A 64-Year-Old Man Is Evaluated for Persistent Fever and Weakness

question 162

Multiple Choice

A 64-year-old man is evaluated for persistent fever and weakness.  He has a history of aortic valve replacement for aortic stenosis.  Physical examination reveals a new cardiac murmur with scattered petechiae and splinter hemorrhages seen on his extremities.  Echocardiogram shows a vegetation involving one of the aortic valve leaflets, and blood cultures grow enterococci.  As part of the patient's treatment, 240 mg of intravenous gentamicin is started.  The pharmacy calculates that, in this patient, gentamicin has a volume of distribution of 30 L, a half-life of 4 hours, and demonstrates first-order and one-compartment kinetics.  Which of the following is the most likely serum drug concentration just before the next dose 8 hours later?

• A)0)5 mg/L
• B)1 mg/L
• C)1)5 mg/L
• D)2 mg/L
• E)3 mg/L

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Definitions:

Alien Species

Organisms introduced into areas outside their natural habitat, potentially causing harm to native species and ecosystems.

Natural Competitors

Organisms that compete for the same resources within an ecological community, such as food, space, or mates.

Biodiversity

The diversity of living organisms globally or within a specific ecosystem or habitat.

Biological Evolution

The process by which species of organisms change over time through genetic variation and natural selection.