a specific pattern of malformations known as **Retinoic Acid Embryopathy**, which typically includes craniofacial abnormalities (microtia/anotia, cleft palate), cardiovascular defects (transposition of great vessels), and CNS anomalies (hydrocephalus). Due to its high lipid solubility and long half-life, it is strictly contraindicated in pregnancy (FDA Category X). **Incorrect Options:** * **Niacin (Vitamin B3):** Deficiency causes Pellagra (Dermatitis, Diarrhea, Dementia, Death), but it is not associated with the structural teratogenicity seen with retinoids. * **Thiamine (Vitamin B1):** Deficiency leads to Beriberi or Wernicke-Korsakoff syndrome. It is essential for carbohydrate metabolism and is safe during pregnancy. * **Folic Acid (Vitamin B9):** Unlike retinoids, folic acid is **protective**. Supplementation is mandatory periconceptionally to prevent **Neural Tube Defects (NTDs)** like spina bifida. **High-Yield Clinical Pearls for NEET-PG:** * **Isotretinoin Rule:** Female patients must use two forms of contraception and have two negative pregnancy tests before starting therapy (iPLEDGE program). * **Critical Period:** The most sensitive period for teratogenicity is organogenesis (**weeks 3 to 8** of gestation). * **Other Classic Teratogens:** * **Thalidomide:** Phocomelia (seal-like limbs). * **Valproate:** Neural tube defects (inhibits folate). * **Warfarin:** Fetal Warfarin Syndrome (stippled epiphyses, nasal hypoplasia). * **Phenytoin:** Fetal Hydantoin Syndrome (cleft lip/palate, hypoplastic nails).

Q: In pregnancy, all of the following drugs are contraindicated except:

Propylthiouracil. **Explanation:** The correct answer is **Propylthiouracil (PTU)**. In pregnancy, managing hyperthyroidism requires balancing maternal health with fetal safety. PTU is the drug of choice during the **first trimester** because it is more highly protein-bound than Methimazole, resulting in less placental transfer and a lower risk of fetal scalp defects (Aplasia cutis) and choanal atresia. **Analysis of Options:** * **Propylthiouracil (PTU):** It is not contraindicated; rather, it is preferred in early pregnancy. While it carries a risk of maternal hepatotoxicity, its limited transplacental passage makes it safer for the embryo during organogenesis. * **ACE Inhibitors (e.g., Enalapril):** These are strictly contraindicated (Category D/X). They interfere with fetal renal development, leading to **oligohydramnios**, renal dysgenesis, hypocalvaria (skull defects), and IUGR. * **Angiotensin Receptor Blockers (ARBs):** Like ACE inhibitors, ARBs are contraindicated as they act on the same Renin-Angiotensin system, causing similar fetotoxic effects (fetal hypotension and renal failure). * **Thalidomide:** A notorious teratogen (Category X). It causes **Phocomelia** (seal-like limbs/flipper limbs) and internal organ malformations. It is never used in pregnancy. **High-Yield Clinical Pearls for NEET-PG:** * **Switching Rule:** PTU is used in the **1st trimester**; Methimazole is preferred in the **2nd and 3rd trimesters** to avoid PTU-induced maternal liver failure. * **Warfarin:** Contraindicated (causes Fetal Warfarin Syndrome/Chondrodysplasia punctata); **Heparin** is the anticoagulant of choice. * **Anticonvulsants:** Valproate is the most teratogenic (Neural Tube Defects); **Levetiracetam** or **Lamotrigine** are generally preferred.

Q: An adolescent developed metabolic acidosis after taking a certain medication. What is the causative drug?

