Determination of cisplatin and cis-diammineaquachloroplatinum(II) ion by liquid chromatography using post-column derivatization with diethyldithiocarbamate

Developments in on-line, post separation sample manipulation in the last 22 years: Pharmaceutical and biomedical applications

On-line post separation sample manipulation is a powerful approach increasing the sensitivity and selectivity in chemical analysis. Post separation sample manipulation includes the treatment of the analytes after their separation through a suitable separation technique, mainly liquid chromatography and capillary electrophoresis. Typically, post separation approaches include either the addition of a reagent/solvent to derivatize the analyte/enhance the sensitivity, pH change, or the conversion of the analyte through a photochemical/electrochemical system (reagent-free systems). This review focuses on the developed methods using post-column manipulation of sample with pharmaceuticals and biomedical applications, covering the period from 2000 to midle-2023. Chemistries combined with fluorescence, UV-vis and mass spectrometric detection are discussed employing both liquid chromatography and electrophoretic techniques for separation. Noteworthy instrumental modifications are also discussed.

Using HPLC for the determination of platinum drugs in biological matrixes after derivatization with diethyldithiocarbamate

Challenges and pitfalls in the application of diethyldithiocarbamate derivatization for LC analysis of cisplatin and oxaliplatin, as well as the suitability of this method for different biological matrices with implications for use in routine practice have been identified. The LC of platinum drugs presents a significant challenge. They are polar compounds with poor retention on reverse phase packings. Cisplatin also exhibits poor absorption in UV and ionization in mass spectrometry. Therefore, we developed and optimized a derivatization approach for the LC analysis of total platinum in plasma, plasma ultrafiltrate, peritoneal fluid, and urine. Derivatization in urine proved to be difficult due to the complexity of the matrix, and extended testing was required. Our results highlight the important issues affecting the efficiency, reliability, and suitability of platinum drug derivatization. Although precolumn derivatization is less selective than its postcolumn counterpart, the application of precolumn derivatization is a simple, rapid, and universal approach for the determination of platinum drugs by HPLC. One of its major advantages is that it allows a more affordable analysis using UV detection without the need for additional high-end instrumentation such as a MS detector.

Electrospray ionization mass spectrometry for the hydrolysis complexes of cisplatin: implications for the hydrolysis process of platinum complexes

Non-enzyme-dependent hydrolysis of the drug cisplatin is important for its mode of action and toxicity. However, up until today, the hydrolysis process of cisplatin is still not completely understood. In the present study, the hydrolysis of cisplatin in an aqueous solution was systematically investigated by using electrospray ionization mass spectrometry coupled to liquid chromatography. A variety of previously unreported hydrolysis complexes corresponding to monomeric, dimeric and trimeric species were detected and identified. The characteristics of the Pt-containing complexes were investigated by using collision-induced dissociation (CID). The hydrolysis complexes demonstrate distinctive and correlative CID characteristics, which provides tools for an informative identification. The most frequently observed dissociation mechanism was sequential loss of NH₃ , H₂ O and HCl. Loss of the Pt atom was observed as the final step during the CID process. The formation mechanisms of the observed complexes were explored and experimentally examined. The strongly bound dimeric species, which existed in solution, are assumed to be formed from the clustering of the parent compound and its monohydrated or dihydrated complexes. The role of the electrospray process in the formation of some of the observed ions was also evaluated, and the electrospray ionization-related cold clusters were identified. The previously reported hydrolysis equilibria were tested and subsequently refined via a hydrolysis study resulting in a renewed mechanistic equilibrium system of cisplatin as proposed from our results. Copyright © 2017 John Wiley & Sons, Ltd.

Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC/ESI-MS/MS) Study for the Identification and Characterization of In Vivo Metabolites of Cisplatin in Rat Kidney Cancer Tissues: Online Hydrogen/Deuterium (H/D) Exchange Study

