Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 991: Which of the following drugs is least likely to cause pancreatitis as a side effect?

A. Captopril (Correct Answer)
B. Furosemide
C. Valproic acid
D. Didanosine

Explanation: ***Captopril*** - **Captopril**, an ACE inhibitor, is among the drugs **least commonly associated** with drug-induced pancreatitis [1]. - While ACE inhibitors can have various side effects, **pancreatitis is exceedingly rare** and not a primary concern compared to other agents [3]. *Furosemide* - **Furosemide**, a loop diuretic, has been linked to cases of **drug-induced pancreatitis**, although the mechanism is not fully understood. - The risk is generally low but documented, making it a more likely cause than captopril. *Valproic acid* - **Valproic acid** is well-known for its association with **pancreatitis**, with a significantly higher risk compared to many other medications. - Pancreatitis can be a serious and dose-dependent side effect of valproic acid therapy. *Didanosine* - **Didanosine**, an antiretroviral nucleoside reverse transcriptase inhibitor, is particularly notable for causing **pancreatitis** as a common and severe adverse effect [2]. - Patients on didanosine require close monitoring for signs of pancreatitis due to its elevated risk [2].

Question 992: Which of the following drugs causes osteoporosis on long-term use?

A. Etidronate
B. Prednisolone (Correct Answer)
C. Calcitriol
D. Phenytoin

Explanation: ***Prednisolone*** - **Glucocorticoids** like prednisolone inhibit osteoblast function, reduce calcium absorption from the gut, and increase renal calcium excretion, all contributing to **bone loss** and **osteoporosis** with long-term use. - This effect is a significant concern in patients requiring chronic corticosteroid therapy for inflammatory or autoimmune conditions. - **Prednisolone is the most important and well-established cause of drug-induced osteoporosis.** *Etidronate* - **Etidronate** is a **bisphosphonate** drug used to treat and prevent osteoporosis by inhibiting osteoclast activity, thereby reducing bone resorption. - Therefore, it protects against osteoporosis rather than causing it. *Phenytoin* - **Phenytoin** is an antiepileptic drug that can interfere with **vitamin D metabolism** through induction of hepatic enzymes, leading to decreased calcium absorption. - Long-term use can result in **osteomalacia** (defective mineralization) and may also contribute to **osteoporosis** (decreased bone mass). - However, glucocorticoids remain the most clinically significant cause of drug-induced osteoporosis. *Calcitriol* - **Calcitriol** is the active form of **vitamin D** (1,25-dihydroxyvitamin D3), used to increase calcium absorption from the gut and promote bone mineralization. - It is used in the treatment of conditions like hypoparathyroidism, renal osteodystrophy, and osteoporosis to improve bone health and calcium balance.

Question 993: All of the following cause hypothyroidism except which of the following?

A. Lithium
B. PAS
C. Captopril (Correct Answer)
D. Amiodarone

Explanation: ***Captopril*** - **Captopril** is an **ACE inhibitor** primarily used to treat hypertension and heart failure; it is not known to cause hypothyroidism. - Its mechanism of action involves inhibiting the conversion of angiotensin I to angiotensin II, which does not directly affect thyroid hormone synthesis or release. *PAS (Para-aminosalicylic acid)* - **PAS** can interfere with **iodine uptake** by the thyroid gland, leading to reduced thyroid hormone synthesis. - While historically used for tuberculosis, its thyroid-suppressing effect is a recognized side effect that can induce **hypothyroidism**. *Lithium* - **Lithium** can inhibit the **release of thyroid hormones** from the thyroid gland and can also interfere with iodine metabolism. - It is frequently associated with the development of **hypothyroidism** in patients treated for bipolar disorder. *Amiodarone* - **Amiodarone** contains a large amount of **iodine**, which can induce both hyperthyroidism and hypothyroidism. - Its complex effects on thyroid function include inhibition of **T4 to T3 conversion** and direct cytotoxicity to thyroid follicular cells.

Question 994: What is the primary advantage of the newer liposomal preparation of amphotericin B?

A. Lower tissue uptake in the kidneys.
B. Reduced nephrotoxicity. (Correct Answer)
C. Similar efficacy and antifungal spectrum as conventional preparations.
D. All of the above

Explanation: ***Reduced nephrotoxicity*** - The liposomal formulation encapsulates **amphotericin B**, reducing its direct interaction with renal tubular cells. - This encapsulation minimizes the drug's impact on kidney function, which is a major dose-limiting toxicity of conventional amphotericin B. *Similar efficacy and antifungal spectrum as conventional preparations* - While maintaining efficacy is a goal, the primary advantage of liposomal amphotericin B is its **improved safety profile**, specifically reduced toxicity. - The efficacy and spectrum are generally comparable to the conventional form, but this is not the main reason for its development or preference. *Lower tissue uptake in the kidneys* - This statement is partially true in that the liposomal formulation is designed to **reduce drug accumulation specifically in the kidneys**, which contributes to lower nephrotoxicity. - However, the most direct and crucial advantage is the resulting *reduction in nephrotoxicity* itself, rather than just the mechanism of lower uptake. *All of the above* - This option is incorrect because while liposomal amphotericin B does have similar efficacy and reduced kidney uptake, the overarching primary advantage that makes it clinically superior is the **significantly reduced nephrotoxicity**.

