Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Suspensions”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed1976

Effect of polymers on dissolution from drug suspensions.

The effect of three viscosity grades of methylcellulose on the dissolution-dialysis rate of nitrofurantoin suspensions was investigated using a cell designed to provide a large surface area for dialysis. Apparent dialytic rate constants of drug dispersions and solutions were measured in 0.1 N HC1 and in pH 7.4 buffer. Samples containing methylcellulose had lower rates of dialysis, with the lowest rate being observed for samples in which the polymer was used as the suspending agent. The reduced rate of dialysis of the drug suspension containing methylcellulose is thought to be due to complexation of the drug in solution with the polymer as well as formation of microscopic regions of high viscosity surrounding the undissolved drug particles leading to a reduction in the dissolution rate of the drug. An empirical relationship was obtained to enable the estimation of the effective drug concentration in the dissolution chamber for drug dispersions. The method is based on utilizing dialysis rate data of drug solutions. This relationship could be used for comparing suspension formulations in terms of the amount of drug available for dialysis.

Chemistry, Pharmaceutical↗
PubMed1977

Dissolution profiles for multisized prednisolone acetate suspensions.

Particle-size measurements and in vitro dissolution characteristics of commercial and formulated suspensions of prednisolone acetate were determined using a resistance particle counter and a spinning filter apparatus, respectively. Significant differences in dissolution rates were noted for the commercial suspensions. Particle size affected dissolution but did not account for all observed variations in the dissolution rate. Formulation differences, specifically the presence of hydroxypropyl methylcellulose, in suspensions seemed to be important in dissolution.

Chemistry, Pharmaceutical↗
PubMed1982

Conductivity studies of suspension systems in different states of aggregation.

The electrical conductivity effects of dispersed, coagulated, and flocculated systems were investigated using sulfamerazine powder, an insoluble, hydrophobic drug to prepare the suspension systems. For the dispersed systems, a peak in conductivity was observed at a drug concentration between 5 and 15%. The critical coagulating concentration was defined as the concentration of drug at which a maximum in specific conductance was observed. At this concentration, a maximum number of charged particles were in the system. Coagulated suspensions showed higher conductance values than the dispersed systems at equivalent concentrations; however, the critical coagulating concentration value appeared to be the same. For flocculated suspensions there was an increase in conductance with drug concentration with no perceptible peak conductance value.

Chemistry, Pharmaceutical↗
PubMed1983

Studies on the absorption of practically water-insoluble drugs following injection VII: plasma concentration after different subcutaneous doses of a drug in aqueous suspension in rats.

The response patterns of the time profile of plasma drug level to dose elevation after subcutaneous administration of a practically water-insoluble drug in aqueous suspension were investigated. Equations to predict the plasma drug concentration at any time and the time Tmax at which it reaches the maximum (Cmax) at different doses were derived using empirical equations describing the subcutaneous absorption kinetic process as an input function of one- and two-compartment models. Computer simulation for the one-compartment model showed that Cmax tended to increase curvilinearly with dose elevation accompanied by the retardation of Tmax. It also showed that this tendency was noticeable in dose elevation at fixed injection volume and became more significant for drugs with a smaller absorption rate and/or a larger elimination rate. This suggested that a more effective means of raising the drug plasma level for such drugs would be improvement of the formulation. The validity of the information obtained from the simulation was confirmed by various subcutaneous administration experiments of N1-acetylsulfamethoxazole aqueous suspensions in rats. Further, the multiple-point injection method was ascertained to be useful for avoiding the nonlinear increase in plasma drug concentration with dose elevation appearing in the subcutaneous administration of aqueous suspensions.

Absorption↗
PubMed1985

Assay of nitrofurantoin oral suspensions contaminated with 3-(5-nitrofurfurylideneamino)hydantoic acid.