In vivo rat kidney tissue metabolites of an anticancer drug, cisplatin (cis-diamminedichloroplatinum [II]) (CP) which is used for the treatment of testicular, ovarian, bladder, cervical, esophageal, small cell lung, head and neck cancers, have been identified and characterized by using liquid chromatography positive ion electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with on line hydrogen/deuterium exchange (HDX) experiments. To identify in vivo metabolites, kidney tissues were collected after intravenous administration of CP to adult male Sprague-Dawley rats (n = 3 per group). The tissue samples were homogenized and extracted using newly optimized metabolite extraction procedure which involves liquid extraction with phosphate buffer containing ethyl acetate and protein precipitation with mixed solvents of methanol-water-chloroform followed by solid-phase clean-up procedure on Oasis HLB 3cc cartridges and then subjected to LC/ESI-HRMS analysis. A total of thirty one unknown in vivo metabolites have been identified and the structures of metabolites were elucidated using LC-MS/MS experiments combined with accurate mass measurements. Online HDX experiments have been used to further support the structural characterization of metabolites. The results showed that CP undergoes a series of ligand exchange biotransformation reactions with water and other nucleophiles like thio groups of methionine, cysteine, acetylcysteine, glutathione and thioether. This is the first research approach focused on the structure elucidation of biotransformation products of CP in rats, and the identification of metabolites provides essential information for further pharmacological and clinical studies of CP, and may also be useful to develop various effective new anticancer agents.

Distribution study of cisplatin in rat kidney and liver cancer tissues by using liquid chromatography electrospray ionization tandem mass spectrometry

A sensitive and rapid liquid chromatography positive ion electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method has been developed and validated for the quantitative determination and distribution of cisplatin (CP) in kidney and liver tissues after intravenous administration of drug to adult male Sprague Dawley rats. Oxaliplatin (OXP) was used as an internal standard. The tissue samples were homogenized and extracted using conventional liquid-liquid extraction method with phosphate buffer containing ethyl acetate and then subjected to LC-MS analysis. The chromatographic separation was achieved on an Agilent ZORBAX SB C-18 column (50 × 2.1 mm, 1.8 µm) using the mobile phase consisting of 0.1% formic acid in water (Solvent A) : methanol (Solvent B) (40 : 60; v/v) in an isocratic elution followed by detection with positive ion electrospray ionization tandem mass spectrometry using the transitions of m/z 301 > 265 for CP and m/z 398 > 310 for OXP in multiple reaction monitoring mode. The calibration curve was linear in the range of 5.0-7000 and 10.0-6000 ng/ml for kidney and liver tissue homogenates, respectively. The method revealed good performances in terms of within-batch, between-batch precision (1.31-5.70%) and accuracy (97.0-102.24%) for CP in both kidney and liver tissue homogenates including lower and upper limits of quantification. The recoveries from spiked control samples were >81.0% and >87.0 % for CP and OXP, respectively. Matrix effect was found to be negligible, and the stability data were within the acceptable limits. Further, the validated LC/ES-MS/MS method was successfully applied to investigate the distribution of CP in kidney and liver tissues after intravenous administration of CP to male Sprague Dawley rats. The results showed that the higher amount of CP was distributed in kidney followed by liver, which indicated that CP mainly accumulated in kidney tissues and renal excretion might be a primary and main elimination route. This is the first research approach focused on the quantitative determination and distribution of CP in rat kidney and liver tissue homogenates by using LC/ESI-MS/MS, which could provide essential information for further pharmacological and clinical studies of CP.

A liquid chromatography electrospray ionization tandem mass spectrometric study (LC/ESI-MS/MS) of in vivo metabolites of cisplatin in rat liver and brain tissues: deuterated experiments

In vivo rat liver and brain tissue metabolites of an anticancer drug, cisplatin, have been identified and characterized by using LC/ESI-MS/MS in combination with on-line H/D exchange experiments.

Development and Validation of a Simple and Sensitive Spectrometric Method for Estimation of Cisplatin Hydrochloride in Tablet Dosage Forms: Application to Dissolution Studies

Cisplatin hydrochloride is an important chemotherapeutic drug for cancer treatment. It has a low molar absorptivity in the UV region and has no fluorescence. Therefore, a selective derivatizing reaction is required for its detection in bulk and pharmaceutical dosage form if detection by UV spectrophotometry is sought. In view of this, a simple, accurate, rapid, and cost-effective spectrophotometric method for its estimation has been developed by the complexation of the drug with ortho-phenylene diamine and monitoring the absorbance of formed green color at 706 nm. The method has been validated and successfully applied for the assay and dissolution studies of cisplatin hydrochloride tablets. The method demonstrated good linearity over the range from 0.4 to 1.4 μg/mL with a correlation coefficient of 0.9999. The accuracy of the method was 99.98%. The precision demonstrated relative standard deviation of less than 2.5%. The developed method was successfully applied for dissolution studies of sustained release tablets of cisplatin with a cumulative release of 86.7% in 12 hours. The proposed method can be applied in routine quality control in the pharmaceutical industries since it is precise, accurate, simple, and economic.