Acetazolamide. ### Explanation **Correct Option: A. Acetazolamide** Acetazolamide is a **Carbonic Anhydrase (CA) inhibitor** that acts primarily on the proximal convoluted tubule (PCT) of the kidney. It inhibits the enzyme carbonic anhydrase, preventing the reabsorption of sodium bicarbonate ($NaHCO_3$). This leads to increased urinary excretion of bicarbonate (alkaline urine), resulting in a depletion of the body's alkali reserve. The clinical consequence is a **Hyperchloremic Normal Anion Gap Metabolic Acidosis**. **Analysis of Incorrect Options:** * **B. Phenformin:** While Biguanides (like Phenformin and Metformin) are notorious for causing **Lactic Acidosis**, Phenformin has been largely withdrawn globally due to this high risk. However, in the context of standard pharmacological mechanisms involving bicarbonate loss, Acetazolamide is the classic textbook cause of metabolic acidosis. * **C. Verapamil:** This is a Calcium Channel Blocker (CCB) used for hypertension and arrhythmias. Its primary side effects include constipation, peripheral edema, and bradycardia, but it does not typically cause metabolic acidosis. * **D. Triamterene:** This is a potassium-sparing diuretic. While it can cause hyperkalemia and a mild metabolic acidosis (similar to Spironolactone), it is less commonly associated with significant systemic acidosis compared to the direct bicarbonate-wasting effect of Acetazolamide. **High-Yield Clinical Pearls for NEET-PG:** * **Acetazolamide Uses:** Glaucoma (decreases aqueous humor), Mountain Sickness (induces mild acidosis to stimulate respiration), and Urinary Alkalization. * **Side Effects:** Metabolic acidosis, hypokalemia, paresthesia, and sulfonamide-like hypersensitivity reactions. * **Acid-Base Tip:** Remember that "Proximal Renal Tubular Acidosis (Type 2 RTA)" is the physiological equivalent of Acetazolamide's mechanism of action.

Q: Which is a short-acting non-depolarizing neuromuscular blocker?

Mivacurium. **Explanation:** Neuromuscular blockers (NMBs) are classified based on their mechanism of action (Depolarizing vs. Non-depolarizing) and their duration of action (Short, Intermediate, or Long-acting). **1. Why Mivacurium is correct:** Mivacurium is a benzylisoquinolinium derivative and is the only **short-acting non-depolarizing** NMB currently used. Its short duration (approx. 15–20 minutes) is due to its rapid metabolism by **plasma cholinesterase** (pseudocholinesterase), similar to succinylcholine. **2. Analysis of Incorrect Options:** * **Pancuronium:** This is a **long-acting** non-depolarizing NMB (duration >60 minutes). It is known for its vagolytic effect, which can cause tachycardia. * **Succinylcholine:** While it is short-acting, it is a **depolarizing** NMB. It acts as an agonist at nicotinic receptors, causing persistent depolarization. * **Rapacurium:** Although it was a rapid-onset, short-acting non-depolarizing agent, it was **withdrawn** from the market worldwide due to the high risk of severe bronchospasm. **3. High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Most non-depolarizing drugs are metabolized by the liver or excreted by kidneys. Exceptions are **Atracurium and Cisatracurium**, which undergo **Hofmann elimination** (spontaneous degradation in plasma), making them safe in liver/kidney failure. * **Mivacurium Caution:** Since it is metabolized by plasma cholinesterase, its action is prolonged in patients with **pseudocholinesterase deficiency**. * **Histamine Release:** Mivacurium can cause histamine release, potentially leading to hypotension and flushing. * **Reversal:** Non-depolarizing blocks are reversed using Neostigmine (acetylcholinesterase inhibitor).

Q: What is the mechanism of action of thalidomide?

Immunomodulation. **Explanation:** Thalidomide is a complex drug originally introduced in the 1950s as a sedative, but it is now primarily classified as an **immunomodulatory imide drug (IMiD)**. **Why Immunomodulation is Correct:** Thalidomide exerts its effects through multiple pathways: 1. **TNF-α Inhibition:** It suppresses the production of Tumor Necrosis Factor-alpha (TNF-α), a potent pro-inflammatory cytokine. 2. **Cereblon Binding:** It binds to the protein **Cereblon**, part of an E3 ubiquitin ligase complex, leading to the degradation of transcription factors (like Ikaros and Aiolos) essential for B-cell and T-cell function. 3. **Anti-angiogenesis:** It inhibits the growth of new blood vessels by suppressing VEGF and bFGF. **Analysis of Incorrect Options:** * **A. Antimicrobial:** Thalidomide has no direct action against bacteria, viruses, or fungi. While used in Leprosy, it treats the *reaction* (ENL), not the *infection* (*M. leprae*). * **B. Antiemetic:** Though historically used for morning sickness (leading to the thalidomide tragedy), it is no longer indicated or classified as an antiemetic due to extreme toxicity. * **C. Anti-allergic:** It does not stabilize mast cells or block histamine receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Current Indications:** 1. **Erythema Nodosum Leprosum (ENL):** Drug of choice for Type 2 Lepra reaction. 2. **Multiple Myeloma:** Used in combination with dexamethasone. * **Teratogenicity:** It is a potent human teratogen causing **Phocomelia** (seal-like limbs) if taken during the first trimester (specifically days 27–40 of gestation). * **Side Effects:** Peripheral neuropathy (most common dose-limiting toxicity) and thromboembolism.

