Functionalized Carbon Nano-Onions as a Smart Drug Delivery System for the Poorly Soluble Drug Carmustine for the Management of Glioblastoma

The drug delivery system for transporting anticancer agents to targeted tissues in the body is a challenging issue. In search of a suitable biocompatible carrier having controlled and sustained drug release properties of poorly soluble drugs, carbon nano-onions (CNOs) were loaded with an anticancer drug, bis-chloroethyl nitrosourea (BCNU/carmustine). CNOs being autofluorescent, drug-loaded functionalized CNOs (f-CNO-BCNU) can be detected in vivo. Transmission electron microscopy (TEM) and differential light scattering (DLS) techniques were used to analyze the sizes of these f-CNOs. The molecular study revealed that the f-CNO-BCNU readily and noncovalently binds with the folate receptors present on the cancer cell surface in excess. Computer modeling and molecular dynamics simulation followed by binding free energy calculation shows f-CNOs have -29.9 kcal/mol binding free energy, and it noncovalently binds the receptor FRα using loop dynamics of three essential loops present in the protein along with polar stabilization interactions provided by Asp55 and Glu86 residues present in the active site. The f-CNO effectively decreased cancer cell viability with a low IC50 value (the concentration that led to 50% killing of the cells). The cell-based Franz diffusion assay was performed to study the drug release profile. The f-CNO-BCNUs also decreased the mitochondrial membrane potential of U87 cells, increased reactive oxygen species release, and caused a loss of mitochondrial membrane integrity. The f-CNOs also increased the percentage of apoptotic cells observed by the Annexin V assay. Based on observed results, it can be concluded that the f-CNO-BCNU efficiently targets the cancer cells, enhances the bioavailability of carmustine, and can be used as a smart chemotherapeutic agent. This strategy offers better patient compliance and greater bioavailability of the drug.

Covalent inhibition of P. falciparum ferredoxin-NADP+ reductase: Exploring alternative strategies for the development of new antimalarial drugs

The protozoan Plasmodium falciparum is the main aetiological agent of tropical malaria. Characteristic of the phylum is the presence of a plastid-like organelle which hosts several homologs of plant proteins, including a ferredoxin (PfFd) and its NADPH-dependent reductase (PfFNR). The PfFNR/PfFd redox system is essential for the parasite, while mammals share no homologous proteins, making the enzyme an attractive target for novel and much needed antimalarial drugs. Based on previous findings, three chemically reactive residues important for PfFNR activity were identified: namely, the active-site Cys99, responsible for hydride transfer; Cys284, whose oxidation leads to an inactive dimeric form of the protein; and His286, which is involved in NADPH binding. These amino acid residues were probed by several residue-specific reagents and the two cysteines were shown to be promising targets for covalent inhibition. The quantitative and qualitative description of the reactivity of few compounds, including a repurposed drug, set the bases for the development of more potent and specific antimalarial leads.

Inhibition of bcl-2 and cox-2 Protein Expression after Local Application of a New Carmustine-Loaded Clinoptilolite-Based Delivery System in a Chemically Induced Skin Cancer Model in Mice

Our research has focused on in vitro and in vivo evaluations of a new Carmustine (BCNU)-loaded clinoptilolite-based delivery system. Two clinoptilolite ionic forms-hydrogen form (HCLI) and sodium form (NaCLI)-were prepared, allowing a loading degree of about 5-6 mg BCNU/g of zeolite matrix due to the dual porous feature of clinoptilolite. Clinoptilolite-based delivery systems released 35.23% of the load in 12 h for the BCNU@HCLI system and only 10.82% for the BCNU@NaCLI system. The BCNU@HCLI system was chosen to develop gel and cream semisolid dosage forms. The cream (C_BCNU@HCLI) released 29.6% of the loaded BCNU after 12 h in the Nylon synthetic membrane test and 31.6% in the collagen membrane test, higher by comparison to the gel. The new cream was evaluated in vivo in a chemically induced model of skin cancer in mice. Quantitative immunohistochemistry analysis showed stronger inhibition of B-cell lymphoma-2 (bcl-2) and cyclooxygenase 2 (cox-2) protein expression, known markers for cancer survival and aggressiveness, after the treatment with C_BCNU@HCLI by comparison to all the control treatment types, including an off-label magistral formula commercially available Carmustine cream as reference, bringing evidence that a clinoptilolite-based delivery systems could be used as a cancer drug carriers and controlled release systems (skin-targeted topical delivery systems).

