|Articles about Biomaterials|
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| Effects of pH and catalyst concentration on photocatalytic oxidation of aqueous ammonia and nitrite in titanium dioxide suspensions
Zhu, X., S. R. Castleberry, et al. (2005), Environ Sci Technol 39(10): 3784-91.
Abstract: Batch experiments were conducted to study the effects of titanium dioxide (TiO2) concentration and pH on the initial rates of photocatalytic oxidation of aqueous ammonium/ ammonia (NH4+/NH3) and nitrite (NO2-) in UV-illuminated TiO2 suspensions. While no simple kinetic model could fit the data at lower TiO2 concentrations, at TiO2 concentrations > or = 1 g/L, the experimental data were consistent with a model assuming consecutive first-order transformation of NH4+/NH3 to NO2- and NO2- to nitrate (NO3-). For TiO2 concentrations > or = 1 g/L, the rate constants for NO2 photocatalytic oxidation to NO3 were far more dependent on TiO2 concentration than were those for NH4+/NH3 oxidation to NO2-, suggesting that, without sufficient TiO2, complete oxidation of NH4+/NH3 to NO3- will not occur. Initial NH4+/NH3 photocatalytic oxidation rates were proportional to the initial concentrations of neutral NH3 and not total NH3(i.e., [NH4+] + [NH3]). Thus, the pH-dependent equilibrium between NH4+ and NH3, and not the pH-dependent electrostatic attraction between NH4+ and the TiO2 surface, is responsible for the increase in rates of NH4+/NH3 photocatalytic oxidation with increasing pH. Electrostatic adsorption, however, can partly explain the pH dependence of the initial rates of NO2- photocatalytic oxidation. Initial rates of NO2- photocatalytic oxidation were 1 order of magnitude higher for NO2- versus NH4+/NH3, indicating thatthe rate of NH4+/NH3 photocatalytic oxidation to NO3- was limited by NH4+/NH3 oxidation to NO2- under our experimental conditions.
| Effects of phosphatidylserine coatings on titanium on inflammatory cells and cell-induced mineralisation in vitro
Bosetti, M., A. W. Lloyd, et al. (2005), Biomaterials 26(36): 7572-8.
Abstract: Ideally an active bone biomaterial should increase the mineralisation rate at the bone healing sites, keeping at the same time the inflammation process to levels required for tissue regeneration. Our studies suggest that in addition to improving the nucleation process for new bone formation, coating titanium with phospholipids may reduce the inflammatory response, which was shown to vary depending on the formulation employed. As phosphatidylserine reduced the inflammatory response to the greatest extent, in the second part of this study we examined its effect on osteoblast mineralisation. These studies demonstrated that phosphatidylserine improves the nucleation process for bone formation, by promoting the formation of bone-like tissue, so the high mineralisation potential of phosphatidylserine-coated titanium, together with the lower level of inflammatory response, supports the further development of this technology for coating osteointegrative devices.
| Effects of products liability on bulk suppliers of biomaterials
Baker, F. D. (1995), Food Drug Law J 50(3): 455-60.
| Effects of pulmonary surfactant system on rifampicin release from rifampicin-loaded PLGA microspheres
Tomoda, K., S. Kojima, et al. (2005), Colloids Surf B Biointerfaces 45(1): 1-6.
Abstract: Pulmonary surfactants little affected the release ratio of rifampicin from rifampicin-loaded poly(lactide-co-glycolide) PLGA microspheres. The release ratio of rifampicin was depending on pH of pulmonary surfactant solution, showing that rifampicin-loaded PLGA microspheres have an ideal property to deliver rifampicin into alveolar macrophages inside of which Mycobacterium tuberculosis bacilli reside and to kill them. That is, little amount of rifampicin is released in alveolar lining liquid before the microspheres are phagocytosed by alveolar macrophages, then rifampicin is released in phagosome or cytoplasm, but little amount of rifampicin is released in lysosome of alveolar macrophages after the microspheres are internalized. Pulmonary surfactants also little affected the changes in molecular weight of residual PLGA during its hydrolytic degradation process. From the electrophoretic mobility measurements of PLGA microspheres, it was shown that pulmonary surfactants changed the surface charge density of PLGA microspheres by adsorbing on their surfaces.
| Effects of radiofrequency energy on human chondromalacic cartilage: an assessment of insulation material properties
Meyer, M. L., Y. Lu, et al. (2005), IEEE Trans Biomed Eng 52(4): 702-10.
