The recommended children's dosage of Keflex is 25 to 50 mg/kg/day in divided doses. The maximum daily safe dosage for a child weighing 42 lb is: Round to the nearest tenth.

(Number Only, do not enter mg, kg, or day with your answer)

The correct answer is choice A: Avoiding use for more than 3 days.

Choice A rationale:

Recommending avoiding the use of decongestant nose drops for more than 3 days is crucial due to the risk of rebound congestion. Decongestant nose drops work by constricting blood vessels in the nasal passages to alleviate congestion. Prolonged use can lead to a phenomenon known as rebound congestion, where the nasal passages become more congested once the medication wears off, causing the person to use the drops more frequently. This can result in a cycle of worsening congestion and overuse of the medication, which can be counterproductive and harmful. Limiting the use of decongestant nose drops to 3 days helps prevent this rebound effect and encourages the use of alternative treatments if congestion persists.

Choice B rationale:

Administering drops until nasal congestion subsides is not the recommended approach. Prolonged use of decongestant nose drops can lead to rebound congestion, as mentioned earlier. Using the drops until congestion subsides might extend their use beyond the safe period and increase the risk of adverse effects.

Choice C rationale:

Keeping drops to use again for nasal congestion is not advised. While it's important to follow the medication's storage instructions, relying on decongestant nose drops for recurring nasal congestion can lead to overuse and rebound congestion. This choice does not address the potential risks associated with prolonged use.

Choice D rationale:

Administering drops after feedings and at bedtime is not a standard recommendation for decongestant nose drops. The timing of administration is not a primary concern in the context of decongestant use. Instead, the focus should be on the duration of use and the potential for rebound congestion.

The correct answer is choice B. Reduce gastric acid production.

Choice A rationale:

Preventing reflux is not the primary purpose of prescribing a histamine receptor antagonist. Histamine receptor antagonists work by reducing gastric acid production, which in turn can help alleviate symptoms of gastroesophageal reflux disease (GERD). They do not directly prevent the physical reflux of stomach contents into the esophagus.

Choice B rationale:

The primary purpose of prescribing a histamine receptor antagonist for an infant diagnosed with gastroesophageal reflux is to reduce gastric acid production. Histamine stimulates acid secretion in the stomach, and these medications (e.g., ranitidine, famotidine) block histamine receptors on stomach cells, leading to decreased acid secretion. This helps reduce the acidity of stomach contents that could contribute to esophageal irritation in GERD.

Choice C rationale:

Preventing hematemesis (vomiting blood) is not a primary action of histamine receptor antagonists. While reducing gastric acid production might indirectly help prevent complications such as bleeding due to irritation and inflammation of the esophagus, it's not the main purpose of these medications.

Choice D rationale:

Increasing gastric acid production is the opposite of the intended effect of histamine receptor antagonists. These medications are specifically used to decrease gastric acid production and provide relief from conditions where excess acid is causing problems, such as GERD.