The drug Ondansetron action is?

Correct Answer: C

Rationale: Ondansetron is a medication commonly used to prevent nausea and vomiting, particularly in patients receiving chemotherapy or undergoing surgery. Its mechanism of action involves blocking the effects of serotonin, specifically by antagonizing serotonin 5-HT3 receptors in the chemoreceptor trigger zone of the brain and the gastrointestinal tract. By inhibiting serotonin signaling, ondansetron helps to alleviate nausea and vomiting in affected individuals. This action is distinct from the other options provided, making option C the correct answer for the drug Ondansetron.

Correct Answer: D

Rationale: Heparin is an anticoagulant that enhances the activity of antithrombin III, a natural inhibitor of thrombin and factor Xa, to prevent clotting. The statement that it inhibits clotting by decreasing antithrombin III effects is false, as heparin actually potentiates antithrombin III, making this the incorrect option. Its oral bioavailability is negligible (not 20-30%), as it's a large polysaccharide requiring parenteral administration (e.g., IV or subcutaneous), so this is false. Heparin is highly plasma protein-bound, not low, contradicting that option. The correct statement, replaced in the fourth slot, is that heparin binds to antithrombin III, causing a conformational change that accelerates its anticoagulant effect. This mechanism is fundamental to its clinical use in thrombosis prevention, distinguishing it from oral anticoagulants like warfarin.

Correct Answer: A

Rationale: Stimulants are drugs that increase the body's activity levels. They work on the central nervous system to enhance alertness, attention, and energy. Examples of stimulants include caffeine, amphetamines, and nicotine. Stimulants can increase heart rate, blood pressure, and metabolism, leading to heightened physical and mental activity.

Correct Answer: C

Rationale: Thiopental, a barbiturate, persists 24 hours post-surgery. Physiologic metabolism is correct-its lipophilicity causes redistribution to fat, with slow hepatic metabolism, normal in the elderly. Hepatitis or insufficiency lacks evidence. Renal failure doesn't primarily clear it. Trauma (E) is unrelated. This reflects thiopental's pharmacokinetics, not pathology.

Correct Answer: D

Rationale: Trastuzumab is a targeted therapy used specifically for HER2-positive breast cancer. If the patient's cancer cells do not overexpress the HER2 receptor, trastuzumab will not be effective. The decision to use targeted therapy is based on the molecular characteristics of the tumor, not the patient's age, insurance coverage, or estrogen receptor status. The nurse should explain that targeted therapies are tailored to the specific biology of the cancer, and trastuzumab is only appropriate for HER2-positive tumors.