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 ["2590/2000"]
Explanation
INTAKE:.
Step 1: Jevity (Tube feeding) 50 mL/hr × 12 hours = 600 mL.
Step 2: oz free water tube feeding flush. Convert ounces to milliliters: 6 oz × 30 mL/oz = 180 mL.
Step 3: units of PRBCs (250 mL/each) = 2 × 250 mL = 500 mL.
Step 4: Zosyn IV 50 mL.
Step 5: oz ice chips. Convert ounces to milliliters (ice chips are typically calculated as half their volume in liquid): 4 oz × 30 mL/oz = 120 mL; 120 mL ÷ 2 = 60 mL.
Step 6:.9% NS 100 mL/hr × 12 hours = 1200 mL.
Step 7: Total Intake = 600 mL + 180 mL + 500 mL + 50 mL + 60 mL + 1200 mL = 2590 mL. OUTPUT:.
Step 1: NG Suction: 50 mL.
Step 2: Urine: 1850 mL.
Step 3: Wound vac: 100 mL.
Step 4: Total Output = 50 mL + 1850 mL + 100 mL = 2000 mL. Answer: INTAKE: 2590 mL / OUTPUT: 2000 mL.
Correct Answer is A
Explanation
Choice A rationale
The knee joint, a modified hinge joint, primarily facilitates movement within the sagittal plane. Flexion involves decreasing the angle between the femur and tibia, bending the knee, while extension involves increasing this angle, straightening the knee. These movements are achieved through the coordinated action of muscles like the quadriceps femoris and hamstrings, acting on the condyles of the femur and tibia.
Choice B rationale
Inversion and eversion are movements specific to the ankle and foot. Inversion involves turning the sole of the foot inward, towards the midline of the body, while eversion involves turning the sole of the foot outward, away from the midline. These movements are mediated by the subtalar and transverse tarsal joints, not the knee.
Choice C rationale
Supination and pronation are rotatory movements primarily associated with the forearm and hand. Supination involves rotating the forearm so the palm faces anteriorly or superiorly, while pronation involves rotating it so the palm faces posteriorly or inferiorly. These actions are controlled by muscles acting on the radius and ulna, not the knee joint.
Choice D rationale
Circumduction is a complex movement combining flexion, extension, abduction, and adduction, commonly seen in ball-and-socket joints like the shoulder or hip. Rotation, where a bone pivots around its own longitudinal axis, is also more prominent in these joints. While the knee has minimal rotational capability when flexed, it's not a primary movement.
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