Honokiol inhibits lung tumorigenesis through inhibition of mitochondrial function

Honokiol is an important bioactive compound found in the bark of Magnolia tree. It is a nonadipogenic PPARγ agonist and capable of inhibiting the growth of a variety of tumor types both in vitro and in xenograft models. However, to fully appreciate the potential chemopreventive activity of honokiol, a less artificial model system is required. To that end, this study examined the chemopreventive efficacy of honokiol in an initiation model of lung squamous cell carcinoma (SCC). This model system uses the carcinogen N-nitroso-trischloroethylurea (NTCU), which is applied topically, reliably triggering the development of SCC within 24 to 26 weeks. Administration of honokiol significantly reduced the percentage of bronchial that exhibit abnormal lung SCC histology from 24.4% bronchial in control to 11.0% bronchial in honokiol-treated group (P = 0.01) while protecting normal bronchial histology (present in 20.5% of bronchial in control group and 38.5% of bronchial in honokiol-treated group. P = 0.004). P63 staining at the SCC site confirmed the lung SCCs phenotype. In vitro studies revealed that honokiol inhibited lung SCC cells proliferation, arrested cells at the G1-S cell-cycle checkpoint, while also leading to increased apoptosis. Our study showed that interfering with mitochondrial respiration is a novel mechanism by which honokiol changed redox status in the mitochondria, triggered apoptosis, and finally leads to the inhibition of lung SCC. This novel mechanism of targeting mitochondrial suggests honokiol as a potential lung SCC chemopreventive agent.

Microencapsulation of chemotherapeutics into monodisperse and tunable biodegradable polymers via electrified liquid jets: control of size, shape, and drug release

This paper describes microencapsulation of antitumor agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, Carmustine) into biodegradable polymer poly(lactic-co-glycolic) acid (PLGA) using an electrojetting technique. The resulting BCNU-loaded PLGA microcapsules have significantly higher drug encapsulation efficiency, more tunable drug loading capacity, and (3) narrower size distribution than those generated using other encapsulation methods.

Resorbable polymer microchips releasing BCNU inhibit tumor growth in the rat 9L flank model

Sustained local delivery of single agents and controlled delivery of multiple chemotherapeutic agents are sought for the treatment of brain cancer. A resorbable, multi-reservoir polymer microchip drug delivery system has been tested against a tumor model. The microchip reservoirs were loaded with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU was more stable at 37 degrees C within the microchip compared to a uniformly impregnated polymeric wafer (70% intact drug vs. 38%, at 48 h). The half-life of the intact free drug in the microchip was 11 days, which is a marked enhancement compared to its half-life in normal saline and 10% ethanol (7 and 10 min, respectively) [P. Tepe, S.J. Hassenbusch, R. Benoit, J.H. Anderson, BCNU stability as a function of ethanol concentration and temperature, J. Neurooncol. 10 (1991) 121-127; P. Kari, W.R. McConnell, J.M. Finkel, D.L. Hill, Distribution of Bratton-Marshall-positive material in mice following intravenous injections of nitrosoureas, Cancer Chemother. Pharmacol. 4 (1980) 243-248]. A syngeneic Fischer 344 9L gliosarcoma rat model was used to study the tumoricidal efficacy of BCNU delivery from the microchip or homogeneous polymer wafer. A dose-dependent decrease in tumor size was found for 0.17, 0.67, and 1.24 mg BCNU-microchips. Tumors treated with 1.24 mg BCNU-microchips showed significant tumor reduction (p=0.001) compared to empty control microchips at two weeks. The treatment showed similar efficacy to a polymer wafer with the same dosage. The microchip reservoir array may enable delivery of multiple drugs with independent release kinetics and formulations.

