title: A rapid method for the separation and analysis of leaked and liposomal entrapped phosphoramide mustard in plasma.
abstract: Pharmacokinetic studies of liposomal drugs should include simultaneous determination of leaked and entrapped drug in biological specimens. Due to the limited stability of many liposomal preparations in biological samples, a rapid analytical procedure is often necessary. Phosphoramide mustard (PM), a key cytotoxic metabolite of a widely used alkylating drug cyclophosphamide, has recently been entrapped into a liposomal formulation and the preparation has been found to be rather unstable in plasma. We have, therefore, developed a rapid method for the separation of liposome-associated PM from the unassociated drug and a method for their quantitation in plasma. This method involves the use of size exclusion mini-gel column and requires minutes to process. Due to the use of internal standards, this method tolerates low recovery and requires the collection of a single fraction of each of liposome-associated PM and the unassociated drug. The recovery of liposomal PM from the first fraction of the gel column was found to be 82.4 +/- 7.9% (SD, n = 8), whereas that of liposome-unassociated PM from the major fraction was 16.8 +/- 2.8% (SD, n = 8). However, the low recovery problem of liposome-unassociated PM was circumvented by adding the internal standard [alpha, beta-2H8] PM prior to separation, thus compensating for the loss of liposome-unassociated PM due to incomplete collection. Two types of standard curve were constructed for quantitation of liposome-associated PM and unassociated PM and the linearity for both was excellent. Assay validation indicated that within-run RSD values at 213 ng, 426 ng and 1065 ng for liposomal PM were 4.2, 4.3 and 3.0%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: School of Pharmacy, University of Southern California, Los Angeles 90033.
authors: A A
authors: AA
authors: Srigritsanapol
authors: K K
authors: KK
authors: Chan
mesh_terms: D000818:Animals; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007275:Injections, Intravenous; D008081:Liposomes; D008297:Male; D010752:Phosphoramide Mustards / Q000097:blood* / Q000302:isolation & purification / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D008081:Liposomes; D010752:Phosphoramide Mustards; C030090:phosphoramide mustard