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PubMed2001

The effect of particle size on bioavailability in cyclosporine preparations based on submicron dispersions.

The effect of particle size on bioavailability of 9 different formulations with cyclosporine A was studied. A common feature of all the formulations was the ability to form submicron dispersions under dilution. The composition of individual formulations was chosen in such a way that they were based on same or similar excipients. For each formulation, pharmacokinetic study was carried out in beagle dogs. On groups of 10 dogs, the average AUC was evaluated. Particle size of formulations under dilution in water was measured by laser scattering method. According to the results of particle size measurement, the formulations were sorted out into groups of similar particle size distribution by use of two methods of multivariate statistical analysis. The average AUC within groups and between-groups was compared, and the effect of particle size on bioavailability was evaluated.

Animals↗
PubMed2000

Freeze-drying of polycaprolactone and poly(D,L-lactic-glycolic) nanoparticles induce minor particle size changes affecting the oral pharmacokinetics of loaded drugs.

The present study was geared at identifying the conditions to stabilize poly (D,L-lactic-glycolic) (PLGA) and polycaprolactone (PCL) nanoparticles (NP) by freeze-drying with several cryoprotective agents. Differential scanning calorimetry and freeze-thawing studies were used to optimize the lyophilization process. These studies showed that all samples were totally frozen at -45 degrees C and evidenced the necessity of adding sucrose, glucose, trehalose or gelatine to preserve the properties of NP regardless of the freezing procedure. However, only 20% sucrose and 20% glucose exerted an acceptable lyoprotective effect on PLGA and PCL NP, respectively. Nonetheless, the final to initial size ratios ( approximately 1.5) indicated that particle size was slightly affected in both cases. In vivo studies with CyA-loaded PCL NP whose sizes matched those obtained after NP preparation (100 nm) and after being lyophilized (160 nm) showed that the changes of particle size might have some relevance on drug pharmacokinetics. The MRT was significantly (P<0.05) modified after an oral CyA dose of 5 mg/kg and the treatment with 160-nm sized CyA-loaded NP produced a higher drug partition into the liver of Wistar rats potentially affecting the toxic and immunosuppressive profile of the drug. Therefore, although the particle size changes induced by NP lyophilization were slight, they need to be carefully evaluated and cannot be neglected.

Administration, Oral↗
PubMed2006

Low-density lipoprotein (LDL) particle size in healthy prepubertal children: the STRIP study.

BACKGROUND: Small, dense low-density lipoprotein (LDL) particles (diameter < 255 Angstrom) are highly atherogenic, and in adults they are associated with an elevated risk of coronary heart disease (CHD). AIM: To examine possible contributors to LDL particle size distribution in healthy prepubertal children. METHODS: We determined LDL particle size in 176 7-y-old children by non-denaturing polyacrylamide gel electrophoresis. Children were divided into two groups in two ways: by using the median of their average LDL particle diameter (261.2 Angstrom) or by using the LDL peak particle diameter (255 Angstrom) as the cut-off point. RESULTS: Children with smaller LDL particles did not significantly differ from children with larger LDL particles with respect to anthropometric variables, serum triglyceride concentration (in all children < 1.7 mmol/L), apoE phenotype, amount and quality of dietary fat, or child's family history of CHD. Furthermore, LDL particle size did not correlate with any of the anthropometric, lipid or nutrient variables. Children with average LDL particle size below the median had higher serum insulin and lower high-density lipoprotein (HDL) cholesterol and apoA-1 concentrations than those with LDL particle size above the median. CONCLUSION: Our data suggest that many factors related to the development of small, dense LDL particles might have their major impact after the onset of puberty.

Anthropometry↗
PubMed1998

The role of the drug/excipient particle size ratio in the percolation model for tablets.

