Clinical Pharmacology and Drug Toxicity — MCQs

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

Question 801: What is the usual daily dose of fenofibrate for managing hyperlipidemia in adults?

A. 300 mg
B. 150 mg
C. 250 mg
D. 200 mg (Correct Answer)

Explanation: ***200 mg*** - The usual daily dose of **fenofibrate (non-micronized formulation)** for managing hyperlipidemia in adults is **200 mg once daily**. - This dose effectively reduces **triglycerides** and increases **HDL cholesterol** in patients with dyslipidemia. - **Micronized formulations** may use 160 mg or 145 mg daily due to better bioavailability. - Dose adjustment is required in **renal impairment** to reduce the risk of myopathy. *300 mg* - A 300 mg dose **exceeds the standard recommended daily dose** for fenofibrate and increases the risk of adverse effects including myopathy, hepatotoxicity, and gastrointestinal disturbances. - Higher doses do not provide additional lipid-lowering benefit and are not recommended. *150 mg* - While 150 mg is close to the therapeutic range, it represents a **submaximal dose** for standard non-micronized fenofibrate formulations. - Some micronized formulations use 145-160 mg, but **200 mg is the standard dose for conventional fenofibrate**. *250 mg* - A 250 mg dose is **not a standard therapeutic dose** for fenofibrate in managing hyperlipidemia. - This dose would increase adverse effects without additional clinical benefit and is not supported by clinical guidelines.

Question 802: Which drug is most likely to induce photosensitivity?

A. Metronidazole
B. Tetracycline (Correct Answer)
C. Ivermectin
D. Fluconazole

Explanation: ***Tetracycline*** - **Tetracyclines** are well-known to cause **photosensitivity reactions**, leading to exaggerated sunburns, rashes, or skin discoloration upon sun exposure. - This adverse effect is thought to be due to an interaction between the drug and UV light, leading to the formation of reactive oxygen species and subsequent cell damage. *Metronidazole* - While metronidazole can cause a variety of side effects, significant **photosensitivity** is generally not considered a common or prominent adverse reaction. - It is often associated with a **disulfiram-like reaction** when consumed with alcohol, as well as gastrointestinal upset and a metallic taste. *Ivermectin* - **Ivermectin** is primarily used as an antiparasitic agent and is not typically associated with **photosensitivity** as a common side effect. - Its main adverse effects are usually related to the Mazzotti reaction during treatment of onchocerciasis or other systemic symptoms like dizziness or nausea. *Fluconazole* - **Fluconazole**, an antifungal medication, has a relatively low incidence of causing **photosensitivity** compared to other drug classes. - Common side effects include gastrointestinal disturbances, headache, and elevated liver enzymes, but severe phototoxic reactions are rare.

Question 803: A 55-year-old patient with gout has high uric acid levels; which drug should be avoided?

A. Probenecid
B. Allopurinol
C. Febuxostat
D. Aspirin (Correct Answer)

Explanation: ***Aspirin*** - High doses of **aspirin** can increase serum uric acid levels, which is detrimental for a patient with gout desiring to lower uric acid. - While low-dose aspirin (<300 mg/day) might have a minor uricosuric effect, higher doses are **anti-uricosuric** and should generally be avoided in gout. *Probenecid* - **Probenecid** is a **uricosuric agent** that helps excrete uric acid via the kidneys, making it beneficial for patients who underexcrete uric acid. - It works by inhibiting the reabsorption of uric acid in the renal tubules, thereby lowering serum uric acid levels. *Allopurinol* - **Allopurinol** is a **xanthine oxidase inhibitor** that reduces the production of uric acid by blocking the enzyme responsible for its synthesis. - It is a cornerstone treatment for chronic gout to lower uric acid levels and prevent recurrent attacks. *Febuxostat* - **Febuxostat** is also a **xanthine oxidase inhibitor**, similar to allopurinol, used to reduce uric acid production. - It is often considered an alternative for patients who cannot tolerate allopurinol or who do not achieve target uric acid levels with allopurinol.

Question 804: A 50-year-old diabetic with chronic kidney disease is being treated for hypertension. Which of the following antihypertensives would be inappropriate in this patient?

