Melphalan pharmacokinetics in children with malignant disease: influence of body weight, renal function, carboplatin therapy and total body irradiation.

AIM: To analyse the pharmacokinetics of melphalan in 52 children (0.3-18 years) and determine whether any clinical factors affect the pharmacokinetic parameters Additionally, to examine whether a test melphalan dose can predict the pharmacokinetics of a full dose, when there are 5 intervening days of carboplatin therapy.
METHODS: Melphalan concentrations were measured in 14 blood samples collected from each child following doses ranging from 30 to 180 mg m(-2). The pharmacokinetics were analysed with Kinetica 4.0.
RESULTS: Children who did not have carboplatin (n = 27) had median melphalan clearance (CL) of 15.5 l h(-1) m(-2) (interquartile range: 12.4-19.9 l h(-1) m(-2)) and steady state volume of distribution (Vss) of 14.9 l m(-2) (interquartile range: 12.7-18.3 l m(-2)). Children who had carboplatin (n = 25) had 34% lower median CL (10.2 l h(-1) m(-2)) and 18% lower median Vss (12.2 l m(-2)) (P < 0.001). Melphalan elimination was impaired in a separate group of three children given concomitant carboplatin and etoposide. Stepwise multiple linear regression indicated that weight, carboplatin, glomerular filtration rate (GFR) and total body irradiation (TBI) significantly affected CL, while weight and carboplatin influenced Vss. A test dose (10 mg m(-2)) tended to underpredict the area-under-the-concentration-vs.-time-curve for a full (180 mg m(-2)) dose in 19 individuals given carboplatin.
CONCLUSIONS: In children, melphalan CL is influenced by weight, carboplatin, TBI and GFR. Vss is influenced by weight and carboplatin.