Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Carbonic anhydrase inhibitor should not be given in:

Sulfonamide hypersensitivity. ***Sulfonamide hypersensitivity*** - Carbonic anhydrase inhibitors (CAIs) are **sulfonamide derivatives**, so they are absolutely contraindicated in patients with a history of **sulfonamide allergy**. - Administration to such patients can lead to severe **hypersensitivity reactions**, including rash, fever, and even anaphylaxis. *Epilepsy* - **Acetazolamide**, a carbonic anhydrase inhibitor, can be used as an **adjunct therapy for certain types of epilepsy**, such as absence seizures. - It works by reducing neuronal excitability through its effects on pH, thus it is not contraindicated but rather sometimes indicated. *High altitude sickness* - Carbonic anhydrase inhibitors like **acetazolamide** are commonly used to **prevent and treat high altitude cerebral and pulmonary edema** by inducing metabolic acidosis and stimulating respiration. - This is a recognized therapeutic indication, not a contraindication. *Glaucoma* - CAIs are a **primary treatment for glaucoma** (both open-angle and angle-closure) because they reduce the production of aqueous humor, thereby lowering intraocular pressure. - They are used both systemically and topically for this purpose, making it an indication, not a contraindication.

Q: All of the following are causes of drug-induced lupus, except:

Clofibrate. ***Clofibrate*** - Clofibrate is a **fibric acid derivative** (fibrate) used to treat hyperlipidemia and is not known to cause drug-induced lupus. - Its primary mechanism of action involves activating **PPAR-alpha**, leading to decreased triglyceride levels and increased HDL production. *Penicillamine* - Penicillamine is a known cause of **drug-induced lupus**, often leading to symptoms mimicking systemic lupus erythematosus. - It is a chelating agent used to treat conditions like **Wilson's disease** and severe rheumatoid arthritis. *Hydralazine* - Hydralazine is a classic and frequent cause of **drug-induced lupus**, particularly at higher doses. - It is an **antihypertensive medication** that acts as a direct vasodilator. *Chlorpromazine* - Chlorpromazine, an antipsychotic medication, can induce a **lupus-like syndrome** in some susceptible individuals. - It is a **phenothiazine derivative** primarily used to treat schizophrenia and other psychotic disorders.

Q: A 6-year-old boy is admitted to the ward with drowsiness, dull deep tendon reflexes and seizures. On examination the child has a line on gums and there is a history of constipation. Which will be most appropriate drug that should be used for this child?

EDTA. ***EDTA*** - The child presents with **lead encephalopathy** (drowsiness, seizures, dull reflexes) indicated by neurological symptoms, **gingival line**, and constipation. - **CaNa₂EDTA** is the **first-line chelator** for severe lead poisoning with encephalopathy, administered **intravenously** for rapid lead removal from tissues. *Penicillamine* - Penicillamine is primarily used for **copper** and **mercury** poisoning, not lead toxicity. - It has **limited efficacy** in lead chelation and significant **side effects** including nephrotoxicity and bone marrow suppression. *DMSA* - **DMSA** is only indicated for **mild to moderate** lead poisoning **without encephalopathy** in pediatric patients. - It is administered **orally** and is insufficient for severe cases with neurological manifestations like seizures and altered consciousness. *BAL* - **BAL (dimercaprol)** is used as an **adjunct** with EDTA in severe lead encephalopathy, typically given **4 hours before** EDTA to prevent lead redistribution to the brain. - As **monotherapy**, BAL can paradoxically **redistribute lead** to the central nervous system and worsen neurological symptoms.

Q: Antidote for acetaminophen poisoning is?

N-Acetyl cysteine. ***N-Acetyl cysteine*** - **N-acetyl cysteine (NAC)** is the specific antidote for acetaminophen (paracetamol) poisoning, acting by replenishing hepatic **glutathione stores**. - **Glutathione** is crucial for detoxifying the toxic metabolite **N-acetyl-p-benzoquinone imine (NAPQI)**, preventing liver damage. *Penicillamine* - **Penicillamine** is a chelating agent used primarily in conditions like **Wilson's disease** (copper toxicity) and **rheumatoid arthritis**. - It has no role in the treatment or detoxification of **acetaminophen poisoning**. *Glycolamine* - **Glycolamine** is not a recognized pharmaceutical antidote for any specific poisoning. - This compound is not therapeutically relevant in toxicology scenarios, particularly for **acetaminophen overdose**. *Fomipezole* - **Fomepizole** is an antidote used for poisoning by **methanol** and **ethylene glycol**, not acetaminophen. - It works by inhibiting **alcohol dehydrogenase**, preventing the formation of toxic metabolites from these alcohols.

Q: Dicobalt EDTA is used as an antidote for which poisoning?