Analytical methodologies for metallomics studies of antitumor Pt-containing drugs

Pt-containing drugs are nowadays essential components in cancer chemotherapy. However, drug resistance and side effects limit the efficiency of the treatments. In order to improve the response to Pt-based drugs, different administration strategies or new Pt-compounds have been developed with little success. The reason for this failure could be that the mechanism of action of these drugs is not completely understood. In this way, metallomics studies may contribute to clarify the interactions of Pt-containing drugs within the organism. This review is mainly focused on the role of Analytical Chemistry on the study of the interactions between Pt-based drugs and biomolecules. A summary of the analytical techniques and the most common sample treatment procedures currently used in metallomics studies of these drugs is presented. Both are of paramount importance to study these complex samples preserving the drug-biomolecule interaction. Separation and detection techniques must be carefully selected in order to achieve the intended goals. The use of multidimensional hyphenated techniques is usually necessary for a better understanding of the Pt-based drugs interactions in the organism. An overview of Pt-drugs biological interactions is presented, considering the different sample matrices and the drugs course through the organism. Samples analysed in the included studies are blood, urine, cell cytosol, DNA as well as the drugs themselves and their derivatives. However, most of these works are based on in vitro experiments or incubations of standards, leading in some cases to contradictory results depending on the experimental conditions used. Though in vivo experiments represent a great challenge due to the high complexity and the low concentrations of the Pt-adducts in real samples, these studies must be undertaken to get a deeper understanding of the real interactions concerning Pt-containing drugs.

Analytical methodologies for the determination of cisplatin

cis-Diamminedichloroplatinum(II) (cisplatin) is a important chemotherapeutic drug for cancer treatment since 1978. Unfortunately, because of the severe side-effects like nephrotoxicity, ototoxicity, etc., they are administered in small doses at low concentration establishing the maximum limit dosage to 100 mg/m(2) (21 days). A variety of analytical methods have been proposed for the determination of cisplatin in biological fluids and tissues that permit the accurate determination at or below the part per billion level in the native sample. The purpose of the current review is to provide a systematic survey of the latest analytical techniques for the determination of cisplatin in biological samples.

Kinetics of Cisplatin and its monohydrated complex with sulfur-containing compounds designed for local otoprotective administration

The anticancer drug cisplatin can cause permanent inner ear damage. We have determined the second-order degradation rate constant, k(Nu), of cisplatin and its more toxic monohydrated complex (MHC) in the presence of each of the sulfur-containing nucleophiles N-acetyl-l-cysteine, l-cysteine methyl ester, 1,3-dimethyl-2-thiourea, d-methionine, and thiosulfate, compounds that are under evaluation for local administration to prevent cisplatin-induced ototoxicity. MHC was isolated from a hydrolysis solution of cisplatin using liquid chromatography (LC). The degradations were evaluated by measuring the disappearance of MHC and cisplatin at 37 degrees C and pH 7.4 in the presence of each of the nucleophiles using LC and photometric detection. The k(Nu) of MHC and of cisplatin was 0.044 M(-1)sec(-1) and 0.012 M(-1)sec(-1) with N-acetyl-l-cysteine, 0.24 M(-1)sec(-1) and 0.067 M(-1)sec(-1) with l-cysteine methyl ester, 0.16 M(-1)sec(-1) and 0.074 M(-1)sec(-1) with 1,3-dimethyl-2-thiourea, 0.070 M(-1)sec(-1) and 0.069 M(-1)sec(-1) with d-methionine, and 3.9 M(-1)sec(-1) and 0.091 M(-1)sec(-1) with thiosulfate, respectively. Our results suggest that thiosulfate, as being the strongest nucleophile, is a promising candidate for local application in order to reduce the inner ear content of MHC and cisplatin. However, otoprotection is a multifactorial event, and it remains to be established how important nucleophilicity is for the effectiveness of the protecting agent.