A. Amlodipine
B. Hydrochlorothiazide (Correct Answer)
C. Enalapril
D. Losartan

Explanation: ***Hydrochlorothiazide*** - **Thiazide diuretics** like hydrochlorothiazide are generally ineffective in patients with **moderate to severe chronic kidney disease (CKD)** due to reduced glomerular filtration rate (GFR <30 mL/min). - They also have the potential to exacerbate **hyperglycemia** in diabetic patients and may worsen **dyslipidemia**. - **Loop diuretics** (like furosemide) are preferred over thiazides when diuretic therapy is needed in advanced CKD. *Amlodipine* - **Dihydropyridine calcium channel blockers** like amlodipine are effective antihypertensives that are generally safe and kidney-neutral in patients with CKD. - They do not negatively impact **glucose metabolism** and can be a good option for hypertension in diabetics. *Enalapril* - **ACE inhibitors** like enalapril are often first-line agents in diabetic patients with hypertension and CKD because they protect the kidneys by reducing **proteinuria** and slowing the progression of kidney disease. - While they can cause an initial slight increase in **serum creatinine** (up to 30% is acceptable), this is often indicative of improved intraglomerular hemodynamics and is generally beneficial for long-term kidney outcomes. - **Important monitoring**: Watch for **hyperkalemia** and avoid in bilateral renal artery stenosis or severe hyperkalemia (K+ >5.5 mEq/L). *Losartan* - **Angiotensin receptor blockers (ARBs)** like losartan are similar to ACE inhibitors in their renoprotective effects and are also considered first-line for hypertension in diabetic patients with CKD, particularly if ACE inhibitors are not tolerated (due to cough). - They effectively lower **blood pressure** and reduce **albuminuria**, benefiting long-term kidney health. - **Same monitoring requirements** as ACE inhibitors apply: watch for **hyperkalemia** and acute kidney injury, especially in volume-depleted states.

Question 805: Which of the following is not a side effect of amiodarone?

A. Photosensitivity
B. Pulmonary fibrosis
C. Osteoporosis (Correct Answer)
D. Thyroid dysfunction

Explanation: ***Osteoporosis*** - **Osteoporosis** is *not* a recognized or commonly reported side effect of amiodarone in standard clinical practice. - Unlike the other options listed, osteoporosis is not included in the major adverse effects profile that clinicians monitor for during amiodarone therapy. - While amiodarone can affect bone metabolism indirectly through thyroid dysfunction, direct bone effects are not a clinically significant concern. *Photosensitivity* - **Photosensitivity** is a well-documented dermatologic side effect of amiodarone, occurring in up to 50% of patients with sun exposure. - Can lead to **blue-gray skin discoloration** (slate-gray pigmentation), particularly in sun-exposed areas. - Patients require **sunscreen** use and protective clothing as preventive measures. *Pulmonary fibrosis* - **Pulmonary fibrosis** is one of the most serious and potentially **life-threatening** complications of amiodarone therapy. - Occurs in 5-15% of patients, particularly with **long-term use** or higher doses. - Presents with **progressive dyspnea**, dry cough, and characteristic findings on chest imaging (interstitial infiltrates). - Requires regular **pulmonary function monitoring** and chest X-rays. *Thyroid dysfunction* - **Thyroid dysfunction** is a major side effect occurring in 15-20% of patients on chronic amiodarone therapy. - Can cause both **hypothyroidism** (more common) and **hyperthyroidism** (more dangerous). - Results from amiodarone's **high iodine content** (37% iodine by weight) and direct effects on thyroid hormone synthesis and metabolism. - Mandatory **thyroid function tests** (TSH, free T4) at baseline and every 6 months during therapy.

Question 806: Which drug for glaucoma can cause heterochromia iridis?

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

Explanation: ***Latanoprost*** - **Latanoprost** is a **prostaglandin analog** commonly used to treat glaucoma by increasing uveoscleral outflow. - A well-known side effect of latanoprost, and other prostaglandin analogs, is **heterochromia iridis**, which is a gradual change in eye color, typically making blue or green eyes turn brown. *Dorzolamide* - **Dorzolamide** is a **carbonic anhydrase inhibitor** that reduces aqueous humor production. - It does not cause heterochromia; common side effects include ocular burning, stinging, and blurred vision. *Brimonidine* - **Brimonidine** is an **alpha-2 adrenergic agonist** that decreases aqueous humor production and increases uveoscleral outflow. - While effective for glaucoma, it does not lead to changes in iris pigmentation. *Timolol* - **Timolol** is a **beta-blocker** used as an ophthalmic solution that works by reducing the production of aqueous humor. - Common side effects include dry eyes and ocular discomfort, but it is not associated with heterochromia.

Question 807: Which antihypertensive is considered the first-line treatment with the most extensive safety data for chronic hypertension in pregnancy?

A. Methyldopa (Correct Answer)
B. Labetalol
C. Hydralazine
D. ACE inhibitors

Explanation: ***Methyldopa*** - **Methyldopa** has been used for decades to treat **chronic hypertension in pregnancy** and has the most extensive data demonstrating its safety for both the mother and the fetus. - It is a centrally acting **alpha-2 adrenergic agonist** that reduces sympathetic outflow, leading to vasodilation and decreased blood pressure. *Labetalol* - **Labetalol** is an **alpha and beta-blocker** also considered a first-line agent, but its long-term safety data in pregnancy is not as extensive as methyldopa. - It is often used as an alternative or in cases where methyldopa is not sufficiently effective, especially for more acute or severe hypertension. *Hydralazine* - **Hydralazine** is a **direct vasodilator** often used for **hypertensive emergencies** in pregnancy, especially for managing severe hypertension or preeclampsia. - It is not typically recommended as a first-line agent for **chronic hypertension** due to a higher incidence of side effects like reflex tachycardia and fluid retention when used long-term. *ACE inhibitors* - **ACE inhibitors** (and ARBs) are **contraindicated in pregnancy** due to their association with severe fetal adverse effects, including **renal malformations**, **oligohydramnios**, and **fetal death**. - Their use should be avoided throughout pregnancy, and women on these medications should switch to safer alternatives upon conception or when planning pregnancy.

