Clinical Pharmacology and Drug Toxicity — MCQs

A 58-year-old woman had a mitral valve replacement, and was placed on anticoagulants and prophylactic antibiotics following her surgery. Five days after her surgery, she developed a sharply demarcated, erythematous rash on her left thigh. Two days after the rash appeared, large hemorrhagic bullae began to form in the area of the rash. Which of the following medications most likely caused the patient's rash?

Q729

Both hepatic and renal failures can be caused by which of the following:

Q730

An otherwise healthy 32-year-old woman comes to the physician because of severe headaches and visual disturbances. Physical examination shows papilledema. Which of the following medications is most likely implicated in the development of the suspected diagnosis in this patient?

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

Question 721: Vaccination causing intussusception is

A. Rotavirus (Correct Answer)
B. BCG
C. Poliovirus
D. Parvovirus

Explanation: ***Rotavirus*** - **Rotavirus vaccine** has been associated with a small, but statistically significant, increased risk of **intussusception**, particularly with earlier vaccine formulations. - The mechanism is thought to involve lymphoid hypertrophy in the Peyer's patches, which can act as a lead point for the telescoping of the bowel. *BCG* - The **BCG (Bacillus Calmette-Guérin) vaccine** protects against tuberculosis and is administered intradermally. - It is known for localized reactions such as **ulceration at the injection site** and potential regional lymphadenitis, but not intussusception. *Poliovirus* - **Poliovirus vaccines** (both inactivated polio vaccine (IPV) and oral polio vaccine (OPV)) are highly effective in preventing poliomyelitis. - Common side effects are usually mild, such as soreness at the injection site for IPV, with **no known association with intussusception**. *Parvovirus* - There is currently **no routine widely available parvovirus vaccine for humans**. - **Parvovirus B19 infection** in humans can cause erythema infectiosum (fifth disease) and, in some cases, hydrops fetalis or transient aplastic crisis, but it is not linked to intussusception or vaccine-related adverse events.

Question 722: Toxic focal myopathy is an adverse effect of:

A. Penicillin
B. Aminoglycosides
C. Insulin
D. Narcotics (Correct Answer)

Explanation: ***Narcotics*** - **Narcotics**, particularly **pentazocine**, when injected repeatedly into the same muscle group, can lead to **toxic focal myopathy**. - This condition involves localized muscle damage, necrosis, and woody fibrosis at the injection site due to the direct toxic effect of the drug on muscle tissue. - Pentazocine-induced myopathy is a well-documented adverse effect in patients with chronic intramuscular injections. *Penicillin* - **Penicillin** is generally associated with **hypersensitivity reactions** like rash, anaphylaxis, or interstitial nephritis. - It is not typically known to cause focal myopathy as a direct adverse effect. *Aminoglycosides* - **Aminoglycosides** are primarily associated with **nephrotoxicity** and **ototoxicity**. - They can also cause **neuromuscular blockade**, but not focal muscle damage through direct toxicity to muscle tissue. *Insulin* - **Insulin** administration can cause **lipohypertrophy** or **lipoatrophy** at injection sites due to fat tissue changes. - However, it does not directly lead to **toxic focal myopathy** involving muscle tissue damage.

Question 723: Prolonged allopurinol therapy in a patient with gout is NOT indicated for:

A. Acute gouty arthritis (Correct Answer)
B. Tophi
C. Urate nephropathy
D. Evidence of bone/joint damage

Explanation: ***Acute gouty arthritis*** - Allopurinol is a **urate-lowering therapy** used for the chronic management of **hyperuricemia** and prevention of future gout flares, but it is not indicated for the acute treatment of a gouty arthritis attack [1]. - Starting allopurinol during an acute flare can sometimes **exacerbate the attack** by causing rapid fluctuations in serum uric acid levels. *Tophi* - Tophi are **deposits of urate crystals** in soft tissues, a clear indication of advanced gout and chronic hyperuricemia [2]. - Allopurinol therapy is indicated to reduce uric acid levels to dissolve existing tophi and prevent new ones from forming. *Urate nephropathy* - **Urate nephropathy** (or uric acid nephrolithiasis) occurs due to the precipitation of uric acid crystals in the kidneys, leading to kidney damage and stones [1], [2]. - Allopurinol reduces uric acid production, thereby preventing crystal formation and is therefore indicated. *Evidence of bone/joint damage* - Chronic gout can lead to **erosions and structural damage** in bones and joints due to persistent urate crystal deposition and inflammatory responses [2]. - Long-term allopurinol therapy is crucial to lower uric acid levels and prevent further damage, as well as to promote the regression of existing urate deposits.

