Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Dialysis is useful in poisoning with all of the following, EXCEPT:

Copper sulphate. The effectiveness of hemodialysis in treating poisoning depends on specific pharmacokinetic properties of the toxin. For a drug to be dialyzable, it must have a **low molecular weight, low volume of distribution ($V_d$), low protein binding, and high water solubility.** **Why Copper Sulphate is the correct answer:** Copper sulphate poisoning cannot be managed with dialysis because copper has a **high volume of distribution** and binds extensively to plasma proteins (like albumin and ceruloplasmin) and tissues. Dialysis only removes substances present in the free, unbound form within the intravascular compartment. The definitive treatment for copper poisoning is chelation therapy with **D-Penicillamine**. **Analysis of incorrect options:** * **Methyl alcohol & Ethylene glycol:** These are low molecular weight, water-soluble alcohols with small volumes of distribution [1]. Dialysis is highly effective at removing both the parent compounds and their toxic metabolites (formic acid and glycolic acid) [2]. * **Barbiturates:** Long-acting barbiturates (like Phenobarbital) have low protein binding and low $V_d$, making them amenable to removal via dialysis or hemoperfusion. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Dialyzable drugs (BLAST-ED):** **B**arbiturates (Long acting), **L**ithium, **A**lcohols (Methanol, Ethanol), **S**alicylates, **T**heophylline, **E**thylene glycol, **D**epakote (Valproate). * **Drugs NOT dialyzable:** Digoxin, Benzodiazepines, Opioids, Copper, and Organophosphates (due to high $V_d$ or high protein binding). * **Hemoperfusion** is preferred over dialysis for drugs that are highly protein-bound but have a small $V_d$, such as Carbamazepine or Phenytoin.

Q: Which of the following drugs contains two sulfhydryl groups in a molecule?

BAL. **Explanation:** The correct answer is **BAL (British Anti-Lewisite)**, also known as **Dimercaprol**. **1. Why BAL is correct:** BAL is a classic heavy metal chelator. Chemically, it is **2,3-dimercapto-1-propanol**. The term "mercapto" refers to the **sulfhydryl (-SH) group**. As the name "di-mercapto" implies, each molecule contains **two sulfhydryl groups**. These groups act as ligands that bind to heavy metals (like arsenic, mercury, and gold), forming a stable, non-toxic, heterocyclic ring complex that is excreted in the urine. **2. Why other options are incorrect:** * **EDTA (Ethylenediaminetetraacetic acid):** This is a polyamino carboxylic acid. It acts as a hexadentate ligand but **does not contain sulfhydryl groups**. It chelates metals (primarily calcium and lead) through its nitrogen and oxygen atoms. * **Penicillamine:** While Penicillamine is a degradation product of penicillin and contains **one sulfhydryl group** (it is D-beta-beta-dimethylcysteine), it does not contain two. It is used primarily for Wilson’s disease (copper chelation) and cystinuria. **Clinical Pearls for NEET-PG:** * **BAL Administration:** It is highly lipid-soluble and must be administered via **deep intramuscular injection** in an oily vehicle (peanut oil). * **Contraindication:** BAL is contraindicated in **Iron and Cadmium poisoning** because the BAL-metal complex is nephrotoxic. * **Water-soluble analogs:** Succimer (DMSA) and Unithiol (DMPS) are water-soluble derivatives of BAL that can be given orally and have a better safety profile. * **Specific Antidote Rule:** BAL is the first-line chelator for **Arsenic, Mercury (acute), and Gold** poisoning. In **Lead poisoning**, it is often used in combination with EDTA (especially in lead encephalopathy).

Q: Which drug is contraindicated in pregnancy?