S-nitrosoglutathione and hypoxia-inducible factor-1 confer chemoresistance against carbamoylating cytotoxicity of BCNU in rat C6 glioma cells

BCNU (1,3-bis[2-chloroethyl]-1-nitrosourea) is the mainstay in glioblastoma multiform chemotherapy with only minimal effects. BCNU may kill tumor cells via carbamoylating cytotoxicity, which irreversibly inhibits glutathione reductase with resultant accumulation of oxidized form of glutathione causing oxidative stress. S-nitrosoglutathione (GSNO) is a product of glutathione and nitric oxide interaction. We report that GSNO formation may underlie carbamoylating chemoresistance mediated by activation of inducible nitric oxide synthase. Transactivation of hypoxia-inducible factor-1 (HIF-1)-responsive genes reduces oxidative stress caused by glutathione depletion. We also noted that preconditioning of C6 glioma cells to induce HIF-1 and its downstream genes confers chemoresistance against carbamoylating cytotoxicity of BCNU.

BCNU-loaded PEG-PLLA ultrafine fibers and their in vitro antitumor activity against Glioma C6 cells

The purpose of the present study was to develop implantable BCNU-loaded poly(ethylene glycol)-poly(L-lactic acid) (PEG-PLLA) diblock copolymer fibers for the controlled release of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU was well incorporated and dispersed uniformly in biodegradable PEG-PLLA fibers by using electrospinning method. Environmental Scanning Electron Microscope (ESEM) images indicated that the BCNU-loaded PEG-PLLA fibers looked uniform and their surfaces were reasonably smooth. Their average diameters were below 1500 nm. The release rate of BCNU from the fiber mats increased with the increase of BCNU loading amount. In vitro cytotoxicity assay showed that the PEG-PLLA fibers themselves did not affect the growth of rat Glioma C6 cells. Antitumor activity of the BCNU-loaded fibers against the cells was kept over the whole experiment process, while that of pristine BCNU disappeared within 48 h. These results strongly suggest that the BCNU/PEG-PLLA fibers have an effect of controlled release of BCNU and are suitable for postoperative chemotherapy of cancers.

2-Acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylcarbonylamino)- phenylcarbamoylsulfanyl]propionic acid and its derivatives as a novel class of glutathione reductase inhibitors

Glutathione reductase (GR) catalyzes the reduction of oxidized glutathione to reduced glutathione. The enzyme is an attractive target for the development of antimalarial agents, agents to decrease malarial drug resistance and anticancer agents. In addition, inhibition of the enzyme has been employed as a tool in research for various purposes. In this paper, we present a rational design of 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylcarbonylamino)phenylcarbamoylsulfanyl]propionic acid and its derivatives as irreversible GR inhibitors. The K(i) and k(inact) values of 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylcarbonylamino)phenylcarbamoylsulfanyl]propionic acid, the most potent derivative of the series, are 88 muM and 0.1 min(-1), respectively. Although the K(i) value of the inhibitor is in the micromolar range, it is more potent than N,N-bis(2-chloroethyl)-N-nitrosourea, which is currently the most commonly employed irreversible GR inhibitor with a reported IC(50) value of 646 microM. Additional attractive features of the inhibitor include its ready availability through a one-step synthesis and good solubility in both organic and aqueous solutions.

