Explanation: Amlodipine and diltiazem are both calcium channel blockers, but belong to different subclasses (amlodipine is a dihydropyridine; diltiazem is a non-dihydropyridine). Prescribing both simultaneously may cause therapeutic duplication, increasing risk of side effects like hypotension or bradycardia. Prior authorization is not usually required for these drugs. NDC not covered refers to insurance/formulary issues unrelated here. Refill too soon applies when refilling the same medication too early, not different drugs.

Explanation: Fentanyl is a potent synthetic opioid analgesic that is used for pain management, especially in acute and critical care settings. It carries a high risk of causing significant patient harm if used in error due to its potency and potential for respiratory depression. That’s why it is classified as a high-alert medication. It is not an adrenergic agonist, insulin, or neuromuscular blocker.

Explanation: Clindamycin is a lincosamide antibiotic, not a macrolide. Therefore, it can be a safe alternative for patients who are allergic to macrolides. Erythromycin, Azithromycin, and Clarithromycin are all macrolide antibiotics and should be avoided in patients with known macrolide allergies.

Explanation: 1 tablespoonful (tbsp) is equal to 15 mL. Since the prescription says 15 mL per dose, this equals 1 tablespoonful per dose. Thus, the patient should take 1 tablespoonful three times a day (t.i.d.).

Explanation: Grapefruit juice can inhibit the enzyme CYP3A4 in the liver and intestines, which is responsible for metabolizing simvastatin. This can lead to increased levels of simvastatin in the blood, raising the risk of serious side effects like muscle toxicity (myopathy or rhabdomyolysis). Ibuprofen, lisinopril, and doxycycline are not significantly affected by grapefruit juice.