Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Seal like limbs i.e. phocomelia is a specific side effect of -

Thalidomide. ***Thalidomide*** - **Phocomelia**, characterized by severely shortened or absent limbs resembling those of a seal, is a classic and well-documented **teratogenic effect** of thalidomide. - This drug, when taken during early pregnancy (especially between weeks 4 and 8), disrupts limb bud development. *Doxorubicin* - **Doxorubicin** is an **anthracycline antibiotic** used in cancer chemotherapy, known for its significant **cardiotoxicity**, leading to dilated cardiomyopathy. - While it has various side effects, **phocomelia** is not a reported teratogenic effect of doxorubicin. *Cyclophosphamide* - **Cyclophosphamide** is an **alkylating agent** used in chemotherapy and immunosuppression, with notable side effects including **hemorrhagic cystitis** and **myelosuppression**. - Although it is a teratogen and can cause various fetal malformations, it is not specifically associated with **phocomelia**. *Terazosin* - **Terazosin** is an **alpha-1 blocker** primarily used to treat hypertension and benign prostatic hyperplasia (BPH). - Its main side effects include **orthostatic hypotension** and dizziness; it is not known to be teratogenic or associated with **phocomelia**.

Q: In snake envenomation, antivenom treatment is started by giving a dose of:

10 vials. ***10 vials*** - The initial dose of **antivenom** for significant snake envenomation is commonly **10 vials** given intravenously. - This dosage aims to quickly neutralize the circulating **venom toxins** and halt the progression of envenomation effects. *4 vials* - While a smaller dose might be considered in mild cases, **4 vials** is generally insufficient for the initial treatment of moderate to severe snake envenomation. - Underdosing can lead to ongoing **tissue damage** and systemic effects. *2 vials* - An initial dose of **2 vials** of antivenom is typically too low to effectively counteract the venom in clinically significant snakebites. - This dosage would likely result in continued **toxemia** and worsening of symptoms. *20 vials* - An initial dose of **20 vials** is an exceptionally high amount and is generally reserved for extremely severe cases or when there is a poor response to the standard initial dose. - Administering an unnecessarily large dose can increase the risk of **adverse reactions** to the antivenom.

Q: All of the following can be used to decrease intraocular pressure in glaucoma except?

Dexamethasone. ***Dexamethasone*** - **Corticosteroids** like dexamethasone are known to **increase intraocular pressure** by reducing the outflow of aqueous humor, thus exacerbating glaucoma. - This effect is often dose-dependent and can lead to **steroid-induced glaucoma** in susceptible individuals. *Mannitol* - **Mannitol** is an osmotic diuretic used to **rapidly decrease intraocular pressure** by drawing fluid out of the vitreous humor. - It is often used in acute angle-closure glaucoma or before ocular surgery. *Clonidine* - **Clonidine** is an alpha-2 adrenergic agonist that can **decrease aqueous humor production**, thereby reducing intraocular pressure. - While it has been studied for glaucoma, its systemic side effects often limit its use. *Methazolamide* - **Methazolamide** is a **carbonic anhydrase inhibitor** that reduces the production of aqueous humor. - This reduction in fluid production directly leads to a decrease in intraocular pressure, making it a common glaucoma treatment.

Q: Which drug is not given in Wilson disease?

Calcium. ***Calcium*** - **Calcium** is not used in the management of **Wilson disease**. - Its role is primarily in bone health and metabolic functions not directly related to **copper chelation** or **absorption**. *Trientine* - **Trientine** is a **chelating agent** that binds to **copper** and is used as a first-line treatment for **Wilson disease**, especially in patients intolerant to **penicillamine**. - It helps remove excess copper from the body, reducing its toxic effects on organs. *Zinc* - **Zinc** is used as maintenance therapy in **Wilson disease** by inducing metallothionein in the intestinal cells, which sequesters copper and prevents its absorption. - It works by blocking the **absorption of copper** from the diet [1]. *Penicillamine* - **Penicillamine** is a well-established **chelating agent** used to bind and remove excess **copper** in patients with **Wilson disease**. - It is often the initial treatment but can have significant side effects, leading to the use of alternative agents like **trientine**.

Q: A patient presents with painful oral ulcers and target lesions on extremities. Which drug is MOST likely to cause this condition?

