Methotrexate cerebrospinal fluid and serum concentrations after intermediate-dose methotrexate infusion.

Twenty-nine children with acute lymphocytic leukemia were given 24-hr infusions of intermediate-dose methotrexate (MTX, 1000 mg/m2) with and without intrathecal (IT) MTX (12 mg/m2), followed by leucovorin rescue. There was substantial interpatient variability in MTX systemic clearance (98.3 +/- 51 ml/min/m2), inducing total steady-state serum MTX concentrations ranging from 5.4 to 33.7 microM. The cerebrospinal fluid (CSF) concentration at the end of the infusion was 0.27 (+/- 0.1) microM when no IT-MTX was given and correlated with total steady-state (24-hr) serum concentration of MTX. By stepwise regression, the CSF MTX concentration correlated better with the nonprotein bound (free) steady-state serum MTX concentration (r = 0.66, P less than 0.01) than with total steady-state serum MTX concentration. Mean CSF: serum MTX concentration ratio was 0.023 (+/- 0.04) when no IT MTX was given. When an IT MTX dose (12 mg/m2) was given at the start of the MTX infusion, the steady-state CSF MTX concentration was 1.1 (+/- 0.4) microM, leading to a mean CSF: serum ratio of 0.073 (+/- 0.05). Despite 7-hydroxy-MTX serum concentrations exceeding MTX concentrations immediately after infusion, 7-hydroxy-MTX was not detectable in CSF of most patients (21 of 29), and was less than 50% of the concurrent MTX concentration when detectable. These data establish the substantial interpatient variability in CSF distribution of MTX after intermediate-dose MTX infusions and establish a significant correlation between steady-state free concentration of MTX in serum and CSF MTX concentration.

A simple preparation of the methotrexate metabolites 7-hydroxymethotrexate and 4-deoxy-4-amino-N10-methylpteroic acid.

Simple and convenient preparations of two metabolites of the antineoplastic drug methotrexate (MTX) are described. MTX is incubated in a Tris-HCl rabbit liver homogenate to produce 7-hydroxymethotrexate. Filtration, lyophilization, and recrystallization from water gives a chromatographically pure product. Analytical amounts of 4-deoxy-4-amino-N10-methylpteroic acid (DAMPA) are prepared by 0.05 N NaOH hydrolysis of an amide bond within the MTX molecule. Preparative high-performance liquid chromatography was used for purification of DAMPA. Nominal molecular weights of these metabolites have been confirmed by fast atom bombardment mass spectrometry. These synthetic methods provide a simple and efficient source of these compounds for use as standards in analytical methods, drug metabolism and cytotoxicity studies, and therapeutic drug monitoring.

Disposition of intermediate-dose methotrexate in children with acute lymphocytic leukemia.

Intermediate-dose methotrexate (MTX 200 mg/m2 iv in a bolus dose, followed by 800 mg/m2 iv, infused over 24 hours) is being used as a component of therapy for children with acute lymphocytic leukemia. To define the extent of interpatient variability in MTX disposition, with this dosage and schedule, the systemic clearance of MTX was measured in 69 children (total doses, 717; median, 10 doses per patient). The mean (+/- SD) systemic clearance was 91.6 (+/- 25.2) ml/min/m2 and ranged from 50-161 ml/min/m2. Renal clearance was measured in 16 of these patients and averaged 50.7 (+/- 14) ml/min/m2 during the MTX infusion (0-24 h), at which time mean systemic clearance was 8.7 (+/- 19) and nonrenal clearance was 31.1 (+/- 11.8) ml/min/m2. Measurement of 7-hydroxy-methotrexate in serum and urine was consistent with the substantial amount of nonrenal (metabolic) clearance observed in these patients. Cerebrospinal fluid MTX concentrations, measured at 24 hours, were 0.26 (+/- 0.1) microM when only the intravenous MTX was given and 1.08 (+/- 0.8) microM when an intrathecal dose (12 mg/m2) was also given at the start of the 24-hour infusion. This study establishes that there is substantial interpatient variability in MTX disposition in children and suggests a possible cause of variable patient response to MTX.

High-performance liquid chromatographic assay of methotrexate, 7-hydroxymethortrexate, 4-deoxy-4-amino-N10-methylpteroic acid and sulfamethoxazole in serum, urine and cerebrospinal fluid.

An automated high-performance liquid chromatographic system is described for separation and quantitation of the antineoplastic drug methotrexate and metabolites, and the antibiotic sulfamethoxazole in body fluids. The 40-min analysis utilizes a reversed-phase C18 column and gradient elution with detection by absorbance of ultraviolet light at 308 nm. The minimum detectable quantities with this assay are: methotrexate 4.4 ng (9.8 X 10(-12) mole); 4-deoxy-4-amino-N10-methylpteroic acid 11.9 ng (3.7 X 10(-11) mole); 7-hydroxymethotrexate 30 ng (6.5 X 10(-11) mole); sulfamethoxazole 125 ng (4.9 X 10(-10) mole). This analytical method should prove useful for therapeutic monitoring and pharmacokinetic studies of these compounds.

A rapid method for isolating phorbol from croton oil.

The published method for isolating phorbol from croton oil has been improved and made more rapid, mainly by the addition of silica-gel column chromatography. The spectral characteristics are recorded, including the 13C nuclear magnetic resonance (NMR) spectrum.