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Disposition of chloramphenicol in low birth weight infants
Insights
Chloramphenicol (CL) drug levels in neonates vary significantly with age. Postnatal age impacts CL half-life, necessitating careful monitoring in low birth weight infants to prevent toxicity.
Area of Science:
- Neonatal Pharmacology
- Infectious Diseases
- Drug Metabolism
Background:
- Chloramphenicol (CL) is an antibiotic rarely used in neonates due to toxicity risks.
- Neonatal use is limited by potential vascular collapse from adult-tolerated doses.
- CL may be necessary for infections resistant to other antibiotics.
Purpose of the Study:
- To investigate chloramphenicol (CL) drug disposition in low birth weight infants.
- To determine the relationship between postnatal age and CL pharmacokinetics.
- To assess the need for therapeutic drug monitoring in this population.
Main Methods:
- Studied 13 low birth weight infants using an assay for active chloramphenicol (CL).
- Divided infants into two groups based on postnatal age: 1-8 days (Group I) and 11 days-8 weeks (Group II).
- Measured serum CL concentrations and calculated half-lives (T1/2) at various dosages.
Main Results:
- Serum CL concentrations varied widely across both groups.
- Group I (younger infants) showed significantly longer CL half-lives (T1/2) compared to Group II (older infants).
- T1/2 in Group I ranged from 10 to over 48 hours, while Group II ranged from 5.5 to 15.7 hours.
Conclusions:
- Postnatal age is a significant factor influencing chloramphenicol (CL) half-life in low birth weight infants.
- There is an inverse relationship between CL T1/2 and postnatal age.
- Therapeutic drug monitoring of CL is essential in low birth weight infants due to pharmacokinetic variability.
Abstract:
Although infrequently an antibiotic of first choice for neonates, chloramphenicol (CL) may be indicated in selected instances of infection caused by aminoglycoside-resistant enterobacteriaciae, anaerobes, and ampicillin-resistant Haemophilus influenzae. Use of CL in neonates has been limited since the recognition that vascular collapse may occur as a consequence of dosage regimens tolerated by adults. With an assay that detects only active CL, we studied drug disposition in 13 low birth weight infants, eight between 1 and 8 days of age (group I), and five between 11 days and 8 weeks of age (group II). Peak serum CL concentrations ranged from 11.2 to 36.2 microgram/ml in group I and from 10.0 to 36.2 microgram/ml in group II, at doses ranging from 15 to 50 mg/kg/day, and 25 to 50 mg/kg/day, in groups I and II, respectively. Serum CL half-lives (T1/2) ranged from 10 to 36 hours in four of the eight group I patients; three of the remaining patients had T1/2 greater than 48 hours and the fourth patient accumulated CL in the interval between doses. T1/2 in group II ranged from 5.5 to 15.7 hours. Observed differences in T1/2 between groups I and II were statistically significant (P = .05) and could not be accounted for by factors other than postnatal age. These preliminary data suggest that although there appears to be an inverse relationship between CL T1/2 and postnatal age, there is sufficient variability in serum levels that monitoring must be performed in low birth weight infants treated with this drug.