Frusemide. **Explanation:** The correct answer is **Frusemide (C)**. While several drugs in this list have safety concerns, Frusemide is generally avoided in pregnancy because it can cause **placental hypoperfusion**. Diuretics reduce maternal plasma volume, which may compromise blood flow to the fetus, potentially leading to intrauterine growth restriction (IUGR). It is only used in rare, life-threatening situations like maternal pulmonary edema. **Analysis of Options:** * **A. Enalapril:** This is a classic **teratogen** (ACE inhibitor). It is contraindicated, especially in the 2nd and 3rd trimesters, as it causes fetal renal dysgenesis, oligohydramnios, and skull defects. However, in the context of this specific question (often sourced from standard textbooks like K.D. Tripathi), Frusemide is highlighted for its specific effect on placental perfusion. * **B. Hydralazine:** This is a **safe** and frequently used drug for the management of hypertensive emergencies in pregnancy (Preeclampsia/Eclampsia). It is a direct vasodilator. * **D. Aldactone (Spironolactone):** This is generally avoided due to its **anti-androgenic effects**, which can interfere with the sexual differentiation of a male fetus (feminization). **NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC) for Chronic Hypertension in Pregnancy:** Labetalol (Alpha + Beta blocker). * **Other Safe Antihypertensives:** Methyldopa (central alpha-2 agonist), Nifedipine (CCB). * **Absolute Contraindications:** ACE inhibitors and ARBs (Renal issues), Statins (Teratogenic), Warfarin (Fetal Warfarin Syndrome/Chondrodysplasia punctata). * **Magnesium Sulfate ($MgSO_4$):** DOC for seizure prophylaxis and control in Eclampsia.

Q: Which schedule of the Drugs and Cosmetics Act mandates that a drug must be sold by retail only upon production of a prescription from a Registered Medical Practitioner?

Schedule H. ### Explanation **Correct Option: A. Schedule H** The Drugs and Cosmetics Act (1940) and Rules (1945) classify drugs into various schedules to regulate their manufacture, sale, and distribution. **Schedule H** contains a list of "Prescription Drugs." By law, these drugs can only be sold by retail upon the production of a valid prescription from a **Registered Medical Practitioner (RMP)**. The label of these drugs must display the symbol ‘Rx’ and a warning stating that they are not to be sold without a prescription. **Analysis of Incorrect Options:** * **Schedule M:** This schedule specifies the **Good Manufacturing Practices (GMP)** and requirements for factory premises, plants, and equipment for pharmaceutical products. * **Schedule P:** This deals with the **Life period (expiry date)** and storage conditions of various drugs (e.g., Insulin, Antibiotics). * **Schedule W:** This previously listed drugs that were to be marketed under **Generic names** only (though this schedule has largely been omitted/merged in recent amendments). **High-Yield Clinical Pearls for NEET-PG:** * **Schedule H1:** Introduced in 2013 to curb the misuse of antibiotics and anti-TB drugs. It requires the pharmacist to maintain a separate register with patient and prescriber details, retained for 3 years. * **Schedule X:** Includes psychotropic drugs and narcotics (e.g., Ketamine, Amphetamines). These require a double-copy prescription, and the pharmacist must keep one copy for 2 years. * **Schedule G:** Drugs that must be taken under **medical supervision** (e.g., Metformin, Antihistamines) but do not necessarily require a formal prescription for every refill like Schedule H. * **Schedule Y:** Guidelines for **Clinical Trials** and import/manufacture of new drugs.

Q: All of the following drugs can induce a Systemic Lupus Erythematosus (SLE)-like syndrome except?

Chloramphenicol. **Explanation:** Drug-Induced Lupus Erythematosus (DILE) is a clinical syndrome that mimics idiopathic SLE, typically characterized by arthralgia, myalgia, fever, and pleuritis, but notably sparing the kidneys and CNS. **Why Chloramphenicol is the Correct Answer:** Chloramphenicol is a broad-spectrum antibiotic primarily associated with **Bone Marrow Suppression** (dose-dependent) and **Aplastic Anemia** (idiosyncratic). It is also known for causing **Gray Baby Syndrome** in neonates. It does not have a known association with inducing an SLE-like syndrome. **Analysis of Incorrect Options:** * **Hydralazine:** This is the drug with the **highest risk** of inducing DILE. The risk is significantly higher in "slow acetylators" as the drug is metabolized by the N-acetyltransferase (NAT) enzyme. * **Isoniazid (INH):** A primary anti-tubercular drug that frequently induces antinuclear antibodies (ANA). Like hydralazine, it is metabolized by acetylation and can trigger lupus-like symptoms. * **Sulphonamides:** These drugs are known triggers for various hypersensitivity reactions, including DILE and Stevens-Johnson Syndrome (SJS). **NEET-PG High-Yield Pearls:** 1. **Classic Triad of DILE Drugs:** Remember the mnemonic **"SHIP"** — **S**ulphonamides/Sulfasalazine, **H**ydralazine, **I**soniazid, and **P**rocainamide. 2. **Serology:** The hallmark of DILE is the presence of **Anti-Histone Antibodies** (>95% of cases). Unlike idiopathic SLE, Anti-dsDNA antibodies are usually absent. 3. **Metabolism Link:** DILE is most common in **Slow Acetylators**. 4. **Management:** Symptoms typically resolve spontaneously within weeks after **discontinuing** the offending drug.