Enhancement of the stability of BCNU using self-emulsifying drug delivery systems (SEDDS) and in vitro antitumor activity of self-emulsified BCNU-loaded PLGA wafer

The main purpose of this study was to develop self-emulsifying drug delivery systems (SEDDS) for the improvement of the stability of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) after released from poly (D,L-lactide-co-glycolide) (PLGA) wafer and to evaluate its in vitro antitumor activity against 9L gliosarcoma cells. The in vitro stability test of BCNU was characterized by the BCNU amount in phosphate buffered saline (PBS, pH 7.4) at 37 degrees C. SEDDS increased in vitro half-life of BCNU up to 130 min compared to 45 min of intact BCNU. Self-emulsified (SE) BCNU was fabricated into wafers with flat and smooth surface by compression molding. In vitro release of BCNU from SE BCNU-loaded PLGA wafer was prolonged up to 7 days followed first order release kinetics. Beside, the cytotoxicity of SE BCNU-loaded PLGA wafer against 9L gliosarcoma cells was higher than intact BCNU-loaded PLGA wafer which is more susceptible to hydrolysis. SE BCNU degraded much more slowly than the intact BCNU in PLGA matrix at 25 degrees C. These results strongly suggest that the self-emulsion system increased the stability of BCNU after released from PLGA wafer. From these results, it could be expected that the penetration depth of BCNU could be improved in brain tissue using self-emulsion system.

BCNU-loaded poly(D, L-lactide-co-glycolide) wafer and antitumor activity against XF-498 human CNS tumor cells in vitro

Implantable polymeric device that can release chemotherapeutic agent directly into central nervous system (CNS) has had an impact on malignant glioma therapy. The purpose of our study was to develop an implantable polymeric device, which can release intact 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) for long-term period over 1 month, and to evaluate its cytotoxicity against XF 498 human CNS tumor cells in vitro. BCNU was incorporated into biodegradable poly(D,L-lactide-co-glycolide) (PLGA), by using spray-drying method. BCNU-loaded PLGA microparticles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction, and differential scanning calorimetry. SEM observation of the microparticles showed that the microparticles were spherical, i.e. microspheres. Homogeneous distribution of BCNU in PLGA microsphere was confirmed by significant reduction of crystallinity of BCNU. Microspheres were fabricated into wafers with flat and smooth surface by direct compression method. In vitro release of BCNU in pH 7.4 phosphate buffered saline was prolonged up to 8 weeks after short initial burst period. Antitumor activity of BCNU-loaded PLGA wafer against XF 498 human CNS tumor cells continued over 1 month and, PLGA only did not affect the growth of the cells. Meanwhile, the cytotoxic activity of BCNU powder disappeared within 12 h. These results strongly suggest that the BCNU/PLGA formulations increase release period of carmustine in vivo and also be useful in the development of implantable polymeric device for malignant glioma.

Stabilization and preformulation of anticancer drug--SarCNU

The stability of SarCNU (NSC364432), 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea in several pharmaceutically acceptable solvents was investigated by high pressure liquid chromatography (HPLC). The influences of light, ionic strength, pH, buffer concentration, and the following excipients: benzyl alcohol, ascorbic acid, sodium bisulfite, and disodium EDTA were studied at room temperature. The stability of the drug was also determined in water, EtOH, PG, Capmul PG, DMSO, and in different combinations of these cosolvents at four different temperatures. The degradation of the drug, which is catalyzed not only by general but also by specific acid and base, follows first order kinetics. Antioxidants, EDTA, and light have no effect on the degradation rate, suggesting oxidation is not a major degradation pathway. The t(90) in pure cosolvent is 25-50 times higher than that in water or semi-aqueous vehicles. Neat EtOH can be used to store the drug in a nonaqueous concentrate that is diluted with aqueous solvent prior to injection.

