Which of the following is used to calculate the loading dose of a drug required to reach an initial target blood concentration

Correct Answer: D

Rationale: The loading dose of a drug required to reach an initial target blood concentration is based on the volume of distribution (Vd) of the drug. The volume of distribution represents the theoretical volume that would be necessary to contain the total amount of the administered drug at the same concentration as in the blood plasma. The loading dose is calculated by multiplying the target blood concentration by the volume of distribution of the drug. This initial dose helps to rapidly achieve the desired drug concentration in the body, especially when a drug has a long half-life or when steady-state levels need to be reached more quickly. Understanding the volume of distribution of a drug is crucial in dosage calculation to ensure therapeutic efficacy and avoid potential toxicity.

Correct Answer: D

Rationale: The loading dose of a drug required to reach an initial target blood concentration is based on the volume of distribution (Vd) of the drug. The volume of distribution represents the theoretical volume that would be necessary to contain the total amount of the administered drug at the same concentration as in the blood plasma. The loading dose is calculated by multiplying the target blood concentration by the volume of distribution of the drug. This initial dose helps to rapidly achieve the desired drug concentration in the body, especially when a drug has a long half-life or when steady-state levels need to be reached more quickly. Understanding the volume of distribution of a drug is crucial in dosage calculation to ensure therapeutic efficacy and avoid potential toxicity.

Correct Answer: C

Rationale: In order to prevent graft-versus-host disease (GVHD) in a severely immunocompromised patient receiving a blood transfusion, the physician will order irradiation of the donor blood. GVHD is a rare but serious complication that can occur when the donor's T lymphocytes attack the recipient's tissues. Irradiation of the blood eliminates the T lymphocytes, thereby reducing the risk of GVHD in immunocompromised patients. Diphenhydramine hydrochloride (Benadryl) and acetaminophen (Tylenol) are commonly used to manage transfusion reactions but do not specifically prevent GVHD. Administering the transfusion slowly over several hours does not directly address the risk of GVHD.

Correct Answer: B

Rationale: The area where the highest percentage of sodium and water are reabsorbed back into the bloodstream is the proximal tubule. In the nephron, the proximal tubule is responsible for reabsorbing approximately 65-70% of filtered sodium and water. This reabsorption is crucial for maintaining the body's electrolyte balance and blood volume. The proximal tubule is lined with specialized cells that actively transport sodium ions out of the tubular fluid, creating an osmotic gradient that allows for passive reabsorption of water. This efficient reabsorption process helps to ensure that essential substances are conserved while waste products are excreted in the urine.

Correct Answer: B

Rationale: Oral drugs face first-pass metabolism in the liver, reducing bioavailability, so higher doses are needed for therapeutic effect compared to IV (100% bioavailability), sublingual (bypasses liver), or rectal (partial bypass). Oral route's loss to metabolism drives dosage needs, a pharmacokinetic distinction.