Pharmacokinetics of high-dose intravenous melphalan in patients undergoing peripheral blood hematopoietic progenitor-cell transplantation.
The pharmacokinetics of melphalan following high-dose (140 mg/m2) i.v. administration were determined in 20 patients with advanced malignancies undergoing peripheral blood hematopoietic progenitor-cell transplantation. Melphalan was assayed in plasma by a specific HPLC method with UV detection. Plasma levels of melphalan declined in a biexponential fashion with a mean terminal half-life of 83 minutes (range 52-168 minutes). Estimated peak plasma concentrations ranged from 1.65 to 14.5 micrograms/ml. Plasma levels were lower than the limit of quantitation of the method used (20 ng/ml) 24 hours after drug administration. The average volume of distribution and total clearance were 317 ml/min/m2 (range 127-797 ml/min/m2) and 37.9 l/m2 (range 15.4-108 l/m2), respectively. These parameters are similar to those reported in the literature. A weak correlation was found between total clearance of melphalan and creatinine clearance (p < 0.05). No relationship between the pharmacokinetics of melphalan and myelosuppression and non-hematologic toxicities was recovered. This pharmacokinetic study indicates that on the assumption that there is no more circulating melphalan after seven elimination half-lives, it may be possible to reinfuse autologous PBPC 10-20 hours after melphalan administration.