The nurse is preparing to administer heparin intravenously (IV). Which response by the nurse would be appropriate when the patient asks when the medication will start working?

Choice A reason: Intravenous heparin has an immediate onset, as it rapidly enhances antithrombin activity, inhibiting thrombin and factor Xa, preventing clot formation. This quick action makes it ideal for acute conditions like pulmonary embolism, providing instant anticoagulation, with effects measurable by aPTT within minutes of administration.

Choice B reason: A 5- to 10-minute onset is too slow for IV heparin, which acts immediately upon entering the bloodstream. Subcutaneous heparin has a delayed onset (20-60 minutes), but IV delivery ensures rapid anticoagulant effects, making this timeframe incorrect for IV administration.

Choice C reason: A 20-minute onset is inaccurate for IV heparin. Its immediate binding to antithrombin provides instant anticoagulation, unlike oral anticoagulants like warfarin, which take days. The 20-minute timeframe may apply to subcutaneous heparin, not IV, which acts within seconds to minutes.

Choice D reason: A 1-hour onset is incorrect for IV heparin, which provides immediate anticoagulation by enhancing antithrombin’s inhibition of clotting factors. This rapid action is critical for acute thrombotic conditions. A 1-hour delay applies to drugs with slower absorption, not IV heparin’s direct action.

Choice A reason: Tuberculosis therapy does not stop when symptoms resolve, as residual bacteria may persist, leading to relapse. Standard regimens (e.g., isoniazid, rifampin) last 6-9 months to ensure complete eradication of Mycobacterium tuberculosis, guided by sputum cultures and imaging, not just symptom cessation.

Choice B reason: Lifelong tuberculosis therapy is not typical for active disease. Standard treatment lasts 6-9 months for drug-susceptible tuberculosis, achieving cure in most cases. Lifelong therapy may apply to certain chronic infections, but for tuberculosis, finite regimens are effective, making this statement incorrect.

Choice C reason: Standard treatment for active tuberculosis involves a 6- to 9-month regimen of first-line drugs (isoniazid, rifampin, ethambutol, pyrazinamide). This duration ensures complete bacterial eradication, preventing relapse or resistance. Longer durations may be needed for resistant strains or extrapulmonary disease, aligning with clinical guidelines.

Choice D reason: Therapy does not continue until resistance develops, as this would indicate treatment failure. The goal is to eradicate Mycobacterium tuberculosis before resistance emerges, using combination therapy for 6-9 months. Continuing until resistance occurs is counterproductive and increases the risk of multidrug-resistant tuberculosis.