Inhibition of glutathione S-transferases by antimalarial drugs possible implications for circumventing anticancer drug resistance

A strategy to overcome multidrug resistance in cancer cells involves treatment with a combination of the antineoplastic agent and a chemomodulator that inhibits the activity of the resistance-causing protein. The aim of our study was to investigate the effects of antimalarial drugs on human recombinant glutathione S-transferase (GSTs) activity in the context of searching for effective and clinically acceptable inhibitors of these enzymes. Human recombinant GSTs heterologously expressed in Escherichia coli were used for inhibition studies. GST A1-1 activity was inhibited by artemisinin with an IC(50) of 6 microM, whilst GST M1-1 was inhibited by quinidine and its diastereoisomer quinine with IC(50)s of 12 microM and 17 microM, respectively. GST M3-3 was inhibited by tetracycline only with an IC(50) of 47 microM. GST P1-1 was the most susceptible enzyme to inhibition by antimalarials with IC(50) values of 1, 2, 1, 4, and 13 microM for pyrimethamine, artemisinin, quinidine, quinine and tetracycline, respectively. The IC(50) values obtained for artemisinin, quinine, quinidine and tetracycline are below peak plasma concentrations obtained during therapy of malaria with these drugs. It seems likely, therefore, that GSTs may be inhibited in vivo at doses normally used in clinical practice. Using the substrate ethacrynic acid, a diuretic drug also used as a modulator to overcome drug resistance in tumour cells, GST P1-1 activity was inhibited by tetracycline, quinine, pyrimethamine and quinidine with IC(50) values of 18, 27, 45 and 70 microM, respectively. The ubiquitous expression of GSTs in different malignancies suggests that the addition of nontoxic reversing agents such as antimalarials could enhance the efficacy of a variety of alkylating agents.

Use of pure t-butanol as a solvent for freeze-drying: a case study

1-(2-Chloroethyl)-3-sarcosinamide-1-nitrosourea, (SarCNU) (NSC-364432) is a new antitumor drug that is of interest to the National Cancer Institute. It is intended for use as an intravenous injection. Although SarCNU is sufficiently soluble in water to obtain the desired dosage, it is highly unstable. Its T(90) in aqueous solution at room temperature is less than 6 h. Neat tertiary butyl alcohol (TBA), a low toxicity, high vapor pressure and low melting solvent, was determined to be an excellent freeze-drying medium. Lyophilization of SarCNU from pure TBA produces a uniform cake composed of needle-shaped crystals. Thermal analysis and gas chromatography indicate that the cake contains less than 0.001% residual solvent. The SarCNU cake can be readily reconstituted with either water or an aqueous solution of 40% propylene glycol and 10% ethanol. The reconstituted solutions are stable for 4 and 13 h, respectively.

Determination of the vaporization of solutions of mutagenic antineoplastic agents at 23 and 37 degrees C using a desiccator technique

This study evaluated the ability of mutagenic antineoplastic agents to vaporize at room temperature (23 degrees C) and 37 degrees C. A bacterial mutagenicity assay was used to determine the mutagenicity of these agents in the vapor phase. Open plates of bacteria were exposed to varying amounts of drug solutions in sealed glass containers for 24h. The drug solutions were prepared as they would be for patient treatment and were tested at 0.25, 0.5 and 1.0 ml of each drug solution per 10 l of air. Following exposure, the plates exposed at 23 degrees C were incubated an additional 48 h at 37 degrees C to allow for expression of mutations. Those exposed at 37 degrees C were incubated for an additional 24h at 37 degrees C. Carmustine, cyclophosphamide, ifosfamide, thiotepa, and mustargen demonstrated vaporization at 37 degrees C. Carmustine and mustargen also demonstrated significant vaporization at 23 degrees C, while cyclophosphamide demonstrated a 50% increase in revertants at this temperature. In addition, sodium azide, a known mutagen used as a control was also mutagenic as a vapor at both temperatures. Doxorubicin, cisplatin, etoposide, 5-fluorouracil and mitomycin were not detected as vaporizing in this assay. The study found that vaporization of standard solutions of some antineoplastic agents is possible at room temperature and increases as the temperature increases. Therefore, vaporization of spilled antineoplastic agents may present an additional route of exposure to healthcare workers through inhalation.

