What is the characteristic action of an agonist?

Correct Answer: D

Rationale: The correct answer is D because agonists bind to receptors and initiate a physiologic response. Step 1: Agonists mimic the action of endogenous ligands by binding to receptors. Step 2: This binding activates the receptors, leading to a specific physiological effect. Step 3: Choice A is incorrect because agonists do not alter distribution and metabolism processes. Choice B is incorrect as agonists do not counteract neurotransmitters but rather imitate their effects. Choice C is incorrect as agonists do not block neurotransmitter action, but enhance it by binding to receptors.

Correct Answer: A

Rationale: The correct answer is A: The client is taking St. John’s wort for depression. St. John’s wort is known to interact with morphine sulfate, potentiating its sedative effects due to its impact on liver enzymes. This interaction can lead to increased sedation in the client. Incorrect choices: B: The client has a glass of ginger ale by the bedside. Ginger ale does not interact with morphine sulfate to cause increased sedation. C: A family member has a naloxone pen by the bedside. Naloxone is an opioid antagonist used to reverse opioid overdose, not a causative factor for increased sedation. D: The client is taking metoprolol for hypertension. Metoprolol is a beta-blocker and does not interact with morphine sulfate to cause increased sedation.

Correct Answer: B

Rationale: The correct answer is B: The lungs. Volatile drugs are typically eliminated through exhalation via the lungs due to their ability to evaporate easily into the air. This route is favored for volatile drugs as they can be quickly eliminated through respiration, making it an efficient and rapid process. A: The kidneys primarily excrete water-soluble compounds through urine, not volatile drugs. C: The bile and feces are involved in the excretion of non-volatile, lipophilic drugs, but not volatile drugs. D: The skin is not a primary route of excretion for drugs, especially volatile ones.

Correct Answer: A

Rationale: The correct answer is A because a loading dose allows for a rapid achievement of drug levels in the therapeutic range on the first day. By administering a higher initial dose, the drug concentration quickly reaches the desired level. Choice B is incorrect because a loading dose does not necessarily require multiple half-lives to attain. Choice C is incorrect as renal function typically influences maintenance doses rather than loading doses. Choice D is incorrect because a loading dose is primarily focused on achieving therapeutic levels in the bloodstream, not specifically targeting tissues.

Correct Answer: B

Rationale: The correct answer is B because when the peak level for a drug is above the minimum toxic concentration, it indicates that the concentration will produce an adverse response. This is because high drug levels can lead to toxicity and harmful effects on the body. The other choices are incorrect because: A: Concentration will produce therapeutic effects - This is incorrect because being above the minimum toxic concentration means the drug level is too high for therapeutic effects. C: Time between doses must be shortened - This is incorrect as adjusting the time between doses does not address the issue of drug toxicity. D: Duration of action of the drug is too long - This is incorrect because the duration of action does not directly relate to drug toxicity; it is the concentration level that determines toxicity.