Clinical Pharmacology and Drug Toxicity Practice Questions

Q: Prolonged use of which drug has been implicated in the causation of subacute myelo-optic neuropathy (SMON)?

Quiniodochlor. ***Quiniodochlor*** - **Quiniodochlor** (also known as clioquinol) is an antimicrobial agent whose prolonged use was historically linked to **subacute myelo-optic neuropathy (SMON)**, particularly in Japan. - SMON is characterized by ascending sensory disturbances, motor weakness, and visual impairment due to damage to the spinal cord and optic nerves. *Diloxanide furoate* - **Diloxanide furoate** is an effective luminal amebicide used for asymptomatic carriers of **Entamoeba histolytica**. - Its primary side effects are mild gastrointestinal disturbances, and it is not associated with neurotoxicity like SMON. *Furazolidone* - **Furazolidone** is a nitrofuran antimicrobial used to treat bacterial and protozoal infections, particularly in the gastrointestinal tract. - While it can cause gastrointestinal upset, peripheral neuropathy, and hemolysis in G6PD-deficient individuals, it is not implicated in SMON. *Emetine* - **Emetine** is an alkaloid used as an anti-amebic agent, typically for severe amebiasis. - Its main toxicities include **cardiac toxicity** (e.g., arrhythmias, heart failure), neuromuscular weakness, and gastrointestinal issues, but not SMON.

Q: Which of the following drugs is known to cause cholestasis?

All of the above. ***All of the above***- **Cholestasis [1]** can be induced by various medications, and all three listed drug classes—**erythromycin**, **phenothiazines**, and **oral contraceptives**—are well-documented causes of drug-induced cholestasis. **Erythromycin:**- Associated with **idiosyncratic cholestatic hepatitis**, especially with the estolate form- Mechanism involves bile duct inflammation or obstruction [1]- Typically presents with jaundice [1], pruritus, and elevated alkaline phosphatase **Phenothiazines:**- Can cause **cholestatic jaundice** through hypersensitivity reactions- Effect is often delayed (2-4 weeks after initiation)- Reversible upon discontinuation of the drug **Oral contraceptives:**- Cause cholestasis particularly in susceptible individuals- More common in those with history of **cholestasis of pregnancy**- Estrogen component is primarily responsible for the cholestatic effect

Q: All the following drugs are teratogenic except?

Metoclopramide. ***Metoclopramide*** - **Metoclopramide** is an antiemetic and prokinetic agent generally considered **safe during pregnancy**. - It does **not** have established teratogenic effects and is often used to treat **nausea and vomiting** in pregnant women. *Alcohol* - **Alcohol** is a well-known teratogen, leading to **fetal alcohol syndrome** characterized by facial dysmorphia, growth restriction, and CNS abnormalities. - Even moderate consumption can have detrimental effects on fetal development, particularly brain development. *Phenytoin* - **Phenytoin** is an antiepileptic drug associated with **fetal hydantoin syndrome**, which includes craniofacial anomalies, mental deficits, and distal phalangeal hypoplasia. - It interferes with **folate metabolism** and can increase the risk of neural tube defects. *Warfarin* - **Warfarin** is an anticoagulant that can cause **fetal warfarin syndrome** when used during the first trimester, leading to chondrodysplasia punctata, nasal hypoplasia, and skeletal abnormalities. - Its mechanism involves interfering with **vitamin K-dependent coagulation factors**, affecting fetal bone and cartilage development.

Q: Which of the following is not an early adverse effect of methotrexate?

Hepatic fibrosis. ***Hepatic fibrosis*** - **Hepatic fibrosis** is a *late-onset* adverse effect of **methotrexate** therapy, developing after prolonged use (months to years), rather than in the early stages. [2] - This complication is associated with cumulative doses and pre-existing liver conditions, requiring long-term monitoring rather than immediate concern after starting treatment. [1] *Myelosuppression* - **Myelosuppression** (bone marrow suppression) can occur relatively *early* in methotrexate treatment due to its impact on rapidly dividing cells, including hematopoietic stem cells. [1] - This can lead to **leukopenia**, **anemia**, or **thrombocytopenia**, necessitating close monitoring of blood counts. [2] *Nausea* - **Nausea** is a common *acute* gastrointestinal side effect that frequently occurs within hours or days of methotrexate administration. [3] - It results from the drug's effect on the gastrointestinal tract and can often be mitigated with antiemetics or dose adjustments. *Stomatitis* - **Stomatitis** (inflammation of the mouth lining) is another frequent and *early* adverse effect, often appearing within a few days of methotrexate exposure. [1], [2] - It is caused by the *antimetabolite* action of methotrexate on rapidly dividing oral mucosal cells, leading to painful ulcers.