Q: In metabolism, all of the following reactions are considered Phase I reactions except?

Conjugation. Drug metabolism (biotransformation) typically occurs in two distinct phases to make lipophilic drugs more water-soluble for renal excretion [1]. **Phase I Reactions (Nonsynthetic)** These reactions involve the introduction or unmasking of a functional group (like -OH, -NH2, or -SH) [2]. They generally result in the activation, change in activity, or inactivation of a drug. The primary mechanisms include: * **Oxidation:** The most common Phase I reaction (e.g., via Cytochrome P450) [3]. * **Reduction:** Addition of hydrogen or removal of oxygen [3]. * **Hydrolysis:** Cleavage of a bond by adding water [3]. * **Cyclization and Decyclization.** * **Deamination:** Removal of an amino group (Option D) [3]. **Phase II Reactions (Synthetic)** These involve the **Conjugation** (Option C) of a drug or its Phase I metabolite with an endogenous substance (like glucuronic acid, sulfate, or glycine) [2]. These reactions almost always result in inactive, highly polar metabolites that are easily excreted [2]. **Explanation of Options:** * **Oxidation (A), Reduction (B), and Deamination (D)** are all Phase I reactions as they modify the drug molecule chemically without attaching a large endogenous molecule. * **Conjugation (C)** is the hallmark of Phase II metabolism. **High-Yield NEET-PG Pearls:** 1. **Glucuronidation** is the most common Phase II reaction. 2. **Microsomal enzymes** (located in the SER) catalyze most oxidations and glucuronidation, but **not** acetylation or sulfation (non-microsomal). 3. **Exception to the Rule:** While Phase II usually inactivates drugs, **Morphine-6-glucuronide** is a Phase II metabolite that is more potent than morphine itself.

Question 1

Which of the following is NOT used in erectile dysfunction?

Accepted Answer

Phenylephrine

Answer

PGE-2

Answer

Vardenafil

Answer

Alprostadil

Question 2

What is a prodrug?

Accepted Answer

An inactive substance that is converted into an active drug within the body.

Answer

An active drug that is converted into an inactive metabolite within the body.

Answer

The measure of the amount of drug necessary to produce an effect of a given magnitude.

Answer

A substance that binds to a receptor and elicits a biologic response.

Question 3

Which of the following drugs can result in the teratogenic effect shown in the diagram if given during pregnancy?

Accepted Answer

Retinoic acid

Answer

Niacin

Answer

Thiamine

Answer

Folic acid

Question 4

In pregnancy, all of the following drugs are contraindicated except:

Accepted Answer

Propylthiouracil

Answer

ACE Inhibitors

Answer

Angiotensin Receptor Blockers

Answer

Thalidomide

Question 5

An adolescent developed metabolic acidosis after taking a certain medication. What is the causative drug?

Accepted Answer

Acetazolamide

Answer

Phenformin

Answer

Verapamil

Answer

Triamterene

Question 6

Which one of the following statements about the management of patients with gastrointestinal ulcers is accurate?

Accepted Answer

Sucralfate polymerizes in the gut, forming a protective coat over ulcer beds.

Answer

Histamine-2 receptor blockers are as effective as proton pump inhibitors for treating GI ulcers.

Answer

Antimicrobial regimens that eradicate Helicobacter pylori are more than 98% effective in treating GI ulcers.

Answer

Omeprazole is effective because it activates prostaglandin E1 receptors.

Question 7

Which is a short-acting non-depolarizing neuromuscular blocker?

Accepted Answer

Mivacurium

Answer

Pancuronium

Answer

Succinylcholine

Answer

Rapacurium

Question 8

In which of the following phases of a clinical trial is ethical clearance not required?

Accepted Answer

Phase IV

Answer

Phase I

Answer

Phase II

Answer

Phase III

Question 9

What is the mechanism of action of thalidomide?

Accepted Answer

Immunomodulation

Answer

Antimicrobial

Answer

Antiemetic

Answer

Anti-allergic

Question 10

In metabolism, all of the following reactions are considered Phase I reactions except?

Accepted Answer

Conjugation

Answer

Oxidation

Answer

Reduction

Answer

Deamination

General Pharmacology — MCQs

General Pharmacology — MCQs

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