Comparative effects of (SBE)7m-beta-CD and HP-beta-CD on the stability of two anti-neoplastic agents, melphalan and carmustine

The purpose of this study was to evaluate and compare the potential use of two parenterally safe beta-cyclodextrins derivatives, (SBE)7m-beta-CD and HP-beta-CD, as solubilizers and stabilizers for melphalan and carmustine, two very unstable antineoplastic agents. Phase solubility and chemical stability of the compounds in the presence of the cyclodextrins were studied. UV, fluorescence, and several NMR techniques were used to probe the potential causes for the differences observed. The phase solubility method was found to provide only qualitative data on the binding of melphalan to the cyclodextrins since rapid degradation and the presence of products of degradation complicated the interpretation of the results. Qualitatively, however, the solubilizing potential was similar for the two cyclodextrins. The chemical stability studies indicate that both of the drugs had similar binding constants for both cyclodextrins; however, the intrinsic reactivities in the complexes were significantly lower with (SBE)7m-beta-CD than for HP-beta-CD. The main cause for this distinct difference appeared to correlate with differences in the site of binding and the polarity of the binding site.

Synthesis and cytotoxic activity of N-(2-chloroethyl)-N-nitroureas and N-(2-chloroethyl)-N-nitrocarbamates

As analogs of the widely used anti-tumor agents, N-(2-chloroethyl)-N-nitrosoureas, N-(2-chloroethyl)-N-nitroureas and N-(2-chloroethyl)-N-nitrocarbamates were synthesized by nitration following the reaction of the appropriate amines or alcohols with 2-chloroethyl isocyanate. All tested compounds exert cytotoxic effect with IC50 values of 10(-4) to 10(-6) M and most of them show somewhat higher cytotoxicity in nitrogen than in air.

Internal morphology of poly(D,L-lactide-co-glycolide) BCNU-loaded microspheres. Influence on drug stability

The solvent extraction/evaporation process has been used to form poly(D,L-lactide-co-glycolide) (PLAGA) BCNU-loaded microspheres designed for use as intracranial controlled-release implants. Their actual payload could reach 25% with a 20-50 microns size distribution. Scanning electron microscopy showed that such carriers had a smooth surface and a spherical geometry. Differential scanning calorimetry analyses carried out on drug-loaded microspheres established that the PLAGA Tg was markedly shifted towards the low temperatures along with the disappearance of the BCNU melting endotherm. Annealing experiments performed at room temperature did not induce any change of the loaded microsphere DSC profiles. These features indicated that the BCNU acted as a plasticizer for the coating material and formed with it a solid solution. Similarly, stability of encapsulated BCNU was assessed in different conditions of storage. It appeared that drug degradation increased with temperature increase: 5.4, 8.8, 32.4 and 51.2% of decomposition after 3 month storage at -18, 4, room temperature (RT) and 37 degrees C respectively. Since the free drug was stable at 4 degrees C and experienced only 10.6% decomposition at RT during the same storage time, the state of solid solution involving the intimate mixing of the drug and the polyester in the matrix favors a progressive decomposition of BCNU. However, keeping the microspheres 6 months at -18 degrees C or 3 months at 4 degrees C prevents a loss of drug superior to 10%.

In vitro reactivity of the antineoplastic drug carmustin and acrolein with model peptides

The in vitro interaction of the antineoplastic drug 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) and acrolein with model peptides has been investigated in order to provide a detailed description of their electrophilic reactivity towards biological macromolecules. Following incubation with these substances, the modified species were separated by HPLC and identified by fast atom bombardment mass spectrometry, whereas the reactive amino acids within the peptide structure were assigned by tandem mass spectrometry. Incubation with BCNU led essentially to the formation of an N-terminal carbamoyl derivative that slowly decomposed to form three isomeric structures and a very minor ethylated adduct. Alkylation with acrolein gave rise to a mixture of different adducts due to the reaction of both the double bond and the carbonyl group. Two species containing intramolecular cross-links were also observed. These results constitute the prerequisite for in vitro and in vivo studies on the modification of haemoglobin in patients following treatment with antineoplastic drugs.

