Knowing a drug's half-life enables the physician to determine the:

The aortic valve is best auscultated at the second intercostal space (ICS) along the right sternal border. This anatomical landmark corresponds to the superficial projection of the aorta and is where the sounds of aortic valve closure and blood flow through the aorta are most clearly transmitted to the chest wall. Optimal sound transmission is achieved by minimizing intervening tissue. Pulmonic rationale:

The pulmonic valve is best auscultated at the third intercostal space (ICS) along the left sternal border, also known as Erb's point. While the pulmonic area is typically at the second ICS left sternal border, Erb's point provides a broader area for detecting murmurs related to both the pulmonic and aortic valves. This location provides good sound transmission for the pulmonary artery. Tricuspid rationale:

The tricuspid valve is best auscultated at the fourth intercostal space (ICS) along the left sternal border. This location overlies the right ventricle and the tricuspid valve, allowing for clear detection of its closure sounds and any associated murmurs. The proximity of the valve to the chest wall at this point facilitates optimal auscultation. Mitral rationale:

The mitral valve is best auscultated at the fifth intercostal space (ICS) at the midclavicular line (MCL). This location is also known as the apex of the heart, where the left ventricle's impulse is strongest. Sounds produced by the mitral valve, particularly during its closure, are best heard here due to the direct anatomical projection and maximal cardiac impulse. .

Choice A rationale

The "prn" abbreviation stands for "pro re nata," which is Latin for "as needed.”. This indicates that the medication should be administered based on the patient's symptoms or specific needs, rather than on a fixed schedule. The nurse assesses the patient and administers the medication only when the patient exhibits the conditions for which the medication is prescribed, adhering to the minimum 6-hour interval for safety and therapeutic efficacy. This allows for individualized pain management.

Choice B rationale

This statement is incorrect because a "prn" order does not imply around-the-clock administration. Around-the-clock dosing is typically for scheduled medications where a consistent drug level is desired to manage chronic conditions or prevent symptoms, regardless of the patient's immediate need. Administering a prn medication routinely could lead to unnecessary drug exposure or adverse effects.

Choice C rationale

While waiting 6 hours between doses is crucial to prevent drug accumulation and toxicity, stating "I must wait 6 hours before administering this medication to you" is an incomplete explanation for a PRN order. The primary determinant for administration is the patient's need, not simply the passage of time. The 6-hour interval is a safety parameter to ensure adequate drug clearance and prevent exceeding therapeutic thresholds.

Choice D rationale

Administering a medication "over 6 hours" refers to the duration of infusion, not the frequency of administration. This statement is typically relevant for intravenous infusions where the drug is diluted and infused slowly over a specific period. A prn order for oral medication generally means an immediate dose is given when needed, and the interval between doses is 6 hours, not the infusion time.