A high-performance liquid chromatographic assay for determination of cisplatin in plasma, cancer cell, and tumor samples

A method for determination of cis-diaminedichloroplatinum (II) (cisplatin) in ultrafiltered plasma, cell, and tumour samples is described. Cisplatin separation was carried out on a reversed-phase column using methanol-acetonitrile-water as the mobile phase. The flow rate was maintained constant at 1.6 mL/min and analysis was performed at 23 degrees C. Detection was carried out by absorbance at 254 nm. The method was linear in the range of 0.2-10 microg/mL, and the coefficients of variation were <10%. Using this technique, we measured the intracellular accumulation of cisplatin in cancer cells and in tumours of mice receiving treatment with cisplatin and evaluated the pharmacokinetics of cisplatin in nu/nu mice after intraperitoneal (i.p.) administration. The method proved to be adequate for measuring cisplatin both in vitro and in vivo and could be suitable for studies of cisplatin pharmacokinetics in animal models.

High-Dose Cisplatin With Amifostine: Ototoxicity and Pharmacokinetics

OBJECTIVES/HYPOTHESIS

Ototoxicity is a common side effect of high-dose cisplatin treatment. Thiol-containing chemoprotectors ameliorate cisplatin ototoxicity under experimental conditions. The trial was initiated to test the efficacy of amifostine protection in high-dose cisplatin treatment (125-150 mg/m) for metastatic malignant melanoma, to correlate the ototoxic outcome with cisplatin pharmacokinetics, and to evaluate the importance of using a selective analytical method for the quantification of cisplatin.

STUDY DESIGN

Prospective study of 15 patients with stage IV malignant melanoma.

METHODS

Clinical follow-up of therapeutic response, pure-tone audiometry, and analysis of cisplatin and its monohydrated complex in blood ultrafiltrate by liquid chromatography with postcolumn derivatization were performed. Ultrafiltered blood platinum was analyzed by inductively coupled plasma mass spectrometry.

RESULTS

Ototoxicity and gastrointestinal toxicity were the most prominent side effects. Three patients ultimately required hearing aids. All patients had audiometric changes at one or more frequencies after the second treatment course, and all but one patient reported auditory symptoms. No correlation was found between hearing loss and blood cisplatin pharmacokinetics. Platinum levels determined by inductively coupled plasma mass spectrometry were higher than total platinum levels calculated from cisplatin and monohydrated complex concentrations obtained by liquid chromatography analysis.

CONCLUSION

Ototoxicity was unacceptable despite amifostine treatment. Cisplatin pharmacokinetics during the first treatment course were not predictive of hearing loss. Amifostine caused a lowering of dose-normalized area under the concentration-time curve for cisplatin and monohydrated complex. Use of the unselective inductively coupled plasma mass spectrometry analysis leads to an overestimation of active drug. Selective analysis of cisplatin is especially important when evaluating cisplatin pharmacokinetics during chemoprotector treatment.

Liquid chromatographic determination of oxaliplatin in blood using post-column derivatization in a microwave field followed by photometric detection

Oxaliplatin ([(1R,2R)-1,2-cyclohexanediamine-N,N']oxalato(2-)-O,O'-platinum) is the first platinum drug with significant activity for metastatic colon cancer. The analysis of oxaliplatin has previously almost exclusively been based on the determination of the platinum content in plasma or ultrafiltrate using flameless atomic absorption spectroscopy (FAAS) or inductively coupled plasma mass spectrometry (ICPMS). A new method for quantitative determination of the free fraction of the intact drug in blood ultrafiltrate is presented here. Blood was ultrafiltrated centripetally at 4 degrees C and the ultrafiltrate was analyzed by liquid chromatography. Oxaliplatin was separated on a Hypercarb column using a mobile phase of methanol/succinic acid buffer pH 7.0 (9/1, v/v). Post-column derivatization was performed by adding N,N-diethyldithiocarbamate in methanol and with microwave heating of a Teflon tubing. The derivative was quantified by photometric detection at 344 nm. The coefficient of variation of standard blood samples was 4.9 and 2.5% at 0.100 and 1.00 microg/ml, respectively. The limit of quantitation was 0.04 microg/ml.