Allopurinol. ***Allopurinol*** - **Allopurinol** is a well-known cause of drug-induced **Stevens-Johnson Syndrome (SJS)** or **Toxic Epidermal Necrolysis (TEN)**, which presents with typical mucocutaneous lesions like painful oral ulcers and target lesions on the skin. - The drug is frequently implicated, especially in patients with **renal impairment** or those started on high doses, making it the most likely choice given the severe symptoms. *Metformin* - **Metformin** is a common medication for type 2 diabetes, primarily causing **gastrointestinal side effects** like nausea, diarrhea, and abdominal discomfort. - It is **rarely associated** with severe cutaneous adverse reactions like SJS/TEN. *Atorvastatin* - **Atorvastatin** is a statin commonly used for hyperlipidemia, and its most common side effects include **myalgia**, headache, and gastrointestinal issues. - While it can rarely cause *rashes*, it is **not a typical or frequent cause** of severe mucocutaneous reactions such as target lesions or painful oral ulcers characteristic of SJS/TEN. *Amlodipine* - **Amlodipine**, a calcium channel blocker, is typically associated with side effects such as **edema**, headache, and flushing. - Although drug eruptions can occur with amlodipine, **severe mucocutaneous reactions** like SJS/TEN presenting with target lesions and oral ulcers are **exceedingly rare** and not characteristic of this drug.

Q: A 68-year-old with depression and chronic pain is on amitriptyline. What side effect may arise if given oxybutynin for overactive bladder?

Severe dry mouth. ***Severe dry mouth*** - Both **amitriptyline** (a tricyclic antidepressant) and **oxybutynin** (an anticholinergic for overactive bladder) have significant anticholinergic effects. - The combination of these two drugs can lead to an additive effect, causing pronounced anticholinergic side effects such as **severe dry mouth**, blurred vision, constipation, and cognitive impairment. *Bradycardia* - **Anticholinergic drugs** typically cause **tachycardia** (increased heart rate) by blocking the parasympathetic nervous system's muscarinic receptors on the heart, rather than bradycardia. - While amitriptyline can affect cardiac conduction, severe bradycardia is not a typical **additive anticholinergic side effect** in this context. *Increased sweating* - **Anticholinergic drugs** like amitriptyline and oxybutynin inhibit the activity of sweat glands, which are primarily innervated by cholinergic nerves. - Therefore, the combination of these drugs would likely lead to **decreased sweating** (anhidrosis) rather than increased sweating. *Urinary incontinence* - **Oxybutynin** is prescribed specifically to treat **overactive bladder** and reduce urinary incontinence by relaxing the detrusor muscle. - Therefore, it would improve rather than worsen urinary incontinence; however, it can cause **urinary retention** due to its anticholinergic effect, especially in older male patients.

Q: Which drug is the primary treatment for Wilson’s disease?

Penicillamine. ***Penicillamine*** - **Penicillamine** is a **chelating agent** that binds to copper, forming a complex that is then excreted in the urine. - **Historically considered first-line**, but now generally reserved as an **alternative chelator** due to: - High **side effect profile** (20-30% discontinuation rate) - Risk of **neurological worsening** (up to 50% in neurologically presenting patients) - **Hypersensitivity reactions**, bone marrow suppression, and nephrotic syndrome - **Trientine** has largely replaced penicillamine as the preferred chelator in current practice. *Activated charcoal* - **Activated charcoal** is used to treat **acute toxic ingestions** by adsorbing toxins in the gastrointestinal tract, preventing their absorption. - It is **not effective** for the chronic management of copper overload in Wilson's disease. - Has **no role** in Wilson's disease treatment. *Deferoxamine* - **Deferoxamine** is a **chelating agent** primarily used to treat **iron overload**, particularly in patients with hemochromatosis or those receiving multiple transfusions. - It has **no role** in the treatment of copper accumulation in Wilson's disease. - **Not effective** for copper chelation. *Zinc acetate* - **Zinc acetate** is an important treatment option for Wilson's disease. - **First-line therapy** for **presymptomatic/asymptomatic patients**. - Used for **maintenance therapy** after initial chelation. - Zinc works by **blocking copper absorption** from the gut and promoting metallothionein synthesis (which binds copper intracellularly). - **Does not chelate existing copper stores**, making it less suitable for symptomatic patients with significant copper burden requiring rapid removal.

Q: Which immunosuppressant blocks IL-2 production?

Tacrolimus. ***Tacrolimus*** - Tacrolimus is a **calcineurin inhibitor** that works by binding to **FKBP-12**, forming a complex that inhibits calcineurin. - This inhibition prevents the dephosphorylation of **NFAT**, thereby blocking its translocation to the nucleus and subsequent **IL-2 gene transcription**. *Sirolimus* - Sirolimus is an **mTOR inhibitor** that works downstream from the IL-2 receptor, blocking **T-cell proliferation** in response to IL-2, rather than blocking IL-2 production itself. - It binds to **FKBP-12** but targets the **mTOR complex**, which is crucial for cell growth and division. *Methotrexate* - Methotrexate is an **antimetabolite** that inhibits **dihydrofolate reductase**, interfering with **DNA synthesis** and thus suppressing the proliferation of rapidly dividing cells, including lymphocytes. - Its primary action is not directly blocking IL-2 production but rather reducing the overall immune cell expansion. *Mycophenolate* - Mycophenolate mofetil is a **reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH)**, an enzyme critical for the *de novo* synthesis of guanosine nucleotides. - This preferentially inhibits the proliferation of **lymphocytes**, which are highly dependent on the *de novo* pathway for purine synthesis, but does not directly block IL-2 production.

