G. P. Kaijser

Determination of chloroacetaldehyde, a metabolite of oxazaphosphorine cytostatic drugs, in plasma

A derivatization high-performance liquid chromatographic method with ultraviolet detection to monitor the plasma concentration of chloroacetaldehyde, a neurotoxic metabolite of oxazaphosphorine drugs, is presented. To prevent the rapid degradation of chloroacetaldehyde, the plasma samples are stabilized with formaldehyde. The method is linear in the concentration range 1-250 nmol/ml. Blood samples from a patient who was treated with a ten-day continuous infusion of ifosfamide were assayed. The chloroacetaldehyde concentrations did not exceed 10 nmol/ml.

Gas chromatographic determination of 2- and 3-dechloroethylifosfamide in plasma and urine

The metabolic oxidation of one of the chloroethyl groups of the antitumour drug ifosfamide leads to the formation of the inactive metabolites 2- and 3-dechloroethylifosfamide together with the neurotoxic metabolite chloroacetaldehyde. A very sensitive capillary gas chromatographic method, requiring only 50 microliters of plasma or urine, has been developed to measure the amounts of the drug and the two inactive metabolites in a single run. Calibration curves were linear (r > 0.999) in the concentration ranges from 50 ng/ml to 100 micrograms/ml in plasma and from 100 ng/ml to 1 mg/ml in urine.

Chromatographic analysis of the enantiomers of ifosfamide and some of its metabolites in plasma and urine

The enantiomers of the cytostatic drug ifosfamide and the two metabolites 2- and 3-dechloroethylifosfamide were isolated from plasma and urine by liquid-liquid extraction with ethyl acetate, resolved on a Chirasil-L-val gas chromatographic column and detected by a nitrogen-phosphorus-selective flame ionisation detector. Resolution of the racemic compounds for identification purposes was also accomplished with high-performance liquid chromatography on a chiral column. The validated gas chromatographic method was suitable to determine the total concentrations and the enantiomeric composition of ifosfamide and its dechloroethylated metabolites in plasma and urine samples from treated patients. Some metabolic preferences in the metabolism of ifosfamide were found.

Determination of 4-hydroxyifosfamide in biological matrices by high-performance liquid chromatography

A high-performance liquid chromatographic method has been developed for the determination of 4-hydroxyifosfamide, a metabolite of ifosfamide, in plasma of cancer patients. The analyte is derivatized to 7-hydroxyquinoline, which can be detached fluorimetrically. The calibration graph is linear in the concentration range 0.05-25 microM, the limit of detection being 40 nM. Any inference from acrolein, another metabolite of ifosfamide, was ruled out. 4-Hydroxyifosfamide is very unstable in plasma and a stabilization procedure by adding citric acid has been developed. Thus treated, the samples were stable for 4 days. Analysis of a patients plasma samples revealed that the 4-hydroxifosfamide concentration did not exceed 10 microM.

The risks of handling cytotoxic drugs

Results of various biological and physical/chemical tests of the urines or blood of health-care personnel working with cytotoxic drugs are discussed. The outcomes of these tests are conflicting and inconclusive. The physical/chemical tests seem to be an alternative method. However, until now it has not been possible to establish the threshold concentration in urine or blood beneath which no effect has to be expected. Therefore, the interpretation of the concentration of cytotoxic drugs and/or the metabolites in the urine or blood is difficult. As long as one will not be able to provide conclusive data on the health hazards when working with cytotoxic drugs, protective measures have to be taken in order to lower the risk as much as possible.

A systematic study on the chemical stability of ifosfamide

The degradation kinetics of ifosfamide in aqueous solution have been investigated over the pH region 1-13 at 70 degrees C. A stability indicating high-performance liquid chromatographic assay with UV detection was used to separate degradation products from the parent compound. The degradation kinetics were studied as related to pH, buffer composition, ionic strength, temperature and drug concentration. A pH-rate profile at 70 degrees C, obtained from (pseudo) first-order kinetic plots, was constructed after corrections for buffer effects were made. The degradation reactions of ifosfamide were found to be largely independent of pH, although proton or hydroxyl catalysis occurs at extreme pH values. Ifosfamide shows maximum stability in the pH region 4-9, corresponding to a half-life of 20 h.

The risks of handling cytotoxic drugs. II. Recommendations for working with cytotoxic drugs.

Presuming that preparation of antineoplastic drugs without proper protection may lead to mutagenic urine (of which the effects are uncertain), one has to take great care when preparing these drugs. Apart from Norway no other country has national regulations issued by the government for handling cytostatic agents. Many organizations in various countries have made their own guidelines, which may be adapted to the situations in local hospitals. The following recommendations have been compiled after a review of the literature. They reflect a personal set of guidelines for preparation, administration and disposal of cytotoxic drugs. They are probably the minimum precautions that should be taken, and have not been approved by any committee or agency. Further precautions must first have their potential benefit weighed against probable inconvenience and additional costs.

Analysis of ifosforamide mustard, the active metabolite of ifosfamide, in plasma

Ifosforamide mustard is the active metabolite of ifosfamide, a cytostatic drug. In this study a sensitive and selective method for the analysis of ifosforamide mustard in plasma is described. The method consists of direct derivatisation of ifosforamide mustard in plasma with diethyldithiocarbamate and subsequent solid-phase extraction of the resulting derivative. The analysis of the derivatisation product was performed by high-performance liquid chromatography with UV detection. The calibration graph was linear in the concentration range 0.45-45 microM and the minimum detectable concentration was 0.45 mumol. The samples were stabilised by addition of semicarbazide and sodium chloride. A patients plasma sample was analysed by means of the described method. The ifosforamide mustard concentration was 2.3 microM.

Gas chromatographic determination of ifosfamide in microvolumes of urine and plasma

In oncology, particularly in pediatric malignancies, high doses (5-10 g/m2) of the oxazaphosphorine ifosfamide play an important role in the treatment of sarcomas. Pharmacokinetic data of ifosfamide and its metabolites in these cases are scanty. Considering the special demands of the determination of ifosfamide in plasma of young children, a very sensitive capillary gas chromatographic method, requiring only 50 microliters of plasma, has been developed. This bioanalysis of ifosfamide shows good linearity and accuracy in the concentration range 10 ng to 100 micrograms per ml of plasma and 25 ng to 1 mg per ml of urine. The absolute limits of detection in plasma and urine are 2 ng/ml and 5 ng/ml, respectively. The stability of various solutions of ifosfamide and trofosfamide was tested and proved to be satisfactory, except for ifosfamide in plasma and urine kept in the refrigerator. The validity of the method for pharmacokinetic purposes is shown in the case of one patient.

Chemical stability of cyclophosphamide, trofosfamide, and 2- and 3-dechloroethylifosfamide in aqueous solutions

The degradation kinetics of various oxazaphospho rines : trofosfamide, cyclophosphamide, and 2- and 3-dechloroethylifosfamide was studied by means of a high-performance liquid chromatographic method. The results were compared with the kinetics of ifosfamide. It appeared that the pres ence and the site of the chloroethyl group influ enced the chemical stability of the compounds.