Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Main function of sodium citrate in ORS?

To correct Acidosis. ***To correct Acidosis*** - **Sodium citrate** provides a source of **bicarbonate** precursor, which helps to correct the **metabolic acidosis** often associated with severe dehydration and diarrhea. - In the body, citrate is metabolized into bicarbonate, raising the blood pH and counteracting the effects of acidosis. *To increase absorption of glucose by cotransport* - The absorption of glucose and sodium is coupled, meaning the presence of **sodium enhances glucose absorption** through the **SGLT1 cotransporter**. - While sodium is essential for glucose absorption, **citrate's primary role is not this direct cotransport mechanism**. *To correct electrolyte imbalance* - ORS formulations contain various electrolytes like **sodium chloride** and **potassium chloride** to rectify electrolyte imbalances caused by diarrhea. - While sodium citrate contributes to sodium levels, its specific function goes beyond just general electrolyte correction to address the **acid-base balance**. *To correct dehydration* - The overall purpose of ORS is to **rehydrate the patient** by providing fluids and electrolytes, which helps restore circulating volume. - While citrate is a component of ORS, **rehydration also depends on the water and other salts** present in the solution, not solely on citrate.

Q: Best method of treatment for methyl alcohol poisoning is:

Ethyl alcohol. ***Ethyl alcohol*** - **Ethanol** (ethyl alcohol) acts as a competitive substrate for **alcohol dehydrogenase**, the enzyme responsible for metabolizing **methanol** into toxic metabolites like formaldehyde and formic acid. - By saturating alcohol dehydrogenase, ethanol prevents the formation of these toxic metabolites, allowing methanol to be excreted unchanged. - **Clinical note**: While **fomepizole** (4-methylpyrazole) is now the preferred first-line antidote when available, **ethanol** remains an effective and widely used alternative, especially in resource-limited settings. - **Administration**: IV ethanol is given to maintain blood ethanol concentration of 100-150 mg/dL. *Calcium gluconate* - **Calcium gluconate** is primarily used to treat **hypocalcemia**, ethylene glycol poisoning (for hypocalcemia), or hydrofluoric acid burns. - It has no role in the management of methyl alcohol poisoning as it does not interfere with the metabolism of methanol or its toxic byproducts. *Amphetamines* - **Amphetamines** are central nervous system stimulants used for conditions like ADHD and narcolepsy. - They have no therapeutic benefit or antidotal properties in the context of methanol poisoning. *1% Ammonia* - **Ammonia** is a strong base and is highly corrosive; it has no medical application as an antidote for methanol poisoning. - Administering ammonia would cause direct tissue damage and exacerbate patient harm due to its toxic and caustic properties.

Q: All of the following are known adverse effects of thalidomide, except:

Diarrhoea. ***Diarrhoea*** - **Diarrhoea** is generally *not* considered a common or significant adverse effect of thalidomide. Constipation is more frequently reported. - While individual reactions vary, thalidomide's primary adverse effect profile does not typically include diarrhoea. *Teratogenicity* - **Teratogenicity** is the most notorious adverse effect of thalidomide, causing severe birth defects like **phocomelia** (shortened or absent limbs) in infants exposed during pregnancy. - Due to this, stringent **risk evaluation and mitigation strategies (REMS)** are in place for thalidomide use. *DVT* - Thalidomide is known to increase the risk of **venous thromboembolism (VTE)**, including **deep vein thrombosis (DVT)** and pulmonary embolism, especially in patients with multiple myeloma. - Prophylactic anticoagulation is often recommended for patients receiving thalidomide, particularly in combination with corticosteroids. *Neuropathy* - **Peripheral neuropathy** is a common and dose-limiting adverse effect of thalidomide, often presenting as numbness, tingling, and pain in the hands and feet. - It can be progressive and potentially irreversible, requiring careful monitoring and dose adjustments.

Q: Which ACE inhibitor is safe in renal failure?

Benazepril. ***Benazepril*** - Among the listed ACE inhibitors, benazepril has the **most favorable excretion profile** in renal failure with approximately **50% renal and 50% hepatic elimination** (dual excretion pathway). - This balanced elimination reduces the risk of drug accumulation compared to predominantly renally excreted ACE inhibitors. - While dose adjustment may still be needed in **severe renal impairment**, benazepril is considered the **safest option among those listed** for patients with renal dysfunction. - **Note:** Fosinopril (not listed here) has true 50/50 dual elimination and requires no dose adjustment in renal failure, making it the ideal choice in clinical practice. *Captopril* - This ACE inhibitor undergoes predominantly **renal excretion (95%)** as unchanged drug and metabolites. - Requires significant **dose reduction** in renal failure to prevent accumulation and adverse effects including **hyperkalemia** and **hypotension**. - Less safe than benazepril in renal impairment due to heavy dependence on renal elimination. *Enalapril* - Enalapril is a prodrug converted to **enalaprilat**, with approximately **90% renal excretion**. - Dose adjustment is mandatory based on **creatinine clearance** in patients with renal failure. - Higher risk of accumulation and toxicity compared to dual-elimination ACE inhibitors like benazepril.