Question 724: Pseudo tumor cerebri is caused by?

A. Vitamin B1 excess
B. Vitamin D excess
C. Vitamin E excess
D. Vitamin A excess (Correct Answer)

Explanation: ***Vitamin A excess*** - **Hypervitaminosis A**, or excess vitamin A, is a known cause of **pseudotumor cerebri** (also called **idiopathic intracranial hypertension**). - This condition involves increased **intracranial pressure**, often without an obvious structural cause. *Vitamin B1 excess* - Excess intake of **vitamin B1 (thiamine)** is generally considered benign and is not known to cause pseudotumor cerebri. - Thiamine is a **water-soluble vitamin**, and excess amounts are typically excreted in urine. *Vitamin D excess* - **Vitamin D toxicity** primarily leads to **hypercalcemia**, which can cause kidney stones, bone pain, and gastrointestinal symptoms. - While it can have neurological effects due to hypercalcemia, it typically does not directly cause pseudotumor cerebri. *Vitamin E excess* - **Vitamin E excess** can interfere with **blood clotting** and may increase the risk of bleeding, especially in individuals taking anticoagulants. - There is no established link between hypervitaminosis E and the development of pseudotumor cerebri.

Question 725: Abatacept, a drug inhibiting co-stimulation is used for:

A. Rheumatoid arthritis (Correct Answer)
B. SLE
C. Sjogren syndrome
D. Scleroderma

Explanation: ***Rheumatoid arthritis***- **Abatacept** is a **selective T-cell co-stimulation modulator** that inhibits the activation of T lymphocytes, which are crucial in the pathogenesis of rheumatoid arthritis.- By binding to **CD80 and CD86** on antigen-presenting cells, it prevents their interaction with **CD28** on T cells, thus blocking a key co-stimulatory signal required for full T-cell activation [1].*SLE (Systemic Lupus Erythematosus)*- While T-cell activation plays a role in SLE, abatacept has shown **limited efficacy** in clinical trials for this condition, and its use is not standard.- The dominant mechanism in SLE often involves **B-cell overactivity** and autoantibody production, making other targeted therapies more effective.*Sjogren syndrome*- Sjogren syndrome is characterized by lymphocytic infiltration of exocrine glands, but abatacept is **not a primary treatment** or widely indicated for this condition.- The main focus of treatment for Sjogren's is typically symptomatic management and immunosuppression with other agents.*Scleroderma (Systemic Sclerosis)*- Scleroderma involves **fibrosis** and vascular damage with complex immunological mechanisms, but abatacept has **not demonstrated significant benefit** in clinical studies.- The disease often has more prominent involvement of **fibroblasts** and different immunological pathways that are not adequately targeted by abatacept.

Question 726: All of the following statements about MMR vaccine are true EXCEPT:

A. All live vaccines without exception are contraindicated in pregnant women (Correct Answer)
B. MMR is a live vaccine
C. Adverse events from MMR vaccine include fever (usually 6-12 days following vaccination), rash in 5% of vaccinated persons, arthralgia, aseptic meningitis, lymphadenopathy
D. Evidence shows that aseptic meningitis is associated with all mumps vaccine strains except the Jeryl Lynn strain

