Drugs that are receptor antagonists, such as beta blockers, may cause:

Correct Answer: B

Rationale: Step 1: Receptor antagonists block the action of agonist drugs by binding to the receptors. Step 2: Beta blockers are receptor antagonists that block beta-adrenergic receptors. Step 3: Abrupt discontinuation of beta blockers can lead to an exaggerated response due to unopposed stimulation of beta receptors. Step 4: This can cause rebound effects like increased heart rate and blood pressure. Step 5: Therefore, an exaggerated response if abruptly discontinued is the correct answer. Summary: A: Down-regulation of drug receptors is incorrect because antagonists blocking receptors do not lead to down-regulation. C: Partial blockade of agonist drug effects is incorrect as antagonists fully block agonist effects. D: Exaggerated response to competitive drug agonists is incorrect as antagonists reduce the response to agonists.

Correct Answer: C

Rationale: The correct answer is C: Change drug molecules to a form that an excretory organ can excrete. Phase I and Phase II reactions in the liver modify drugs to make them more water-soluble and easily excreted by the kidneys or liver. Phase I reactions typically involve oxidation, reduction, or hydrolysis to introduce or unmask functional groups, while Phase II reactions conjugate the drug with polar molecules like glucuronide or sulfate. This transformation makes the drug more suitable for elimination through urine or bile. Choice A is incorrect because Phase I and II reactions do not necessarily inactivate prodrugs, but rather prepare them for elimination. Choice B is incorrect because altering drug properties to cross membranes is typically not the primary purpose of drug metabolism. Choice D is incorrect because increasing ionization and polarity may not always be the goal of drug metabolism, but rather enhancing excretion through conjugation reactions.

Correct Answer: B

Rationale: The correct answer is B: When the amount of drug in the body remains constant. Steady state is achieved when the rate of drug administration equals the rate of drug elimination, leading to a constant drug concentration in the body. Option A is incorrect as it only refers to absorption and excretion, not overall drug levels. Option C is incorrect as it specifically mentions the maximum tolerated concentration, which is not necessarily related to steady state. Option D is incorrect as it includes all options, which are not all true statements about steady state.

Correct Answer: C

Rationale: Rationale: 1. Phase I metabolism involves enzymes like cytochrome P450, requiring proteins as cofactors. 2. Protein malnutrition reduces enzyme production, hindering the oxidative-reductive process. 3. Iron is necessary for cytochrome P450 activity, so iron deficiency impairs drug metabolism. 4. Option C is correct as both protein malnutrition and iron deficiency inhibit Phase I metabolism. Summary: - Choice A is incorrect because protein malnutrition affects enzyme production. - Choice B is incorrect because iron deficiency hampers cytochrome P450 activity. - Choice D is incorrect as both elements are essential for Phase I drug metabolism.

Correct Answer: D

Rationale: The correct answer is D because drug antagonism refers to the situation where one drug diminishes the effect of another drug when taken together. This occurs when the drugs have opposing actions on the body or compete for the same receptors. In contrast: A: Major physiological psychological dependence is related to addiction, not drug antagonism. B: The modification of drug effects by concurrent administration of another drug is known as drug interaction, not antagonism. C: The ability to be metabolized before another dose is administered is not related to drug antagonism.