A novel stability-indicating analytical method development for simultaneous determination of carboplatin and decitabine from nanoparticles.

Drug resistance is one of the main problems of cancer treatment. For this reason, combination therapy is commonly used for years. The combination of a chemotherapeutic, carboplatin, and the epigenetic drug decitabine is a new approach to modulate drug resistance. Nanoparticulate systems can overcome the drawbacks associated with the drug combinations. An analytical method that can detect and quantify carboplatin and decitabine which is encapsulated into the nanoparticles is necessary for nanoparticle development. In the literature, there is no analytical method in which carboplatin and decitabine are determined simultaneously. The primary purpose of this study is to develop and validate a novel, and stability-indicating high-performance liquid chromatography method for simultaneous determination of carboplatin and decitabine in pharmaceutical preparations in addition to developing the first nanoformulation for this drug combination. Therefore, various experimental parameters were optimized. The chromatographic separation was achieved using an XSelect® CSH C18 (250 × 4.6 mm I.D., 5 µm) column and a mobile phase consisting of methanol:water (containing 0.1% phosphoric acid) (3:97, v/v). The mobile phase pH was adjusted to 7.0 with 5 M NaOH. The developed method was successfully applied for the simultaneous determination and quantification of carboplatin and decitabine co-encapsulated in nanoparticles and released into in vitro dissolution medium.

Real-time detection of carboplatin using a microfluidic system.

A microfluidic sensor system based on a carbon nanotube-epoxy composite electrode was fabricated to allow detection of the presence of the anti-cancer drug carboplatin in healthy tissue in real time during chemotherapy. Detection of carboplatin was carried out by observing the effects of the drug on the differential pulse voltammetry of free purine bases using a novel carbon nanotube-epoxy composite electrode. In free solution these electrodes performed better than glassy carbon electrodes for oxidation of the free purine bases AMP and GMP, and than DNA-modified carbon nanotube-epoxy composite sensors for detection of carboplatin. On-line carboplatin detection was performed using a computer-controlled microfluidic platform. The methodology for on-line carboplatin detection was optimised in terms of the analysis time and to allow repeated carboplatin measurement using the same electrode. Microdialysis sampling and our microfluidic platform were combined to give a proof-of-concept system for real-time carboplatin detection with a limit of detection of 0.014 µM carboplatin in the sampled media. This paper is dedicated to Craig Lunte's pioneering work in analysis and microdialysis.

Effects of ambroxol hydrochloride on concentrations of paclitaxel and carboplatin in lung cancer patients at different administration times.

Our previous preliminary study revealed a synergistic effect of ambroxol hydrochloride with chemotherapeutic agents such as paclitaxel and carboplatin in lung cancer. However, the optimal conditions such as administration time and drug concentration of ambroxol hydrochloride to achieve the maximum synergistic effect remained unclear. Therefore, concentration changes of the chemotherapy drugs paclitaxel and carboplatin in the sputum were observed after ambroxol hydrochloride administration at different times in order to determine the most effective time frame of ambroxol hydrochloride administration. In this study, 470 cases of non-small cell lung cancer (NSCLC) were divided into different groups with ambroxol hydrochloride administered at different time points prior to chemotherapy, while another 171 cases received no ambroxol hydrochloride prior to chemotherapy. The results showed the concentrations of paclitaxel and carboplatin in sputum of patients treated with ambroxol hydrochloride were significantly higher than those of the control group, suggesting that ambroxol hydrochloride significantly increased the local concentrations of chemotherapeutic agents in lung tissues of NSCLC. Furthermore, the intravenous administration of ambroxol hydrochloride more than 48 hours before chemotherapy showed an optimized schedule and much greater efficacy in increasing drug concentrations than that of the control group. No statistical differences were found in the rates of grade 2 or above myelosuppression between the ambroxol intervention and control groups. Taken together, these results demonstrate that ambroxol hydrochloride administered intravenously more than 48 hours prior to chemotherapy optimally increased the concentrations of paclitaxel and carboplatin in lung tissue without significantly increasing hematologic toxicity.

How much platinum passes the placental barrier? Analysis of platinum applications in 21 patients with cervical cancer during pregnancy.