Question 808: Which of the following drugs is most commonly used for the acute management of migraine?

A. Amitriptyline
B. Ibuprofen
C. Sumatriptan (Correct Answer)
D. Propranolol

Explanation: ***Sumatriptan*** - **Triptans** such as sumatriptan are **serotonin 5-HT1B/1D receptor agonists** that cause **vasoconstriction** of intracranial blood vessels and inhibit neuropeptide release. - They are considered **first-line agents** for the acute management of moderate to severe migraine attacks. - Sumatriptan is the most commonly recommended and used triptan for acute migraine treatment. *Amitriptyline* - **Amitriptyline** is a **tricyclic antidepressant** primarily used for **migraine prophylaxis** (prevention), not acute treatment. - Its mechanism involves modulating neurotransmitter levels in the brain to reduce migraine frequency. *Ibuprofen* - **Ibuprofen** is a **non-steroidal anti-inflammatory drug (NSAID)** that can be used for **mild to moderate migraine** attacks. - While effective for milder cases, **triptans are superior** for moderate to severe migraines and are the **standard first-line choice** in acute migraine management guidelines. *Propranolol* - **Propranolol** is a **beta-blocker** primarily used for **migraine prophylaxis**, meaning it is taken regularly to prevent migraines. - It reduces the frequency and severity of migraine attacks but is not effective for stopping an acute attack once it has started.

Question 809: Rituximab is used in all of the following conditions except:

A. Rheumatoid arthritis
B. Systemic lupus erythematosus
C. Paroxysmal nocturnal hemoglobinuria (Correct Answer)
D. Non-Hodgkin lymphoma

Explanation: ***Paroxysmal nocturnal hemoglobinuria*** - **Eculizumab**, a C5 complement inhibitor, is the primary treatment for paroxysmal nocturnal hemoglobinuria to prevent complement-mediated hemolysis and thrombosis. - Rituximab targets CD20 B cells and would not directly address the underlying complement dysregulation in PNH. *Non-Hodgkin lymphoma* - Rituximab is a cornerstone of therapy, especially for **B-cell non-Hodgkin lymphomas**, as it targets the CD20 antigen expressed on malignant B cells. - It is often used in combination with chemotherapy regimens like **R-CHOP** (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone). *Rheumatoid arthritis* - Rituximab is approved for the treatment of **moderate to severe rheumatoid arthritis** in patients who have had an inadequate response to TNF inhibitors. - It works by depleting B cells, which play a role in the autoimmune pathogenesis of RA. *Systemic lupus erythematosus* - While not officially FDA-approved for SLE, rituximab is used **off-label** in some severe, refractory cases of SLE, particularly those with significant renal or hematological involvement. - It targets B cells, which are central to autoantibody production and immune complex formation in SLE.

Question 810: Which of the following is a common adverse effect of long-term corticosteroid therapy?

A. Osteoporosis (Correct Answer)
B. Bradycardia
C. Hypoglycemia
D. Hypothyroidism

Explanation: ***Osteoporosis*** - **Corticosteroids** induce **osteoporosis** by increasing **osteoclast activity** and decreasing **osteoblast activity**, leading to bone demineralization and increased fracture risk. - Long-term use also reduces **calcium absorption** from the gut and increases **renal calcium excretion**, contributing to negative calcium balance. - This is one of the **most common and clinically significant** long-term adverse effects, often requiring prophylactic treatment with calcium, vitamin D, and bisphosphonates. *Bradycardia* - **Bradycardia** (slow heart rate) is not a side effect of **corticosteroids**; rather, they can sometimes cause **tachycardia** or **palpitations** due to fluid retention and electrolyte imbalances. - **Corticosteroids** typically lead to **sodium and water retention**, which can increase blood pressure and heart rate, not decrease it. *Hypoglycemia* - **Corticosteroids** cause **hyperglycemia**, not **hypoglycemia**, by increasing **gluconeogenesis** and causing **insulin resistance**. - Long-term corticosteroid therapy can lead to **steroid-induced diabetes mellitus**, requiring monitoring of blood glucose levels. - This is the opposite metabolic effect - corticosteroids raise blood sugar levels. *Hypothyroidism* - **Hypothyroidism** is not a known adverse effect of **corticosteroid therapy**; instead, **corticosteroids** can sometimes suppress **TSH (thyroid-stimulating hormone)** transiently. - **Corticosteroids** can inhibit the peripheral conversion of **T4 to T3**, leading to temporary changes in **thyroid function tests**, but this does not typically cause clinical hypothyroidism and resolves with discontinuation.

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