Abstract: The objective of this study was to establish guidelines for the selection of an insulation material used to surround the electrode of radiofrequency energy (RFE) probes used for thermal chondroplasty. These guidelines were established by identifying which insulation materials resulted in the least amount of chondrocyte death while smoothing the surface of chondromalacic cartilage. RFE causes electrolyte oscillation and molecular friction in the tissue to heat it and subsequently smooth the surface. Material properties investigated included the coefficient of thermal expansion (CTE), thermal conductivity (TC), and volume resistivity (VR). Fresh human chondromalacic cartilage samples of Outerbridge grades II and III were obtained from patients undergoing total knee arthroplasty. Stiffness measurements were taken pretreatment and posttreatment. RFE was applied to a 1-cm2 area for 15 s in a paintbrush treatment pattern. The insulation materials evaluated included Macor (decrease CTE, decrease TC, increase VR; in relation to CTE = 10 x 10(-6)/degrees C at 20 degrees C, TC = 3 W/mK, VR=1 x 10(14) ohm x cm), zirconia toughened alumina (ZTA) and 99.5% alumina (decrease CTE, increase TC, increase VR), aluminum nitride (decrease CTE, increase TC, decrease VR), Teflon (PTFE) (increase CTE, decrease TC, increase VR), partially stabilized zirconia (YTZP) (decrease CTE, decrease TC, decrease VR), and Ultem (increase CTE, decrease TC, decrease VR). There were no significant differences between pretreatment and posttreatment stiffness of the cartilage for any material investigated. Subjectively scored scanning electron microscopy (SEM) images revealed that the surfaces of all samples treated with RFE were relatively smooth with melted fronds. Prototype probes made with Macor, 99.5% alumina, and ZTA had TC < or = 30 W/mol x K and resulted in a mean of 35% less cell death (176+/-56 microm, 130+/-48 microm, and 114+/-33 microm, respectively) than aluminum nitride, PTFE, and YTZP (246+/-68 microm, 231+/-108 microm, and 195+/-89 microm, respectively). Macor, 99.5% alumina, and ZTA prototype probes all had VR > or = 1 x 10(14) ohm x cm and resulted in a mean 37% less cell death than aluminum nitride or YTZP. There was no apparent relationship between CTE and the depth of chondrocyte death.
| Effects of recombinant human bone morphogenetic protein-2 on human bone marrow cells cultured with various biomaterials
Kim, K. J., T. Itoh, et al. (1997), J Biomed Mater Res 35(3): 279-85.
Abstract: Recombinant human bone morphogenetic protein-2 (rhBMP-2) is known to induce orthotopic and ectopic bone formation in vivo. Several in vitro studies using rat or mouse clonal cell lines have shown that rhBMP-2 may be involved in the differentiation of osteoblasts from osteoblast precursor cells or stromal cells in the bone marrow. However, there is little information available about the effects of rhBMP-2 on cultured human bone marrow cells. We investigated the effects of rhBMP-2 cultured on human bone marrow cells and osteoblastic cells on various biomaterials. Human bone cells were divided into fresh bone marrow cells, fibroblast colony-forming units (cfu-F, stromal precursors), and osteoblastic cells. The cells were cultured with or without rhBMP-2 on various biomaterials, including titanium alloy, pure titanium, cobalt alloy, and hydroxyapatite. It was found that rhBMP-2 (500 ng/mL) significantly stimulated alkaline phosphatase production by fresh bone marrow cells and cfu-F. However, when cultured on titanium alloy or pure titanium, only fresh bone marrow cells showed an increase of alkaline phosphatase production after rhBMP-2 stimulation. Production of osteocalcin, a marker of mature osteoblasts, was not stimulated by rhBMP-2 in any combinations tested. These findings suggest that rhBMP-2 may be involved in inducing the differentiation of osteoblast precursor cells into osteoblastic cells rather than stimulating further differentiation of osteoblastic cells into mature osteoblasts. In addition, grafts of fresh human bone marrow cells of cfu-F stimulated by rhBMP-2 may have the potential to promote bone formation at sites of nonunion as well as around titanium joint prostheses.
| Effects of resin hydrophilicity on water sorption and changes in modulus of elasticity
Ito, S., M. Hashimoto, et al. (2005), Biomaterials 26(33): 6449-59.