PURPOSE: In previous papers, a linear relationship between drug particle size and drug percolation threshold was found in inert matrix tablets. The main objectives of the present work are: to study the influence of the excipient particle size on the drug percolation threshold and to investigate if the change in the drug percolation threshold is due either to the absolute or to the relative drug particle size. METHODS: Matrix tablets have been prepared using KCl (7 different particle size fractions) as a drug model and Eudragit RS-PM (4 granulommetric fractions) as matrix forming material. In vitro release assays were carried out on the 66 lots of tablets. The drug percolation thresholds were estimated following the method of Bonny and Leuenberger. RESULTS: The particle size of the excipient has shown an opposite effect to the drug size on the drug percolation threshold. Nevertheless, the influence of drug and excipient sizes on the drug percolation threshold are of the same magnitude. CONCLUSIONS: The drug percolation threshold depends linearly on the relative drug particle size. This finding is in agreement with percolation theory and can facilitate the use of the percolation threshold as a preformulation parameter to improve the pharmaceutical dosage forms design.

Chemistry, Pharmaceutical↗
PubMed1998

Influence of hydroxyapatite particle size on bone cell activities: an in vitro study.

Over the past decade, a large number of biomaterials have been proposed as artificial bone fillers for repairing bone defects. The material most widely used in clinical medicine is hydroxyapatite. The aim of our investigation was to study the effect of hydroxyapatite size mechanism on osteoblasts. The osteoblasts were cultured in vitro with 0.1% (1 mg/mL) of various sized hydroxyapatite particles (0.5-3.0, 37-63, 177-250, and 420-841 microm) for 1 h, 3 h, 1 day, 3 days, and 7 days. The results showed that adding hydroxyapatite particles to osteoblast cultures can significantly affect osteoblast cell count. Osteoblast populations decreased significantly. Osteoblast mean surface areas also changed significantly. Transforming growth factor-beta1 (TGF-beta1) concentrations in culture medium decreased significantly with the addition of hydroxyapatite particles. Prostaglandin E2 (PGE2) concentrations in medium increased significantly. The changes in TGF-beta1 and PGE2 concentration were more significant and persisted longer in smaller-particle groups. The inhibitory effects of hydroxyapatite particles on osteoblast cell cultures were mediated by the increased synthesis of PGE2. Caution should be exercised before using a hydroxyapatite product which could easily break down into fine particles.

Alkaline Phosphatase↗
PubMed1999

Trace elements total content and particle sizes distribution in the air particulate matter of a rural-residential area in north Italy investigated by instrumental neutron activation analysis.

The concentrations (ng/m3) of more than 30 trace elements have been determined in the total air particulate of a rural-residential area in north Italy. By collecting the aerosols with multistage impactors the distribution of the trace elements in the different size-fractionated particles has been also investigated. The fine 'inhalable' fraction with particles of less than 10 microns in equivalent aerodynamic diameter (PM10) as well as the subsequent finest 'respirable' fractions with particles of 0-1.1 microns (alveolar), 1.1-4.6 microns (bronchial) and 4.6-9 microns (tracheo-pharynx) have been analyzed and evaluated. Apart from Pb, Cd and, in some cases, Ni and Cu which have been determined by ETAAS (electrothermal atomic absorption spectroscopy), all measurements have been carried out by instrumental neutron activation analysis (INAA).

Air Pollutants↗
PubMed1975

The effect of particle size on absorption of inhaled lead.

Baboons were exposed to dust clouds of Ph3O4 of different size distribution but of the same total gravimetric concentration. Blood samples were taken immediately after each exposure of 4 hours and the total blood lead was determined. The exposure to the lead-bearing dust was stopped after four weeks, but the blood sampling continued for another six weeks. Graphs are presented comparing the patterns of lead absorption obtained with different sized lead particles. The coarser lead particles resulted in a higher blood lead concentration than the finer.

Absorption↗
PubMed2002

Effects of particle size of alfalfa-based dairy cow diets on site and extent of digestion.