Q: Alkaline diuresis in drug poisoning is not done in?

Morphine. ***Morphine*** - **Morphine** is an **alkaline drug**, so its elimination is actually enhanced by **acidification of the urine**, not alkalinization. - Alkaline diuresis would decrease the ionization of morphine in the renal tubules, leading to **increased reabsorption** and reduced excretion. *Aspirin* - **Aspirin (acetylsalicylic acid)** is an **acidic drug**, and **alkaline diuresis** is effective in increasing its excretion by trapping the ionized form in the renal tubules. - This process prevents reabsorption and promotes clearance, which is a standard treatment for aspirin overdose. *Methotrexate* - **Methotrexate** is a **weak organic acid**, and **alkaline diuresis** is crucial in reducing its toxicity, especially in high-dose therapy. - By increasing urine pH, the renal elimination of methotrexate is significantly enhanced, preventing kidney damage and systemic accumulation. *Phenobarbitone* - **Phenobarbitone** is a **weak acid**, and **alkaline diuresis** is a well-established method to increase its renal excretion in cases of overdose. - Alkalinization of the urine promotes the ionization of phenobarbitone, reducing its reabsorption by the renal tubules and accelerating its elimination.

Q: Interstitial nephritis is associated with all of the following medications except:

INH. ***INH*** - **Isoniazid (INH)** is primarily associated with **hepatotoxicity** (liver damage) and **peripheral neuropathy**, not typically interstitial nephritis. - While many drugs can rarely cause various adverse effects, INH is not a recognized common cause of **drug-induced interstitial nephritis**. *Beta-lactam antibiotics* - **Beta-lactam antibiotics**, including penicillins and cephalosporins, are among the most common causes of **drug-induced acute interstitial nephritis (AIN)**. - AIN is an **allergic hypersensitivity reaction** characterized by inflammation of the kidney's tubules and interstitium. *Diuretics* - Certain **diuretics**, particularly **thiazide diuretics** and **loop diuretics**, have been implicated in causing **acute interstitial nephritis**. - The mechanism is thought to be an **allergic or hypersensitivity reaction** within the renal tubules and interstitium. *Allopurinol* - **Allopurinol**, used to treat gout and hyperuricemia, is a known cause of **drug-induced acute interstitial nephritis**. - Renal involvement with allopurinol can range from mild tubular dysfunction to severe **acute kidney injury** due to AIN.

Q: Which of the following conditions is not associated with an increased risk of neuropathy caused by Isoniazid (INH)?

Hyperthyroidism. ***Hyperthyroidism*** - **Hyperthyroidism** is not typically associated with an increased risk of isoniazid-induced neuropathy. The neuropathy due to INH is primarily linked to **pyridoxine (vitamin B6) deficiency**. - While hyperthyroidism can cause its own set of neurological symptoms, it does not directly impair pyridoxine metabolism or exacerbate INH's neurotoxic effects. *Uremia* - **Uremia** (renal failure) can increase the risk of INH-induced neuropathy due to impaired drug excretion, leading to higher plasma concentrations of INH and its metabolites. - Patients with uremia often have compromised nutritional status and may experience vitamin deficiencies, further contributing to pyridoxine depletion. *Diabetes mellitus* - **Diabetes mellitus** is a significant risk factor for INH-induced neuropathy because it is an independent cause of **peripheral neuropathy** itself, making patients more susceptible to additional nerve damage. - Diabetic patients may also have altered pyridoxine metabolism or suboptimal nutritional intake, predisposing them to INH toxicity. *Poor nutrition* - **Poor nutrition**, particularly malabsorption or inadequate dietary intake, directly contributes to **pyridoxine (vitamin B6) deficiency**. - Isoniazid's mechanism of neurotoxicity involves interfering with pyridoxine metabolism, so pre-existing deficiency significantly increases the risk of neuropathy.

Q: Permission from DCGI [Drug controller general, India] is needed before which phase of drug trial?

Phase 3. ***Phase 3*** - Permission from the **DCGI (Drug Controller General of India)** is mandatory before initiating **Phase 3** clinical trials as per **Schedule Y** of the Drugs and Cosmetics Rules. - Phase 3 trials involve **large-scale studies in Indian patients** to establish efficacy and safety in the target population, requiring explicit regulatory approval. - This is the critical regulatory checkpoint where DCGI evaluates the Phase 1 and 2 data before allowing widespread testing in Indian subjects. *Phase 1* - Phase 1 trials can be conducted after approval from the **Institutional Ethics Committee (IEC)** without requiring prior DCGI permission. - These trials in healthy volunteers focus on safety, pharmacokinetics, and dose-ranging studies. - DCGI is informed but explicit permission is not mandatory at this stage. *Phase 2* - Phase 2 trials also proceed with **IEC approval** and do not require prior DCGI permission. - These trials evaluate therapeutic efficacy and dose determination in a limited number of patients. - Results from Phase 2 are submitted to DCGI when seeking Phase 3 approval. *Phase 4* - Phase 4 trials are **post-marketing surveillance** studies conducted after drug approval. - These are conducted under the Post-Marketing Surveillance (PMS) framework. - While regulatory oversight exists, these are not pre-market trials requiring permission to initiate.

