A patient with asthma is admitted to an emergency department with a respiratory rate of 22 breaths per minute, a prolonged expiratory phase, tight wheezes, and an oxygen saturation of 90% on room air. The patient reports using fluticasone [Flovent HFA] 110 mcg twice daily and has used 2 puffs of albuterol [Proventil HFA], 90 mcg/puff, every 4 hours for 2 days. The nurse will expect to administer which drug?

Choice A reason: Morphine, an opioid, binds to mu, kappa, and delta receptors in the brain, spinal cord, and gastrointestinal tract. Mu receptors in the gut slow peristalsis, causing constipation, while central receptors relieve pain. This multi-receptor binding explains both therapeutic and side effects, making this the correct choice.

Choice B reason: Constipation from morphine occurs at therapeutic, not just toxic, doses due to mu receptor activation in the gastrointestinal tract, which reduces motility. Toxicity may worsen side effects, but constipation is a common effect at standard doses, making this choice inaccurate for explaining morphine’s mechanism.

Choice C reason: Morphine’s receptors (e.g., mu) regulate multiple processes, but the drug itself isn’t selective to multifunctional receptors. It binds broadly to opioid receptors, causing both analgesia and side effects like constipation. This choice misrepresents morphine’s non-selective binding, making it less accurate than choice A.

Choice D reason: Morphine’s effects, including analgesia and constipation, result from specific receptor binding, not coincidental processes. It activates opioid receptors in the brain for pain relief and in the gut for reduced motility. This choice incorrectly suggests constipation is unrelated to morphine’s pharmacological action, making it incorrect.

Choice A reason: Patient weight: 198 lbs ÷ 2.2 = 90 kg. Dose: 1 mg/kg × 90 kg = 90 mg. Volume: 90 mg ÷ (30 mg/0.3 mL) = 90 × 0.3/30 = 0.9 mL. This delivers the correct anticoagulant dose for conditions like DVT, making it the accurate choice.

Choice B reason: For 90 kg (198 lbs ÷ 2.2), the dose is 90 mg. Volume: 90 mg ÷ (30 mg/0.3 mL) = 0.9 mL. Choice B (1.2 mL) delivers 120 mg (1.2 × 30/0.3), overdosing Lovenox, increasing bleeding risk, making it incorrect.

Choice C reason: The correct volume for 90 mg is 0.9 mL (90 ÷ 30 mg/0.3 mL). Choice C (0.6 mL) delivers 60 mg (0.6 × 30/0.3), underdosing Lovenox, reducing anticoagulant efficacy, which could fail to prevent thrombosis, making this choice incorrect.

Choice D reason: For 90 mg, the volume is 0.9 mL. Choice D (0.3 mL) delivers 30 mg (0.3 × 30/0.3), significantly underdosing Lovenox for a 90 kg patient, risking inadequate anticoagulation and thrombotic events, making this choice incorrect.