A reversed-phase high-performance liquid chromatographic (HPLC) analysis of oral suspensions for nitrofurantoin (1) and 3-(5-nitrofurfurylideneamino)hydantoic acid (2), an impurity derived from 1, is presented. The concentration of the impurity ranged from 20 to 300 micrograms/mL in several lots of commercial oral suspensions. Conversion of 1 to 2 with citrate buffer, an excipient in the oral suspension, was achieved; selective hydantoin ring cleavage was accomplished in preference to the generally observed cleavage at the azomethine linkage. The hydantoic acid 2 was synthesized and identified by NMR, IR, TLC, and elemental analysis.

Chromatography, High Pressure Liquid↗
PubMed2002

Effect of additives on electrokinetic properties of colloidal alumina suspension.

Additive interactions and their effects on electrokinetic properties of colloidal alumina suspension are presented in this study. Dibasic ammonium citrate (DAC), natural egg albumin, and octanol-2 are chosen as additives. The surface charge behavior of a 5% (w/v) colloidal alumina suspension in the presence of these additives has been studied in detail. The optimum dosage of DAC to have a stable suspension is found to be 3 mg/g of alumina whereas it is 105 and 164 mg/g of alumina for albumin and octanol-2, respectively. Albumin was found to be a better dispersant than DAC and interacts more strongly than DAC with the surface of alumina, while octanol-2 shows physisorbing characteristics. Turbidity measurements indicate that albumin and DAC interact. When the DAC : albumin molar ratio exceeds 10, the turbidity of the solution is higher than the turbidity of pure albumin, indicating the formation of complexes.

Albumins↗
PubMed1986

Multicenter, double-blind, placebo-controlled trial of terfenadine suspension in the treatment of fall-allergic rhinitis in children.

Children, aged 6 to 12 years, with fall-pollenosis symptoms, were evaluated for their response to a new antihistamine, terfenadine, in a multicenter (six centers) 1-week, double-blind, placebo-controlled trial. All had positive skin tests to grass/weed pollens and/or mold spores prevalent in the fall at each center. Patients were administered placebo or terfenadine as suspension on a randomized basis, with children weighing less than 30 kg receiving terfenadine suspension, 30 mg twice daily, and those weighing greater than 30 kg receiving 60 mg, twice daily. Of the 119 children enrolled, 79 received terfenadine and 40 received placebo. All but two (lost to follow-up) were included for the evaluation of drug safety, whereas 16 were excluded from the efficacy evaluation (11 receiving terfenadine and five receiving placebo) because of protocol noncompliance. Overall, varying degrees of control of symptoms were observed in 85% of the patients in the group taking terfenadine as compared to 60% in the group taking placebo. The symptoms of rhinorrhea, nasal congestion, and sneezing demonstrated the best response. There was no difference between the two groups in adverse events or side effects. Before and after treatment complete blood count, biochemical profile, and urinalysis revealed that there was no change from beginning to end and no difference between the groups. We conclude that terfenadine suspension is a safe, nonsedating antihistamine with an incidence of side effects no different from that of placebo. It is more effective than placebo in controlling symptoms of fall pollenosis in children.

Benzhydryl Compounds↗
PubMedDate not supplied

Respective effects of hindlimb suspension, confinement and spaceflight on myotendinous junction ultrastructure.

This study compares the effects of 14-day confinement and spaceflight with the respective effects of 8, 18 and 29-day hindlimb suspension on rat soleus and plantaris MTJ ultrastructure. Independently of the experimental situation, greater morphological changes were observed in the soleus as compared to the plantaris MTJ. 18 days of suspension and 14 days of confinement resulted in ultrastructural modifications of the digit-like processes in the soleus MTJ. Additional changes were observed in the myofibrils, microtendon and tendon after 29 days of suspension and 4 days of spaceflight. These results emphasize the influence of the intensity and duration of the muscle loading on the MTJ ultrastructure.

Animals↗
PubMed1992

High density barium sulfate suspension for MRI: optimization of concentration for bowel opacification.

