Which of the following is a first-line drug for the treatment of active tuberculosis?

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: Nystatin lozenges must dissolve slowly in the mouth to ensure prolonged contact with oral mucosa, effectively treating candidiasis by disrupting fungal cell membranes. Slow dissolution maximizes local antifungal activity, targeting Candida albicans in the oral cavity, a common complication of inhaled corticosteroid use.

Choice B reason: Rinsing the mouth with water before using an inhaler is appropriate for corticosteroids to prevent thrush but is irrelevant for nystatin lozenges. Nystatin treats existing oral candidiasis, and rinsing beforehand may reduce its contact time with affected mucosa, decreasing efficacy.

Choice C reason: Rinsing with mouthwash after an inhaler is not standard for nystatin or corticosteroid use. Mouthwash may contain alcohol, irritating oral mucosa or reducing nystatin’s antifungal effect. Rinsing with water after corticosteroids prevents thrush, but this instruction is misapplied to nystatin lozenges.

Choice D reason: Chewing nystatin lozenges is incorrect, as it reduces contact time with oral mucosa, decreasing antifungal efficacy. Swallowing the drug shifts its action to the gastrointestinal tract, ineffective for oral candidiasis. Slow dissolution ensures targeted treatment of Candida in the mouth, preventing recurrence.