Effects of temperature, solution composition, and type of container on the stability and absorption of carmustine

The stability and absorption of carmustine were studied comparatively in glass flasks and Stedim 6 bags. Stedim 6 is a new, multilayer, polyethylene-lined film. When stored at room temperature (22 degrees C +/- 2 degrees C) in the dark, carmustine decomposed in 5% dextrose solution and more so in 0.9% sodium chloride solution. When stored at 4 degrees C +/- 0.5 degrees C, the losses were identical in the glass flasks and Stedim 6 bags (about 11% after 72 hours). As long as they are kept in the dark at 4 degrees C, carmustine admixtures can be prepared up to 48 hours before administration, in either dextrose or sodium chloride isotonic solutions, and stored in either glass flasks or Stedim 6 bags.

Comparative study on protective gloves for handling cytotoxic medicines: a model study with carmustine

The quality of protective gloves was studied. Protective gloves are part of the personal safety equipment for staff handling cytotoxic drugs. A study using raster electron microscopic photography, measurement of thickness by micrometer screw and permeability of carmustine by high pressure liquid chromatographic assay was carried out. The results show differences between different types of gloves.

Alteration of the inner surface of venous catheters by antineoplastic drugs

Septic complications and thrombosis are frequent causes of long-term venous catheter implantation failure and tend to occur more frequently in oncology than in patients using catheters for hyperalimentation only. The purpose of this in vitro study was to study extensively the inner surface behaviour and the possible changes in their mechanical properties of various silicone and polyurethane catheters after exposure to a flow of the most common antineoplastic drugs. Silicone catheters appeared to be the best choice for cytostatic drug infusions because of their chemical stability, but the addition of an opacifier imposes a protective inner and outer layer to improve their surface properties for biocompatibility.

BCNU stability as a function of ethanol concentration and temperature

BCNU is increasingly used in low ethanol (ETOH) concentrations, 5% dextrose-water (D5W), or normal saline (NS) solutions, especially for intra-arterial and prolonged (e.g., 3 day) intravenous (IV) infusions. Little work, however, has been done to evaluate BCNU decomposition rates in concentrations, diluents, and temperatures similar to those employed clinically. This study examined BCNU solutions in ETOH, NS, and D5W to evaluate, conclusively, initial recovery and decomposition rates in these three diluents. Initial BCNU recovery rates were: 95.6 +/- 0.3% (100% D5W), 89.6 +/- 0.5% (15% ETOH), and 85.2 +/- 0.5% (NS) (P less than 0.001). Study of all solutions revealed no measurable BCNU decomposition over 24 hrs (0 degrees C) and no significant difference in decomposition rates between any of the diluents (19.5 degrees C). At 37 degrees C, the solutions showed different half-lives: 14.3 +/- 0.19 hrs (15% ETOH), 10.6 +/- 0.02 hrs (10% ETOH), 8.2 +/- 0.21 hrs (5% ETOH), 7.3 +/- 0.06 hrs (NS), and 6.8 +/- 0.07 hrs (D5W) (P less than 0.001). Decomposition rates between all three temperatures (19.5 degrees C, 37 degrees C, and 50 degrees C) were significantly different (P less than 0.01) for each diluent. Dissolving BCNU powder into either D5W or NS required only 5 min when hand-shaken at body temperature. This study of initial recovery and decomposition rates suggests that, although BCNU decomposition rates were significantly increased at body temperature (37 degrees C), it was quite low and essentially unaffected by different diluents at room temperature (i.e., 19.5 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)