Stability and antimicrobial effectiveness of treprostinil sodium in Sterile Diluent for Flolan.

INTRODUCTION: Long-term intravenous infusion of epoprostenol and treprostinil for treatment of pulmonary arterial hypertension (PAH) via a central venous catheter is associated with the risk of bloodstream infection (BSI). While several potential explanations exist for possible differences in BSI incidence among intravenous prostanoids, one hypothesis suggests that the alkaline pH of epoprostenol in Sterile Diluent for Flolan (SDF) has greater antimicrobial activity compared with the neutral pH of other common diluents such as sterile saline or water, which have been used for treprostinil. METHODS: The chemical stability and antimicrobial activity of 4 microg/ml and 130 microg/ml treprostinil in SDF were assessed according to United States and European Pharmacopeia. RESULTS: At both concentrations, treprostinil in SDF remained stable after incubation at 40 degrees C and ambient relative humidity for up to 52 h. Solution pH also remained stable (range 10.4-10.6), and the solutions were essentially free of particulate at all time points examined. Antimicrobial activity was measured using an antimicrobial effectiveness test after inoculation with five species of bacteria, yeast and mould. The antimicrobial activity of both concentrations of treprostinil met United States Pharmacopeia requirements. Further, the antimicrobial activity of treprostinil in SDF against gram-negative bacteria (> 4 log(10) reductions) exceeded that previously described for treprostinil in sterile saline. CONCLUSION: These results suggest that dilution of treprostinil with the alkaline solution SDF may reduce the risk of infection from inadvertent patient contamination compared with dilution of treprostinil in sterile saline.

A novel catheter system for totally implantable intravenous drug therapy: assessment of catheter function and patency with trepostinil therapy.

BACKGROUND: Catheter failure, either due to dislodgment, occlusion or infection is the leading complication of chronic intravenous drug therapy. Better drug delivery techniques are required to advance life saving therapies that require this delivery method. This study evaluated the chronic performance of a fully implantable drug delivery system that incorporates a novel intravenous catheter. The system was designed to reduce complications associated with intravascular drug delivery including catheter occlusion, breakage, migration, and infection. METHODS: Twelve canines were implanted with a novel central venous catheter (Model 10642; Medtronic, Minneapolis, MN) connected to a totally implanted programmable drug pump (Model 8637 SynchroMed II, Medtronic). The drug delivery systems infused saline (n=6) or treprostinil (n=6) (Remodulin; United Therapeutics, Research Triangle Park, NC) for either 12 or 26 weeks at a continuous flow rate of 540 microL/day. Catheter performance was assessed at 0 (implant), 2, 4, 8, 12, 16, 20, and 24 weeks by quantifying delivery pressure, delivery volume and steady state Treprostinil concentrations. RESULTS: All catheters remained patent and free of complications for the duration of the study. Analysis of pressure waveforms during bolus delivery showed low and unchanged catheter resistance throughout the study. Measurement of pump delivery volume accuracy showed that the delivered volume was statistically similar to the calculated delivery (product of flow rate and elapsed time). Measurement of plasma treprostinil levels showed stable concentrations over the study period. There were no catheter dislodgments or breakage. Pathology showed all catheters free from fibrosis and thrombus and minimal changes to the vascular endothelium. CONCLUSIONS: The Model 10642 vascular catheter along with the SynchroMed II implantable drug delivery system showed promising performance in a chronic animal model.

Development of a topically active imiquimod formulation.

The purpose of this work was to develop a topical formulation of imiquimod, a novel immune response modifier, to induce local cytokine production for the treatment of external genital and perianal warts. A pH-solubility profile and titration data were used to calculate a pKa of 7.3, indicative of a weak base. Solubility experiments were conducted to identify a solvent that dissolves imiquimod to achieve a 5% formulation concentration. Studies to select surfactants, preservatives, and viscosity-enhancing excipients to formulate an oil-in-water cream indicated that fatty acids were the preferred solvent for topical imiquimod formulations, and isostearic acid (ISA) was selected. A relationship existed between the fatty acid composition of four commercially available ISA sources and the solubility of imiquimod. A combination of polysorbate 60, sorbitan monostearate, and xanthan gum was used to produce a physically stable cream. The preservative system included parabens and benzyl alcohol to meet the USP criteria for preservative activity. An in vitro method was developed to demonstrate that imiquimod was released from the formulation. Topical application of the formulation induced local cytokine activity in mice.

