A patient with the diagnosis of schizophrenia is hospitalized and is taking a phenothiazine drug. Which statement by this patient indicates that he is experiencing a common adverse effect of phenothiazines?

Correct Answer: D

Rationale: The correct answer is D: “My mouth has been so dry lately.” This statement indicates the patient is experiencing xerostomia, a common adverse effect of phenothiazines due to their anticholinergic properties. Xerostomia results in decreased salivary flow, leading to dry mouth. Choices A, B, and C are less likely to be related to phenothiazine use. A is a common symptom of schizophrenia, B could indicate increased appetite which is not a common side effect, and C is not a typical side effect of phenothiazines.

Correct Answer: C

Rationale: The correct answer is C because dextromethorphan suppresses the cough reflex by directly acting on the cough center in the brain. This drug inhibits the signals that trigger the cough reflex, leading to reduced coughing. Choice A is incorrect as dextromethorphan does not depress the central nervous system like opioids. Choice B is incorrect because dextromethorphan does not anesthetize stretch receptors. Choice D is incorrect as dextromethorphan does not affect the viscosity of bronchial secretions.

Correct Answer: C

Rationale: The correct answer is C because bioavailability is determined by the extent of absorption and hepatic first-pass effect. Absorption refers to how much of a substance is taken up by the body, while the hepatic first-pass effect is the initial metabolism of a drug in the liver before it reaches systemic circulation. These factors directly impact the amount of a substance that is available to produce its desired effect. Rheological parameters of blood (A) are unrelated to bioavailability. The amount of a substance obtained orally and quantity of intakes (B) may affect bioavailability indirectly but do not determine it. Glomerular filtration rate (D) is related to renal excretion, not bioavailability.

Correct Answer: D

Rationale: The correct answer is D because the ED50 is a measure of potency, not efficacy. Efficacy refers to the maximum effect of a drug, while potency is the comparative measure of the doses needed to produce the same effect. Therefore, A is incorrect because efficacy can be more important clinically than potency in certain situations. B is true as efficacy is indeed the maximum effect of a drug. C is also correct as it accurately describes potency as a comparative measure. In summary, D is incorrect because the ED50 is a measure of potency, not efficacy, making it the exception among the statements provided.

Correct Answer: A

Rationale: The correct answer is A: Procaine. It is a short-acting drug due to its rapid metabolism by plasma esterases, resulting in a shorter duration of action compared to the other choices. Procaine's quick onset and short duration make it suitable for minor procedures. Tetracaine, Bupivacaine, and Ropivacaine are all long-acting local anesthetics with slower metabolism and longer durations of action, making them more suitable for prolonged surgeries or chronic pain management.