Clearance:

Correct Answer: A

Rationale: Clearance (CL = rate of elimination / plasma concentration) is the amount of drug removed per unit time relative to concentration, a true statement defining its calculation. It's constant for first-order kinetics drugs at therapeutic levels, true. Lithium's clearance is moderate, not very high, handled by kidneys, so that's false. Phenytoin's clearance decreases with concentration (zero-order at high doses), not independent, making that false. Clearance isn't inversely proportional to Vd but related via half-life. This definition is essential for dosing regimens, ensuring steady-state maintenance.

Correct Answer: B

Rationale: Phenytoin is an anticonvulsant medication commonly used in the treatment of seizures, including tonic-clonic (grand mal) seizures, complex partial seizures, and seizures occurring during neurosurgery. It works by stabilizing the excitable cell membranes in the brain, thereby reducing abnormal electrical activity that can lead to seizures. Phenytoin is not used as an antidiabetic, mood stabilizer, or antianxiety agent.

Correct Answer: D

Rationale: The correct explanation for the prescription of the ACE inhibitor lisinopril for a patient with diabetes who does not have hypertension is that this medication has cardioprotective properties. ACE inhibitors, such as lisinopril, have been shown to have beneficial effects beyond just lowering blood pressure. They have been found to reduce the risk of cardiovascular events and complications in patients with diabetes, even in the absence of hypertension. Therefore, the prescription of lisinopril for a patient with diabetes may be for its cardioprotective properties rather than for hypertension control.

Correct Answer: A

Rationale: Nicotinic acetylcholine (N ACh) receptors are ligand-gated ion channels, directly opening to allow sodium and potassium flux upon acetylcholine binding, producing rapid effects without second messengers—key in neuromuscular transmission. Alpha-adrenergic (a NE) receptors couple to G-proteins, using second messengers like IP3 or cAMP. D2A dopamine receptors inhibit adenylate cyclase via Gi proteins, involving cAMP. Mu opioid receptors (µ) also use Gi proteins, reducing cAMP and opening potassium channels indirectly. 5HT2 serotonin receptors activate phospholipase C, generating IP3. The nicotinic receptor's direct ion channel linkage distinguishes it, enabling fast synaptic responses without the delay of intracellular signaling cascades.

Correct Answer: B

Rationale: Sertraline carries a suicide risk warning, especially early on. Moodiness and disconnection suggest potential ideation, requiring urgent clinic assessment for safety. Diphenhydramine masks symptoms. Holding medication risks withdrawal. Doubling the dose could worsen effects. B ensures immediate evaluation, making it the best response.