Which of the following drugs most likely interacted with metoclopramide, thus triggering the adverse effects reported by the patient?

Correct Answer: A

Rationale: Amitriptyline is a tricyclic antidepressant that can interact with metoclopramide, leading to increased risk of side effects such as confusion, hallucinations, and irregular heart rhythm. This interaction is well-documented in medical literature and is a known pharmacodynamic interaction between the two drugs.

Correct Answer: B

Rationale: The most likely reason for the adverse effects reported by the patient is the decreased renal elimination of lithium caused by the antihypertensive treatment with hydrochlorothiazide. Thiazide diuretics like hydrochlorothiazide can decrease renal elimination of lithium, leading to an increase in lithium levels in the blood and potential toxicity. This interaction can result in symptoms such as lithium toxicity, which may present as mood swings and other adverse effects in a patient with bipolar disorder receiving lithium therapy. Therefore, choice B is the correct answer.

Correct Answer: A

Rationale: The appropriate drug for the patient at this time would be Amitriptyline. The patient, who was previously discharged on valproic acid for bipolar disorder, is now experiencing depressive symptoms after discontinuing therapy. Amitriptyline, a tricyclic antidepressant, would be suitable for treating the patient's depression. Tricyclic antidepressants like Amitriptyline are commonly used in the treatment of mood disorders, including bipolar depression. Therefore, choice A is the correct answer.

Correct Answer: C

Rationale: Amiloride is a potassium-sparing diuretic that can help reduce excessive urination and fluid intake in patients with symptoms of diabetes insipidus. It works by affecting the reabsorption of sodium and water in the kidneys, helping to balance fluid levels and decrease urinary output. Furosemide, hydrochlorothiazide, spironolactone, and conivaptan are not typically used to treat the specific symptoms described in the case.

Correct Answer: B

Rationale: Norepinephrine is a neurotransmitter that plays a role in regulating blood pressure. Drugs that increase norepinephrine levels can lead to elevated blood pressure, as seen in this patient. Atomoxetine, phenylephrine, guanfacine, and clonidine do not directly affect norepinephrine levels in a way that would cause high blood pressure.