Knowing a drug's half-life enables the physician to determine the:
Peak plasma level.
Onset of action.
Schedule for repeated doses to maintain the drug level over 24 hours.
Duration of effectiveness.
The Correct Answer is C
Choice A rationale
The peak plasma level represents the maximum concentration of a drug achieved in the bloodstream after administration. While half-life influences the time to reach steady state, it does not directly determine the magnitude of the peak plasma level, which is more dependent on dose, absorption rate, and distribution volume.
Choice B rationale
Onset of action refers to the time it takes for a drug to exert its therapeutic effects after administration. While related to pharmacokinetic properties, the half-life primarily dictates the duration of drug presence and accumulation, not the immediate time to initial effect, which is more influenced by absorption and distribution.
Choice C rationale
A drug's half-life is the time it takes for the plasma concentration of a drug to be reduced by 50%. This pharmacokinetic parameter is critical for determining appropriate dosing intervals to maintain therapeutic drug levels within a desired range over a 24-hour period, preventing accumulation or sub-therapeutic concentrations.
Choice D rationale
The duration of effectiveness refers to the length of time a drug produces its therapeutic effect. While the half-life influences how long a drug remains in the system, the duration of effectiveness is also dependent on the drug's mechanism of action, receptor binding, and the patient's individual physiological responses, not solely on half-life.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale
Cerumen, or earwax, is a normal physiological secretion produced by the apocrine and sebaceous glands in the external auditory canal. While excessive or impacted cerumen can lead to conductive hearing loss or harbor bacterial growth, its mere presence, especially in a healthy individual, is not indicative of an external ear infection. An infection would typically present with pain, redness, discharge, or fever.
Choice B rationale
Cerumen is a natural substance composed of exfoliated skin cells, fatty acids, cholesterol, and lysozymes. It serves a protective role by lubricating the ear canal, trapping dust and foreign particles, and possessing antibacterial and antifungal properties. Its presence in the external auditory meatus, as observed in this patient, is a normal physiological finding.
Choice C rationale
While skin conditions like eczema can affect the external ear canal and lead to inflammation, itching, and scaling, the presence of cerumen alone does not indicate eczema lesions. Eczema would typically present with characteristic erythematous, pruritic, and possibly weeping or crusted lesions, which are distinct from normal cerumen.
Choice D rationale
Cerumen production is a normal bodily function and its presence is not an indicator of poor hygiene. Attempts to excessively clean the ear canal with cotton swabs can actually push cerumen deeper, leading to impaction, rather than indicating poor hygiene. The ear is generally self-cleaning, with cerumen naturally migrating out of the canal.
Correct Answer is ["75"]
Explanation
Step 1 is 1.5 L × 1000 mL/L = 1500 mL.
Step 2 is 1500 mL ÷ 20 hours = 75 mL/hour.
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