Abstract: As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high concentrations, the adhesive becomes more hydrophilic. Water sorption by polymers causes plasticization and lowers mechanical properties. The purpose of this study was to compare the water sorption and modulus of elasticity (E) of five experimental neat resins (EX) of increasing hydrophilicity, as ranked by their Hoy's solubility parameters and five commercial resins. METHODS: After measuring the initial modulus of all resin disks by biaxial flexure, half the specimens were stored in hexadecane and the rest were stored in water. Repeated measurements of stiffness were made for 3 days. Water sorption and solubility measurements were made in a parallel experiment. RESULTS: None of the specimens stored in oil showed any significant decrease in modulus. All resins stored in water exhibited a time-dependent decrease in modulus that was proportional to their degree of water sorption. Water sorption of EX was proportional to Hoy's solubility parameter for polar forces (delta(p)) with increasing polarity resulting in higher sorption. The least hydrophilic resin absorbed 0.55 wt% water and showed a 15% decrease in modulus after 3 days. The most hydrophilic experimental resin absorbed 12.8 wt% water and showed a 73% modulus decrease during the same period. The commercial resins absorbed between 5% and 12% water that was associated with a 19-42% reduction in modulus over 3 days.
| Effects of selective oxidation of chitosan on physical and biological properties
Yoo, S. H., J. S. Lee, et al. (2005), Int J Biol Macromol 35(1-2): 27-31.
Abstract: Chitosan was selectively oxidized at C-6 primary alcohol groups by TEMPO in the presence of sodium hypochlorite (NaOCl) and sodium bromide (NaBr), and also non-specifically oxidized only by NaOCl. Sequentially oxidized chitosan samples from 25 to 100% were produced by 25% increment, from both oxidation processes. By introducing carbonyl groups in chitosan structure with either oxidizing process, the water solubility was shown to be enhancing from all the oxidized sample groups. At the 25% of non-specific oxidation, 0.56% of solubility was detected but there was no proportional increase in solubility as the oxidation level increased. Moreover, the decreases in solubility were observed at 50%-oxidized (0.43%) and 100%-oxidized (0.45%) chitosan samples. During the specific oxidation process, 25%-oxidized 6-oxychitosan had the highest solubility, and the solubility decreased substantially from 0.72 to 0.15% as the degree of oxidation increased from 25 to 100%. Possibly, excessive incorporation of negative charges on chitosan resulted in the aggregation among 6-oxychitosan molecules by charge-charge interactions. The strongest cholic acid-retardation index (CRI, %) of highly soluble 25%-oxidized 6-oxychitosan was consistently observed until 24h of dialysis, which means the CRI is closely related to the water solubility of 6-oxychitosan. Therefore, the solubility improvement should be considered for enhancing the biological activity such as bile acid-binding capacity. Also, it was suggested that negative charge increase in chitosan structure above a certain level led to adverse effect on the binding capacity.
| Effects of silicon coating on bond strength of two different titanium ceramic to titanium
Ozcan, I. and H. Uysal (2005), Dent Mater 21(8): 773-9.
Abstract: OBJECTIVES: This study investigated the effect of silicon coating (SiO2) by magnetron sputtering on bond strength of two different titanium ceramics to titanium. METHODS: Sixty cast titanium specimens were prepared following the protocol ISO 9693. Titanium specimens were divided into two test and control groups with 15 specimens in each. Test groups were silicon coated by the magnetron sputtering technique. Two titanium ceramics (Triceram and Duceratin) were applied on both test (coated) and control (uncoated) metal specimens. The titanium-ceramic specimens were subjected to a three point flexural test. The groups were compared for their bond strength. SEM and SEM/EDS analyses were performed on the delaminated titanium surfaces to ascertain bond failure. RESULTS: The mean bond strength of Ti-Duceratin, Ti-Triceram, Si-coated Ti-Duceratin and Si-coated Ti-Triceram were 17.22+/-2.43, 23.31+/-3.18, 23.21+/-3.81 and 24.91+/-3.70 MPa, respectively. While the improvement in bond strength was 30% for Duceratin, it was statistically insignificant for Triceram. An adhesive mode of failure was observed in the Duceratin control group. In the silicoated Duceratin specimen, the bonded ceramic boundaries were wider but less than in the silicoated Triceram specimen. In the coated Triceram specimen, the ceramic retained areas were frequent and the failure mode was generally cohesive. SIGNIFICANCE: Silicon coating was significantly effective in both preventing titanium oxide layer formation and in improving bond strength for Duceratin. However, it was of less value for Triceram.
| Effects of soluble metals on human peri-implant cells
Hallab, N. J., S. Anderson, et al. (2005), J Biomed Mater Res A 74(1): 124-40.