Effects of ratio of alfalfa silage to alfalfa hay and forage particle size on nutrient intakes, site of digestion, rumen pools, and passage rate of ruminal contents were evaluated in a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. The diets consisted of 60% barley-based concentrate and 40% forage made up either of 50:50 or 25:75 of alfalfa silage:alfalfa hay and alfalfa hay was either chopped or ground. Lactating dairy cows surgically fitted with ruminal and duodenal cannulas were used and offered ad libitum access to a total mixed ration. Intakes of nutrients were increased by increasing ratio of silage to hay but were not affected by particle size of forage. Change in ratio of silage to hay of diets did not affect site and extent of digestion. However, increased forage particle size of the diets improved digestibility of fiber and N in the total tract, and as well as digestibility of organic matter, starch, and acid detergent fiber in the intestine. There was a shift of starch digestion from the rumen to the intestine when forage particle size was increased, although total digestion of starch was not changed. Ruminal microbial protein synthesis and microbial efficiency also improved with increasing forage particle size. Cows fed ground hay versus chopped hay had significantly lower rumen wet mass regardless of the ratio of silage to hay. Reduced forage particle size also lowered ruminal nutrient pool size for cows fed the high silage diet. Ruminal passage rates of liquid and solid were decreased by reducing the ratio of silage to hay, and retention time of solids in the total tract was shortened by reducing forage particle size. These results indicate that manipulating ratio of silage to hay in the diets of dairy cows changed feed intake but had little effect on digestion. In contrast, increased forage particle size in dairy cow diets improved fiber digestion and microbial protein synthesis in the rumen, and shifted starch digestion from the rumen to the intestine. Dietary particle size, expressed as physically effective neutral detergent fiber, was a reliable indication of ruminal microbial protein synthesis and nutrient digestion.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Low-density lipoprotein particle size, insulin resistance, and proinsulin in a population sample of 58-year-old men.

The relationship between insulin sensitivity and low-density lipoprotein (LDL) peak particle size was examined in 104 clinically healthy 58-year-old men recruited from the general population. Insulin sensitivity was measured by the euglycemic hyperinsulinemic clamp method with adjustment for lean body mass. LDL peak particle size was determined by gradient gel electrophoresis, and insulin, proinsulin, and 32,33 split proinsulin were determined by 2-site immunoradiometric assays. The results showed that 16 subjects (15%) had pattern B, with a predominance of small LDL particles. These cases and a small LDL peak particle size were characterized by the features of the insulin resistance syndrome, ie, general and central obesity, elevated diastolic blood pressure, low serum concentrations of high-density lipoprotein (HDL) and apolipoprotein A1 (apoA1), increases in serum triglycerides and circulating insulin peptides, and low insulin-mediated glucose uptake. The correlation between insulin sensitivity and LDL peak particle size was significant (r = .33, P = .001) and independent of obesity. In a traditional multiple regression analysis, LDL peak particle size was independently associated not with insulin-mediated glucose uptake but with circulating triglycerides and HDL cholesterol, which together explained 67% of the variability in LDL particle size (P = .000). Of all insulin peptides, only proinsulin showed an independent relation to LDL peak particle size, but it disappeared after adjustment for other variables. We conclude that a small LDL particle size was associated with insulin resistance among these clinically healthy men, but this was not independent of serum triglycerides and HDL cholesterol. Serum proinsulin was more directly related to LDL particle size than insulin.

Glucose↗
PubMed2004

Effect of particle size on mixing degree in dispensation.

By using lactose colored with erythrocin, we examined the effect of particle size on mixing degree during the preparation of triturations with a mortar and pestle. We used powders with different distributions of particle sizes, i.e., powder that passed through 32-mesh but was trapped on a 42-mesh sieve (32/42-mesh powder), powder that passed through a 42-mesh sieve but was trapped on a 60-mesh sieve (42/60-mesh powder), powder that passed through a 60-mesh sieve but was trapped on a 100-mesh sieve (60/100-mesh powder), and powder that passes through a 100-mesh sieve (> 100-mesh powder). The mixing degree of colored powder and non-colored powder whose distribution of particle sizes was the same as that of the colored powder was excellent. The coefficient of variation (CV) value of the mixing degree was 6.08% after 40 rotations when colored powder was mixed with non-colored powder that both passed through a 100-mesh sieve. The CV value of the mixing degree was low in the case of mixing of colored and non-colored powders with different particle size distributions. After mixing, about 50% of 42/60-mesh powder had become smaller particles, whereas the distribution of particle sizes was not influenced by the mixing of 60/100-mesh powder. It was suggested that the mixing degree is affected by distribution of particle sizes. It may be important to determine the mixing degrees for drugs with narrow therapeutic ranges.

