BCSE Pharmacology and Toxicology 2

Question 1

Which enzyme is primarily responsible for metabolizing warfarin in the liver?

Accepted Answer

CYP2C9

Answer

CYP2C9 is the primary hepatic enzyme responsible for the metabolism of the S-enantiomer of warfarin, which accounts for most of its anticoagulant activity.

Question 2

A patient presents with bradycardia, miosis, salivation, and urinary incontinence after exposure to an organophosphate pesticide. Which receptor is being overstimulated?

Accepted Answer

Muscarinic acetylcholine receptor

Answer

Organophosphates inhibit acetylcholinesterase, leading to accumulation of acetylcholine and overstimulation of muscarinic receptors, producing the classic SLUDGE syndrome.

Question 3

Which mechanism explains the development of tolerance to opioids with chronic use?

Accepted Answer

Receptor desensitization and downregulation

Answer

Chronic opioid exposure leads to desensitization and downregulation of mu-opioid receptors, requiring higher doses to achieve the same analgesic effect.

Question 4

A patient taking lithium develops polyuria and polydipsia. Which mechanism best explains this adverse effect?

Accepted Answer

Lithium antagonizes ADH action at the collecting duct

Answer

Lithium induces nephrogenic diabetes insipidus by inhibiting adenylyl cyclase in renal collecting duct cells, reducing the response to antidiuretic hormone (ADH).

Question 5

Which antidote is most appropriate for acetaminophen overdose presenting within 8 hours of ingestion?

Accepted Answer

N-acetylcysteine

Answer

N-acetylcysteine replenishes glutathione stores and acts as a precursor to sulfate, detoxifying the hepatotoxic NAPQI metabolite produced during acetaminophen overdose.

BCSE - Basic and Clinical Sciences Examination Practice Test

BCSE - Basic and Clinical Sciences Examination Practice Test

BCSE Pharmacology and Toxicology 2