. Vancomycin pharmacokinetics in preterm infants. CLINICS. 2007;62(4):405-10. OBJETIVE:The objective of the present study was to evaluate the kinetic disposition of vancomycin in preterm infants with emphasis on the apparent volume of distribution, biological half-life, and total body clearance as well as whether their variations cause significant modification of the trough plasma concentration of the drug, depending on the postconceptional age (PCA) and the postnatal age (PNA). MATERIAL AND METHOD: Twenty-five selected patients were distributed into 2 groups which differed significantly in terms of mean PCA (31.2-32.3 weeks in group 1, n = 13; 33.5-34.1 weeks in group 2, n = 12: CI95%, P < .001) and PNA (group 1, 12.0-18.5 days; group 2, 18.0-34.0 days, CI95%, P < .05). The parents were informed and signed a written consent for participation of the infants in the protocol that had been previously approved by the Ethics Committee of the hospital. RESULTS: Apparent volume of distribution was significantly increased in group 1 compared with patients of group 2 (0.85 vs. 0.56 L/kg, respectively; P = .01,). Additionally multiple linear regression revealed a good linear correlation (r = 0.85) of trough plasma concentration of vancomycin with the apparent volume of distribution and also with the biological half-life in patients of group 1, while a good correlation (r = 0.91) was obtained for the trough plasma concentration with total body clearance in infants of group 2. The influence of these kinetic parameters on the trough concentration of vancomycin in preterm infants seems to vary according to PCA and PNA. CONCLUSION: In conclusion, the trough plasma concentration of vancomycin depends on the pharmacokinetics, and multiple linear correlation indicates that it varies according to the postconceptional and postnatal age of preterm infants.