Chemical Phenomena↗
PubMed2001

Effects of digestion protocols on the isolation and characterization of metal-metal wear particles. I. Analysis of particle size and shape.

Isolation of metal wear particles from hip simulator lubricants or tissues surrounding implants is a challenging problem because of small particle size, their tendency to agglomerate, and their potential for chemical degradation by digestion reagents. To provide realistic measurements of size, shape, and composition of metal wear particles, it is important to optimize particle isolation and minimize particle changes due to the effects of the reagents. In this study (Part I of II), transmission electron microscopy (TEM) was used to examine and compare the effects of different isolation protocols, using enzymes or alkaline solutions, on the size and shape of three different types of cobalt-based alloy particles produced from metal-metal bearings. The effect on particle composition was examined in a subsequent study (Part II). Large particles (<1200 nm) were generated by dry abrasion of CoCrMo alloy against itself and small particles (<300 nm) were generated by hip simulator testing of a metal-metal implant pair in the presence of either distilled-deionized water or a 95% bovine serum solution. The reagents changed particle size and to a lesser extent particle shape. For both large particles and small particles generated in water, the changes in size were more extensive after alkaline than after enzymatic protocols and increased with alkaline concentration and time in solution, up to twofold at 2 h and threefold at 48 h. However, when isolating particles from 95% serum, an initial protective effect of serum proteins and/or lipids was observed. Because of this protective effect, there was no significant difference in particle size and shape for both oval and needle-shaped particles after 2 h in 2N KOH and after enzymatic treatments. However, round particles were significantly smaller after 2 h in 2N KOH than after enzymatic treatments. Particle composition may also have been affected by the 2N KOH treatment, as suggested by a difference in particle contrast under TEM, an issue examined in detail in Part II.

Animals↗
PubMed2000

Effect of rise in simulated inspiratory flow rate and carrier particle size on powder emptying from dry powder inhalers.

The purpose of this study was to evaluate the effect of carrier particle size and simulated inspiratory flow increase rate on emptying from dry powder inhalers (DPIs). Several flow rate ramps were created using a computer-generated voltage signal linked to an electronic proportioning valve with a fast response time. Different linear ramps were programmed to reach 30, 60, 90, and 120 L/minute over 1, 2, or 3 seconds. At the lower flow rates, 100-ms and 500-ms ramps were also investigated. Three DPIs, Spinhaler, Rotahaler, and Turbuhaler, were used to test the effect of flow rate ramp on powder emptying. To test the effect of carrier particle size, anhydrous lactose was sieved into 3 particle sizes, and 20 mg of each was introduced into #2 and #3 hard gelatin capsules for Spinhaler and Rotahaler, respectively. Emptying tests were also carried out using the on/off solenoid valve described in the United States Pharmacopeia (USP) (resulting in no ramp generation). Powder emptying increased from 9% to 46% for Rotahaler and 69% to 86% for Spinhaler from the shallowest (3 seconds to reach peak flow) to the 100-ms ramp for the 53- to 75 microm lactose size range at 30 L/minute. Similar trends were observed for larger particle size fractions at the same flow rate. However, at higher airflow rates (60, 90, and 120 L/minute), there was no significant increase in percentage of emptying within the ramps for a particular particle size range. Trends observed were similar for placebo-filled Turbuhaler and commercially available Rotacaps used with Rotahaler, with the steepest ramp demonstrating more complete emptying. Percentage of powder emptying determined by the USP solenoid valve overestimated the emitted dose compared with the ramp method at 30 L/minute for all 3 devices. Results indicate that there is a significant difference in powder emptying at 30 L/minute from the shallowest to the steepest ramp within a particular size range. Within a particular particle size range, the USP method produced more complete emptying than even the steepest ramp, especially at the lower flow rates. Thus, when the USP device is used to estimate DPI emptying at lower flow rates, the results are likely to overestimate DPI performance significantly.

