Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity Indian Medical PG Practice Questions and MCQs

Question 901: Which ACE inhibitor is safe in renal failure?

A. Captopril
B. Enalapril
C. None of the options
D. Benazepril (Correct Answer)

Explanation: ***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.

Question 902: Which triptan is available in nasal spray form?

A. Sumatriptan (Correct Answer)
B. Rizatriptan
C. Naratriptan
D. Frovatriptan

Explanation: ***Sumatriptan*** - **Sumatriptan** is available in multiple formulations, including **oral, subcutaneous injection, and nasal spray**, making it versatile for migraine treatment [1], [2]. - The nasal spray formulation allows for **faster absorption** and onset of action, which can be beneficial for patients with nausea or vomiting during migraine attacks [1]. *Rizatriptan* - **Rizatriptan** is primarily available in **oral tablet** and **orally disintegrating tablet** (ODT) forms [2]. - It does not have a commonly available nasal spray formulation for migraine treatment [2]. *Naratriptan* - **Naratriptan** is available as an **oral tablet** and is known for its **longer half-life** and generally milder side effect profile compared to sumatriptan [2]. - It is not available in a nasal spray formulation [2]. *Frovatriptan* - **Frovatriptan** is available exclusively as an **oral tablet** and is notable for having the **longest half-life** among triptans, making it useful for preventing recurring migraines [2]. - There is no nasal spray formulation for frovatriptan [2].

Question 903: Which drug is most commonly associated with causing fixed drug eruptions?

A. Aminoglycoside
B. Sulfonamide (Correct Answer)
C. Erythromycin
D. None of the options

Explanation: ***Sulfonamide*** - **Sulfonamides**, particularly **sulfamethoxazole-trimethoprim**, are frequently implicated in causing fixed drug eruptions. - A fixed drug eruption characteristically recurs at the **same cutaneous site** each time the offending drug is administered. *Aminoglycoside* - **Aminoglycosides** are broad-spectrum antibiotics known for potential **ototoxicity** and **nephrotoxicity**. - While they can cause various adverse reactions, fixed drug eruptions are **not a common association** with this drug class. *Erythromycin* - **Erythromycin** is a macrolide antibiotic primarily associated with **gastrointestinal side effects**, such as nausea and abdominal cramping. - Although drug eruptions can occur, fixed drug eruptions are **not typically linked** to erythromycin. *None of the options* - This option is incorrect because **sulfonamides** are well-documented causes of fixed drug eruptions. - Therefore, there is a specific drug class listed that is strongly associated with this condition.

Question 904: Which drug is most commonly associated with causing exanthema?

A. Atropine
B. Phenytoin
C. Sulfonamide (Correct Answer)
D. All of the options

Explanation: ***Sulfonamide*** - **Sulfonamides** are among the **most common causes** of drug-induced exanthema (maculopapular/morbilliform rash). - They account for a significant proportion of cutaneous adverse drug reactions, with exanthema being the most frequent presentation. - The mechanism typically involves a **delayed hypersensitivity reaction** (Type IV) to the drug or its metabolites. - **Classic presentation:** Symmetrical, erythematous, maculopapular rash appearing 7-14 days after drug initiation. *Phenytoin* - **Phenytoin** can cause exanthematous eruptions, but it is more notably associated with **severe cutaneous adverse reactions** such as: - **DRESS syndrome** (Drug Reaction with Eosinophilia and Systemic Symptoms) - **Stevens-Johnson syndrome (SJS)** and **Toxic Epidermal Necrolysis (TEN)** - While exanthema can occur, **sulfonamides** are more frequently implicated in simple morbilliform rashes. *Atropine* - **Atropine** is an anticholinergic agent primarily causing **predictable pharmacological effects**: - Dry mouth, mydriasis, tachycardia, urinary retention - **Allergic skin reactions** with atropine are rare and not a characteristic adverse effect. - Atropine is **not recognized** as a common cause of exanthema. *All of the options* - This is incorrect because **atropine** is not commonly associated with exanthema. - While both sulfonamides and phenytoin can cause exanthema, only **sulfonamides** are considered among the **most common** causes.