OBJECTIVE: Cervical cancer is the most common solid cancer diagnosed in pregnancy. Platinum is an active drug in the treatment of patients with cervical cancer. In the second and third trimesters, platinum is used to prevent cancer progression until fetal maturity is reached. However, knowledge about the transplacental passage of platinum is very limited. STUDY DESIGN: Between May 2008 and June 2014, platinum-based neoadjuvant chemotherapy was applied to 21 consecutive patients with cervical cancer diagnosed in their second trimester. At the time of delivery by cesarean delivery, synchronous samples from maternal blood, umbilical cord blood, and amniotic fluid were taken and analyzed for platinum concentrations. RESULTS: The mean week of gestation at cancer diagnosis was 17 (13-23). On average 3 (range, 2-4) cycles of chemotherapy were applied. Cesarean deliveries were carried out between 30.4 and 36.5 weeks of gestation. Twenty-two healthy babies without renal, hepatic, auditory, or hematopoietic impairment were delivered. Platinum concentrations in umbilical cord blood and amniotic fluid were 23-65% and 11-42% of the maternal blood, respectively. CONCLUSION: This series on in vivo measurement of platinum concentrations in the fetomaternal compartment observed that because of consistently lower platinum values in the fetoplacental unit, a placental filtration mechanism of platinum may be assumed.

Glutathione modified CdTe quantum dots as a label for studying DNA interactions with platinum based cytostatics.

Cisplatin, carboplatin, and oxaliplatin represent three generations of platinum based drugs applied successfully for cancer treatment. As a consequence of the employment of platinum based cytostatics in the cancer treatment, it became necessary to study the mechanism of their action. Current accepted opinion is the formation of Pt-DNA adducts, but the mechanism of their formation is still unclear. Nanomaterials, as a progressively developing branch, can offer a tool for studying the interactions of these drugs with DNA. In this study, fluorescent CdTe quantum dots (QDs, λem = 525 nm) were employed to investigate the interactions of platinum cytostatics (cisplatin, carboplatin, and oxaliplatin) with DNA fragment (500 bp, c = 25 µg/mL). Primarily, the fluorescent behavior of QDs in the presence of platinum cytostatics was monitored and major differences in the interaction of QDs with tested drugs were observed. It was found that the presence of carboplatin (c = 0.25 mg/mL) had no significant influence on QDs fluorescence; however cisplatin and oxaliplatin quenched the fluorescence significantly (average decrease of 20%) at the same concentration. Subsequently, the amount of platinum incorporated in DNA was determined by QDs fluorescence quenching. Best results were reached using oxaliplatin (9.4% quenching). Linear trend (R(2) = 0.9811) was observed for DNA platinated by three different concentrations of oxaliplatin (0.250, 0.125, and 0.063 mg/mL). Correlation with differential pulse voltammetric measurements provided linear trend (R(2) = 0.9511). As a conclusion, especially in the case of oxaliplatin-DNA adducts, the quenching was the most significant compared to cisplatin and nonquenching carboplatin.

Comparison of contamination levels on the exterior surfaces of vials containing platinum anticancer drugs in Japan.

Contamination of the external surface of anticancer drug vials supplied to hospital pharmacies has been recognized as a potential health hazard. The aim of this study was to investigate the levels of contamination on the exterior surface of vials containing platinum anticancer drugs in Japan. Platinum contamination on the exterior surface of vials containing cisplatin or carboplatin was examined using products commercially available in Japan. Cisplatin vials from 42 batches (2 drug contents, 10 products and 5 manufacturers) and carboplatin vials from 28 batches (3 drug contents, 7 products and 3 manufacturers) were used. Five vials were randomly sampled from each batch. Exterior contamination levels of 0.070-144 ng/vial as cisplatin and 0.21-1630 ng/vial as carboplatin were detected. Significant differences in the levels of contamination among the batch numbers were observed in 6 of 10 cisplatin products and 6 of 7 carboplatin products. Significant differences in the levels of contamination were observed in 3 cisplatin products with different contents of drug within the vials and 1 carboplatin product with different contents of drug within the vials. Significant differences in the contamination levels among the cisplatin manufacturers but not carboplatin manufacturers were observed. The degree of contamination of the carboplatin products was significantly higher than that of the cisplatin products. In conclusion, external contamination was confirmed in all cisplatin and carboplatin vials tested. The degree of contamination was different among different batch numbers, drug contents, manufacturers, and platinum anticancer drug.