In this in vitro study of a potential oral MRI contrast agent, barium sulfate suspension (BSS), the object was to examine the effect of varying barium sulfate concentration on signal intensity while keeping suspension additives the same; and to optimize the concentration of a specific preparation of BSS. A phantom was used to test suspensions with concentrations of barium sulfate ranging from 90% to 220% w/v. T1-weighted, T2-weighted, and gradient echo sequences all showed a decrease in signal as concentration was increased to 170%. Between 170% and 220%, the signal intensity was constant on the T1-weighted and T2-weighted sequences. With the proton density and gradient echo sequences, there was a slower rate of decline in the signal intensity in the 170 to 220% range of BSS concentrations. We conclude that BSS with a concentration in the range of 170% to 220% w/v is optimum for the specific preparation used. We speculate that the behavior of the signal-to-noise ratio with changing concentration is explained by factors including proton density, T1 relaxation enhancement, diffusion effects, and magnetic field inhomogeneity, depending on the particular pulse sequence used.

Administration, Oral↗
PubMed1992

A comparative study of controlled-release morphine (CRM) suspension and CRM tablets in chronic cancer pain.

This study compared the efficacy and the adverse effects of controlled-release morphine (CRM) suspension (SAR 213) and CRM tablets (Moscontin) in the treatment of cancer pain. This multicenter, randomized, double-blind, double-dummy, crossover study was carried out on 52 patients. Each patient received both study treatments given at an equivalent dosage of morphine during each of two 7-day periods. The primary outcome variable was the severity of pain assessed three times daily by means of a visual analogue scale. Secondary criteria of efficacy were the severity of pain assessed by verbal rating scale, the need for "rescue" doses of immediate-release morphine, treatment preference, and indices of quality of life (activity, mood, sleep). There were no statistically significant differences in the parameters assessed when comparing the two groups. This study shows that, when prescribed at the same doses, CRM suspension and CRM tablets have similar efficacy and adverse effects, as well as the same duration of action. The results of this first clinical study carried out on CRM suspension are especially relevant for patients with cancer pain who have difficulty swallowing.

Delayed-Action Preparations↗
PubMed2006

Pressure gradients and transport in the murine femur upon hindlimb suspension.

Interstitial fluid flow (IFF) is important in a number of processes, including stimulation of cells and nutrient and waste transport. In bone, it arises from the vascular pressure gradient between the medullary cavity and the lymphatic drainage at the periosteal surface and is enhanced by mechanical loading events. However, little is known about the pressure gradients experienced by bone cells in vivo and the role of the induced IFF in bone adaptation. This study investigated IFF changes in bone, in a disuse model and in ambulatory mice, from pressure gradients measured by telemetry, and by fluorescent tracers. The role of IFF-mediated transport of oxygen was assessed by the levels of hypoxic osteocytes in mouse femur after disuse by hindlimb suspension and with or without femoral vein ligation. Femoral intramedullary pressures in alert mice decreased to 77% upon hindlimb suspension and increased by 25% upon ligation, relative to baseline. To determine relative perfusion of cortical bone by IFF, the localization of intracardiac-injected fluorescent albumin conjugate with osteocytes was monitored. The number of osteocytic lacunae per bone area positive for Texas Red albumin was increased by 31% within 20-40 s, in the ligated femur compared to the contralateral sham femur. This confirmed that interstitial fluid flow was increased by femoral vein ligation and indicated that the increase was proportional to the pressure increase. Unloaded bone osteocytes were not hypoxic when compared to loaded controls and venous ligation did not alter these levels significantly. These results support the hypothesis that disuse by hindlimb suspension leads to decreased pressure gradients, which indicate lower IFF. Similarly, the increased pressure gradients, seen upon venous ligation, increased IFF from marrow to periosteum. While a decrease in intramedullary pressure in disuse suggests a decrease in IFF, this did not lead to hypoxia in osteocytes. We conclude that decreased oxygen convective transport in the mouse hindlimb disuse model does not account for cortical bone loss. This study is important in increasing our understanding of the mechanotransductory pathways involved in bone loading and unloading.