Question 905: Which local anaesthetic is known to cause methemoglobinemia?

A. Procaine
B. Prilocaine (Correct Answer)
C. Ropivacaine
D. Etidocaine

Explanation: ***Prilocaine*** - **Prilocaine** is metabolized into **ortho-toluidine**, which can oxidize hemoglobin to **methemoglobin**, especially at higher doses or in susceptible individuals. - **Methemoglobinemia** symptoms include **cyanosis**, **dyspnea**, and in severe cases, central nervous system depression, due to reduced oxygen-carrying capacity of blood. *Procaine* - **Procaine** is an ester-type local anesthetic. It is metabolized to **para-aminobenzoic acid (PABA)**, which can cause allergic reactions, but it is not associated with methemoglobinemia. - It has a relatively **short duration of action** and is less commonly used now compared to amide-type local anesthetics. *Etidocaine* - **Etidocaine** is an amide-type local anesthetic that is known for its **long duration of action** and high potency. - While it can cause systemic toxicity with high doses due to its cardiac and neurological effects, **methemoglobinemia** is not a characteristic side effect. *Ropivacaine* - **Ropivacaine** is an amide-type local anesthetic similar to bupivacaine, known for its **motor-sparing effect** and use in regional anesthesia. - It is associated with a lower risk of **cardiotoxicity** compared to bupivacaine but does not cause methemoglobinemia.

Question 906: Which of the following antiglaucoma medications can cause drowsiness?

A. Brimonidine (Correct Answer)
B. Latanoprost
C. Dorzolamide
D. Timolol

Explanation: ***Brimonidine*** - **Brimonidine** is an **alpha-2 adrenergic agonist** [1] that can cause central nervous system depression, leading to side effects such as **drowsiness** and fatigue. - This systemic side effect is more common with the topical ophthalmic formulation due to systemic absorption. *Latanoprost* - **Latanoprost** is a **prostaglandin analog** that primarily works by increasing uveoscleral outflow, and its side effects are mainly localized to the eye (e.g., iris color change, eyelash growth). - It does not typically cause systemic side effects like drowsiness because its systemic absorption is minimal. *Dorzolamide* - **Dorzolamide** is a **topical carbonic anhydrase inhibitor** [1] that reduces aqueous humor production, and its most common side effects include local ocular irritation and a bitter taste. - While systemic carbonic anhydrase inhibitors can cause fatigue and drowsiness, the topical formulation has very limited systemic absorption, making drowsiness uncommon. *Timolol* - **Timolol** is a **non-selective beta-blocker** [1] that reduces aqueous humor production and can cause systemic side effects such as bradycardia, bronchospasm, and hypotension. - While some beta-blockers can cause fatigue, **drowsiness** as a prominent side effect is less common compared to alpha-2 agonists.

Question 907: What serious side effect may lead to the discontinuation of felbamate?

A. Seizures
B. Renal impairment
C. Gastrointestinal disorder
D. Aplastic anemia (Correct Answer)

Explanation: ***Aplastic anemia*** - Felbamate is known to cause **aplastic anemia**, a severe and life-threatening condition where the **bone marrow stops producing enough new blood cells**. - Felbamate carries a **black box warning** for both aplastic anemia and **hepatotoxicity (severe liver failure)**, which are the two most serious adverse effects leading to discontinuation. - Due to this significant risk, felbamate is reserved for severe, refractory epilepsy cases, and patients require **regular monitoring** of blood counts and liver function tests. *Renal impairment* - While some medications can cause renal impairment, **felbamate is not primarily associated** with this side effect to the extent of requiring discontinuation. - Its metabolism and excretion are predominantly **hepatic (liver)**, and renal effects are less common or severe. *Gastrointestinal disorder* - Gastrointestinal side effects like nausea or vomiting are **common with many medications**, including felbamate, but are generally **mild and manageable**, rarely leading to discontinuation. - These effects are usually **dose-dependent** and can often be mitigated with supportive care. *Seizures* - Felbamate is an **antiepileptic drug (AED)**, so it is used to treat seizures, not cause them. - If a patient experiences seizures while on felbamate, it usually indicates **inadequate treatment response** or seizure exacerbation, rather than a direct side effect necessitating discontinuation for toxicity.