Gemcitabine causes minimal modulation of carboplatin-DNA monoadduct formation and repair in bladder cancer cells.

We are developing a method to identify cellular resistance to carboplatin by using accelerator mass spectrometry to measure carboplatin-DNA adducts formed from drug microdoses (∼1/100th the therapeutic dose). Such an approach would be particularly useful if it is still valid in combination chemotherapy. We examined whether the addition of gemcitabine, another chemotherapeutic drug, could influence carboplatin-DNA adduct levels. There were no substantial differences in the levels of carboplatin-DNA adducts in cells upon exposure to the carboplatin/gemcitabine combination at various doses and schedules. These data demonstrate that microdosing is feasible for the characterization of carboplatin resistance when given in combination with gemcitabine.

Light-induced deterioration test of carboplatin under clinical settings.

Chemotherapeutic drug dosages are calculated precisely based on the patient's height, body weight, and renal function, etc. To ensure safe and favorable outcomes of treatment, dosing solutions are prepared by appropriate mixing of the drug solutions based on such calculations. The package inserts for many injectable preparations include a warning for storing the product "shielded from light." However, there are no reports of stability assessment of a mixed product against light exposure or the residual amount of active ingredient in the dosing solution during or at the end of treatment. We evaluated the stability of carboplatin from the time of mixing of the dosing solution until the end of drug infusion in a clinical-like setting. With 4-hour exposure to outdoor scattered light, the dosing solution began to show discoloration by 1 hour, becoming dark yellow by 4 hours, with reduction of the percent residual carboplatin to about 23%. To identify the optimal light-shielding shade, the dosing solution was shielded from outdoor scattered light with 1 of 3 protective covers: aluminum foil, yellow plastic shade, and brown plastic shade. The yellow plastic shade prevented any changes of the appearance of the dosing solution during the 4-hour exposure period. The percent residual carboplatin, determined by HPLC, in the dosing solution shielded with a yellow plastic shade was about 85.2% at 2 hours and 78.6% at 4 hours. Thus carboplatin dosing solution should be completely shielded from light until infusion is completed.

Transport of platinum-based pharmaceuticals in water-saturated sand and natural soil: Carboplatin and cisplatin species.

This study reports the transport characteristics of the pharmaceutical compounds carboplatin and cisplatin, and their respective derivatives, in saturated sand and soil columns. Pharmaceuticals are recognized as emerging pollutants of soil and water resources, but studies of the transport characteristics of organometallic pharmaceuticals in soil-water environments are rare. A recent study of oxaliplatin transport in natural soil raises the question of whether or not its behavior is representative of all Pt-based pharmaceuticals behavior in soil-water systems. To address this question, transport behaviors of carboplatin and cisplatin species were studied individually in packed sand columns under unamended conditions, and in packed soil columns under unamended and acetate-amended conditions. In contrast to oxaliplatin, carboplatin species exhibited very low affinity to both sand and soil surfaces: the retention of injected carboplatin was 3% and <6% for sand and soil, respectively. The affinity to soil was practically the same under the different redox conditions. The affinity of carboplatin to sand and soil surfaces was much smaller than the reported oxaliplatin affinity and the values reported in the literature. Cisplatin exhibited transport behavior similar to that of oxaliplatin in soil, including mild sensitivity to redox conditions (e.g., higher retention under acetate-amended conditions), overall exhibiting retention of 64-70% of the injected species. However, cisplatin also exhibited a similar retention in sand (retention of 45-53%), unlike the cases of carboplatin and oxaliplatin. The results indicate that similarly structured pharmaceuticals can exhibit very different transport characteristic in natural soil-water environments, and should therefore be studied and assessed individually.

