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Pharmacokinetics of nafcillin in infants with low birth weights
Insights
Lower nafcillin doses may be sufficient for premature neonates with suspected sepsis. This study in low birth weight infants suggests current dosing might be too high, potentially impacting therapeutic outcomes.
Area of Science:
- Neonatal pharmacology
- Pediatric infectious diseases
- Clinical pharmacokinetics
Background:
- Nafcillin is commonly used for suspected sepsis in neonates.
- Optimal dosing for premature infants requires further pharmacokinetic investigation.
Purpose of the Study:
- To characterize the pharmacokinetics of nafcillin in premature neonates.
- To evaluate current dosing regimens for efficacy and safety in this population.
Main Methods:
- Pharmacokinetic study involving 13 premature neonates with suspected sepsis.
- Nafcillin dosing based on age (<7 days vs. >7 days).
- Blood sampling and microbiological assay for nafcillin concentration measurement.
Main Results:
- Identified distinct pharmacokinetic profiles based on infant age.
- Volume of distribution and elimination rate varied between younger and older infants.
- Data suggests potential for lower effective nafcillin doses in low birth weight infants.
Conclusions:
- Current nafcillin dosing may exceed therapeutic needs in some premature neonates.
- Adjusted dosing based on age and weight could optimize treatment.
- Further research is warranted to refine nafcillin dosage guidelines for neonates.
Abstract:
The pharmacokinetics of nafcillin were studied in 13 premature neonates with suspected sepsis. The mean weight of the infants studied was 1.19 kg (range, 0.73 to 2.21 kg). Infants less than 7 days of age were given 100 mg of nafcillin per kg per 24 h (every 12 h), and infants more than 7 days of age were given 100 mg of nafcillin per kg per 24 h (every 8 h). Blood samples were obtained before the first dose on day 3 of therapy and at 0.5, 1.5, 3, and 6 h thereafter. Nafcillin concentrations were measured by a microbiological assay. A mean volume of distribution of 326 ml/kg and an elimination rate constant of 0.2040 h-1 were obtained in 10 patients less than 21 days of age. Three patients from 24 to 68 days of age had a mean volume of distribution of 303 ml/min and a mean elimination rate constant of 0.3944 h-1 (P less than 0.05). These data suggest that doses of nafcillin lower than those currently recommended may be adequate to achieve desired peak plasma levels of approximately 75 microgram/ml in infants with low birth weights.