Question 908: Which drug is recommended for a truck driver suffering from allergic rhinitis?

A. Cetirizine (Correct Answer)
B. Promethazine
C. Buclizine
D. Hydroxyzine

Explanation: The drug recommended for a truck driver is a second-generation antihistamine like Cetirizine. ***Cetirizine*** - This is a **second-generation antihistamine** that is less sedating compared to first-generation options [2]. - Its **lower risk of drowsiness** makes it suitable for individuals who need to remain alert, such as truck drivers [2]. *Promethazine* - This is a **first-generation antihistamine** known for its significant sedative effects due to its ability to cross the blood-brain barrier [1], [2]. - It would be **unsafe for a truck driver** as it impairs alertness and reaction time [2]. *Buclizine* - This is also a **first-generation antihistamine** with notable sedative properties [1]. - Its use would pose a **driving hazard** due to the likelihood of drowsiness [2]. *Hydroxyzine* - A potent **first-generation antihistamine** with strong sedative and anticholinergic effects [1]. - It is **contraindicated for individuals performing tasks requiring mental alertness**, like driving a truck [2].

Question 909: What is a potential risk associated with the use of thiazolidinediones in the treatment of type 2 diabetes?

A. Heart failure (Correct Answer)
B. Pulmonary fibrosis
C. Myocarditis
D. Renal dysfunction

Explanation: ***Heart failure*** - Thiazolidinediones (TZDs), such as **pioglitazone** and **rosiglitazone**, can cause **fluid retention** and **volume expansion**, which may precipitate or worsen congestive heart failure. - This risk is higher in patients with pre-existing cardiac conditions and is a significant concern for these drugs. *Pulmonary fibrosis* - **Pulmonary fibrosis** is not a known or common adverse effect associated with thiazolidinedione use. - This condition is typically linked to certain other medications (e.g., **amiodarone**, **methotrexate**) or systemic diseases. *Myocarditis* - **Myocarditis**, inflammation of the heart muscle, is not a recognized side effect of thiazolidinediones. - Myocarditis is more commonly caused by viral infections, autoimmune diseases, or hypersensitivity reactions to certain drugs, but not TZDs. *Renal dysfunction* - While TZDs can cause fluid retention, they do not directly cause **renal dysfunction** or damage the kidneys. - In fact, some studies suggest they may have renoprotective effects due to reduced proteinuria, although fluid balance needs careful monitoring in patients with impaired renal function.

Question 910: All of the following are adverse effects of nicotinic acid except:

A. Liver dysfunction
B. Vasodilation
C. Hyperpigmentation
D. Pancreatitis (Correct Answer)

Explanation: ***Pancreatitis*** - **Pancreatitis** is not a commonly reported adverse effect of nicotinic acid (niacin) therapy. - While other gastrointestinal side effects like nausea and vomiting can occur, pancreatic inflammation is not characteristic. *Vasodilation* - **Cutaneous flushing** and **vasodilation** are very common adverse effects of nicotinic acid, mediated by prostaglandin release. - This effect can cause a sensation of warmth, redness, and itching, especially at the start of therapy. *Liver dysfunction* - **Liver dysfunction**, including elevated liver enzymes and rare cases of **hepatotoxicity**, can occur with high doses of nicotinic acid. - Regular monitoring of liver function tests is recommended for patients on niacin therapy. *Hyperpigmentation* - **Hyperpigmentation**, particularly **acanthosis nigricans**, is a known cutaneous side effect of nicotinic acid. - This typically presents as dark, velvety patches on the skin, especially in skin fold areas.

Practice by Chapter

Principles of Clinical Pharmacology

Practice Questions

Therapeutic Drug Monitoring

Practice Questions

Drug Toxicity and Overdose

Practice Questions

Antidotes and Their Applications

Practice Questions

Management of Drug Poisoning

Practice Questions

Drug-Induced Liver Injury

Practice Questions

Drug-Induced Kidney Injury

Practice Questions

Drug-Induced Blood Dyscrasias

Practice Questions

Drug-Induced QT Prolongation

Practice Questions

Pharmacovigilance

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free