Pharmacokinetics of oxaliplatin in humans

Oxaliplatin is a novel platinum complex used for the treatment of metastatic colorectal carcinoma. The pharmacokinetics of the free fraction of oxaliplatin in blood were evaluated in 10 patients given 85 mg/m2 of oxaliplatin using an infusion time of 2 h. Blood samples were collected during and after the infusion and immediately placed on ice. The samples were ultrafiltrated centripetally and the concentration of oxaliplatin in the ultrafiltrate was determined by liquid chromatography in combination with postcolumn derivatization. The in vitro degradation rate was determined in blood from the patients taken immediately before drug administration. The maximal blood concentration (C(max)) and terminal half-life (t1/2) were 1.44 +/- 0.20 (SD) microg/mL and 14.1 min (range: 10.2-24.5), respectively. The area under the blood concentration time curve (AUC), clearance (CL), and distribution volume (V(ss)) were (means +/- SD) 161 +/- 22 microg min/mL, 32.1 +/- 4.2 L/h/m2, and 0.26 +/- 0.06 L/kg, respectively. There was a significant correlation between the clearance of oxaliplatin in the patients and the degradation rate in whole blood (r = 0.746; p = 0.017). Oxaliplatin has a short elimination half-life, which is in a sharp contrast to previously reported elimination half-lives obtained by analysis of the platinum content in plasma and ultrafiltrate. The correlation between in vivo and in vitro data suggests that the degradation in whole blood plays a role for the elimination of the drug.

Simultaneous determination of intact cisplatin and its metabolite monohydrated cisplatin in human plasma

Cisplatin is a cytotoxic platinum compound, used in the treatment of several solid tumors. Cisplatin and to a greater extent its hydrolysis product monohydrated cisplatin are responsible for side-effects like nephrotoxicity. A sensitive, accurate and precise method was developed to simultaneously determine cisplatin and monohydrated cisplatin in plasma. The compounds were separated by high-performance liquid chromatography and quantified by off-line furnace atomic absorption spectrophotometry. The linear ranges for cisplatin and monohydrated cisplatin in deproteinized plasma were 60-600 and 87.5-700 nM, respectively. From plasma, the mean recovery of cisplatin was 83.2% and that of monohydrated cisplatin 79.1%. The lower limits of quantification of cisplatin and monohydrated cisplatin in deproteinized plasma were 60 and 87.5 nM, respectively. Over the whole calibration range, the within- and between-day accuracy of intact cisplatin ranged from 100.7 to 111.4 and 94.8-102.0%, respectively. The within- and between-day accuracy of monohydrated cisplatin ranged from 107.1 to 113.3 and 101.4-104.9%, respectively. The within-day and between-day precision of cisplatin ranged from 3.4 to 11.5 and 7.3-10.3%, respectively. For monohydrated cisplatin, the within-day and between-day precision ranged from 3.7 to 6.2 and 5.6-7.9%, respectively. Currently, the developed assay has been implemented in pharmacokinetic studies of patients treated with cisplatin alone or in combination with other drugs.

D-Methionine and cisplatin ototoxicity in the guinea pig: D-methionine influences cisplatin pharmacokinetics

D-Methionine has recently been advocated as a protectant against cisplatin toxicity. The use of systemic D-methionine as a protector was studied in 58 guinea pigs. Kinetics and distribution of [11CH(3)]D-methionine was analysed by positron emission tomography. Cisplatin and the monohydrated complex of cisplatin was quantified in blood ultrafiltrate using reversed-phase liquid chromatography with post-column derivatisation. Administration of 300 mg/kg of D-methionine caused a 30% decrease in the area under the concentration-time curve (AUC) of cisplatin. The toxic effect of cisplatin was studied after dose adjustment of cisplatin, i.e. with similar cisplatin AUC in the group receiving D-methionine and the saline control group. A significant ototoxic effect, measured as difference in pre- and 96 h post-treatment electrophysiological hearing threshold (auditory brainstem response), was observed at stimulus frequencies of 30 and 20 kHz. There was no difference between the groups in the extent of threshold shift. Quantitative outer hair cell counts showed a similar loss of cells in the two groups. All animals had a significant increase in plasma-creatinine but there was no difference between the groups. The results indicate that protection from cisplatin ototoxicity by systemic D-methionine can be explained by a lowered systemic exposure to the drug.