Cyanide. Cyanide - **Dicobalt EDTA** acts as a **chelating agent** that specifically binds to cyanide ions, forming a stable, non-toxic complex that can be excreted from the body. - This binding prevents cyanide from inhibiting **cytochrome c oxidase** in the mitochondria, thus restoring cellular respiration. *Mushroom* - Treatment for mushroom poisoning is highly dependent on the **species of mushroom** and the toxins involved, and typically involves **supportive care**, activated charcoal, and specific antidotes like **silymarin** or **N-acetylcysteine** for certain types of Amanita poisoning. - Dicobalt EDTA is not indicated for any known form of mushroom toxicity. *Lead* - **Lead poisoning** is treated with **chelating agents** such as **EDTA (calcium disodium EDTA)**, **dimercaprol (BAL)**, or **succimer (DMSA)**, which bind to lead and promote its excretion [1], [2]. - Dicobalt EDTA is specifically formulated for cyanide and would not be effective or safe for lead poisoning due to its cobalt content. *Mercury* - **Mercury poisoning** is typically treated with **chelating agents** like **dimercaprol (BAL)**, **succimer (DMSA)**, or **D-penicillamine**, which help remove mercury from the body [3]. - Dicobalt EDTA does not have affinity for mercury and can be harmful if used for mercury poisoning.

Q: Which drug does NOT cause optic neuropathy?

Penicillin. ***Penicillin*** - Penicillin is a widely used antibiotic that is **not associated with optic neuropathy** - Its primary side effects are **allergic reactions and hypersensitivity** - Visual disturbances or optic nerve damage are **not characteristic** of penicillin therapy *Chloramphenicol* - Known to cause **dose-dependent and duration-dependent optic neuropathy**, especially with prolonged use - Can lead to visual impairment, including reduced visual acuity and color vision defects - May be **irreversible** in some cases *Ethambutol* - **Most notorious** antitubercular drug for causing optic neuritis - Causes **dose-dependent bilateral visual loss** and **red-green color blindness** - Requires regular visual monitoring during therapy - Potentially **irreversible** optic nerve damage *INH (Isoniazid)* - Can cause optic neuropathy, though **less frequently** than ethambutol - Usually associated with **high doses** or prolonged therapy - Risk increases in slow acetylators and those with nutritional deficiencies

Q: Diazepam poisoning is treated by:

Flumazenil. ***Flumazenil*** - **Flumazenil** is a **benzodiazepine receptor antagonist** that competitively binds to the benzodiazepine binding site on the GABA-A receptor, reversing the effects of diazepam. - It is used in cases of severe benzodiazepine overdose causing **respiratory depression** or **severe sedation**. *Resins* - **Resins**, such as **cholestyramine**, are typically used to bind toxins or drugs in the **gastrointestinal tract** that undergo enterohepatic recirculation. - They are generally not effective for reversing the central nervous system depression caused by a benzodiazepine overdose. *Hemofiltration* - **Hemofiltration** is a form of renal replacement therapy used to remove small and middle molecular weight substances from the blood. - While it can remove some drugs, **diazepam** is highly **lipophilic** and extensively **protein-bound**, making it poorly amenable to removal by hemofiltration. *Charcoal* - **Activated charcoal** is used to prevent the absorption of ingested toxins from the gastrointestinal tract. - It is effective when administered soon after ingestion but does not reverse the established effects of an absorbed drug like diazepam in an overdose situation.

Q: Antidote used in methyl alcohol poisoning is?

Fomepizole. ***Fomepizole*** - **Fomepizole** acts as a competitive inhibitor of **alcohol dehydrogenase**, preventing the metabolism of **methanol** into toxic metabolites like **formic acid**. - This prevents the accumulation of highly toxic substances responsible for the metabolic acidosis, visual disturbances, and organ damage seen in **methanol poisoning**. *Alpha methyl dopa* - **Alpha-methyl dopa** is an antihypertensive drug that primarily acts as a central alpha-2 adrenergic agonist, reducing sympathetic outflow. - It is not used in the management of **methanol poisoning** and has no role in inhibiting alcohol metabolism. *Acetyl cysteine* - **Acetylcysteine** is primarily used as an antidote for **acetaminophen (paracetamol) overdose**, where it replenishes glutathione stores, and as a mucolytic agent. - It does not inhibit the metabolism of **methanol** nor does it have any direct therapeutic effect in **methanol poisoning**. *EDTA* - **EDTA (Ethylenediaminetetraacetic acid)** is a chelating agent used to treat **heavy metal poisoning**, such as lead poisoning. - It binds to metal ions, facilitating their excretion from the body, but has no role in the management of **methanol poisoning**.