Q: Atropine is not an antidote in:

Endrin. ***Endrin*** - Endrin is an **organochlorine insecticide**, and its toxicity is primarily mediated through the central nervous system, causing seizures and neurological symptoms. - Atropine is an **anticholinergic drug** and is ineffective because organochlorines do not act on cholinergic receptors; therefore, it is not an antidote for endrin poisoning. *Baygon* - Baygon is a **carbamate insecticide**, which inhibits acetylcholinesterase, leading to cholinergic crisis. - Atropine is an appropriate antidote for Baygon poisoning, as it blocks the effects of excess acetylcholine at muscarinic receptors. *Parathion* - Parathion is an **organophosphate insecticide**, known for irreversible inhibition of acetylcholinesterase, resulting in severe cholinergic toxicity. - Atropine is a crucial antidote for parathion poisoning, used to counteract the muscarinic effects of acetylcholine accumulation. *Tik 20* - Tik 20 typically contains **organophosphate compounds** such as malathion or parathion, which are acetylcholinesterase inhibitors. - As an effective anticholinergic, atropine is indicated in the treatment of poisoning by organophosphates found in products like Tik 20.

Q: A 5-year-old child who has taken 10 iron tablets presents with nausea and abdominal pain. What is the antidote of iron poisoning?

Deferoxamine. ***Deferoxamine*** - **Deferoxamine** is the chelating agent of choice for **iron poisoning**, forming a non-toxic complex that is excreted in urine. - It is indicated in patients with significant iron overdose, often presenting with **gastrointestinal symptoms** (nausea, abdominal pain), metabolic acidosis, or evidence of end-organ damage. *EDTA* - **EDTA (Calcium Disodium Versenate)** is primarily used to treat **lead poisoning** and sometimes other heavy metal intoxications [1]. - It is not effective for iron poisoning and can potentially worsen symptoms due to its affinity for calcium [1]. *British Anti Lewisite* - **British Anti Lewisite (BAL), or dimercaprol**, is an antidote for **arsenic, mercury, and gold poisoning** [2]. - It is not used for iron overdose and has a high incidence of side effects. *Penicillamine* - **Penicillamine** is another chelating agent used to treat **copper poisoning (Wilson's disease)** and sometimes lead or mercury poisoning. - It is not the primary antidote for iron poisoning and has a slower onset of action compared to deferoxamine.

Question 1

Seal like limbs i.e. phocomelia is a specific side effect of -

Accepted Answer

Thalidomide

Answer

Doxorubicin

Answer

Cyclophosphamide

Answer

Terazosin

Question 2

In snake envenomation, antivenom treatment is started by giving a dose of:

Accepted Answer

10 vials

Answer

4 vials

Answer

2 vials

Answer

20 vials

Question 3

All of the following can be used to decrease intraocular pressure in glaucoma except?

Accepted Answer

Dexamethasone

Answer

Mannitol

Answer

Clonidine

Answer

Methazolamide

Question 4

Which drug is not given in Wilson disease?

Accepted Answer

Calcium

Answer

Trientine

Answer

Zinc

Answer

Penicillamine

Question 5

A patient presents with painful oral ulcers and target lesions on extremities. Which drug is MOST likely to cause this condition?

Accepted Answer

Allopurinol

Answer

Metformin

Answer

Atorvastatin

Answer

Amlodipine

Question 6

A 68-year-old with depression and chronic pain is on amitriptyline. What side effect may arise if given oxybutynin for overactive bladder?

Accepted Answer

Severe dry mouth

Answer

Bradycardia

Answer

Increased sweating

Answer

Urinary incontinence

Question 7

Which drug is the primary treatment for Wilson’s disease?

Accepted Answer

Penicillamine

Answer

Activated charcoal

Answer

Deferoxamine

Answer

Zinc acetate

Question 8

Which immunosuppressant blocks IL-2 production?

Accepted Answer

Tacrolimus

Answer

Sirolimus

Answer

Methotrexate

Answer

Mycophenolate

Question 9

Atropine is not an antidote in:

Accepted Answer

Endrin

Answer

Baygon

Answer

Parathion

Answer

Tik 20

Question 10

A 5-year-old child who has taken 10 iron tablets presents with nausea and abdominal pain. What is the antidote of iron poisoning?

Accepted Answer

Deferoxamine

Answer

EDTA

Answer

British Anti Lewisite

Answer

Penicillamine

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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