A nurse is completing a medical interview with a client who has elevated cholesterol levels and takes warfarin. The nurse should recognize that which of the following actions by the client can potentiate the effects of warfarin?

Choice A reason: Applying a new transdermal patch when chest pain is experienced is not a correct instruction, as it may delay the relief of the pain and increase the risk of adverse effects. Transdermal nitroglycerin is a long-acting form of nitrate that is used for the prevention of angina attacks, not for the treatment of acute episodes. The client should use a short-acting form of nitrate, such as sublingual or spray, for the immediate relief of chest pain.

Choice B reason: Applying the transdermal patch in the morning is a correct instruction, as it helps to maintain a steady level of nitrate in the blood throughout the day and prevent angina attacks. Transdermal nitroglycerin has a duration of action of about 12 to 24 hours, depending on the dose and the individual response. The client should apply the patch in the morning and remove it at night, to allow a nitrate-free interval of at least 8 hours and prevent the development of tolerance.

Choice C reason: Applying the transdermal patch in the same location as the previous patch is not a correct instruction, as it may cause skin irritation and reduce the absorption of the medication. Transdermal nitroglycerin should be applied to a clean, dry, and hairless area of the skin, preferably on the chest, upper arm, or back. The client should rotate the application sites and avoid areas that are exposed to heat, moisture, or friction.

Choice D reason: Applying a new transdermal patch once a week is not a correct instruction, as it may not provide adequate protection against angina attacks and increase the risk of rebound angina. Transdermal nitroglycerin should be applied daily, with a nitrate-free interval of at least 8 hours, to maintain a therapeutic level of nitrate in the blood and prevent the loss of efficacy. The client should follow the prescribed dosing schedule and consult the provider before making any changes.

Choice A reason: Taking the medication in the morning is not the correct instruction. Simvastatin is a statin drug that lowers cholesterol levels by inhibiting the enzyme that produces cholesterol in the liver. The liver produces more cholesterol at night, so simvastatin is more effective when taken in the evening or at bedtime.

Choice B reason: Avoiding grapefruit juice is the correct instruction. Grapefruit juice can increase the blood levels of simvastatin and cause serious side effects such as muscle damage, liver damage, and kidney failure. Grapefruit juice inhibits the enzyme that metabolizes simvastatin in the intestine, leading to higher concentrations of the drug in the bloodstream.

Choice C reason: Monitoring for ringing in the ears is not the correct instruction. Ringing in the ears, or tinnitus, is not a common or serious side effect of simvastatin. However, some other medications that lower cholesterol, such as niacin and gemfibrozil, can cause tinnitus. The client should report any unusual or persistent symptoms to the prescriber.

Choice D reason: Expecting brown-colored urine is not the correct instruction. Brown-colored urine, or hematuria, is not a normal or expected side effect of simvastatin. However, it may indicate a serious condition such as rhabdomyolysis, which is a rare but life-threatening complication of statin therapy. Rhabdomyolysis is the breakdown of muscle tissue that releases a protein called myoglobin into the bloodstream. Myoglobin can damage the kidneys and cause brown-colored urine. The client should seek immediate medical attention if they notice any signs of rhabdomyolysis, such as muscle pain, weakness, fever, or dark urine.