Abstract: Despite reports associating tissue necrosis with implant failure, the degree to which processes, such as metal toxicity, negatively impact implant performance is unknown. We evaluated representative human peri-implant cells (i.e., osteoblasts, fibroblasts, and lymphocytes) when challenged by Al+3, Co+2, Cr+3, Fe+3, Mo+5, Ni+2, and V+3 chloride solutions (and Na+2 as a control) over a wide range of concentrations (0.01-10.0 mM). Cell responses were measured using proliferation assays, viability assays, and microscopic cell morphology assessments. Differential effects were found to be less a function of the cell type than of the composition and concentration of metal challenge. No preferential immunosuppression was demonstrated. Below 0.01 mM, no metal was toxic. The most toxic metals (i.e., Co, Ni, and V) reduced proliferation (IC50), and viability (LC50) and cell morphology of osteoblasts, fibroblasts, and lymphocytes by <50% at challenge concentrations <1 mM. All other metals tested required >5 mM to exact the same responses. Below 1 mM, these toxic metals also induced alterations in all cell morphology consisting of loss of filopodia or lamellipodia or changes in cell shape. Metals that were toxic at clinically relevant concentrations (less than previously reported values in peri-implant tissues/fluids) include Co (0.6 mM), Ni (0.8 mM), V (0.5 mM) for lymphocytes and Co (0.8 mM), V (0.3 mM), Al (1-5 mM), Fe (1-5 mM) for fibroblasts, and Co (0.8 mM), Ni (0.7 mM), V (0.1 mM) for osteoblasts. Only Co and V were toxic in vitro at concentrations below that detected in vivo in synovial fluid (V at 0.1 mM and Co at 0.8 mM for fibroblasts, and V at 0.4 mM and Co at 0.8 mM on osteoblasts). Thus, soluble Co and V released from Co- and Ti-based alloys, respectively, could be implicated as the most likely to mediate cell toxicity in the periprosthetic milieu.
| Effects of specific binding reactions on the partitioning behavior of biomaterials
Kopperschlager, G. (2000), Int Rev Cytol 192: 61-97.
Abstract: Affinity partitioning is a special branch of biomaterials separations using aqueous two-phase systems. It combines the capability of diverse biomolecules to partition in aqueous two-phase systems using the principle of biorecognition. As a result, the macromolecule exhibiting affinity for a certain ligand is transferred to that phase where the ligand is present. This chapter describes the present status of the theoretical background of this approach and the properties of various natural and artificial compounds which act as affinity ligands in liquid-liquid systems. The affinity partitioning of proteins (enzymes and plasma proteins), cell membranes, cells, and nucleic acids are described as typical examples. The results are discussed in terms of theoretical understanding and practical application.
| Effects of sterilization on implant mechanical property and biocompatibility
An, Y. H., F. I. Alvi, et al. (2005), Int J Artif Organs 28(11): 1126-37.
Abstract: This article concisely reviews the effects of sterilization on the mechanical properties and surface chemistries of implantable biomaterials. This article also summarizes the biological effects of the sterilization-related changes in the implant. Because there are so many different types of implant materials currently in use (including metals, polymers, and diverse biological materials), the response of tissue to these different materials varies dramatically. This review further discusses the effects of sterilization on in vivo and in vitro tissue response specifically to implantable metals and polyethylene, with the possibility of future biocompatibility testing of the implants sterilized with supercritical phase carbon dioxide sterilization.
| Effects of sucking acidic candy on whole-mouth saliva composition
Jensdottir, T., B. Nauntofte, et al. (2005), Caries Res 39(6): 468-74.
Abstract: Limited information is available on the effects of sucking acidic candies on saliva composition and the protective role of saliva in this relation. Therefore the aim of this study was to determine salivary effects of sucking acidic candies in vivo in relation to individual variations in whole-saliva flow rate (WSFR) and buffer capacity (WSbeta). Ten healthy young males (24 +/- 2 years) sucked a rhubarb-flavoured acidic hard-boiled candy with tartaric acid available on the Danish market. The whole saliva was collected into a closed system, regarding CO2, at different times as follows: firstly, unstimulated saliva for 5 min (baseline), secondly stimulated saliva for 4 min upon sucking the candy, and finally post-stimulated saliva for 10 min. Saliva pH was determined on a blood gas analyser and WSbeta was estimated from the saliva bicarbonate concentration obtained by the analyser and by ionic balance calculation. The erosive potential of the candy in saliva was estimated from the saliva pH values and degree of saturation with respect to hydroxyapatite (DS(HAp)). The results showed that saliva pH dropped from 6.5 (baseline) down to 4.5 at the fourth minute of sucking the candy, and returned to pH 6.5 five minutes after stimulation (post-stimulated). DS(HAp) decreased upon sucking the candy and saliva from all subjects became undersaturated with respect to HAp. Significant positive correlations were obtained between pH and WSFR (r(s) = 0.47; p < 0.05) and between pH and WSbeta (r(s) = 0.65; p < 0.01). In relation to WSbeta we found that 70% of the buffer capacity originating from the bicarbonate buffer system upon sucking the candy was exerted as phase buffering. We conclude that sucking this type of acidic candies changes whole-mouth saliva composition so that it may have erosive potential and that high WSFR and WSbeta have protective effects against these salivary changes.