Question 995: What is the preferred concentration range of lidocaine for topical anesthesia?

A. 2-4% (Correct Answer)
B. 7-12%
C. 12-15%
D. <2%

Explanation: ***Correct Option: 2-4%*** - **Lidocaine** is an **amide-type local anesthetic** commonly used for topical anesthesia to numb localized areas before minor procedures. - The **preferred concentration range for topical application is 2-4%**, which provides effective anesthesia with an acceptable safety profile. - **2% lidocaine gel/cream** is commonly used for skin and genital mucosa. - **4% lidocaine** is standard for oral and respiratory mucous membranes. - **5% lidocaine patches** are used for post-herpetic neuralgia. - This concentration range balances **clinical efficacy** with **minimal systemic toxicity risk**. *Incorrect Option: <2%* - Concentrations below **2%** are generally **suboptimal** for achieving significant topical anesthesia. - These lower concentrations result in **insufficient pain relief** or require longer application times. - While 0.5-1% solutions exist, they are primarily used for infiltration anesthesia, not topical application. *Incorrect Option: 7-12%* - Concentrations in the **7-12%** range are **too high** for routine topical use and increase the risk of **systemic toxicity**. - These concentrations are not standard in clinical practice for general topical anesthesia. - Higher concentrations increase absorption without proportional improvement in efficacy. *Incorrect Option: 12-15%* - Concentrations in the **12-15%** range are **excessively high** and pose substantial **risk of systemic absorption and toxicity**. - Such high concentrations are **not recommended** for topical anesthesia in clinical practice. - Even 10% sprays (used for oropharyngeal anesthesia) require strict dose limitations to prevent toxicity.

Question 996: Which of the following drugs can cause hypotension by releasing histamine from mast cells?

A. Morphine (Correct Answer)
B. Sulfadiazine
C. Procaine
D. Aspirin

Explanation: ***Correct Option - Morphine*** **Morphine** and other opioids can cause **non-immunologic histamine release** from mast cells, leading to **vasodilation**, bronchoconstriction, and systemic hypotension. - The release of histamine directly causes a decrease in **peripheral vascular resistance**, contributing to a drop in blood pressure - This is a **direct pharmacological effect**, not an allergic reaction - Other opioids with similar effects include **codeine** and **meperidine** *Incorrect Option - Procaine* **Procaine** is a local anesthetic that can cause hypotension primarily due to its **direct vasodilatory effect** and cardiovascular depression, rather than histamine release. - While allergic reactions to procaine (which involve histamine) can occur, hypotension in this context is usually related to **systemic absorption** and cardiovascular depression - The mechanism is NOT direct mast cell degranulation *Incorrect Option - Sulfadiazine* **Sulfadiazine** is an antibiotic that may cause hypotension as part of an **allergic reaction** (e.g., anaphylaxis), which would involve histamine. - However, it does not typically cause **direct, non-immunologic histamine release** from mast cells as a primary mechanism - Any histamine release would be **immunologic** (allergic), not direct pharmacological mast cell degranulation *Incorrect Option - Aspirin* **Aspirin** (acetylsalicylic acid) can cause significant hypotension in cases of **overdose** or severe intolerance. - Primary mechanism involves **prostaglandin synthesis inhibition**, which can influence vascular tone - May cause cardiovascular depression in overdose - Does NOT cause direct histamine release from mast cells

Question 997: What is the antidote of choice for Belladonna poisoning?

A. Flumazenil
B. Disulfiram
C. Physostigmine (Correct Answer)
D. Atropine

Explanation: ***Correct: Physostigmine*** - **Physostigmine** is an **acetylcholinesterase inhibitor** that increases acetylcholine levels in the synaptic cleft, effectively reversing the anticholinergic effects of Belladonna poisoning. - It is particularly useful for central nervous system manifestations such as **delirium**, **hallucinations**, and **seizures** associated with Belladonna toxicity. - Physostigmine is preferred because it **crosses the blood-brain barrier**, making it effective for both peripheral and central anticholinergic symptoms. *Incorrect: Flumazenil* - **Flumazenil** is a **benzodiazepine receptor antagonist** used to reverse the sedative effects of benzodiazepine overdose. - It is inappropriate for Belladonna poisoning, which involves **antimuscarinic** effects, not GABAergic effects. *Incorrect: Disulfiram* - **Disulfiram** is used in the treatment of **chronic alcoholism** to produce an unpleasant reaction when alcohol is consumed by inhibiting aldehyde dehydrogenase. - It has no role or antidote activity in cases of **Belladonna poisoning**. *Incorrect: Atropine* - **Atropine** itself is an **anticholinergic agent** that is chemically similar to Belladonna alkaloids (atropine and scopolamine are the main toxic components). - Administering atropine in Belladonna poisoning would **exacerbate the anticholinergic toxidrome** rather than act as an antidote.