Analysis of Variance↗
PubMed2006

Cobalt particle size effects in the Fischer-Tropsch reaction studied with carbon nanofiber supported catalysts.

The influence of cobalt particle size in the range of 2.6-27 nm on the performance in Fischer-Tropsch synthesis has been investigated for the first time using well-defined catalysts based on an inert carbon nanofibers support material. X-ray absorption spectroscopy revealed that cobalt was metallic, even for small particle sizes, after the in situ reduction treatment, which is a prerequisite for catalytic operation and is difficult to achieve using traditional oxidic supports. The turnover frequency (TOF) for CO hydrogenation was independent of cobalt particle size for catalysts with sizes larger than 6 nm (1 bar) or 8 nm (35 bar), while both the selectivity and the activity changed for catalysts with smaller particles. At 35 bar, the TOF decreased from 23 x 10(-3) to 1.4 x 10(-3) s(-1), while the C5+ selectivity decreased from 85 to 51 wt % when the cobalt particle size was reduced from 16 to 2.6 nm. This demonstrates that the minimal required cobalt particle size for Fischer-Tropsch catalysis is larger (6-8 nm) than can be explained by classical structure sensitivity. Other explanations raised in the literature, such as formation of CoO or Co carbide species on small particles during catalytic testing, were not substantiated by experimental evidence from X-ray absorption spectroscopy. Interestingly, we found with EXAFS a decrease of the cobalt coordination number under reaction conditions, which points to reconstruction of the cobalt particles. It is argued that the cobalt particle size effects can be attributed to nonclassical structure sensitivity in combination with CO-induced surface reconstruction. The profound influences of particle size may be important for the design of new Fischer-Tropsch catalysts.

Journal Article↗
PubMed2003

Effects of particle size of alfalfa-based dairy cow diets on chewing activity, ruminal fermentation, and milk production.

Effects offorage particle size measured as physically effective NDF and ratio of alfalfa silage to alfalfa hay of diets on feed intake, chewing activity, particle size reduction, salivary secretion, ruminal fermentation, and milk production of dairy cows were evaluated using a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. The diets consisted of 60% barley-based concentrate and 40% forage, comprised either of 50:50 or 25:75 of alfalfa silage:alfalfa hay, and alfalfa hay was either chopped or ground. Various methods were used to determine physically effective NDF content of the diets. Cows surgically fitted with ruminal and duodenal cannulas were offered ad libitum access to these total mixed diets. The physically effective NDF content of the diets was significantly lower when measured using the Penn State Particle Separator than when measured based on particles retained on 1.18-mm screen. Intake of DM was increased by increasing the ratio of silage to hay but was not affected by physically effective NDF content of diets. Eating time (hours per day) was not affected by the physically effective NDF content of diets, although cows spent more time eating per unit of DM or NDF when consuming high versus low alfalfa hay diets. Ruminating time (hours per day) was increased with increased physically effective NDF content of the diets. Rumen pH was affected more by changing dietary particle size than altering the ratio of silage to hay. Feeding chopped hay instead of ground hay improved ruminal pH status: time during which ruminal pH was above 6.2 increased and time during which ruminal pH was below 5.8 decreased. Milk production was increased by feeding higher concentrations of alfalfa silage due to increased DM intake, but was not affected by dietary particle size. Feed particle size, expressed as mean particle length or physically effective NDF was moderately correlated with ruminating time but not with eating time. Although physically effective NDF and chewing time were not correlated to mean rumen pH, they were negatively correlated to the area between the curve and pH 5.8, indicating a positive effect on reducing the risk of acidosis. Milk fat content was correlated to rumen pH but not to physically effective NDF or chewing activity. These results indicate that increasing physically effective NDF content of the diets increased chewing activity and improved rumen pH status but had limited effect on milk production and milk fat content.

Animal Nutritional Physiological Phenomena↗
PubMed1996

Particle size and drug interactions of injectable corticosteroids used in ophthalmic practice.

