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Chapter 3. Pediatrics

Student Questions

Which pharmacokinetic parameter affects the dose frequency of intravenous gentamicin in a premature neonate?

A. Absorption

B. Distribution

C. Metabolism

D. Elimination

Answer: D

Option A: Incorrect. This is a medication administered by intravenously, so absorption is an issue. Nephrogenesis completes at approximately 36 weeks' gestation; thus, premature neonates and infants have compromised glomerular and tubular function that may correlate with a glomerular filtration rate (GFR). This reduction in GFR affects renal drug clearance; thereby necessitating longer dosing intervals for renally cleared medications, such as gentamicin, to prevent accumulation.

Option B: Incorrect. Extracellular fluid and total body water per kilogram of body weight are increased in neonates and infants, resulting in higher Vd for water-soluble drugs, such as aminoglycosides, and decreases with age. Therefore, neonates and infants often require higher doses by weight (mg/kg) than older children and adolescents to achieve the same therapeutic serum concentrations. This affects dose by weight, not dose frequency.

Option C: Incorrect. Hepatic drug metabolism is most often thought of with regard to the general concept of drug metabolism. Gentamicin is not heavily hepatically metabolized and this this parameter is not likely to affect drug dosing frequency.

Option D: Correct. Nephrogenesis completes at approximately 36 weeks' gestation; thus, premature neonates and infants have compromised glomerular and tubular function that may correlate with a glomerular filtration rate (GFR). This reduction in GFR affects renal drug clearance; thereby necessitating longer dosing intervals for renally cleared medications, such as gentamicin, to prevent accumulation.

Which of the following is an appropriate maintenance fluid requirement for an 8-year-old girl with a weight of 50 pounds (22.7 kg)?

A. ~1050 mL/day

B. ~1200 mL/day

C. ~1550 mL/day

D. ~2100 mL/day

Answer: C

Option A: Incorrect. Using the Holliday Segar method, with a patient weight of 22.7 kg, it would be 1500 mL + 20 mL/kg × 2.7kg =1554 mL.

Option B: Incorrect. Using the Holliday Segar method, with a patient weight of 22.7 kg, it would be 1500 mL + 20 mL/kg × 2.7kg =1554 mL.

Option C: Correct. Using the Holliday Segar method, with a patient weight of 22.7 kg, it would be 1500 mL + 20 mL/kg × 2.7kg =1554 mL.

Option D: Incorrect. Using the Holliday Segar method, with a patient weight of 22.7 kg, it would be ...

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