Q: In chronic lead poisoning, which of the following is elevated?

6-amino levulinic acid. **Explanation:** Lead poisoning (Plumbism) interferes with the heme biosynthetic pathway by inhibiting two key enzymes: **$\delta$-aminolevulinic acid dehydratase (ALAD)** and **Ferrochelatase**. 1. **Why Option B is correct:** Lead directly inhibits the enzyme **$\delta$-aminolevulinic acid dehydratase (ALAD)**. This enzyme is responsible for converting $\delta$-aminolevulinic acid (ALA) into porphobilinogen. When ALAD is inhibited, its substrate, **$\delta$-aminolevulinic acid (ALA)**, accumulates in the blood and is excreted in excess in the urine. This is a hallmark biochemical finding in lead toxicity. 2. **Why other options are incorrect:** * **Porphobilinogen (A):** This is the product of the reaction catalyzed by ALAD. Since ALAD is inhibited, porphobilinogen levels actually decrease or remain low. (Elevated porphobilinogen is characteristic of Acute Intermittent Porphyria). * **Bilirubin (C) & Urobilinogen (D):** These are products of heme degradation. While lead can cause a mild hemolytic anemia, these markers are not specific to lead poisoning and do not represent the primary enzymatic block in the heme pathway. **High-Yield Clinical Pearls for NEET-PG:** * **Enzymes Inhibited:** ALAD and Ferrochelatase (leads to elevated **Free Erythrocyte Protoporphyrin/Zinc Protoporphyrin**). * **Hematological Finding:** Microcytic hypochromic anemia with **Basophilic Stippling** (due to inhibition of pyrimidine 5'-nucleotidase). * **Clinical Signs:** Burtonian lines (blue-purple gums), Lead colic, and "Wrist drop/Foot drop" (peripheral neuropathy). * **Treatment of Choice:** Oral **Succimer** (DMSA) for mild-moderate cases; **Ca-EDTA** or **Dimercaprol** (BAL) for severe/encephalopathic cases.

Question 1

Dialysis is useful in poisoning with all of the following, EXCEPT:

Accepted Answer

Copper sulphate

Answer

Methyl alcohol

Answer

Barbiturates

Answer

Ethylene glycol

Question 2

Pseudotumor cerebri is caused by all except:

Accepted Answer

Digoxin

Answer

Hypervitaminosis A

Answer

Outdated tetracycline

Answer

Nalidixic acid

Question 3

Which of the following drugs contains two sulfhydryl groups in a molecule?

Accepted Answer

BAL

Answer

EDTA

Answer

Pencillamine

Answer

None of the above

Question 4

A patient with congestive heart failure was started on digoxin and diuretics. He later presents with bradycardia, GIT upset, and visual disturbances. His serum potassium was found to be 2.5 mEq/L. What is the most likely reason for these features?

Accepted Answer

Digoxin toxicity

Answer

Left ventricular aneurysm

Answer

Viral gastroenteritis

Answer

Hypokalemia

Question 5

Which drug is contraindicated in pregnancy?

Accepted Answer

Frusemide

Answer

Enalapril

Answer

Hydralazine

Answer

Aldactone

Question 6

Which schedule of the Drugs and Cosmetics Act mandates that a drug must be sold by retail only upon production of a prescription from a Registered Medical Practitioner?

Accepted Answer

Schedule H

Answer

Schedule M

Answer

Schedule P

Answer

Schedule W

Question 7

All of the following drugs can induce a Systemic Lupus Erythematosus (SLE)-like syndrome except?

Accepted Answer

Chloramphenicol

Answer

Isoniazid

Answer

Hydralazine

Answer

Sulphonamides

Question 8

In chronic lead poisoning, which of the following is elevated?

Accepted Answer

6-amino levulinic acid

Answer

Porphobilinogen

Answer

Bilirubin

Answer

Urobilinogen

Question 9

Which of the following drugs is the longest-acting for overactive bladder?

Accepted Answer

Solifenacin

Answer

Oxybutynin

Answer

Trospium

Answer

Flavoxate

Question 10

What is the treatment of choice for opioid overdose?

Accepted Answer

Naloxone IV

Answer

Nalorphine IV

Answer

Haemodialysis

Answer

Forced alkaline diuresis

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

On this page

Practice by Chapter

Want unlimited practice?