A validated liquid chromatography/tandem mass spectrometry assay for cis-amminedichloro(2-methylpyridine)platinum(II) in human plasma ultrafiltrate

The clinical use of platinum drugs as anticancer agents has encountered problems when relating pharmacokinetic profiles with efficacy and toxicity is attempted. This has been mainly due to the lack of specific and sensitive analytical methodology to examine concentrations of the unbound drug in plasma. The presence of a carbocyclic ring on the new drug, cis-amminedichloro(2-methylpyridine)platinum(II) (ZD0473) suggested that it would be possible to develop the first stable isotope dilution LC/MS assay for a platinum drug in human plasma ultrafiltrate samples. The dichloro form of the drug exists in equilibrium with at least two aquated forms in plasma. The molecular form of the drug, therefore, depends on the length of time that the plasma sample is maintained at room temperature before freezing. Therefore, we have developed a method that quantitatively converts the aquated species back to the dichloro form of the parent drug so that a single molecular species can be analyzed. Selected reaction monitoring was performed on the transition of m/z 393 [M + NH4]+ to m/z 304 [M + NH4 -NH3 - 2 x HCl]- for ZD0473, and m/z 400 [M + NH4]+ to m/z 310 [M + NH4 - NH3 - HCl - 2HCl]+ for [2H7]ZD0473. The standard curves were fitted to a quadratic regression over the range from 10 to 5000 ng/mL in human plasma ultrafiltrate. The lower limit of quantitation for ZD0473 was 10 ng/mL for 100 microL of plasma ultrafiltrate. This simple, rapid, reliable, and sensitive method of quantitation had excellent accuracy and precision. The method provided adequate sensitivity for the analysis of plasma ultrafiltrate samples from a phase II study in which ZD0473 was administered to patients as an intravenous infusion at a dose of 150 mg/m2.

Speciation of platinum compounds: a review of recent applications in studies of platinum anticancer drugs

This is a review of investigations involving speciation studies of five important platinum-containing drugs used in cancer treatments. The information presented here is drawn from recent reports published during the period 1995-1999. The work includes detection, separations and identifications of degradation and biotransformation products. In addition, important information is reported on the number and nature of products of reactions of platinum anticancer drugs with thiol compounds. HPLC is employed effectively for separations of reaction products in speciation investigations. Information derived from speciation is very helpful in studies of pharmacokinetics as well as side effects and toxicities of the drugs as they are administered to patients.

Cisplatin-induced hearing loss: influence of the mode of drug administration in the guinea pig

Cisplatin (8 mg/kg) was given intravenously to guinea pigs either as a 15 s bolus injection (25 animals) or as a 1 h infusion (28 animals). To determine the influence of the mode of cisplatin administration and pharmacokinetics on the ototoxic side-effect, the concentrations of cisplatin and the biotransformation product monoaquated cisplatin were determined in blood ultrafiltrate using liquid chromatography with post-column derivatization. Ototoxic effect was evaluated as difference in pre- and 96 h post-exposure auditory brainstem response (ABR) threshold. The cisplatin peak concentration was considerably higher, 19.2+/-2.4 microg/ml, in the bolus injection group than in the infusion group, 6.7+/-0.5 microg/ml (mean+/-S.E.M.). The area under the blood ultrafiltrate concentration time curve (AUC) for cisplatin was slightly greater in the infusion group, 442+/-26 microg/ml/min, than in the bolus injection group, 340+/-5 microg/ml/min. For monoaqua cisplatin, the AUC was not different between the groups (bolus injection: 30.8+/-1. 5 microg/ml/min, infusion: 34.1+/-3.3 microg/ml/min). A significant ototoxic effect was observed in both groups at 20 and 12.5 kHz, but there was no difference between the groups in the extent of threshold shift. The interindividual variability in susceptibility to ABR threshold shift was far greater than the variability in pharmacokinetics, suggesting that other factors are more important in determining the degree of hearing loss.

Determination of platinum (II,IV) and palladium(II) as thiocyanate complexes by capillary zone electrophoresis analysis of carboplatin and similar drugs

The thiocyanate complexes of Pd(II), Pt(II) and Pt(IV) were studied by capillary zone electrophoresis. Pd(II) can be detected in the form of the thiocyanate complex at 305 nm with higher sensitivity than in the form of its chloro complex (absorption maximum 214 nm). A detection limit equal to 5 ppb for Pd has been finally achieved. The possibility of simultaneous determination of Pd(II) and Pt(IV) in the form of thiocyanate complexes has also been demonstrated. When the method optimized for the determination of Pt(II) was applied to the drugs Cykloplatin and Ribocarbo (containing carboplatin) and Platidiam (containing cisplatin), good agreement of the platinum content with the declared value was obtained. Samples of vehicle exhaust particulates (National Institute for Environmental Studies, Japan, No. 8 reference material) were also analyzed.

