Which of the following medications does not interact with warfarin?
Which of the following is the MOST CRITICAL indication for Acyclovir use during pregnancy?
Guanethidine is used in the treatment of which of the following conditions?
Which enzyme is irreversibly inhibited by aspirin?
Which type of vaccine is used for chicken pox?
Which of the following best describes a Type B adverse drug reaction?
Which of the following statements about dopamine is false?
Which of the following is a centrally acting antihypertensive drug?
Which of the following statements about Conivaptan is correct?
Which of the following potassium-sparing diuretics was the first to be shown to reduce cardiac mortality in chronic heart failure patients?
NEET-PG 2012 - Pharmacology NEET-PG Practice Questions and MCQs
Question 31: Which of the following medications does not interact with warfarin?
- A. Barbiturate
- B. Oral contraceptive
- C. Cephalosporins
- D. Benzodiazepines (Correct Answer)
Explanation: ***Benzodiazepines*** - **Benzodiazepines** are generally considered safe to use with warfarin as they are extensively metabolized in the liver, but they do not typically alter the **cytochrome P450 enzymes** responsible for warfarin metabolism. - They also do not interfere with **vitamin K recycling** or **platelet function**, which are key mechanisms through which other drugs interact with warfarin. *Barbiturate* - **Barbiturates** are **potent inducers of hepatic enzymes**, particularly CYP2C9, which is responsible for metabolizing warfarin. - This enzyme induction leads to **increased warfarin metabolism**, reducing its anticoagulant effect and necessitating higher warfarin doses. *Oral contraceptive* - **Oral contraceptives** can **reduce the anticoagulant effect of warfarin** by inducing clotting factors or inhibiting warfarin metabolism. - This interaction can increase the risk of **thromboembolic events** in patients on warfarin. *Cephalosporins* - Certain **cephalosporins**, especially those with a **methylthiotetrazole (MTT) side chain** (e.g., Cefamandole, Cefoperazone, Moxalactam), can **inhibit vitamin K epoxide reductase**. - This inhibition leads to a **decrease in vitamin K-dependent clotting factors**, thus potentiating the anticoagulant effect of warfarin and increasing bleeding risk.
Question 32: Which of the following is the MOST CRITICAL indication for Acyclovir use during pregnancy?
- A. Treatment of disseminated herpes (Correct Answer)
- B. Treatment of chickenpox in the first trimester
- C. Prophylaxis for recurrent herpes during pregnancy
- D. Prevention of cytomegalovirus infection in pregnancy
Explanation: ***Treatment of disseminated herpes*** - **Disseminated herpes** in pregnancy is a severe, life-threatening condition for both the mother and the fetus, making acyclovir use critically indicated. - This systemic infection can lead to **visceral organ involvement**, **encephalitis**, and significantly increased maternal and fetal morbidity and mortality. - Immediate treatment with intravenous acyclovir is essential to prevent **multi-organ failure** and death. *Treatment of chickenpox in the first trimester* - While chickenpox in the first trimester can be serious, leading to **congenital varicella syndrome**, acyclovir's role here is primarily to mitigate maternal illness, not as critical as disseminated herpes. - The risk of congenital varicella syndrome for the fetus is relatively low (around 0.4%) after maternal infection in the first trimester. *Prophylaxis for recurrent herpes during pregnancy* - **Prophylactic acyclovir** in the third trimester is commonly used to prevent recurrent genital herpes and reduce the risk of **neonatal herpes**, but it is not as acutely critical as treating disseminated disease. - This intervention aims to prevent transmission during delivery rather than managing an immediate, life-threatening maternal or fetal condition. *Prevention of cytomegalovirus infection in pregnancy* - Acyclovir has **minimal activity against CMV** and is not indicated for CMV prevention or treatment. - **Ganciclovir** or **valganciclovir** are the antivirals used for CMV, not acyclovir.
Question 33: Guanethidine is used in the treatment of which of the following conditions?
- A. Ptosis
- B. Bell's palsy
- C. Thyrotoxic ophthalmopathy (Correct Answer)
- D. Horner's syndrome
Explanation: ***Thyrotoxic ophthalmopathy*** - Guanethidine is an **adrenergic neuron blocker** that can be used topically to reduce the sympathetic overactivity in the eye associated with thyrotoxicosis. - It helps alleviate symptoms like **retraction of the eyelids** and proptosis by blocking norepinephrine release from sympathetic nerve endings. *Ptosis* - **Ptosis** is primarily caused by weakness of the levator palpebrae superioris muscle or oculomotor nerve dysfunction, not sympathetic overactivity. - Guanethidine would not address the underlying muscular or neurologic deficit causing ptosis. *Bell's palsy* - **Bell's palsy** involves sudden, temporary weakness or paralysis of the muscles on one side of the face due to a dysfunction of the facial nerve. - Treatment typically involves corticosteroids and antivirals; guanethidine has no role in its management. *Horner's syndrome* - **Horner's syndrome** is characterized by miosis, ptosis, and anhidrosis, resulting from damage to the sympathetic nerve supply to the eye and face. - Guanethidine's mechanism of action would exacerbate, rather than treat, the existing sympathetic deficit in Horner's syndrome.
