Disposition of Chloramphenicol in Low Birth Weight Infants

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 is 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, drug disposition was studied in 13 low birth weight infants, 8 between 1-8 days of age (group I) and 5 between 11 days and 8 wk of age (group II). Peak serum CL concentrations ranged from 11.2-36.2 .mu.g/ml in group I and from 10.0-36.2 .mu.g/ml in group II, at doses ranging from 15-50 mg/kg per day and 25-50 mg/kg per day, in groups I and II, respectively. Serum CL half-lives (t1/2) ranged from 10-36 h in 4 of the 8 group I patients; 3 of the remaining patients had t1/2 greater than 48 h and the 4th patient accumulated CL in the interval between doses. The t1/2 in group II ranged from 5.5-15.7 h. 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.