Animals↗
PubMed2006

Colloid vibration potential in a suspension of spherical colloidal particles.

When a sound wave is applied to a suspension of colloidal particles in an electrolyte solution, the colloid vibration potential (CVP) is produced in the suspension. The CVP is proportional to the difference between the mass density of the particles and that of the electrolyte solution. For a suspension of biological colloids such as cells, whose mass density is only slightly different from the electrolyte solution, its CVP becomes very small so that the magnitude of the ion vibration potential (IVP) of the electrolyte solution exceeds that of CVP. This causes difficulty in analyzing the CVP in biological systems. In the present paper, we show that even in such cases the phase of CVP becomes much greater than that of IVP.

Colloids↗
PubMed2005

Dynamic mechanical properties of suspensions of micellar casein particles.

Small micellar casein particles, so-called submicelles, were obtained by removing colloidal calcium phosphate from native casein by adding sodium polyphosphate. Aqueous submicelle suspensions were characterized using light scattering and rheology as a function of concentration and temperature. The casein submicelles behave like soft spheres that jam at a critical concentration (C(c)) of about 100 g L(-1). The viscosity does not diverge at C(c), but increases sharply, similarly to that of multiarm star polymers. C(c) increases weakly with increasing temperature, which leads to a strong decrease of the viscosity close to and above C(c). Concentrated submicelle suspensions show strong shear-thinning above a critical shear rate and the shear stress becomes independent of the shear rate. The critical shear rates at different temperatures and concentrations are inversely proportional to the zero-shear viscosity. At much higher shear rates, the shear stress fluctuates strongly in time indicating inhomogeneous flow. The frequency dependence of casein submicelle suspensions is characterized by elastic behavior at high frequencies (concentrations) and viscous behavior at low frequencies (concentrations).

Calcium Phosphates↗
PubMed2006

Photosensitized degradation of losartan potassium in an extemporaneous suspension formulation.

During development of an extemporaneous suspension formulation for losartan potassium, previously unknown degradation products were observed in experimental suspensions prepared in a commercial cherry syrup vehicle. These degradates increased rapidly when analytical solutions prepared from that suspension were exposed to ambient light. The structures of the degradates were determined using a combination of preparative HPLC, LC/MS, (13)C and (1)H NMR (1D and 2D), and mechanistic chemistry. Each degradate results from destruction of the imidazole ring of losartan. Formation of the two major degradates required exposure to light (UV or visible) and the presence of oxygen. Experiments using Rose Bengal (a singlet oxygen photosensitizer) and 1,4-diazabicyclooctane (DABCO; a singlet oxygen quencher) established that the major photodegradates are formed via the intermediacy of singlet oxygen. The identity of the photosensitizer in the formulation was not unequivocally determined; however, the experiments implicated the artificial flavoring in fulfilling this role.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2006

Osteopontin is associated with nuclear factor kappaB gene expression during tail-suspension-induced bone loss.

Osteoporosis due to unloading-induced bone loss is a critical issue in the modern aging society. Although the mechanisms underlying this phenomenon are largely unknown, osteopontin (OPN) is one of the critical mediators required for unloading-induced bone loss [M. Ishijima, S.R. Rittling, T. Yamashita, K. Tsuji, H. Kurosawa, A. Nifuji, D.T. Denhardt, and M. Noda, Enhancement of osteoclastic bone resorption and suppression of osteoblastic bone formation in response to reduced mechanical stress do not occur in the absence of osteopontin, J Exp Med, 193 (2001) 399-404]. To clarify the molecular bases for OPN actions, we carried out microarray analyses on the genes expressed in the femoral bone marrow cells in wild type and OPN-/- mice. The removal of the mechanical load induced bone loss in wild type, but not in OPN-/- mice, as previously reported. Expression analysis of 9586 cDNAs on a microarray system revealed that OPN deficiency blocked tail-suspension-induced expression of ten genes (group A). This observation was confirmed based on semi-quantitative RT-PCR analyses. On the other hand, expression of four genes (group B) was not altered by tail suspension in wild type but was enhanced in OPN-deficient mice. NF-kappaB p105 subunit gene (Nfkb1) was found in group A and Bax in group B. p53 gene expression was upregulated by tail suspension in wild type mice, but it was no longer observed in OPN-/- mice. These data indicate that OPN acts to mediate mechanical stress signaling upstream to the genes encoding apoptosis-related molecules, and its action is associated with alteration of the genes.