Explanation: ***Correct Answer: All live vaccines without exception are contraindicated in pregnant women*** - This statement is **FALSE**, making it the correct answer to this EXCEPT question - While **most live vaccines are contraindicated in pregnancy** (including MMR), the word **"without exception"** makes this statement incorrect - **Exceptions exist**: Yellow fever vaccine may be administered during pregnancy if travel to endemic areas is unavoidable and the risk of disease outweighs the theoretical vaccine risk - The absolute nature of this statement contradicts clinical guidelines that recognize situational exceptions *True Statement - MMR is a live vaccine* - **MMR vaccine** contains **live-attenuated viruses** of measles, mumps, and rubella - This live-attenuated nature produces robust, long-lasting immunity - Being a live vaccine necessitates contraindications in immunocompromised patients and pregnant women *True Statement - Adverse events from MMR vaccine* - **Fever** typically occurs **6-12 days post-vaccination** (not immediately), reflecting viral replication - **Rash** occurs in approximately **5% of vaccinees** - Other documented adverse events include **arthralgia** (especially in adult women), **aseptic meningitis** (rare), and **lymphadenopathy** - These adverse events are far less severe than complications from natural measles, mumps, or rubella infection *True Statement - Aseptic meningitis and vaccine strains* - **Urabe** and **Leningrad-Zagreb** mumps vaccine strains have been associated with higher rates of vaccine-associated **aseptic meningitis** (approximately 1 in 100,000 to 1 in 1 million doses) - The **Jeryl Lynn strain** (used in the United States and many other countries) has **negligible or no association** with aseptic meningitis - This safety profile makes the Jeryl Lynn strain the preferred mumps component in MMR vaccines

Question 727: The fluoride level that can cause renal toxicity is

A. Above 5 micromol/litre
B. Above 20 micromol/litre
C. Above 80 micromol/litre
D. Above 50 micromol/litre (Correct Answer)

Explanation: ***Above 50 micromol/litre*** - Clinically significant renal toxicity from fluoride is generally observed at plasma fluoride concentrations exceeding **50 micromol/L**, which is the established threshold in medical literature. - This level is particularly associated with **methoxyflurane anesthesia**, where fluoride metabolism leads to nephrotoxicity manifesting as **polyuria, polydipsia, and nephrogenic diabetes insipidus**. - At these concentrations, fluoride interferes with renal tubular function, causing **high-output renal failure** and electrolyte disturbances. *Above 20 micromol/litre* - While some subclinical renal effects may begin around 20 micromol/L, this is **below the threshold** for clinically significant renal toxicity. - This level may cause mild tubular dysfunction but does not typically result in the **overt nephrotoxicity** that characterizes fluoride-induced renal damage. - The consensus threshold for **clinical renal toxicity is 50 micromol/L**, not 20 micromol/L. *Above 5 micromol/litre* - A plasma fluoride level of 5 micromol/L is well within the **safe range** and is commonly seen with therapeutic fluoride exposure. - This level is associated with **dental prophylaxis** and normal environmental exposure without any renal toxicity. *Above 80 micromol/litre* - This represents a **severely toxic** fluoride level causing profound renal damage, but the threshold for **initial renal toxicity** is much lower at 50 micromol/L. - At 80 micromol/L, patients would experience severe systemic toxicity including **cardiac arrhythmias, CNS effects**, and potentially fatal complications.

Question 728: A 58-year-old woman had a mitral valve replacement, and was placed on anticoagulants and prophylactic antibiotics following her surgery. Five days after her surgery, she developed a sharply demarcated, erythematous rash on her left thigh. Two days after the rash appeared, large hemorrhagic bullae began to form in the area of the rash. Which of the following medications most likely caused the patient's rash?