Q: At what percentage of carboxyhemoglobin is the risk of death significantly increased?

70%. ***70%*** - A carboxyhemoglobin (COHb) level of **70% or higher** is the widely recognized clinical threshold at which the risk of death becomes **significantly increased** and mortality is highly probable. - This represents the standard cutoff in toxicology literature where **severe tissue hypoxia**, cardiovascular collapse, and central nervous system depression become life-threatening. - At this level, immediate aggressive treatment including hyperbaric oxygen therapy is critical to prevent fatal outcomes. *75%* - While a COHb level of 75% is undoubtedly lethal, this exceeds the **established threshold** of 70% where mortality risk is already considered significantly elevated. - This is not the standard clinical reference point used in toxicology for defining high mortality risk. - The question asks for the threshold percentage, not just any lethal level. *80%* - An 80% COHb level represents a concentration well above the recognized threshold for significantly increased mortality. - This value is far beyond the 70% cutoff where death risk becomes critically high. - While certainly fatal, this is not the standard clinical threshold cited in medical literature. *82%* - At 82%, this represents an extremely high COHb level that is almost universally fatal, but it exceeds the **recognized clinical threshold** of 70%. - This percentage is not the standard reference point used to define significantly increased mortality risk. - Medical consensus identifies 70% as the key threshold, making this option incorrect despite its lethality.

Q: A patient with pulmonary tuberculosis, who is receiving anti-tuberculosis therapy consisting of rifampicin, isoniazid, ethambutol, and pyrazinamide, should be advised to take which of the following supplements?

Pyridoxine. ***Pyridoxine*** - **Isoniazid** in the anti-tuberculosis regimen can cause **peripheral neuropathy** by interfering with **pyridoxine (vitamin B6)** metabolism. - Supplementation with **pyridoxine** is advised to prevent this neurotoxic side effect, especially in patients at higher risk such as those with diabetes, malnutrition, or alcoholism. *Niacin* - **Niacin (vitamin B3)** deficiency can lead to **pellagra**, characterized by dermatitis, diarrhea, and dementia. - While important for general health, niacin supplementation is not specifically required to counteract side effects of standard anti-tuberculosis drugs. *Riboflavin* - **Riboflavin (vitamin B2)** is essential for various metabolic processes and cellular energy production. - There is no direct significant depletion or interference with riboflavin metabolism caused by the common anti-tuberculosis drugs. *Thiamine* - **Thiamine (vitamin B1)** deficiency can lead to **beriberi** and neurological symptoms, particularly in those with chronic alcoholism. - While thiamine is crucial for neurological function, antitubercular drugs do not specifically deplete or interfere with its metabolism to the extent of requiring routine supplementation.

Q: Ergometrine is contraindicated in:

Eclampsia. ***Eclampsia*** - Ergometrine is an **ergot alkaloid** that causes generalized **vasoconstriction**, which can lead to a dangerous increase in blood pressure. - In a patient with **eclampsia** (characterized by hypertension, proteinuria, and seizures), this vasoconstriction can worsen **hypertension** and increase the risk of **stroke, seizures, or cardiac events**, making it an absolute contraindication. - **Pre-eclampsia and severe hypertension** are also contraindications for the same reason. *Induction of labour* - Ergometrine is **absolutely contraindicated during active labor** because it causes **tetanic (sustained, continuous) uterine contractions** rather than the coordinated contractions needed for delivery. - These sustained contractions can cause **fetal hypoxia** (due to impaired placental blood flow), **uterine rupture**, and **fetal distress**. - It is used only **after delivery of the baby** (third stage of labor) to contract the uterus and prevent postpartum hemorrhage. *Abortion* - Ergometrine can be used in cases of **incomplete abortion** to help contract the uterus and expel retained products of conception, thereby reducing blood loss. - It is not contraindicated in abortion management when used appropriately under medical supervision. *Post partum hemorrhage* - Ergometrine is a **first-line agent for the prevention and treatment of postpartum hemorrhage** because it effectively contracts the uterus, reducing blood loss. - Its ability to induce strong, sustained uterine contractions makes it highly effective in this setting, unless there are specific contraindications like **severe hypertension or eclampsia**.

Q: Which of the following drugs is NOT associated with hypertrichosis?

Barbiturates. ***Barbiturates*** - **Barbiturates** are medications primarily used as sedatives, hypnotics, or anticonvulsants. - They are **not typically associated** with hypertrichosis (excessive hair growth) as a side effect. *Minoxidil* - **Minoxidil** is a well-known drug that causes **hypertrichosis** as a systemic side effect, especially when used orally for hypertension. - Its topical formulation is specifically used to **promote hair growth** in androgenetic alopecia. *Cyclosporine* - **Cyclosporine**, an immunosuppressant often used in organ transplant recipients and for autoimmune diseases, frequently causes **hypertrichosis**. - This side effect can be **significant** enough to affect patient adherence to treatment. *Phenytoin* - **Phenytoin**, an anticonvulsant, is commonly associated with several side effects, including **gingival hyperplasia** and **hypertrichosis**. - The excessive hair growth can be **generalized** and affects many individuals on long-term therapy.

