UPSC-CMS 2012 - Pharmacology PYQs Practice Questions

Q: Which of the following statements is true about antibiotic therapy?

It has its greatest effect on multiplying organisms. ***It has its greatest effect on multiplying organisms*** - Most **antibiotics** target processes essential for bacterial growth and replication, such as cell wall synthesis, protein synthesis, or DNA replication. - Therefore, their efficacy is highest against **actively multiplying bacteria**, as these processes are most vulnerable during periods of rapid growth. *It enhances the intracellular killing of organisms by phagocytes* - Antibiotics primarily act directly on bacteria, either **killing them (bactericidal)** or inhibiting their growth (bacteriostatic), rather than directly augmenting host immune cell functions like intracellular killing by phagocytes. - While antibiotics reduce the bacterial load, which aids phagocytosis, they do not directly enhance the phagocyte's intrinsic killing mechanisms. *It facilitates killing of organisms by activation of complements* - The **complement system** is part of the innate immune response and is activated by antibodies or microbial surface components; antibiotics do not directly activate this system. - Antibiotic action is independent of complement activation, although a reduced bacterial load can indirectly influence the overall immune response. *It enhances the uptake of organisms by phagocytes* - Enhancing the uptake of organisms by phagocytes (opsonization) is primarily mediated by host immune components such as **antibodies** and **complement proteins**, which coat bacteria to facilitate recognition. - Antibiotics do not directly opsonize bacteria or enhance phagocytic uptake; their role is to inhibit or kill bacteria directly. [Practice more Pharmacology PYQs on OnCourse]

Q: Which of the following local anaesthetics causes irreversible cardiac arrest if it is given intravenously ?

Bupivacaine. ***Bupivacaine*** - Bupivacaine is known for its **cardiotoxicity**, which can lead to severe and often irreversible **cardiac arrest** if inadvertently administered intravenously. - This is due to its high potency, slow dissociation from cardiac sodium channels, and increased lipid solubility, leading to prolonged cardiac depression. *Lignocaine* - While lignocaine (lidocaine) can cause cardiac toxicity in overdose, it is generally considered less cardiotoxic than bupivacaine, and cardiac arrest is more readily reversible. - It is commonly used intravenously as an antiarrhythmic, indicating a safer cardiac profile at therapeutic doses. *Cocaine* - Cocaine is a vasoconstrictor and stimulant; its primary cardiovascular effects are **tachycardia**, hypertension, and arrhythmias due to inhibition of norepinephrine reuptake, rather than direct myocardial depression leading to irreversible cardiac arrest from intravenous injection in the same manner as bupivacaine. - Cocaine toxicity can cause myocardial ischemia and infarction, but not the same profound, irreversible cardiac depression seen with bupivacaine. *Prilocaine* - Prilocaine is associated with **methemoglobinemia** as a dose-dependent side effect, especially in large doses, due to its metabolite o-toluidine. - While it can cause cardiovascular depression at very high doses, it does not have the same potent and often irreversible direct negative inotropic effects on the heart as bupivacaine. [Practice more Pharmacology PYQs on OnCourse]

Q: The anticonvulsant of choice in the treatment of generalized tonic-clonic seizures is

Phenytoin. ***Phenytoin*** - **Historical Context (2012):** Phenytoin was traditionally considered a first-line anticonvulsant for **generalized tonic-clonic seizures** due to its ability to stabilize neuronal membranes and prevent seizure propagation by **blocking voltage-gated sodium channels**. - **Current Guidelines:** While phenytoin remains effective, it is now generally considered a **second-line agent** due to its narrow therapeutic index, significant side effects (gingival hyperplasia, hirsutism, osteomalacia), and multiple drug interactions. **Valproate, levetiracetam, and lamotrigine** are now preferred first-line options per modern ILAE guidelines. - **Note:** This question reflects the 2012 exam standards when phenytoin was still widely taught as first-line therapy. *Diazepam* - **Diazepam** is a **benzodiazepine** primarily used for the **acute termination of seizures** (status epilepticus), not as long-term maintenance therapy for generalized tonic-clonic seizures. - It acts by enhancing **GABA-A receptor** activity, leading to rapid CNS depression and seizure termination. *Phenobarbital* - **Phenobarbital** is a **barbiturate** that can be used for generalized tonic-clonic seizures but is generally a **second or third-line agent** due to significant sedative effects, cognitive impairment, and potential for drug interactions. - Its mechanism involves increasing **GABA-mediated chloride influx**, causing neuronal hyperpolarization. *Magnesium sulphate* - **Magnesium sulfate** is specifically indicated for the prevention and treatment of seizures in **eclampsia and preeclampsia**, not for generalized tonic-clonic seizures in other contexts. - It exerts anticonvulsant effects by acting as an **NMDA receptor antagonist** and reducing neuronal excitability. [Practice more Pharmacology PYQs on OnCourse]

Q: The drugs which may interfere with the efficacy of oral contraceptives and increase the failure rates are all of the following EXCEPT

Ampicillin. ***Ampicillin (Correct Answer)*** - While previously thought to reduce oral contraceptive efficacy, **current evidence shows ampicillin has NO significant interaction** with oral contraceptives. - The old theory suggested some antibiotics might alter gut flora and reduce **enterohepatic recirculation of estrogen**, but this has been largely **debunked for ampicillin and most antibiotics**. - **Unlike the enzyme inducers listed below**, ampicillin does not significantly affect OC metabolism or efficacy. *Phenytoin (Incorrect - DOES interfere)* - **Phenytoin is a potent enzyme inducer** (cytochrome P450 enzymes). - This induction enhances the metabolism of estrogen and progestin components, **reducing their plasma concentrations and effectiveness**. - Backup contraception is recommended when using phenytoin with oral contraceptives. *Barbiturates (Incorrect - DOES interfere)* - **Barbiturates are potent enzyme inducers**, similar to phenytoin. - They increase hepatic metabolism of oral contraceptive steroids, leading to **lower circulating hormone levels and increased risk of contraceptive failure**. - Alternative contraception should be considered. *Rifampicin (Incorrect - DOES interfere)* - **Rifampicin is one of the strongest inducers of hepatic microsomal enzymes**, particularly CYP3A4. - This leads to **rapid and substantial increase in metabolism of both estrogen and progestin**, drastically reducing OC efficacy. - **Non-hormonal contraception is strongly recommended** during rifampicin therapy. [Practice more Pharmacology PYQs on OnCourse]

Question 1

Which of the following statements is true about antibiotic therapy?

Accepted Answer

It has its greatest effect on multiplying organisms

Answer

It enhances the intracellular killing of organisms by phagocytes

Answer

It facilitates killing of organisms by activation of complements

Answer

It enhances the uptake of organisms by phagocytes

Question 2

Which of the following local anaesthetics causes irreversible cardiac arrest if it is given intravenously ?

Accepted Answer

Bupivacaine

Answer

Lignocaine

Answer

Cocaine

Answer

Prilocaine

Question 3

The anticonvulsant of choice in the treatment of generalized tonic-clonic seizures is

Accepted Answer

Phenytoin

Answer

Diazepam

Answer

Phenobarbital

Answer

Magnesium sulphate

Question 4

The drugs which may interfere with the efficacy of oral contraceptives and increase the failure rates are all of the following EXCEPT

Accepted Answer

Ampicillin

Answer

Phenytoin

Answer

Barbiturates

Answer

Rifampicin

UPSC-CMS 2012 — Pharmacology