Question 998: SIADH is associated with which of the following drugs?

A. Vincristine (Correct Answer)
B. Erythromycin
C. 5-FU
D. Methotrexate

Explanation: ***Vincristine*** - **Vincristine** is a well-known chemotherapeutic agent associated with inducing **SIADH (Syndrome of Inappropriate Antidiuretic Hormone)** secretion. - This side effect is thought to be due to its **neurotoxic effects**, specifically on the hypothalamus or posterior pituitary, leading to increased ADH release. *Erythromycin* - **Erythromycin** is a macrolide antibiotic primarily known for its gastrointestinal side effects like nausea, vomiting, and abdominal cramps due to its action as a **motilin receptor agonist**. - It is not commonly associated with SIADH, although prolonged use in sensitive individuals might cause other electrolyte disturbances, but not typically hyponatremia from SIADH. *5-FU* - **5-fluorouracil (5-FU)** is an antimetabolite chemotherapy drug with common side effects including myelosuppression, mucositis, and dermatological reactions like hand-foot syndrome. - While it can cause various systemic toxicities, **SIADH is not a recognized or common side effect** of 5-FU. *Methotrexate* - **Methotrexate** is an antifolate chemotherapy and immunosuppressant drug that can cause significant side effects such as myelosuppression, nephrotoxicity, hepatotoxicity, and mucositis. - Although it can lead to kidney damage and fluid retention, **SIADH is not typically associated with methotrexate** use.

Question 999: Which medication is used for suppression of lactation?

A. Bromocriptine (Correct Answer)
B. DMPA
C. Pyridoxine
D. D-Norgestrel

Explanation: ***Bromocriptine*** - **Bromocriptine** is a **dopamine agonist** that suppresses prolactin secretion from the anterior pituitary, thereby inhibiting lactation - Acts by stimulating **D2 dopamine receptors**, which inhibits prolactin release - Historically used for lactation suppression, though its use has declined due to potential cardiovascular side effects (**hypotension**, **stroke**, **myocardial infarction**) - **Cabergoline** (another dopamine agonist) is now preferred when pharmacological suppression is needed due to better tolerability - **Non-pharmacological methods** (breast binding, ice packs, avoiding stimulation) are now first-line recommendations *Pyridoxine* - **Pyridoxine (Vitamin B6)** has been anecdotally mentioned for lactation suppression, but lacks strong scientific evidence - Does not directly affect **prolactin secretion** or milk production mechanisms - Not recommended for this indication *DMPA* - **DMPA (Depot Medroxyprogesterone Acetate)** is a **progestin-only injectable contraceptive** used postpartum - Safe for breastfeeding mothers as its primary function is **contraception**, not lactation suppression - Does not actively suppress established lactation *D-Norgestrel* - **D-Norgestrel** is a **progestin** component found in some oral contraceptive pills - Primary role is **contraception**, not lactation suppression - Progestin-only contraceptives are compatible with breastfeeding

Question 1000: What deficiency is commonly associated with the use of Dilantin (phenytoin)?

A. Folic acid deficiency (Correct Answer)
B. Thiamine deficiency
C. Nicotinamide deficiency
D. Riboflavin deficiency

Explanation: ***Folic acid deficiency*** - **Phenytoin** is known to interfere with **folate metabolism** and absorption in the gastrointestinal tract, leading to a deficiency. - This deficiency can result in **megaloblastic anemia** with prolonged use. *Thiamine deficiency* - **Thiamine deficiency** (beriberi) is not typically associated with phenytoin use but rather with alcoholism, malnutrition, or malabsorption. - While certain antiepileptics might cause various nutritional deficiencies, thiamine is not a primary concern with phenytoin. *Nicotinamide deficiency* - **Nicotinamide (niacin) deficiency** causes pellagra and is characterized by dermatitis, diarrhea, and dementia. It is not directly linked to phenytoin. - This deficiency is often seen in individuals with diets poor in niacin, like corn-based diets, or in chronic alcoholism. *Riboflavin deficiency* - **Riboflavin deficiency** (ariboflavinosis) can cause angular stomatitis, cheilosis, and glossitis, but it is not a common side effect of phenytoin. - While various drug interactions can affect nutrient levels, phenytoin's primary known interaction is with folate.

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Principles of Clinical Pharmacology

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Drug-Induced Liver Injury

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Drug-Induced Blood Dyscrasias

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