Q: Which of the following is a primary use of Levamisole?

Antihelminthic. ***Antihelminthic*** - Levamisole is **primarily classified as an antihelminthic drug**, used to treat parasitic worm infections. - It acts as a **nicotinic receptor agonist** in nematodes, causing spastic paralysis of the worms, leading to their expulsion. - It was historically used in humans for treating ascariasis and hookworm infections, and is still used in **veterinary medicine** for deworming livestock. - This is its **primary pharmacological classification** in standard medical textbooks. *Immunomodulator* - Levamisole does have **immunomodulatory properties** that were discovered secondary to its antihelminthic use. - It was used as **adjuvant therapy in colon cancer** (with 5-FU) to enhance immune response. - However, this is a **secondary use**, not its primary classification, and has been largely discontinued due to severe side effects like agranulocytosis. *Immunostimulant* - While levamisole can stimulate certain aspects of cell-mediated immunity, this overlaps with its immunomodulatory effects. - This is **not its primary pharmacological classification** - it remains primarily an antihelminthic agent. *None of the options* - This is incorrect because **antihelminthic** is clearly the primary and correct classification of levamisole in pharmacology. - Its antihelminthic action was its original and primary therapeutic application.

Q: Acetaminophen [Paracetamol] induced liver toxicity is due to which metabolite?

NAPQI. ***NAPQI*** - **N-acetyl-p-benzoquinone imine (NAPQI)** is a highly reactive and toxic metabolite produced during acetaminophen metabolism, especially in overdose situations [1, 3]. - When glutathione stores are depleted due to excessive NAPQI formation, this metabolite covalently binds to hepatic macromolecules, causing **hepatocellular damage and necrosis** [1, 3].*N-acetylcysteine* - **N-acetylcysteine (NAC)** is the antidote for acetaminophen overdose, not the toxic metabolite itself [2, 3]. - NAC works by replenishing hepatic **glutathione stores**, which helps detoxify NAPQI and prevent liver injury [2, 3].*Co-Q* - **Coenzyme Q10 (CoQ10)** is an endogenous antioxidant and electron carrier in the mitochondrial respiratory chain. - It is not a metabolite of acetaminophen and plays no direct role in acetaminophen-induced liver toxicity.*Cytochrome 'C'* - **Cytochrome c** is a protein involved in the electron transport chain in mitochondria and plays a critical role in apoptosis. - While cellular damage from NAPQI can eventually lead to cytochrome c release and apoptosis, cytochrome c itself is not a metabolite of acetaminophen or the direct cause of toxicity.

Question 1

Main function of sodium citrate in ORS?

Accepted Answer

To correct Acidosis

Answer

To increase absorption of glucose by cotransport

Answer

To correct electrolyte imbalance

Answer

To correct dehydration

Question 2

Best method of treatment for methyl alcohol poisoning is:

Accepted Answer

Ethyl alcohol

Answer

Calcium gluconate

Answer

Amphetamines

Answer

1% Ammonia

Question 3

All of the following are known adverse effects of thalidomide, except:

Accepted Answer

Diarrhoea

Answer

DVT

Answer

Neuropathy

Answer

Teratogenicity

Question 4

Which ACE inhibitor is safe in renal failure?

Accepted Answer

Benazepril

Answer

Captopril

Answer

Enalapril

Answer

None of the options

Question 5

Alkaline diuresis in drug poisoning is not done in?

Accepted Answer

Morphine

Answer

Aspirin

Answer

Phenobarbitone

Answer

Methotrexate

Question 6

Interstitial nephritis is associated with all of the following medications except:

Accepted Answer

INH

Answer

Diuretics

Answer

Allopurinol

Answer

Beta-lactam antibiotics

Question 7

Which of the following conditions is not associated with an increased risk of neuropathy caused by Isoniazid (INH)?

Accepted Answer

Hyperthyroidism

Answer

Uremia

Answer

Diabetes mellitus

Answer

Poor nutrition

Question 8

Permission from DCGI [Drug controller general, India] is needed before which phase of drug trial?

Accepted Answer

Phase 3

Answer

Phase 1

Answer

Phase 2

Answer

Phase 4

Question 9

Which of the following is a primary use of Levamisole?

Accepted Answer

Antihelminthic

Answer

Immunostimulant

Answer

None of the options

Answer

Immunomodulator

Question 10

Acetaminophen [Paracetamol] induced liver toxicity is due to which metabolite?

Accepted Answer

NAPQI

Answer

Co-Q

Answer

Cytochrome 'C'

Answer

N-acetylcysteine

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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