Bio-transformation of drugs takes place mainly in the

Correct Answer: D

Rationale: The correct answer is D: Liver. Bio-transformation of drugs mainly occurs in the liver due to the presence of enzymes responsible for metabolizing drugs. The liver plays a crucial role in breaking down drugs into metabolites that can be excreted from the body. The kidney (A) primarily filters and eliminates waste products, not metabolize drugs. The spleen (B) is involved in filtering blood and immune response, not drug metabolism. The brain (C) is mainly responsible for neurological functions, not drug metabolism. Thus, the liver is the primary site for bio-transformation of drugs.

Correct Answer: C

Rationale: - Endorphin is a neuropeptide hormone, not an eicosanoid derived from fatty acids. - Prostacyclin, leukotrienes, and prostaglandins are all eicosanoids produced from fatty acids. - Endorphins are produced in the brain and nervous system, mainly known for their role in pain regulation. - Eicosanoids play roles in inflammation, blood clotting, and regulating blood pressure. - Therefore, the correct answer is C, Endorphin, as it is not an eicosanoid derived from fatty acids.

Correct Answer: B

Rationale: The correct answer is B: Fatty tissue. Drugs with a large volume of distribution (Vd) distribute extensively into tissues, especially those with high lipid content like fatty tissue. Lipophilic drugs tend to accumulate in fatty tissues due to their high lipid solubility. This leads to a higher volume of distribution as the drug is not primarily confined to the blood but distributed into tissues. Choices A, C, and D are incorrect because drugs with a large Vd are not typically confined to the GI tract, interstitial tissue, or intravascular fluid, as they distribute widely throughout the body.

Correct Answer: C

Rationale: The correct answer is C because competitive antagonists compete with the agonist for the same binding site, leading to a decrease in the potency of the drug. This occurs because the antagonist reduces the number of available binding sites for the agonist, requiring a higher concentration of the agonist to achieve the same effect. Option A is incorrect as efficacy is related to the maximal effect of a drug, not affected by competitive antagonists. Option B is incorrect because a leftward shift in the dose-response curve indicates an increase in potency, which is not the case with competitive antagonists. Option D is incorrect because competitive antagonists do affect the agonist dose-response curve by reducing potency.

Correct Answer: C

Rationale: Facilitated diffusion is the most likely permeation process for the transfer of albuterol through the bronchial mucosa. This process involves the use of carrier proteins to facilitate the movement of molecules across the membrane. Since albuterol is a relatively small molecule with a molecular weight of 239 daltons, it is more likely to utilize facilitated diffusion rather than bulk flow transport, endocytosis, or active transport. Lipid diffusion is not as efficient for larger molecules like albuterol, making facilitated diffusion the most suitable choice for this scenario.