Explanation: Cephalosporins and penicillins both belong to the beta-lactam class of antibiotics and share similar chemical structures. Due to this similarity, there is a potential cross-sensitivity in patients with a penicillin allergy, especially with first-generation cephalosporins. While macrolides, aminoglycosides, and glycopeptides are different classes, they do not have significant cross-reactivity with penicillins.

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.