Correct Answer: C

Rationale: The correct instruction for a client prescribed Verapamil is to avoid drinking grapefruit juice. Grapefruit juice can inhibit the metabolism of Verapamil, leading to increased blood levels of the medication. This can result in a higher risk of adverse effects, such as hypotension and bradycardia. Therefore, it is essential for the client to avoid grapefruit juice while taking Verapamil to prevent potential complications.

Correct Answer: C

Rationale: Sucralfate can interfere with the absorption of phenytoin. To prevent this interaction, the client should allow a 2-hour interval between taking sucralfate and phenytoin. This interval helps ensure that each medication is absorbed effectively without affecting the other's absorption.

Correct Answer: D

Rationale: Oxybutynin is an anticholinergic medication that can increase intraocular pressure. It is contraindicated in clients with glaucoma, as it can worsen the condition. Glaucoma is a condition characterized by increased intraocular pressure, and using Oxybutynin can further elevate this pressure, potentially leading to serious complications such as vision impairment or damage to the optic nerve.

Correct Answer: A

Rationale: St. John's wort should be avoided by clients taking Warfarin as it can reduce the medication's effectiveness. The nurse should also advise the client to avoid other supplements that may interact with Warfarin, such as garlic and ginseng.

Correct Answer: A

Rationale: Grapefruit juice should be avoided when taking Atorvastatin because it can increase the blood levels of the medication, potentially leading to a higher risk of adverse effects like muscle pain and liver damage. It is important to follow this instruction to ensure the safe and effective use of Atorvastatin.