Which of the following drugs has the largest volume of distribution?

Correct Answer: C

Rationale: The volume of distribution (Vd) is a pharmacokinetic parameter that indicates the extent of a drug's distribution in the body. The drug with the largest Vd will have the most extensive distribution. In this case, Drug R has the largest Vd of 100 L, indicating that it has the largest volume of distribution among the options provided.

Correct Answer: B

Rationale: The cimetidine-diazepam interaction, where the sedative effect of diazepam increased significantly due to the inhibition of the cytochrome P-450 system by cimetidine, can be best defined as potentiation. Potentiation refers to the enhancement of one drug's effect by another, leading to a greater overall effect than either drug alone. In this case, cimetidine potentiates the sedative effect of diazepam by inhibiting its metabolism, resulting in increased sedation.

Correct Answer: C

Rationale: The adverse drug reaction that best explains the patient's disorder is an idiosyncratic reaction. Idiosyncratic reactions are unpredictable and occur rarely in response to a drug. In this case, the baby's presentation of microcephaly, broad nasal bridge, short nose, cleft palate, and hypoplasia of the distal phalanges are consistent with a teratogenic effect of a drug taken by the mother during pregnancy. The use of phenytoin for seizures during pregnancy is known to be associated with such birth defects, indicating an idiosyncratic reaction.

Correct Answer: A

Rationale: In this question, the correct answer is A) Aqueous diffusion. Ethanol, being a small, hydrophilic molecule, can pass through the aqueous pores in the intestinal membrane via passive diffusion. This process does not require energy input and is driven by the concentration gradient. Option B) Bulk flow transport is not relevant in the context of intestinal absorption of ethanol as it refers to the movement of large amounts of fluid and solutes together. Option C) Facilitated diffusion involves the use of carrier proteins to help substances across the membrane, but ethanol does not rely on these proteins for absorption. Option D) Active transport requires energy to move molecules against their concentration gradient, which is not the case with ethanol absorption. Educationally, understanding the permeation processes involved in drug absorption is crucial in pharmacology. The principles of passive diffusion, facilitated diffusion, and active transport are fundamental in comprehending how drugs are absorbed, distributed, metabolized, and excreted in the body. This knowledge is essential for pharmacists and healthcare professionals to ensure the efficacy and safety of drug therapies.

Correct Answer: C

Rationale: The most likely cause of the patient's disorder is a genetic polymorphism of CYP2C9. Genetic polymorphisms can affect the metabolism of drugs, including warfarin, leading to variations in drug response and potential adverse effects. In this case, the patient's red urine may be a result of altered metabolism of warfarin due to genetic variations in the CYP2C9 isozyme, which plays a key role in the biotransformation of the drug. This can result in increased levels of unmetabolized warfarin in the body, potentially leading to adverse effects such as red urine.