The kinetics and cytotoxicity of cisplatin and its monohydrated complex

This paper examines the monohydrated complex of cisplatin (MHC) with respect to kinetics and cytotoxicity. Equilibrium mixtures of cisplatin and hydrated species have been used in previous studies of a similar nature. To our knowledge, this is the first paper examining MHC after isolation and quantification. This was accomplished using liquid chromatography with porous graphitic carbon. MHC and cisplatin were quantified over time in a suspension of the small-cell lung cancer cell line U-1285. Cytotoxicity was evaluated using the fluorescent microculture cytotoxicity assay. MHC was significantly more cytotoxic than cisplatin at the high end of the drug concentrations tested. In culture media with low chloride ion concentrations, the stability of MHC was related to changes in pH. At a pH of between 6.0 and 7.2, MHC was rapidly converted to cisplatin. In culture media with a pH above 7.2, MHC was considerably more stable. These findings might have clinical significance given that MHC circulates in the blood stream of patients receiving cisplatin infusions and that solid tumours often have environments that are extremely acidotic.

High-performance liquid chromatographic determination of cisplatin as platinum(II) in a pharmaceutical preparation and blood samples of cancer patients

An high-performance liquid chromatographic (HPLC) method has been developed for the determination of cisplatin, based on precolumn derivatization of platinum(II) with bis(salicylaldehyde)tetramethylethylenediimine, extraction in chloroform and elution from a 3 microm Hypersil ODS column with methanol-acetonitrile-water as mobile phase and detection at 254 nm. Copper(II), iron(II), nickel(II), palladium(II), dioxouranium(IV) separated completely and did not affect the determination of platinum(II). The method was applied for the determination of cisplatin as platinum(II) in a pharmaceutical preparation and in blood samples of cancer patients after infusion of cisplatin.

Blood flow-independent accumulation of cisplatin in the guinea pig cochlea

Considerable interindividual variability in the ototoxic effect of cisplatin has become the unpredictable dose-limiting factor in its use as curative as well as palliative therapy. The drug accumulates in highly vascular areas in the cochlea, causing dose-related hair cell loss. The purpose of this study was to assess blood flow-dependent aspects of cisplatin absorption in the cochlea in order to better understand factors that may influence cisplatin-induced ototoxicity. The effect of reduced cochlear blood flow on the ototoxic action of cisplatin was studied in guinea pigs. Before cisplatin administration the cochlear vasculature in each animal was unilaterally pre-constricted, by the application of 2% epinephrine to the round window. A 20-30% reduction in cochlear blood flow, assessed by laser Doppler flowmetry, was maintained before and after intravenous infusion of 0.1% cisplatin. Cisplatin infusion affected cochlear blood flow but not vessel conductivity. The cochlear blood flow decrease, maintained by local epinephrine application to the round window during cisplatin infusion, did not alter the cisplatin-induced hearing loss. In addition, the concentration of free cisplatin in scala tympani perilymph did not differ between epinephrine-treated and non-treated ears. Our results indicate that cisplatin transport into the cochlea is not an energy-dependent process in the lateral wall vasculature.

Pharmacokinetics of cisplatin and its monohydrated complex in humans

The pharmacokinetics of cisplatin and its cytotoxic hydrolysis product cis-diammineaquachloroplatinum(II) ion (monohydrated complex) were investigated in seven patients after they received a 1-h infusion of cisplatin in normal saline at 100 mg/m2. The concentrations of intact cisplatin and the monohydrated complex were determined in blood by liquid chromatography with post-column derivatization, using diethyldithiocarbamate as the reagent. A pharmacokinetic model was developed assuming that a fraction of the dose (2.3%) is present as the monohydrated complex in the infusion solution and that reversible reactions between cisplatin and its monohydrated complex prevail. The clearances of cisplatin and the monohydrated complex were 0.32 +/- 0.05 and 0.27 +/- 0.11 L/min/m2, respectively. The apparent volume of distribution was considerably smaller for the monohydrated complex (4 +/- 2 L/m2) than for cisplatin (11 +/- 2 L/m2). The elimination rate constants were 0.030 +/- 0.002 and 0.07 +/- 0.02 min-1 for cisplatin and the monohydrated complex, respectively. The area under the time-concentration curve for the monohydrated complex was approximately 15% of that for cisplatin. It is concluded that the significant amounts of the monohydrated complex present in blood are due to the fraction already present in the administered dose and to the fraction formed in blood.