Accumulation, fractionation, and analysis of platinum in toxicologically affected tissues after cisplatin, oxaliplatin, and carboplatin administration.

Antitumoral Pt-containing drugs present side effects like nephrotoxicity and ototoxicity. Several systematic experiments have been carried out with Wistar rats treated with cisplatin, carboplatin, and oxaliplatin to study Pt-drugs accumulation and elimination, and Pt-biomolecule distribution in the cells and cytosols of ear, kidney, and liver. Inductively coupled plasma-mass spectrometry (ICP-MS) analysis shows a cisplatin accumulation capability between oxaliplatin (the highest) and carboplatin (the lowest). The maximum concentration of Pt in all the organs studied was achieved around the first week after cisplatin treatment. During the first 30 days, the elimination was very fast, decreasing in the subsequent 60 days in all the organs. Analysis of cytosols by liquid chromatography (LC)-ICP-MS showed an analogous behavior. In most samples, the distribution of the three drugs in the cellular and cytosolic fractions was similar for all the tissues. For kidney and ear, approximately 60% and 30%, respectively, of the metal accumulated was present in the cytosol, the cytosolic fractions smaller than 50 KDa being especially important. Cisplatin-biomolecule interaction strength under denaturing conditions was evaluated by LC-ICP-MS and showed a quite strong bond.

Analysis of platinum content in biodegradable carboplatin-impregnated beads and retrospective assessment of tolerability for intralesional use of the beads in dogs following excision of subcutaneous sarcomas: 29 cases (2011-2014).

OBJECTIVE To evaluate platinum content in biodegradable carboplatin-impregnated beads and retrospectively assess tolerability and outcome data for dogs treated by intralesional placement of such beads following surgical excision of subcutaneous sarcomas. DESIGN Evaluation study and retrospective case series. SAMPLE 9 carboplatin-impregnated beads and 29 client-owned dogs. PROCEDURES Platinum content in 9 carboplatin-impregnated beads from 3 lots was measured by spectrophotometry, and calculated carboplatin content was compared with the labeled content. Medical records were searched to identify dogs with subcutaneous sarcomas for which treatment included placement of carboplatin-impregnated beads between 2011 and 2014. Signalment, tumor characteristics, surgical and histologic data, adverse events, and local recurrences were recorded. Associations between variables of interest and adverse events or local disease-free interval were analyzed. RESULTS In vitro analysis identified a mean ± SD platinum content of 5.38 ± 0.97 mg/bead. Calculated carboplatin content (10.24 ± 1.84 mg/bead) was significantly greater than the labeled amount (4.6 mg/bead). Bead weight and total platinum content differed significantly among lots, but platinum content per bead weight did not. Mild-to-moderate local adverse events were reported for 11 of 29 tumors; all resolved without additional surgery. No dogs had signs of systemic toxicosis. Overall local disease-free rates 1, 2, and 3 years after surgery were 70%, 70%, and 58%, respectively, as determined by Kaplan-Meier analysis. CONCLUSIONS AND CLINICAL RELEVANCE Carboplatin-impregnated beads were well tolerated; however, results of in vitro tests indicated that caution is needed because of manufacturing inconsistencies.

HPLC method for the determination of carboplatin and paclitaxel with cremophorEL in an amphiphilic polymer matrix.

Simple and rapid reversed phase HPLC methods for individual as well as simultaneous analysis of paclitaxel and carboplatin with cremophorEL (CrEL) in an amphiphilic polymer matrix were developed. Different analytical performance parameters such as linearity, accuracy, precision, specificity, limit of detection (LOD) and limit of quantification (LOQ) were determined according to ICH guidelines. All the analytical methods were developed by reverse phase HPLC on C-18 column with a mobile phase comprising of water-acetonitrile run on isocratic mode for the analysis of carboplatin and gradient mode for individual analysis of paclitaxel and for simultaneous analysis of the two drugs at a flow rate of 1 ml/min at 227 nm. The proposed methods for independent analysis of the drugs elute out carboplatin in 4.3 min and paclitaxel in 10.5 min while in simultaneous analysis carboplatin shows R(t) at 4 min and paclitaxel at 18 min with a continuous run for 17 more minutes to elute out CrEL. These methods were found to be specific as none of the components of the media, i.e. polymer, CrEL and buffer interfered with the drug peaks. The linearity of the calibration curves for each analyte in the desired concentration range was found to be good (r(2)>0.9995). The methods were accurate and precise with recoveries ranging from 98 to 101% for each drug and relative standard deviation (%RSD) <2%. Peaks corresponding to each of the drug showed positive value for the minimum peak purity index over the entire range of integrated chromatographic peak thus indicating the purity of the peaks. Stability analysis of the two drugs revealed that the drugs remain stable during the period of study.

