Which of the following is most likely the main site of distribution of infliximab?

Correct Answer: A

Rationale: Infliximab, as a monoclonal antibody, is a large molecule that is more likely to distribute to tissues like fat due to their ability to store and release drugs slowly. Fat tissue is a common site of distribution for large molecules and lipophilic drugs. Therefore, fat tissue is the most likely main site of distribution for infliximab.

Correct Answer: D

Rationale: Rationale: 1. Target site blood flow affects drug distribution by determining how quickly drug reaches the intended site. 2. Plasma protein binding affects distribution as only free drug is active and can reach target tissues. 3. Blood flow to the site of absorption impacts how rapidly drug is absorbed and distributed. 4. Option D is correct as both target site blood flow and blood flow to the site of absorption are crucial in drug distribution. Option A alone doesn't consider absorption, while option B focuses only on binding, neglecting absorption. Option C is specific to absorption and does not encompass target site blood flow.

Correct Answer: A

Rationale: The correct answer is A: Intramuscular. Enteral routes involve administration through the gastrointestinal tract, such as oral, sublingual, and rectal. Intramuscular administration bypasses the GI tract, making it a parenteral route. Therefore, it is not an enteral route. Oral involves swallowing, sublingual is under the tongue, and rectal is through the rectum, all entering the GI tract for absorption.

Correct Answer: D

Rationale: The correct answer is D: Lungs. Lungs have the largest surface area for drug absorption due to alveoli and extensive capillary network. The large surface area allows for rapid absorption of drugs into the bloodstream. Rectum, vagina, and eye have smaller surface areas and are not as efficient for drug absorption compared to the lungs. Lungs provide a direct route to the bloodstream, making them an ideal site for drug absorption.

Correct Answer: B

Rationale: The correct answer is B because physiologic changes in older adults affect all pharmacokinetic processes, leading to increased risk for drug reactions. These changes include decreased renal function, altered drug metabolism, reduced liver enzyme activity, and changes in body composition. Option A is incorrect because the blood-brain barrier remains intact with age. Option C is incorrect as older adults have decreased drug-metabolizing enzymes. Option D is incorrect because while immune response may decline with age, it is not the primary factor contributing to increased drug reactions in older adults.