When a patient asks the nurse what is the most common cause of myocardial ischemia, which statement is the correct response?

Choice A reason:
Vitamin K (phytonadione) is the antidote for warfarin overdose. It works by promoting the synthesis of clotting factors that are inhibited by warfarin, thereby reversing the anticoagulant effects. In cases of excessive warfarin intake, administering vitamin K helps restore normal clotting function.

Choice B reason:
Protamine sulfate is the antidote for heparin overdose, not warfarin. It works by neutralizing the anticoagulant effects of heparin, but it has no effect on warfarin-induced anticoagulation. Therefore, it is not appropriate for this situation.

Choice C reason:
A PTT lab test measures the effectiveness of the intrinsic pathway of coagulation and is primarily used to monitor heparin therapy. It is not relevant for managing warfarin overdose, as warfarin affects the extrinsic pathway, which is measured by the PT/INR test.

Choice D reason:
While an INR lab test is essential for monitoring the therapeutic levels of warfarin, the immediate need in this situation is to reverse the effects of the overdose. Administering vitamin K is the necessary intervention to counteract the excessive anticoagulation caused by warfarin.

Choice A reason:
Taking an antacid one hour after ranitidine is recommended because antacids can affect the absorption of H2 receptor blockers like ranitidine. Ranitidine works by reducing stomach acid production, whereas antacids neutralize existing acid. Taking the antacid too close to the ranitidine can reduce the effectiveness of the ranitidine by altering the stomach's pH balance and affecting its absorption.

Choice B reason:
Taking an antacid and ranitidine at the same time does not enhance their effect. In fact, this can interfere with the absorption and effectiveness of ranitidine. Antacids can increase the pH of the stomach, which may reduce the absorption of ranitidine, thus diminishing its acid-reducing effects.

Choice C reason:
Taking both medications at the same time before meals is not advisable for the same reason as above. The simultaneous administration can reduce the effectiveness of ranitidine, as the increased pH caused by the antacid can interfere with the absorption of the H2 receptor blocker, thereby not providing the intended therapeutic effect.

Choice D reason:
The patient can take both medications, but they should be timed correctly to ensure optimal effectiveness. Saying that the patient needs to be on one medication only is incorrect. Both medications can be used together, but the antacid should be taken after ranitidine to avoid any interaction that might impair the effectiveness of ranitidine.