Question 34: Which enzyme is irreversibly inhibited by aspirin?
- A. Lipooxygenase
- B. Cyclooxygenase (Correct Answer)
- C. Thromboxane synthase
- D. Phospholipase
Explanation: ***Cyclooxygenase*** - **Aspirin** irreversibly inhibits **cyclooxygenase (COX-1 and COX-2)** by acetylating a serine residue in the enzyme's active site. - This irreversible inhibition prevents the production of **prostaglandins, thromboxane**, and **prostacyclin**, thereby reducing inflammation, pain, fever, and platelet aggregation. *Lipooxygenase* - **Lipooxygenase** is involved in the synthesis of **leukotrienes**, which are mediators of inflammation and allergic responses. - Aspirin does not directly inhibit lipooxygenase; rather, it primarily targets the COX pathway. *Thromboxane synthase* - **Thromboxane synthase** is an enzyme downstream of COX, responsible for converting prostaglandin H2 into **thromboxane A2**. - While aspirin's effect on platelet aggregation is due to reduced thromboxane A2 synthesis via COX inhibition, it does not directly inhibit thromboxane synthase itself. *Phospholipase* - **Phospholipase A2** is responsible for releasing **arachidonic acid** from cell membrane phospholipids, which is the initial step in both the cyclooxygenase and lipooxygenase pathways. - Aspirin does not directly inhibit phospholipase A2; its action occurs later in the cascade.
Question 35: Which type of vaccine is used for chicken pox?
- A. Live vaccine (Correct Answer)
- B. Killed vaccine
- C. Conjugated vaccine
- D. Toxoid vaccine
Explanation: ***Live vaccine*** - The chickenpox vaccine (Varicella vaccine) is a **live-attenuated vaccine**, meaning it contains a weakened form of the **Varicella-zoster virus** (Oka strain). - This weakened virus can still replicate in the body, stimulating a strong and long-lasting immune response similar to natural infection but without causing severe disease. *Killed vaccine* - **Killed (inactivated) vaccines** use viruses or bacteria that have been inactivated through heat or chemicals, making them unable to replicate. - While effective for some diseases (e.g., inactivated polio, influenza), they typically require **multiple doses** and might provide less durable immunity compared to live vaccines. *Conjugated vaccine* - **Conjugated vaccines** are designed to improve the immune response to polysaccharide antigens (e.g., bacterial capsules) by linking them to a carrier protein. - This technology is primarily used for **bacterial infections** like *Haemophilus influenzae* type b (Hib) or pneumococcal disease, not viral illnesses like chickenpox. *Toxoid vaccine* - **Toxoid vaccines** contain inactivated bacterial toxins (toxoids) rather than the whole organism. - Examples include **tetanus and diphtheria vaccines**, which protect against diseases caused by bacterial toxins, not viral infections like chickenpox.
Question 36: Which of the following best describes a Type B adverse drug reaction?
- A. Augmented effect of drug
- B. Effect seen on chronic use of drug
- C. Delayed effect of drug
- D. Unpredictable bizarre reaction (Correct Answer)
Explanation: ***Unpredictable bizarre reaction*** - Type B reactions are **unpredictable**, **bizarre**, and not directly related to the drug's known pharmacological actions. - They often involve **immunological reactions** or genetic predispositions, such as allergies or idiosyncratic responses. *Augmented effect of drug* - This describes a **Type A** adverse drug reaction, which is predictable and results from an **exaggerated pharmacological effect** of the drug. - It is typically dose-dependent and can be managed by adjusting the dosage. *Effect seen on chronic use of drug* - This description can apply to several types of adverse reactions, but it commonly relates to **Type C (chronic) reactions**, where effects occur only after prolonged exposure. - These reactions might be due to **cumulative toxicity** or adaptive changes in the body. *Delayed effect of drug* - This aligns with **Type D (delayed) adverse drug reactions**, which manifest long after the drug exposure has ended or after a period of latency. - Examples include **carcinogenesis** or teratogenesis, occurring months or years later.
Question 37: Which of the following statements about dopamine is false?