Animals↗
PubMed1963

Studies on rapidly frozen suspensions of yeast cells by differential thermal analysis and conductometry.

Few, if any, yeast cells survived rapid cooling to -196 degrees C and subsequent slow warming. After rapid freezing, the suspensions absorbed latent heat of fusion between -15 degrees and 0 degrees C during warming, and the relation between the amount of heat absorbed and the concentration of cells was the same as that in equivalent KCl solutions, indicating that frozen suspensions behave thermally like frozen solutions. The amount of heat absorbed was such that more than 80 per cent of the intracellular solution had to be frozen. The conductometric behavior of frozen suspensions showed that cell solutes were still inside the cells and surrounded by an intact cell membrane at the time heat was being absorbed. Two models are consistent with these findings. The first assumes that intracellular freezing has taken place; the second that all freezable water has left the cells and frozen externally. The latter model is ruled out because rapidly cooled cells do not shrink by an amount equal to the volume of water that would have to be withdrawn to prevent internal freezing.

Cell Count↗
PubMedDate not supplied

Computer simulation of concentrated fluid-particle suspension flows in axisymmetric geometries.

To investigate the particle migration effects and fluid-particle interaction occurring in the flow of highly concentrated fluid-particle suspensions, a numerical method has been developed for effective computer simulation in arbitrary axisymmetric geometries. In the mathematical flow model the suspension is treated as a generalized Newtonian fluid where the effective flow properties of the suspension (density and viscosity) are determined by the local volume fraction of the particles. The description of the particle motion is governed by a modified transport equation with diffusion coefficients accounting for the effects of shear-induced particle migrations. The strongly coupled system of flow and transport equations is solved by applying the Galerkin finite element method and a velocity-pressure projection scheme. The numerical results in tube flow demonstrate strong particle migration towards the center of the tube and an increasing blunting of the velocity profiles which is in good agreement with an available analytical solution. In the case of flow through a stenosed tube model, particle concentration is lowest at the site of maximum constriction whereas a strong accumulation of particles can be seen in the recirculation zone downstream of the stenosis.

Computer Simulation↗
PubMed2003

Gas chromatographic method for determining very long chain fatty acids that compose D003 in aqueous suspensions from 20 to 200 mg/ml, used in pharmacological and toxicological studies.

D003 is a natural mixture of fatty acids (C(24:0) to C(36:0)), which shows antiplatelet, antithrombotic, and cholesterol-lowering effects in experimental models. A specific gas chromatographic method, using a BPX-5 wide-bore column and 1-nonadecanoic acid as internal standard, was developed and validated to determine the content of D003 in 20-200 mg/ml aqueous suspensions, which are used in pharmacological and toxicological studies. Fatty acids were extracted with chloroform and converted to methyl esters derivatives using 5% aqueous HCl-methanol. The method was linear for suspensions ranging from 10 to 250 mg/ml (correlation coefficient=0.9998) and showed a good accuracy, with average recoveries (98.5-101.28%) no significantly different from 100%, according to the Student t-test (P=0.05). The RSDs were <2.2%, indicating that the method has a good repeatability. The intermediate precision was good too, with RSDs between 1.20 and 2.10%. This method is suitable for quality control of these suspensions.

Chromatography, Gas↗