Correct Answer: C

Rationale: Propranolol undergoes extensive first-pass metabolism in the liver. When administered orally, propranolol is extensively metabolized by the liver before reaching systemic circulation, leading to reduced bioavailability. This process is known as first-pass hepatic metabolism, which significantly affects the drug's effectiveness and necessitates higher oral doses compared to other routes of administration.

Correct Answer: D

Rationale: Regular insulin usually peaks around 1 to 5 hours after administration. This peak time frame is important to consider when managing blood glucose levels and timing meals to coincide with insulin activity.

Correct Answer: D

Rationale: The correct instruction for the client who has a new prescription for Levothyroxine to treat hypothyroidism is not to discontinue the medication without consulting the provider. Abrupt cessation could lead to the return of hypothyroid symptoms, emphasizing the importance of medical guidance when considering any changes to the treatment plan.

Correct Answer: B

Rationale: Grapefruit juice can inhibit the metabolism of amlodipine, a calcium channel blocker, leading to increased drug levels in the blood. This can result in potentiated side effects and potential toxicity. Therefore, it is important for the client to avoid grapefruit juice while taking amlodipine.

Correct Answer: B

Rationale: When treating tuberculosis, using a combination of multiple medications is crucial to reduce the risk of bacterial resistance. The use of four medications helps to target the bacteria from different angles, making it harder for them to develop resistance to the treatment. This approach is essential to ensure the effectiveness of the treatment regimen and to prevent the spread of drug-resistant strains of tuberculosis.