- A. Improves renal perfusion
- B. Causes Vasoconstriction
- C. Causes increase in GI Ischemia (Correct Answer)
- D. Positive ionotropic
Explanation: ***Causes increase in GI Ischemia*** (FALSE Statement) - This statement is **incorrect and misleading** as dopamine does not primarily "cause increase in GI ischemia" - While dopamine at **higher doses** can cause **splanchnic vasoconstriction** via alpha-1 receptors, this is not characterized as "causing GI ischemia" in standard pharmacology - GI ischemia is a potential adverse effect in susceptible patients, but not a primary pharmacological effect or standard clinical description of dopamine *Positive inotropic* (TRUE Statement) - Dopamine is a **catecholamine** with dose-dependent effects; at **moderate doses (5-10 mcg/kg/min)**, it stimulates **beta-1 adrenergic receptors** in the heart - This beta-1 stimulation leads to increased **myocardial contractility** and **heart rate**, thus exerting a **positive inotropic effect** - This is a well-established therapeutic effect of dopamine *Improves renal perfusion* (TRUE Statement) - At **low doses (0.5-3 mcg/kg/min)**, dopamine selectively activates **dopamine-1 (D1) receptors** in the renal vasculature - This activation causes **renal vasodilation**, leading to increased **renal blood flow**, improved **glomerular filtration rate**, and enhanced **sodium excretion** - This "renal dose" effect is a classic pharmacological property of dopamine *Causes Vasoconstriction* (TRUE Statement) - At **high doses (>10 mcg/kg/min)**, dopamine primarily stimulates **alpha-1 adrenergic receptors** - This leads to generalized **vasoconstriction**, increasing **systemic vascular resistance** and **blood pressure** - This dose-dependent alpha effect is well-documented
Question 38: Which of the following is a centrally acting antihypertensive drug?
- A. Phenoxybenzamine
- B. Propranolol
- C. Prazosin
- D. Methyldopa (Correct Answer)
Explanation: ***Methyldopa*** - **Methyldopa** is a **prodrug** that is converted to **alpha-methylnorepinephrine** in the brain, which then stimulates **alpha-2 adrenergic receptors** in the brainstem. - This stimulation reduces **sympathetic outflow** from the central nervous system, leading to decreased heart rate, stroke volume, and peripheral vascular resistance, thus lowering blood pressure. *Phenoxybenzamine* - **Phenoxybenzamine** is an **alpha-1 and alpha-2 adrenergic receptor antagonist** (non-selective alpha blocker) that primarily acts peripherally. - It causes **vasodilation** by blocking alpha-1 receptors on smooth muscle, which reduces peripheral vascular resistance. *Propranolol* - **Propranolol** is a **non-selective beta-blocker** that primarily acts on peripheral beta-adrenergic receptors. - It reduces heart rate and cardiac output by blocking **beta-1 receptors** in the heart and can also affect beta-2 receptors in the lungs and vasculature. *Prazosin* - **Prazosin** is a **selective alpha-1 adrenergic receptor antagonist** that acts primarily on peripheral blood vessels. - It causes **vasodilation** in both arteries and veins by blocking alpha-1 receptors, which reduces both preload and afterload, lowering blood pressure.
Question 39: Which of the following statements about Conivaptan is correct?
- A. It is a vasopressin antagonist. (Correct Answer)
- B. It selectively acts on V2 receptors.
- C. It is administered orally.
- D. All of the options.
Explanation: ***It is a vasopressin antagonist.*** * **Conivaptan** is a non-peptide, dual **vasopressin V1A and V2 receptor antagonist**, meaning it blocks the action of vasopressin. * By blocking vasopressin, it promotes **aquaresis** (excretion of solute-free water), which is beneficial in conditions like **hyponatremia**. * *It selectively acts on V2 receptors.* * **Conivaptan** is a **dual antagonist**, blocking both **V1A and V2 receptors**, not just V2. * **Tolvaptan**, in contrast, is a selective **V2 receptor antagonist**. * *It is administered orally.* * **Conivaptan** is typically administered intravenously, particularly in hospital settings for acute hyponatremia. * **Tolvaptan** is the orally administered vasopressin antagonist. * *All of the options.* * Since Conivaptan is not selectively acting on V2 receptors and is not administered orally, this option is incorrect.
Question 40: Which of the following potassium-sparing diuretics was the first to be shown to reduce cardiac mortality in chronic heart failure patients?
- A. Spironolactone (Correct Answer)
- B. Amiloride
- C. Triamterene
- D. Eplerenone
Explanation: ***Spironolactone*** - **Spironolactone** was the first potassium-sparing diuretic shown to reduce **cardiac mortality** in patients with **chronic heart failure** in the **RALES trial** (Randomized Aldactone Evaluation Study). - Its beneficial effects in heart failure are primarily attributed to its **aldosterone receptor antagonist** properties, which counteract the harmful effects of aldosterone on the myocardium and vasculature, rather than just its diuretic effect. *Amiloride* - **Amiloride** is a potassium-sparing diuretic that works by directly inhibiting **epithelial sodium channels (ENaC)** in the collecting duct. - While it helps in potassium conservation, it has not been shown to significantly reduce cardiac mortality in chronic heart failure patients in clinical trials. *Triamterene* - **Triamterene** is another potassium-sparing diuretic that also directly inhibits **ENaC** in the collecting duct, similar to amiloride. - Like amiloride, it is used to prevent hypokalemia but lacks evidence for significant **cardiac mortality reduction** in chronic heart failure. *Eplerenone* - **Eplerenone** is a selective **aldosterone receptor antagonist**, similar to spironolactone, with fewer hormonal side effects. - While it has been shown to reduce **cardiac mortality** in chronic heart failure (e.g., in the EMPHASIS-HF trial), it was introduced later than spironolactone and was not the *first* to demonstrate this benefit.