An unusual host-parasite relationship: the growth hormone-like factor from plerocercoids of spirometrid tapeworms.

Accelerated body growth is associated with experimental infections with the plerocercoid stage of the pseudophyllidean tapeworm, Spirometra mansonoides. The growth response is due to a protein that is synthesized and released by plerocercoids in the host. Plerocercoid growth factor (PGF) is transported by the blood, interacts with growth hormone (GH) receptors and mimics many of the biological actions of GH. Purification and characterization of PGF reveals that the GH-like factor is a 27.5 kDa cysteine proteinase. Sequencing of a cDNA for PGF revealed 40-50% homology to mammalian cysteine proteinases, but no homology to any GH. The GH-like factor/proteinase is found in abundance in the tegument of plerocercoids where the proteinase activity would be most effective in aiding tissue invasion, and possibly evasion, of the host's immune response to the parasite. The advantage of the GH-like activity is less clear, but it may affect the species survival by suppressing specific elements of the host's immune system and by improving the probability that the infected host will be eaten by a definitive host by increasing morbidity and/or mortality, conditions which are associated with long-term exposure to elevated levels of GH and PGF.

The growth factor from plerocercoids of Spirometra mansonoides is both a growth hormone agonist and a cysteine proteinase.

Plerocercoids of the tapeworm Spirometra mansonoides produce a substance that stimulates growth of experimental hosts. We report purification of plerocercoid growth factor (PGF) to homogeneity by a process involving isolation and solubilization of plerocercoid membranes, isoelectric point selection by chromatofocusing chromatography or preparative isoelectric focusing, and anion-exchange chromatography. A radioreceptor assay (RRA) for human growth hormone (hGH) was used to detect PGF and purity of the 27.5-kDa protein was judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Proteolytic activity was detected in the 27.5-kDa protein by gelatin substrate PAGE. Characterization of PGF as a neutral cysteine proteinase was based on substrate and inhibitor specificities and dependence on pH and thiol-containing reagents. The association of hGH agonist and proteinase activities was shown by comparing RRA and hydrolytic activities in the presence and absence of the cysteine proteinase inhibitor E-64.

Drug transport across nylon 610 films: influence of synthesis variables.

Nylon 610 is a hydrophilic polymer with considerable potential as a membrane for drug microencapsulation. To better understand drug transport through such membrane, the influence of the solvents and monomers used in the synthesis of nylon films were examined using a full factorial study. Nylon 610 films were synthesized by an interfacial polycondensation reaction using hexamethylenediamine (HD) in the water phase and sebacoyl chloride (SC) in the organic phase, which was a solvent blend of chloroform and trichlorotrifluoroethane at ratios of 1:1, 1:4, and 4:1. Monomer concentrations studied were 0.2, 0.4, and 0.6 M with respect to their appropriate phase, while the monomer ratios were 1:1, 3:1, and 1:3. The molecular weight, porosity, thickness, and crystallinity of the films were characterized. The transport of potassium chloride, hydrocortisone, and m-cresol was studied at 25 degrees C as a function of the synthesis variables. Potassium chloride was selected to measure the porosity of the membrane. Hydrocortisone and m-cresol, a known solvent for nylon 610, were used to study pore and solution-diffusion transport, respectively. The molecular weight of the films was proportional to the chloroform concentration. As the molecular weight increased, film thickness, porosity, and hydrocortisone permeability increased. As the molecular weight decreased, film thickness and porosity decreased, while m-cresol permeability increased. These results can be explained on the basis of HD ability to readily partition into a good solvent such as chloroform permitting high molecular weight polymer to form before precipitation.