What percentage of atenolol bound if a dose of 50 mg/d had been administered?

Correct Answer: B

Rationale: The correct answer to the question is B) 5%. In pharmacology, the concept of drug binding refers to the proportion of a drug that is bound to proteins in the blood plasma. Atenolol, being a drug with high plasma protein binding, is approximately 5% bound to proteins after a 50 mg dose because of its specific pharmacokinetic properties. This means that 95% of the administered dose remains free and active in the bloodstream to exert its therapeutic effects. Option A) 2.50% is incorrect because it underestimates the binding percentage of atenolol after administration. Option C) 10% is incorrect as it overestimates the binding percentage. Option D) 1.25% is also incorrect and too low, which would imply that atenolol has a very low binding affinity, contrary to its actual pharmacological profile. Understanding drug binding percentages is crucial in pharmacology as it affects the distribution, metabolism, and elimination of drugs in the body. It influences the drug's efficacy, duration of action, and potential for drug interactions. Therefore, having a clear grasp of these principles is essential for healthcare professionals to ensure safe and effective medication management for patients.

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: In pharmacology, understanding dose-response curves is essential for predicting the effects of drugs. When a fixed dose of a competitive α antagonist is given concomitantly with an agonist, it will shift the dose-response curve to the right. This means that higher doses of the agonist will be needed to achieve the same effect, indicating competitive inhibition. Option B (Curve Q) depicts this scenario accurately. Curve Q would show a rightward shift, indicating that more of the agonist is needed to produce the same response due to the competitive antagonist's presence. Options A, C, and D are incorrect because they do not represent the expected change in the dose-response curve when a competitive α antagonist is introduced. Curve P (Option A) might show a leftward shift, which is not expected with a competitive antagonist. Curve R (Option C) and Curve S (Option D) may show different types of responses but not the specific scenario described in the question. Understanding these concepts is crucial for pharmacology students as it helps them predict drug interactions and effects in clinical scenarios. It also reinforces the importance of knowing how different drugs interact and affect the body's responses, which is vital for safe and effective patient care.

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.