PURPOSE: The aim of this study is to compare the particle sizes of commercially available corticosteroids for intralesional injection to manufacturers' specifications and to evaluate changes in size when mixed with other steroids and other commonly used solutions. METHODS: The particle sizes of dexamethasone sodium phosphate, methylprednisolone acetate, triamcinolone acetonide, and betamethasone sodium phosphate and beta-methasone acetate were measured with the Coulter counter. Each steroid was mixed with each of the others, lidocaine, and lidocaine with epinephrine, then measured immediately and after 1 hour to determine the effect on particle size. RESULTS: All steroids showed accurate manufacturer specifications. Dexamethasone showed an increase in particle size when mixed with lidocaine alone, immediately and after 1 hour. Triamcinolone showed an increase in particle size only after 1 hour after mixture with lidocaine alone. Triamcinolone, dexamethasone, and methylprednisolone particles increased in size when mixed with lidocaine and epinephrine. Dexamethasone and triamcinolone showed an additional increase in size when allowed to sit for 1 hour after mixture with lidocaine and epinephrine. Mixing steroids caused no increase in particle size. CONCLUSION: Because an increase in the number of particles greater than 20 microns in a solution also increases the likelihood of vascular occlusion, the authors urge care in the mixing of these drugs, especially with lidocaine and epinephrine. If mixture is necessary, the authors recommend that injection take place immediately subsequent.

Anesthetics, Local↗
PubMed1989

Pharmacokinetics of norethindrone: effect of particle size.

In 24 healthy women between the ages of 19 and 35 years who had not used oral contraceptive preparations for at least 60 days, it was found that the smaller the particle size of norethindrone (NET) administered, the higher was the plasma NET level obtained. Three different preparations having particle sizes of NET smaller than 250 microns, 44 microns or 10 microns were tested in a crossover pattern. The time required to reach maximum plasma concentration (Tmax) became shorter with decreasing particle size, 1.69 hr, 1.52 hr and 1.06 hr, respectively. As particle size was reduced, the maximum NET plasma concentration (Cmax) increased for the 3 different 1 mg NET preparations, i.e. 8.66 ng/ml, 10.53 ng/ml and 15.73 ng/ml. A trial with a 2 mg NET preparation made with NET utilizing the 44 microns same material displayed a Tmax similar to the 1 mg NET preparation having the same particle size while the Cmax reached a level of 17.56 ng/ml. The area under the plasma concentration versus time curve from 0-24 hrs and the extrapolated total area under the curve, increased with decreasing particle size. The use of a smaller particle size allows for more rapid dissolution or oral contraceptive tablets when measured in vitro; however, there is no evidence that such faster dissolution leads to a significant difference in efficacy. Oral contraceptive tablets have, since their inception, utilized both large and small NET particle size material in various preparations.

Administration, Oral↗
PubMed2001

Effect of intensive lipid-lowering strategy on low-density lipoprotein particle size in patients with type 2 diabetes mellitus.

A preponderance of small dense LDL particles is strongly associated with the occurrence of atherosclerotic disease. Although several studies have documented an increased prevalence of small dense LDL particles in diabetes mellitus no data are available to show the effect of lipid-lowering treatment upon the improvement of LDL particle size. In the present study we examined the effect of lipid-lowering treatment, following an intensive lipid-lowering strategy for 30 weeks pursuing ADA recommended target lipid levels, on LDL particle size in 50 type 2 diabetic patients with moderate hyperlipidemia. At week 0, 24 patients (48%) were characterized by small dense LDL phenotype pattern B. After the treatment period a shift towards normal LDL particle size was observed in 17 patients but seven patients (29%) showed the more atherogenic LDL subclass pattern B. After treatment, plasma HDL-cholesterol was significantly lower (P<0.05) in these patients compared to those who had LDL subclass pattern A. Multivariate regression analysis revealed VLDL-cholesterol or triglycerides and HDL(3)-cholesterol as independent determinants for LDL particle size. Change in HDL(2)-cholesterol was an independent determinant for change in LDL particle size. In conclusion, a strategy of intensive lipid-lowering, with the intention to reduce triglyceride levels below 1.7 mmol/l, may be insufficient to ensure improvement in LDL size in all patients.

Aged↗