Q: Oximes are contraindicated in which poisoning:

Carbamate. ***Carbamate*** - Traditionally, oximes were considered **contraindicated** in carbamate poisoning based on concerns they could worsen the **cholinergic crisis** by reactivating carbamylated acetylcholinesterase. - Carbamates spontaneously **decarbamylate** from acetylcholinesterase within minutes to hours, so their inhibition is typically **short-lived and reversible**. - **Clinical relevance**: While modern evidence suggests oximes are more likely **ineffective** rather than harmful in carbamate poisoning, they are generally **not recommended** as they provide no therapeutic benefit. For exam purposes, particularly in historical contexts (NEET 2012-2013), carbamate poisoning is the answer for oxime contraindication. *Diazinon* - Diazinon is an **organophosphate**, and oximes like pralidoxime are **strongly indicated** for reactivating **acetylcholinesterase** inhibited by organophosphates. - Oximes are a crucial part of recommended antidotal therapy alongside **atropine** for severe organophosphate poisoning. - Must be administered early (within 24-48 hours) before **aging** of the phosphorylated enzyme occurs. *Phorate* - Phorate is a highly toxic **organophosphate pesticide**, and oximes are **indicated** for treatment of phorate poisoning. - Oximes work by **dephosphorylating** (nucleophilic attack on) the acetylcholinesterase enzyme, which has been inhibited by the organophosphate, restoring its catalytic function. *Malathion* - Malathion is an **organophosphate insecticide**, and oxime reactivators are **effective** in malathion poisoning. - The mechanism involves **cleaving the phosphate bond** from the serine residue on the acetylcholinesterase enzyme, allowing it to metabolize acetylcholine again and reverse cholinergic toxicity.

Q: Drug of choice for beta antagonist toxicity is?

Glucagon. ***Glucagon*** - **Glucagon** is the drug of choice for **beta-blocker overdose** because it bypasses the beta-adrenergic receptors and directly activates **adenylate cyclase** to increase intracellular cAMP [1]. - This action leads to increased heart rate and myocardial contractility, counteracting the cardiac depression caused by beta-blockers [1]. *Adrenaline* - **Adrenaline** (epinephrine) is a beta-agonist, but its effects are blunted in severe **beta-blocker overdose** due to **competitive antagonism** at beta receptors. - While it can be used for its alpha-agonist effects to increase blood pressure, its efficacy in reversing profound bradycardia and myocardial depression may be limited. *ACE inhibitors* - **ACE inhibitors** are used in the management of hypertension and heart failure, primarily by reducing **angiotensin II** formation and inhibiting **bradykinin** degradation. - They have no direct role in reversing the immediate cardiovascular effects of **beta-antagonist toxicity**. *Dopamine* - **Dopamine** is a **catecholamine** with dose-dependent effects, including positive inotropy and chronotropy at higher doses, but it relies on **adrenergic receptor activation**. - Its effects can be attenuated in **beta-blocker overdose**, similar to adrenaline, making it less effective than glucagon as first-line therapy.

Question 1

Carbonic anhydrase inhibitor should not be given in:

Accepted Answer

Sulfonamide hypersensitivity

Answer

Epilepsy

Answer

High altitude sickness

Answer

Glaucoma

Question 2

All of the following are causes of drug-induced lupus, except:

Accepted Answer

Clofibrate

Answer

Penicillamine

Answer

Hydralazine

Answer

Chlorpromazine

Question 3

A 6-year-old boy is admitted to the ward with drowsiness, dull deep tendon reflexes and seizures. On examination the child has a line on gums and there is a history of constipation. Which will be most appropriate drug that should be used for this child?

Accepted Answer

EDTA

Answer

DMSA

Answer

BAL

Answer

Penicillamine

Question 4

Antidote for acetaminophen poisoning is?

Accepted Answer

N-Acetyl cysteine

Answer

Penicillamine

Answer

Glycolamine

Answer

Fomepizole

Question 5

Dicobalt EDTA is used as an antidote for which poisoning?

Accepted Answer

Cyanide

Answer

Mushroom

Answer

Lead

Answer

Mercury

Question 6

Which drug does NOT cause optic neuropathy?

Accepted Answer

Penicillin

Answer

Chloramphenicol

Answer

Ethambutol

Answer

INH

Question 7

Diazepam poisoning is treated by:

Accepted Answer

Flumazenil

Answer

Resins

Answer

Hemofiltration

Answer

Charcoal

Question 8

Antidote used in methyl alcohol poisoning is?

Accepted Answer

Fomepizole

Answer

Alpha methyl dopa

Answer

Acetyl cysteine

Answer

EDTA

Question 9

Oximes are contraindicated in which poisoning:

Accepted Answer

Carbamate

Answer

Diazinon

Answer

Phorate

Answer

Malathion

Question 10

Drug of choice for beta antagonist toxicity is?

Accepted Answer

Glucagon

Answer

Adrenaline

Answer

ACE inhibitors

Answer

Dopamine

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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