A client with a diagnosis of bipolar disorder has begun lithium therapy. What is the primary rationale for the nurse’s instructions regarding the need for regular monitoring of the client’s serum drug levels?

Correct Answer: B

Rationale: The correct answer is B. Regular monitoring of the client's serum lithium levels is crucial to ensure that the drug levels are within a therapeutic range (not too low or too high) to effectively manage bipolar disorder. Maintaining therapeutic levels helps prevent relapse of symptoms and minimizes the risk of toxicity. Monitoring also allows for adjustments in dosage if needed. Choice A is incorrect because blood-drug incompatibilities are not the primary reason for monitoring lithium levels. Choice C is incorrect because monitoring lithium levels is not to determine the need for additional medications. Choice D is incorrect because monitoring is not primarily to confirm adherence, although it can provide information on compliance.

Correct Answer: C

Rationale: The correct answer is C because storage reservoirs increase the length of time a drug is available and active in the body. By administering medroxyprogesterone IM, a storage reservoir is created in the muscle tissue, allowing for a slow and sustained release of the drug over time. This helps maintain therapeutic levels of the medication in the bloodstream, prolonging its effects. Incorrect answers: A: Assuring the drug reaches its intended target tissue is related to factors such as drug transport mechanisms, not storage reservoirs. B: Loading doses are given to achieve therapeutic levels quickly, not necessarily due to storage reservoirs. D: Storage reservoirs are not limited to collagen tissues; they can be present in various tissues depending on the drug's properties.

Correct Answer: C

Rationale: The correct answer is C: Onset of action. This is the point in time when the drug concentration reaches a level where the therapeutic effect begins to be observed. The onset of action signifies the start of the drug's intended effect on the body. The minimum adverse effect level (Choice A) refers to the lowest concentration at which side effects may occur, not the therapeutic effect. The peak of action (Choice B) is the point when the drug's effect is at its maximum, not necessarily the first sign of therapeutic effect. The therapeutic range (Choice D) is the range of drug concentrations that produce the desired therapeutic effect without causing significant side effects, but it does not specifically indicate the onset of therapeutic action.

Correct Answer: C

Rationale: The correct answer is C: Desensitization or down-regulation with continuous use. Receptor agonists continuously activate receptors, leading to desensitization or down-regulation where the receptors become less responsive or decrease in number. This occurs due to the body's attempt to maintain homeostasis in response to constant stimulation. Choices A and D are incorrect because receptor agonists do not typically bind irreversibly or exhibit an inverse relationship between drug concentration and action. Choice B is incorrect as up-regulation is usually observed in response to receptor antagonists, not agonists.

Correct Answer: B

Rationale: The correct answer is B because drugs administered via IV route enter the bloodstream directly, allowing for immediate distribution throughout the body. This rapid distribution leads to fast onset of action. Choice A is incorrect as lipid solubility is not a requirement for IV absorption. Choice C is incorrect because nonionized drugs are not necessarily easily absorbed via IV route. Choice D is incorrect as pinocytosis is not a mechanism for drug absorption via IV route.