Q: Which of the following drugs is not part of the standard immunosuppressive therapy for post-renal transplant patients?

Rituximab. ***Rituximab*** - **Rituximab** is a monoclonal antibody targeting **CD20 on B-lymphocytes**, primarily used in lymphomas, leukemias, and some autoimmune diseases. - While it can be used in highly selected cases for antibody-mediated rejection, it is **not considered standard immunosuppressive therapy** for maintenance of post-renal transplant patients. *Cyclosporine* - **Cyclosporine** is a **calcineurin inhibitor** that plays a central role in most maintenance immunosuppression regimens after renal transplant. - It works by inhibiting the activation of T-lymphocytes, thereby **preventing organ rejection**. *Azathioprine* - **Azathioprine** is an **antimetabolite** that inhibits lymphocyte proliferation and is a common component of standard immunosuppressive regimens. - It works by interfering with purine synthesis, thus **suppressing the immune response**. *Prednisolone* - **Prednisolone** (a corticosteroid) is a fundamental component of most immunosuppressive protocols for **renal transplant recipients**. - It provides broad-spectrum immunosuppression by reducing inflammation and suppressing various immune cells.

Q: Which of the following is not an adverse effect of cyclosporine?

Hypoglycemia. ***Hypoglycemia*** - Cyclosporine is known to cause **hyperglycemia** rather than hypoglycemia, due to its inhibitory effects on insulin secretion and increased insulin resistance. - While it can affect glucose metabolism, causing high blood sugar is the more common and established adverse effect. *Hirsutism* - **Hirsutism**, or excessive hair growth, is a well-known and common adverse effect of cyclosporine, particularly noticeable on the face and body. - This effect is often dose-dependent and can be a significant cosmetic concern for patients. *Nephrotoxicity* - **Nephrotoxicity** is a major and dose-limiting adverse effect of cyclosporine, leading to impaired kidney function. - It can manifest as acute or chronic interstitial nephritis and is a primary reason for careful monitoring of renal parameters. *Hypertension* - **Hypertension** is a frequent adverse effect of cyclosporine, contributing to cardiovascular risk in transplant patients. - The drug's effects on vasoconstriction and fluid retention contribute to increased blood pressure.

Question 1

Prolonged use of which drug has been implicated in the causation of subacute myelo-optic neuropathy (SMON)?

Accepted Answer

Quiniodochlor

Answer

Diloxanide furoate

Answer

Furazolidone

Answer

Emetine

Question 2

Which of the following drugs is known to cause cholestasis?

Accepted Answer

All of the above

Answer

Phenothiazines

Answer

Oral contraceptives

Answer

Erythromycin

Question 3

All the following drugs are teratogenic except?

Accepted Answer

Metoclopramide

Answer

Alcohol

Answer

Phenytoin

Answer

Warfarin

Question 4

Which of the following is not an early adverse effect of methotrexate?

Accepted Answer

Hepatic fibrosis

Answer

Myelosuppression

Answer

Nausea

Answer

Stomatitis

Question 5

At what percentage of carboxyhemoglobin is the risk of death significantly increased?

Accepted Answer

70%

Answer

75%

Answer

80%

Answer

82%

Question 6

A patient with pulmonary tuberculosis, who is receiving anti-tuberculosis therapy consisting of rifampicin, isoniazid, ethambutol, and pyrazinamide, should be advised to take which of the following supplements?

Accepted Answer

Pyridoxine

Answer

Niacin

Answer

Riboflavin

Answer

Thiamine

Question 7

Ergometrine is contraindicated in:

Accepted Answer

Eclampsia

Answer

Induction of labour

Answer

Post partum hemorrhage

Answer

Abortion

Question 8

Which of the following drugs is NOT associated with hypertrichosis?

Accepted Answer

Barbiturates

Answer

Cyclosporine

Answer

Phenytoin

Answer

Minoxidil

Question 9

Which of the following drugs is not part of the standard immunosuppressive therapy for post-renal transplant patients?

Accepted Answer

Rituximab

Answer

Cyclosporine

Answer

Azathioprine

Answer

Prednisolone

Question 10

Which of the following is not an adverse effect of cyclosporine?

Accepted Answer

Hypoglycemia

Answer

Hirsutism

Answer

Nephrotoxicity

Answer

Hypertension

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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