Stability of cisplatin and its monohydrated complex in blood, plasma and ultrafiltrate--implications for quantitative analysis

The stability of cisplatin and its monohydrated complex has been studied in blood, plasma and plasma ultrafiltrate at 37 degrees C (pH 7.4). Intact cisplatin and the monohydrated complex were determined by liquid chromatography with post-column derivatization. The half lives for cisplatin and the monohydrated complex were 1.43 +/- 0.03 h (SEM) and 0.36 +/- 0.03 h (SEM), respectively, in blood and 0.88 +/- 0.05 h (SEM) and 0.26 +/- 0.02 h (SEM), respectively, in plasma. The compounds were unstable at -25 degrees C (t1/2 for cisplatin was 52 +/- 5 h (SEM) and for the monohydrated compound 26 +/- 2 h (SEM)), but at -70 degrees C both compounds were stable for at least 3 weeks. The monohydrated complex was found to be formed to a small extent when cisplatin was added to plasma (37 degrees C, pH 7.4). A sampling procedure using centripetal ultrafiltration of whole blood was evaluated and found applicable if the samples were stored at 0 degree C and ultracentrifuged within 1 h.

Quantitative determination of unchanged cisplatin in rat kidney and liver by high-performance liquid chromatography

A quantitative analytical method for measuring unchanged cisplatin (CDDP) and high- and low-molecular-mass metabolites (fixed and mobile metabolites) in rat kidney and liver was developed. Unchanged CDDP, separated from fixed and mobile metabolites in tissue homogenates by consecutive procedures of fractionation and ultrafiltration, was determined by high-performance liquid chromatography (HPLC) with post-column derivatization. Although unchanged CDDP was found to be partly metabolized to fixed metabolites during the preparation of cytosolic ultrafiltrates, the recovery of unchanged CDDP gave a constant value (about 70%), which was independent of tissue type and CDDP concentration (from 1 to 10 micrograms/ml). The detection limit for unchanged CDDP in the cytosolic ultrafiltrate was 20 ng/ml, corresponding to a concentration detection limit of 65 ng Pt per g of tissue in the kidney and liver. The concentrations of fixed and mobile metabolites were determined as platinum concentrations in the tissue homogenate and in the cytosolic ultrafiltrate using atomic absorption spectrometry after correcting for transformation of unchanged CDDP to fixed metabolites. The distribution of unchanged CDDP, mobile metabolites and fixed metabolites in rat kidney and liver, after bolus injection of CDDP (5 mg/kg), was determined using this method.

Distribution of cisplatin in perilymph and cerebrospinal fluid after intravenous administration in the guinea pig

The concentration of free cisplatin was followed in plasma, scala tympani perilymph and cerebrospinal fluid (CSF) after an intravenous injection (12.5 mg/kg) in guinea pigs. Liquid chromatography with postcolumn derivatization was used for quantitative determination of the drug. The distribution of cisplatin to CSF was fast; at 10 min after drug administration the concentration was 7 micrograms/ml and the CSF:plasma ratio was 0.37. Cisplatin seems to distribute more slowly to the perilymphatic compartment. The highest concentration measured was 4 micrograms/ml at 20 min after the injection, and the perilymph:plasma ratio was 0.40 at that time. The concentration-time curves generated for cisplatin in perilymph and CSF were similar. No accumulation in the perilymphatic compartment or CSF was observed.

Determination of the acid dissociation constant for cis-diammineaquachloroplatinum(II) ion. A hydrolysis product of cisplatin

The biological activity of the anticancer drug cisplatin is supposed to be mediated by its reactive hydrolysis product cis-diammineaquachloroplatinum(II) ion (monoaqua). The monohydrated complex (monoaqua and its deprotonated form monohydroxy) was isolated from an equilibrium mixture of cisplatin in distilled water using a strong cationic exchanger. The structure of the monoaqua complex was established by 252Cf time-of-flight mass spectrometry. The acid dissociation constant was determined at 37 degrees C by studying the influence of pH on the reaction between the monoaqua complex and chloride ion (0.1 M). The concentration of monohydrated compound was determined by liquid chromatography with post-column derivatization using sodium diethyldithiocarbamate as a reagent. The pKa was determined to 6.56 +/- 0.01 (SEM). Thus, at physiological pH, the monoaqua complex is present mostly in its less reactive monohydroxy form.