A drug has a half-life of 2 hours.

If at 0600, the drug level is measured as 200 mg÷L, at what time would the drug level be 25 mg÷L?

This question tests clinical judgment regarding life-threatening adverse reactions to vancomycin. It requires identifying the signs of an anaphylactic or severe infusion-related reaction, which necessitates immediate intervention to maintain the patient's airway, breathing, and circulation, as these symptoms indicate critical physiological instability.

Choice A rationale

Phlebitis is a localized inflammatory reaction of the vein wall. While it requires assessment and site rotation to prevent further tissue damage, it is a localized complication and does not represent a life-threatening systemic emergency.

Choice B rationale

Flushing, hypotension, and wheezing are cardinal signs of an anaphylactic reaction. These systemic symptoms indicate severe bronchospasm and cardiovascular collapse, requiring immediate cessation of the infusion, administration of epinephrine, and urgent medical management to prevent patient mortality.

Choice C rationale

Mild tinnitus is a known side effect related to vancomycin's potential ototoxicity, which is usually dose-related and progressive. While it warrants monitoring and potential dose adjustment, it does not represent an immediate systemic emergency that requires emergency intervention.

Choice D rationale

Mild myalgia and vertigo can occur following vancomycin administration but are not indicative of an immediate, life-threatening crisis. They require monitoring and documentation, but the patient remains hemodynamically stable, making this a secondary priority compared to anaphylaxis.

Step 1 is convert weight in lbs to kg: 55 lbs ÷ 2.2 lbs/kg = 25 kg.

Step 2 is calculate the dose: 30 mcg/kg × 25 kg = 750 mcg. Final calculated answer is 750 mcg.