| Effects of surface undulations of biphasic calcium phosphate tablets on human osteoblast behavior
dos Santos, E. A., A. B. Linhares, et al. (2005), J Biomed Mater Res A 74(3): 315-24.
Abstract: In this work, the in vitro behavior of human osteoblast cells on the undulated surfaces of biphasic calcium phosphate tablets was investigated. The tablets were produced by uniaxial pressing with convex cylindrical undulations occupying only half of the surface area; the other half was flat. Chemical and physical characterization was performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). XRD and FTIR analyses revealed the presence of hydroxyapatite (HA) and alpha-tricalcium phosphate (alpha-TCP) in a well-defined ratio. Moreover, microtopography, evaluated by SEM and AFM, was similar on the flat region and on that with undulations. However, surface undulations induced different cellular arrangements, confirming the influence of the macrotopography on the cells orientation.
| Effects of systematic variation of amino acid sequence on the mechanical properties of a self-assembling, oligopeptide biomaterial
Caplan, M. R., E. M. Schwartzfarb, et al. (2002), J Biomater Sci Polym Ed 13(3): 225-36.
Abstract: In order to elucidate design principles for biocompatible materials that can be created by in situ transformation from self-assembling oligopeptides, we investigate a class of oligopeptides that can self-assemble in salt solutions to form three-dimensional matrices. This class of peptides possesses a repeated sequence of amino acid residues with the type: hydrophobic/negatively-charged/hydrophobic/positively-charged. We systematically vary three chief aspects of this sequence type: (1) the hydrophobic side chains; (2) the charged side chains; and (3) the number of repeats. Each of these has been previously shown to influence the self-assembly properties of these materials. Employing a rheometric assay we measure the shear modulus of gels created from variants of each of these aspects. First, we observe order-of-magnitude changes in shear moduli when we vary oligopeptide length, with biphasic dependence on length. This result may be due to competition between, in short oligopeptides, additional repeats either increasing the diameter of the filaments or increasing the area of interaction between individual molecules and, in large oligopeptides, additional repeats allowing the oligopeptides to fold back upon themselves and decrease their effective length. Second, no statistically significant difference is observed among the hydrophobic variants, suggesting that hydrophobicity and steric overlap are unlikely to play a significant role in filament mechanical properties. Finally, in variation of the charged side chains we observe a small difference in the shear moduli that, if significant, may mean that decreasing the energetic penalty for dehydrating the charged side chains can lead to a stiffer matrix. Overall, we demonstrate that it is possible to achieve order-of-magnitude changes in shear modulus by simple variations of oligopeptide length, while the residue substitutions affect only self-assembly properties. Thus, diverse aspects of these molecules can be designed rationally to yield desirable materials properties of different types.
| Effects of the chemical structure and the surface properties of polymeric biomaterials on their biocompatibility
Wang, Y. X., J. L. Robertson, et al. (2004), Pharm Res 21(8): 1362-73.
Abstract: Polymeric biomaterials have extensively been used in medicinal applications. However, factors that determine their biocompatibility are still not very clear. This article reviews various effects of the chemical structure and the surface properties of polymeric biomaterials on their biocompatibility, including protein adsorption, cell adhesion, cytotoxicity, blood compatibility, and tissue compatibility. Understanding these aspects of biocompatibility is important to the improvement of the biocompatibility of existing polymers and the design of new biocompatible polymers.
| Effects of topically applied biomaterials on paranasal sinus mucosal healing
Maccabee, M. S., D. R. Trune, et al. (2003), Am J Rhinol 17(4): 203-7.