Biological Recovery of Platinum Complexes from Diluted Aqueous Streams by Axenic Cultures.

The widespread use of platinum in high-tech and catalytic applications has led to the production of diverse Pt loaded wastewaters. Effective recovery strategies are needed for the treatment of low concentrated waste streams to prevent pollution and to stimulate recovery of this precious resource. The biological recovery of five common environmental Pt-complexes was studied under acidic conditions; the chloro-complexes PtCl42- and PtCl62-, the amine-complex Pt(NH3)4Cl2 and the pharmaceutical complexes cisplatin and carboplatin. Five bacterial species were screened on their platinum recovery potential; the Gram-negative species Shewanella oneidensis MR-1, Cupriavidus metallidurans CH34, Geobacter metallireducens, and Pseudomonas stutzeri, and the Gram-positive species Bacillus toyonensis. Overall, PtCl42- and PtCl62- were completely recovered by all bacterial species while only S. oneidensis and C. metallidurans were able to recover cisplatin quantitatively (99%), all in the presence of H2 as electron donor at pH 2. Carboplatin was only partly recovered (max. 25% at pH 7), whereas no recovery was observed in the case of the Pt-tetraamine complex. Transmission electron microscopy (TEM) revealed the presence of both intra- and extracellular platinum particles. Flow cytometry based microbial viability assessment demonstrated the decrease in number of intact bacterial cells during platinum reduction and indicated C. metallidurans to be the most resistant species. This study showed the effective and complete biological recovery of three common Pt-complexes, and estimated the fate and transport of the Pt-complexes in wastewater treatment plants and the natural environment.

Presence of cancerostatic platinum compounds in hospital wastewater and possible elimination by adsorption to activated sludge.

Platinum originating from the excreted cancerostatic platinum compounds (CPC) cisplatin, carboplatin and oxaliplatin was monitored over a period of 28 days in the wastewater of the oncologic ward of the Vienna University Hospital. Concentration levels ranging from 4.7 to 145 microg L(-1) were measured by inductively coupled plasma mass spectrometry (ICP-MS). An average ratio of weekly drug emission/drug consumption of 0.27+/-0.12 was assessed. Model studies were carried out for fundamental understanding of CPC interaction with the solid phases present at different stages of the water cycle. Wastewater and activated sludge were spiked with CPC at concentration levels as found in the sewer of the oncologic ward. The platinum concentration remaining in the tested solution was measured after 24 h of incubation. Depending on pH, the three substances exhibited considerably different adsorption rates in wastewater. At pH 7, cisplatin was adsorbed by 88%, whereas only 26% of carboplatin and 54% of oxaliplatin were removed from the aqueous phase. Adsorption by activated sludge was higher, less affected by pH variation and comparable for all investigated CPC (96% for cisplatin, 70% for carboplatin and 74% for oxaliplatin at pH 6.8). In a next step, the dependence of CPC adsorption was tested for wastewater and activated sludge of different sampling sites. Strong variations were found only for wastewater, whereas activated sludge showed more consistent elimination rates (average values: cisplatin 92%, carboplatin 72%, and oxaliplatin 78%). These findings indicate that the major part of the excreted CPC is adsorbed by the solid phase in the water cycle and is thus expected to be removed from the wastewater by sewage treatment plants.

Determination of platinum surface contamination in veterinary and human oncology centres using inductively coupled plasma mass spectrometry.