A. Cefazolin
B. Aspirin
C. Heparin
D. Warfarin (Correct Answer)

Explanation: ***Warfarin*** - The rash described, with sharply demarcated erythema, followed by hemorrhagic bullae, is highly suggestive of **warfarin-induced skin necrosis**. This rare but severe complication typically occurs in the first few days of therapy. - Warfarin blocks vitamin K-dependent clotting factors (II, VII, IX, X) and also protein C and S. Initial decrease in protein C, which has a shorter half-life, leads to a transient hypercoagulable state and microvascular thrombosis, causing skin necrosis in susceptible individuals. *Cefazolin* - **Cefazolin** is a cephalosporin antibiotic. While antibiotics can cause various skin reactions, including generalized rashes or Stevens-Johnson syndrome, it is not typically associated with localized, sharply demarcated hemorrhagic bullae as seen in this case. - **Allergic reactions** to cefazolin usually manifest as urticaria, maculopapular rash, or anaphylaxis, lacking the specific progression to hemorrhagic necrosis. *Aspirin* - **Aspirin** is an antiplatelet agent. Adverse skin reactions to aspirin are uncommon but can include urticaria, angioedema, or aspirin-exacerbated respiratory disease. - It does not characteristically cause **hemorrhagic bullae** or skin necrosis. Its mechanism of action primarily inhibits platelet aggregation, not coagulation factors that would lead to such necrotizing lesions. *Heparin* - **Heparin-induced thrombocytopenia (HIT)** is a well-known complication of heparin, which can lead to thrombotic events, but typically presents with new thrombosis and a drop in platelet count, not localized hemorrhagic bullae or skin necrosis as the primary dermatological manifestation. - **Heparin-induced skin lesions** usually occur at injection sites and often appear as erythematous, pruritic plaques or necrotic lesions only in the context of HIT with associated thrombosis, which differs from the presentation given.

Question 729: Both hepatic and renal failures can be caused by which of the following:

A. Carbon tetrachloride
B. Arsenic
C. Paracetamol toxicity
D. Copper sulphate (Correct Answer)

Explanation: ***Copper sulphate*** - **Copper sulphate poisoning** can lead to systemic toxicity, including severe **hepatic dysfunction** due to direct damage to hepatocytes and diffuse **renal tubular necrosis**, causing acute kidney injury. - Its corrosive nature also causes **gastrointestinal bleeding** and hemolysis, further contributing to multi-organ failure. *Carbon tetrachloride* - Primarily known for causing severe **hepatic necrosis** through its conversion to highly reactive free radicals, particularly in occupational exposures. - While it can induce some renal damage, **liver failure** is its most prominent and direct organ toxicity. *Arsenic* - **Arsenic poisoning** is associated with multi-organ effects, including dermatological, neurological, and cardiovascular issues. - It can cause **acute kidney injury** (typically through ATN) and some liver damage (hepatomegaly, jaundice), but its dominant toxicities are often broader and less specifically targeted to both organs in tandem compared to severe copper poisoning. *Paracetamol toxicity* - Overdose of paracetamol predominantly causes **acute liver failure** due to the depletion of glutathione and accumulation of toxic metabolites (NAPQI). - While severe liver failure can secondarily lead to **renal dysfunction** (hepatorenal syndrome), direct primary renal toxicity is less common than with copper sulphate.

Question 730: An otherwise healthy 32-year-old woman comes to the physician because of severe headaches and visual disturbances. Physical examination shows papilledema. Which of the following medications is most likely implicated in the development of the suspected diagnosis in this patient?

A. Doxycycline
B. Oral contraceptive pill (Correct Answer)
C. All-trans retinoic acid
D. Lithium

Explanation: ***Oral contraceptive pill*** - **Oral contraceptive pills** are a common risk factor for **idiopathic intracranial hypertension (IIH)**, especially in young, obese women. - IIH presents with symptoms like **severe headaches**, **visual disturbances**, and **papilledema** due to increased intracranial pressure. *Doxycycline* - **Tetracycline antibiotics**, including doxycycline, can induce **IIH** as a side effect. - However, the patient is described as "otherwise healthy" and there is no indication of an infection for which doxycycline would be prescribed. *All-trans retinoic acid* - **Retinoids** like all-trans retinoic acid (ATRA) are a known cause of **IIH**, particularly when used for leukemia or severe acne treatment. - The patient, however, is an "otherwise healthy" 32-year-old woman, making ATRA use less likely in the absence of relevant conditions. *Lithium* - **Lithium** can cause various neurological side effects and rarely has been linked to cases of **IIH**. - This patient has no history of psychiatric illness, making lithium exposure unlikely.

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