Abstract: BACKGROUND: Recently, nasal packing made of absorbable biomaterial has become increasingly popular. Although absorbable packs are effective for hemostasis, their impact on healing mucosa is unknown. Some have felt that a biocompatible sinus dressing actually may enhance healing, particularly in areas where the mucosa has been stripped. The aim of this study was to determine the effect of topical MeroGel and FloSeal on paranasal sinus mucosal healing in a rabbit model. METHODS: Bilateral maxillary sinuses of 12 New Zealand white rabbits were surgically opened and stripped of mucosa. The left maxillary sinus of six rabbits had sterile saline-soaked MeroGel placed in the antrum, and the other six rabbits received FloSeal. The right maxillary sinuses of all 12 animals were stripped and otherwise untreated to serve as stripped controls. The animals were killed at 2 weeks and specimens were examined by light microscopy. RESULTS: MeroGel-treated mucosa showed extensive fibrosis of the basal lamina and lamina propria, complete loss of surface epithelium, and loss of the mucociliary blanket. There was minimal resorption of the MeroGel, and MeroGel fibers were frankly incorporated into the regenerated epithelium, associated with an exuberant lymphocytic infiltrate. FloSeal-treated mucosa showed similar fibrosis of the basal lamina and lamina propria with loss of the mucociliary blanket, although to a lesser degree than the MeroGel- treated group. FloSeal showed similar incorporation into the healed mucosa with lymphocytosis. Controls showed expected submucosal gland reduction, lamina propria fibrosis, and loss of cilia, but the lamina propria fibrosis seen in the MeroGel and FloSeal groups was markedly more prominent. CONCLUSION: In a rabbit model, MeroGel and FloSeal appear to increase reactionary fibrosis of healing mucosa. These agents also appear to be incompletely resorbed and grossly incorporated into healing tissue. Mucosal healing may be impaired by the application of these agents.
| Effects of various calcium phosphate biomaterials on reparative dentin bridge formation
Jean, A., B. Kerebel, et al. (1988), J Endod 14(2): 83-7.
| Effects of x-ray irradiation on material properties
Smith, M. A., B. Lundahl, et al. (2005), Med Device Technol 16(3): 16-8.
Abstract: With a new commercial sterilisation technique about to enter the market, this article details a study that compared the effects of existing electron-beam irradiation with X-ray irradiation on different types of plastics commonly used in the manufacture of medical devices. The results are evaluated here.
| Efficacy and tolerability of long-acting injectable naltrexone for alcohol dependence: a randomized controlled trial
Garbutt, J. C., H. R. Kranzler, et al. (2005), Jama 293(13): 1617-25.
Abstract: CONTEXT: Alcohol dependence is a common disorder associated with significant morbidity and mortality. Naltrexone, an opioid antagonist, has been shown to be effective for treatment of alcohol dependence. However, adherence to daily oral pharmacotherapy can be problematic, and clinical acceptance and utility of oral naltrexone have been limited. OBJECTIVE: To determine efficacy and tolerability of a long-acting intramuscular formulation of naltrexone for treatment of alcohol-dependent patients. DESIGN, SETTING, AND PARTICIPANTS: A 6-month, randomized, double-blind, placebo-controlled trial conducted between February 2002 and September 2003 at 24 US public hospitals, private and Veterans Administration clinics, and tertiary care medical centers. Of the 899 individuals screened, 627 who were diagnosed as being actively drinking alcohol-dependent adults were randomized to receive treatment and 624 received at least 1 injection. INTERVENTION: An intramuscular injection of 380 mg of long-acting naltrexone (n = 205) or 190 mg of long-acting naltrexone (n = 210) or a matching volume of placebo (n = 209) each administered monthly and combined with 12 sessions of low-intensity psychosocial intervention. MAIN OUTCOME MEASURE: The event rate of heavy drinking days in the intent-to-treat population. RESULTS: Compared with placebo, 380 mg of long-acting naltrexone resulted in a 25% decrease in the event rate of heavy drinking days (P =.02) [corrected] and 190 mg of naltrexone resulted in a 17% decrease (P =.07). Sex and pretreatment abstinence each showed significant interaction with the medication group on treatment outcome, with men and those with lead-in abstinence both exhibiting greater treatment effects. Discontinuation due to adverse events occurred in 14.1% in the 380-mg and 6.7% in the 190-mg group and 6.7% in the placebo group. Overall, rate and time to treatment discontinuation were similar among treatment groups. CONCLUSIONS: Long-acting naltrexone was well tolerated and resulted in reductions in heavy drinking among treatment-seeking alcohol-dependent patients during 6 months of therapy. These data indicate that long-acting naltrexone can be of benefit in the treatment of alcohol dependence.
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