Which medication is a commonly used antidepressant in the class of selective serotonin reuptake inhibitors (SSRIs)?

Correct Answer: B

Rationale: Step 1: SSRIs are a class of antidepressants that work by increasing serotonin levels in the brain. Step 2: Fluoxetine is an SSRI commonly used to treat depression and other mental health conditions. Step 3: Sertraline, citalopram, and lorazepam are not SSRIs but belong to other classes of medications. Summary: Sertraline, citalopram, and lorazepam are incorrect choices as they do not belong to the SSRI class like fluoxetine does.

Correct Answer: B

Rationale: The correct answer is B: Replacing deficient thyroid hormone. Levothyroxine is a synthetic form of thyroid hormone used to treat hypothyroidism by supplementing the low levels of thyroid hormone in the body. It does not increase TSH production (Choice A), inhibit thyroid hormone synthesis (Choice C), or increase the metabolism of thyroid hormones (Choice D). By providing the missing thyroid hormone, levothyroxine helps restore normal thyroid function and alleviate symptoms of hypothyroidism.

Correct Answer: A

Rationale: The correct answer is A: A selective serotonin reuptake inhibitor (SSRI). Fluoxetine falls under this class by specifically inhibiting the reuptake of serotonin, leading to increased serotonin levels in the brain. This mechanism helps alleviate symptoms of depression. Other choices are incorrect because fluoxetine is not an MAOI (B), TCA (C), or SNRI (D), as it does not primarily target monoamine oxidase enzymes, nor does it have the tricyclic structure or target both serotonin and norepinephrine reuptake.

Correct Answer: A

Rationale: The correct answer is A: Dry cough. Lisinopril, an ACE inhibitor, commonly causes a dry, persistent cough due to its effect on bradykinin levels. This side effect is distinct and prevalent compared to others like fatigue, weight gain, or hyperkalemia. Fatigue and weight gain are less common side effects of lisinopril, while hyperkalemia is a potential but less frequent adverse reaction associated with ACE inhibitors. Overall, the prevalence and mechanism of dry cough make it the most common side effect of lisinopril.

Correct Answer: A

Rationale: The correct answer is A because the therapeutic index (TI) is a measure of a drug's safety margin. A higher TI indicates a safer drug as it represents the ratio between the dose that produces therapeutic effects and the dose that causes toxicity. If the therapeutic dose is much lower than the toxic dose, it results in a higher TI, indicating a safer drug. Choice B is incorrect because a TI of 1 indicates that the therapeutic dose is equal to the toxic dose, which is not desirable. Choice C is incorrect as the presence of unwanted adverse effects does not necessarily impact the TI directly. Choice D is incorrect because the margin of safety for Digoxin is 0.8-2 ng/ml, so a level of 1.8 ng/ml would fall within the safe range, not pose a danger.