The objective of this study was to determine the surface contamination with platinum-containing antineoplastic drugs in veterinary and human oncology centres. Inductively coupled plasma mass spectrometry was used to measure platinum levels in surface samples. In veterinary and human oncology centres, 46.3 and 68.9% of the sampled surfaces demonstrated platinum contamination, respectively. Highest platinum levels were found in the preparation rooms (44.6 pg cm(-2)) in veterinary centres, while maximal levels in human centres were found in oncology patient-only toilets (725 pg cm(-2)). Transference of platinum by workers outside areas where antineoplastic drugs were handled was observed in veterinary and human oncology centres. In conclusion, only low levels of platinum contamination attributable to carboplatin were found in the sampled veterinary oncology centres. However, dispersion of platinum outside areas where antineoplastic drugs were handled was detected in veterinary and human oncology centres. Consequently, not only personnel, but also others may be exposed to platinum.

Particle-water interactions of platinum-based anticancer drugs in river water and estuarine water.

The cytotoxic, platinum-based anticancer drugs, cisplatin, carboplatin and oxaliplatin, enter the aquatic environment largely in municipal wastes via excretion from outpatients undergoing chemotherapy. The environmental behaviour, effects and fate of these drugs are, however, unknown. In this study, the adsorption of the drugs to untreated and chemically modified (oxide-free and organic-free) sediment was examined in both river water and low salinity (S=3.2) estuarine water in order to determine the nature and extent of their interactions with suspended particles. In all cases, adsorption isotherms were linear, and the slopes of the relationships, or distribution coefficients (KDs), ranged from about 10(2) to 10(3) ml g(-1). Overall, adsorption decreased in the order: cisplatin>carboplatin>oxaliplatin; in river water and: cisplatin>carboplatin, oxaliplatin; in estuarine water. There was no clear dependence of adsorption on sediment treatment but, for all sediment types, both cisplatin and carboplatin adsorption was greater in river water than in estuarine water. Qualitatively, these observations are consistent with the rates of formation of reactive, aquated degradation products and the dependencies of these rates on aqueous chloride concentration. We predict that during transport through an estuarine turbidity maximum (of suspended sediment concentration=1 g L(-1)), up to about 45% of cisplatin and 35% of carboplatin are filtered out from the aqueous phase but that no more than 7% of oxaliplatin is retained.

Chemotherapy plus local treatment in the management of intraocular retinoblastoma.

OBJECTIVE: To describe platinum-based chemotherapy combined with local treatment modalities as an alternative to external beam radiotherapy for intraocular retinoblastoma. DESIGN: Platinum levels were measured by atomic absorption analysis in the tumors of 2 patients with retinoblastoma given carboplatin 5 or 2.5 hours before enucleation. Platinum levels in heated vs nonheated Greene melanoma tumors in rabbits were compared. A retrospective review of 172 affected eyes in 136 consecutive patients treated for retinoblastoma between January 1990 and December 1995 was performed. From 1990 to 1992, all treatable eyes initially received systemic carboplatin, 560 mg/m2, followed by 15 to 30 minutes of continuous diode laser hyperthermia (thermochemotherapy). Since 1992, larger tumors were treated initially with 3 monthly cycles of carboplatin, etoposide, and vincristine sulfate to reduce tumor volume (chemoreduction) followed by sequential aggressive local therapy (SALT) during examinations under anesthesia every 2 to 3 weeks. OUTCOME MEASURE: Treatment success was defined as eradication of tumor without enucleation or external beam radiotherapy. RESULTS: Significant therapeutic platinum levels were measured in the human tumors 2.5 and 5 hours after carboplatin administration. Increasing the temperature by 9 degrees C for 15 minutes doubled platinum levels in the rabbit model. Of the 38 eyes with Reese-Ellsworth group 1 through 5b tumors that were treated primarily with thermochemotherapy, all 24 eyes with group 1 and 2 tumors were treated successfully and two of the 4 eyes with group 3 tumors and all 10 eyes with group 5b tumors were treated unsuccessfully. Chemoreduction plus SALT was the primary treatment in 35 eyes and was successful in all 10 eyes with group 1 through 4 tumors and unsuccessful in all 7 eyes with extensive subretinal seeding and all 18 eyes with group 5b tumors with vitreous seeding. Seventy patients received carboplatin or carboplatin, vincristine, and etoposide, with myelosuppression, occasionally associated with bacteremia, being the main side effect. Transfusions were required in 15% of patients. Radiation retinopathy occurred in all 6 eyes treated with iodine 125 plaques. CONCLUSIONS: Thermochemotherapy is successful primary treatment for Reese-Ellsworth group 1 and 2 retinoblastomas. For larger tumors in the absence of vitreous or extensive subretinal seeding, 3 cycles of chemoreduction followed by SALT eradicates residual viable tumor. Chemoreduction plus SALT was not successful in eyes with diffuse vitreous or extensive subretinal seeding. Prior chemotherapy increases the risk for radiation retinopathy following 125I plaque therapy. External beam radiotherapy can safely be avoided in the primary treatment of Reese-Ellsworth groups 1 through 4 nondispersed retinoblastoma.

