The NP chooses to give cephalexin every 8 hours based on knowledge of the drug’s:

Correct Answer: B

Rationale: The correct answer is B: Biological half-life. The biological half-life of a drug determines the duration of action and how frequently it needs to be administered. Cephalexin has a short half-life of around 1 hour, so it needs to be given every 8 hours to maintain therapeutic levels. Explanation for why the other choices are incorrect: A: Propensity to go to the target receptor - While this is important for drug efficacy, it does not dictate the dosing frequency. C: Pharmacodynamics - While pharmacodynamics refers to how a drug works in the body, it does not directly impact the dosing interval. D: Safety and side effects - While safety and side effects are important considerations, they do not determine the dosing frequency.

Correct Answer: B

Rationale: Step 1: Receptor antagonists block the action of agonist drugs by binding to the receptors. Step 2: Beta blockers are receptor antagonists that block beta-adrenergic receptors. Step 3: Abrupt discontinuation of beta blockers can lead to an exaggerated response due to unopposed stimulation of beta receptors. Step 4: This can cause rebound effects like increased heart rate and blood pressure. Step 5: Therefore, an exaggerated response if abruptly discontinued is the correct answer. Summary: A: Down-regulation of drug receptors is incorrect because antagonists blocking receptors do not lead to down-regulation. C: Partial blockade of agonist drug effects is incorrect as antagonists fully block agonist effects. D: Exaggerated response to competitive drug agonists is incorrect as antagonists reduce the response to agonists.

Correct Answer: B

Rationale: The correct answer is B: Greater than the sum of the effects of each drug individually. When two drugs have a synergistic effect, they enhance each other's actions, leading to a combined effect that is more potent than what would be expected by simply adding their individual effects. This occurs due to the drugs targeting different pathways or mechanisms, resulting in increased efficacy. In contrast, option A (The sum of the effects of each drug individually) is incorrect because synergy implies an interaction beyond mere addition. Option C (Less than the effect of each drug individually) is incorrect as synergy typically leads to enhanced effects. Option D (Not predictable) is incorrect because synergy can be anticipated based on the mechanisms of action of the drugs involved.

Correct Answer: C

Rationale: The correct answer is C: Change drug molecules to a form that an excretory organ can excrete. Phase I and Phase II reactions in the liver modify drugs to make them more water-soluble and easily excreted by the kidneys or liver. Phase I reactions typically involve oxidation, reduction, or hydrolysis to introduce or unmask functional groups, while Phase II reactions conjugate the drug with polar molecules like glucuronide or sulfate. This transformation makes the drug more suitable for elimination through urine or bile. Choice A is incorrect because Phase I and II reactions do not necessarily inactivate prodrugs, but rather prepare them for elimination. Choice B is incorrect because altering drug properties to cross membranes is typically not the primary purpose of drug metabolism. Choice D is incorrect because increasing ionization and polarity may not always be the goal of drug metabolism, but rather enhancing excretion through conjugation reactions.

Correct Answer: B

Rationale: The correct answer is B: When the amount of drug in the body remains constant. Steady state is achieved when the rate of drug administration equals the rate of drug elimination, leading to a constant drug concentration in the body. Option A is incorrect as it only refers to absorption and excretion, not overall drug levels. Option C is incorrect as it specifically mentions the maximum tolerated concentration, which is not necessarily related to steady state. Option D is incorrect as it includes all options, which are not all true statements about steady state.