Penetration of carboplatin and cisplatin into rat peritoneal tumor nodules after intraperitoneal chemotherapy.

Platinum distribution was studied in rat peritoneal tumors after i.p. treatment with equimolar doses of carboplatin and cisplatin. Low platinum concentrations (4 ppm) were detected in the periphery of the tumor after carboplatin treatment, whereas no platinum was detected 0.5 mm in from the periphery. In contrast, after cisplatin treatment, high platinum concentrations (29 ppm) were measured in the periphery of the tumor and moderate concentrations (14 ppm) were measured in the center. Only following increased carboplatin doses were low platinum concentrations detectable in the tumor. The total platinum concentration in the tumors was determined after equimolar administration of both drugs. In all, 7 times more platinum was detected after cisplatin treatment than after carboplatin treatment, and 10 times more carboplatin than cisplatin had to be injected to obtain comparable platinum concentrations in the tumors. When single cells were incubated with equimolar concentrations of carboplatin and cisplatin, 6-7 times more platinum was found in cells treated with cisplatin. However, pharmacokinetic studies favored i.p. administration of carboplatin because the clearance of this compound from the peritoneal cavity, expressed as t1/2 beta, was lower than that of cisplatin (239 vs 78 min), resulting in an AUC in the peritoneal cavity for both total and ultrafiltered drug that was almost 3 times higher for carboplatin than cisplatin. The AUC for ultrafiltered carboplatin in plasma was 2-fold that for cisplatin (2,801 +/- 210 vs 1,334 +/- 431 microM m). The present study demonstrated that in spite of the pharmacological advantages of carboplatin, its capacity to penetrate into peritoneal tumors and tumor cells is far lower than that of cisplatin.

Dose-toxicity relationship of carboplatin in combination with cyclophosphamide in ovarian cancer patients.

A study was undertaken to examine the relationships between carboplatin's pharmacokinetic parameters and the myelotoxicity associated with its administration in combination with cyclophosphamide. An additional aim of the study was to test the applicability of the method proposed by Calvert et al. for calculation of the carboplatin dose to be used in the combination regimen. A total of 24 previously untreated ovarian cancer patients were given a combination of 250-500 mg/m2 carboplatin and 500 mg/m2 cyclophosphamide every 4 weeks for 4 months. The pharmacokinetics of carboplatin and the associated myelotoxicity were investigated in 64 courses. The results showed a significant correlation (r = 0.89) between the AUC calculated for carboplatin and that predicted according to Calvert's formula [carboplatin dose in milligrams = AUC (glomerular filtration rate +25)]. We conclude that the model is a useful guide in the calculation of the carboplatin dose to be given in combination with cyclophosphamide, and it enables a more precise prediction of the carboplatin exposure than does the conventional calculation, which is based on milligrams of drug per square meter of body surface. The AUC for carboplatin was a reliable predictor of the myelotoxicity as measured by the relative decrease in thrombocyte count. However, the relationship between AUC and myelotoxicity changed during the treatment because of increasing bone marrow toxicity. Despite this finding, dose calculation based on carboplatin's AUC appears to provide an improvement in the clinical use of the drug, and the method also seems to be fully applicable in combination chemotherapy with cyclophosphamide.

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.