Waxy Materials Research Articles

Effect of Different Waxy Materials on the Release of Ibuprofen from Polyethylene Glycol Based Suppositories

Effect of Different Waxy Materials on the Release of Ibuprofen from Polyethylene Glycol Based Suppositories

Effect of Waxy Materials on the Release Kinetics of Ibuprofen from HPMC Based Sustained Release Matrix Tablet

Effect of Waxy Materials on the Release Kinetics of Ibuprofen from HPMC Based Sustained Release Matrix Tablet

Colloidal Properties of Bio-Oils Obtained by Vacuum Pyrolysis of Softwood Bark. Storage Stability

Bio-oil obtained via the vacuum pyrolysis of softwood bark residues is a multiphase, viscous, unstable system composed of water-soluble and water-insoluble fractions. Using centrifugation, the bio-oil can be separated into an upper layer (ca. 16 wt %) and a bottom layer (ca. 84 wt %). The upper layer exhibits low contents of water, solid, and ash, as well as a low density, a low acidity, a high content of methanol-insoluble materials, a high viscosity, and a high calorific value. The physicochemical properties of the bottom layer are similar to those of the whole bio-oil, except the bottom layer contains greater contents of ash and water. Microscopic analysis of the bio-oil has revealed a multiphase complex colloidal system that is composed of solid particles, three-dimensional structures, and droplets. The upper layer represents the dispersed droplet phase, which is rich in waxy materials (fatty and resin acids) and water-insoluble compounds. It is the upper layer that, overall, provides the unique collo...

4th Central European Symposium on Pharmaceutical Technology / Poster presentations

Using waxy materials, several controlled release tiaprofenic acid (TA) tablets were prepared. [...]

Nonlinear fatty acid terminated polyanhydrides.

A systemic study on the synthesis, characterization, degradation, drug release, and stability of nonlinear fatty acid terminated poly(sebacic anhydride) (PSA) is reported. Ricinoleic acid was transformed into a nonlinear fatty acid by esterification with fatty acid chlorides of C8-C18 chain length in the presence of pyridine. Pure nonlinear fatty acids were obtained by purification of the reaction product using column chromatography. Poly(sebacic acid)s terminated with 30 wt % of various nonlinear fatty acids were synthesized by melt condensation to yield waxy off-white materials with molecular weights in the range of 5000-9000. The terminated polymers are soluble in common organic solvents and melt at temperatures between 70 and 79 degrees C, which allow their fabrication into microspheres and implants. These polymers degrade into their counterparts during a period of a few weeks while constantly releasing an incorporated drug. The incorporation of nonlinear fatty acid terminals to poly(sebacic anhydride) increased the polymer hydrophobicity and decreased polymer crystallinity when compared to PSA or to linear fatty acid terminated PSA. The hydrophobic nonlinear side chains retard water from penetrating into the polymer mass, which resulted in higher stability and surface erosion front mechanism of polymer degradation and drug release.

Molecular modeling of electron trapping in polymer insulators

The presence of space charge in the polymeric insulation of high-voltage cables is correlated with electric breakdown. There is a vast literature concerned with the experimental characterization of space charge and with phenomenological models of space charge formation and discharge. However, a direct link between molecular properties, space charge formation and eventual breakdown has still to be established. In this paper, we suggest a new scheme that constitutes a first step in linking microscopic defects to the formation of space charge. Although our goal is to understand the role of defects at the molecular level in electron trapping and the formation of space charge in polyethylene, we start by considering a “model” material; the wax tridecane (n-C13H28). It is clear that both physical (e.g., conformational defects) and chemical defects (e.g., broken bonds) may be present in insulating materials and may both trap electrons. In the present paper, we focus on the role of physical defects. Our analysis suggests that by defining the defect energy in terms of the molecular electron affinity, a relationship is established between the electron trap and the molecular properties of the material. The electron affinity and its variation with wax molecule conformation have been calculated using density functional theory (DFT, as implemented in the code DMol). By performing molecular-dynamics simulations of amorphous waxes, we are able to determine likely conformational defects, and by using ab initio methods estimate the trapping energies. Conformational defects in these waxy materials are predicted to produce shallow traps with energies below 0.3 eV. These results are used to estimate the energy, number, and residence times of electrons in conformational traps in polyethylene.

Fatty acid terminated polyanhydrides

A systematic study on the synthesis, characterization, degradation, and drug release of fatty acid terminated poly(sebacic acid) (PSA) is reported. Fatty acid terminated sebacic acid polymers were synthesized by melt condensation of acetate anhydrides of linear fatty acids (C8–C18) and sebacic anhydride oligomers to yield waxy off-white materials. Polymers with molecular weights (Mw) in the range of 9,000 and 5,000 were obtained for the 10% and 30% (weight ratio) containing fatty terminals, respectively. Up to about 30% of fatty acid terminals, the final product is mainly fatty terminated polymer with up to about 5% w/w of the symmetric fatty anhydride. Increasing amounts of fatty acid acetate anhydride in the polymerization mixture had little effect on the polymer molecular weight up to a ratio of 40 : 60 (fatty acid acetate : sebacic acid oligomer) which remains in the range of 5,000–8,000. Above this ratio the molecular weight dropped to a level of 2,000–3,000 and the percent of the symmetric anhydride increased to 10–40%. The fatty terminals had little effect on PSA melting point and crystallinity. However, the fatty terminals had a significant effect on the polymer degradation and drug release rate. PSA with 30% w/w of C14–C18 terminals degraded and released the incorporated drug for more than 4 weeks as compared with 10 days for the acetate-terminated PSA. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3337–3344, 1999

Analytical characterization of natural waxes employing pyrolysis–gas chromatography–mass spectrometry

Three natural waxes (bleached beeswax, lanolin, yellow carnauba wax) were investigated by means of pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS). Pyrograms were obtained showing very characteristic signal patterns. Mass spectrometric detection enabled the structural identification of the pyrolytically formed fragments. For a more detailed investigation of the thermal degradation behaviour of waxy materials, relevant model compounds were selected. Hexadecylpalmitate, cholesterylstearate, heptadecanoic acid and 1-hexacosanol were examined under identical Py–GC–MS conditions. From the resulting product distribution general statements were able to be derived according to the thermal degradation pathways of typical wax constituents. The findings obtained from the model compounds were then applied to the interpretation of the real wax pyrograms. As a result, conclusions according to their origin from corresponding wax constituents were drawn for the majority of pyrolysis products. Thus, the extended potential of the method for the compositional analysis of natural waxes is demonstrated.

Cleaning produce — by contacting surfaces of produce with aq cleaning soin comprising detergent surfactant and neutralised orthophosphoric acid in amts to provide removal of waxy materials. (Eng)

Cleaning produce — by contacting surfaces of produce with aq cleaning soin comprising detergent surfactant and neutralised orthophosphoric acid in amts to provide removal of waxy materials. (Eng)

Otoacariasis in Bengal goats of Bangladesh

The clinical findings and therapy of otoacariasis, caused by Psoroptes cuniculi, were studied in 12 Bengal goats. The major presenting signs included marked discomfort, rubbing of the ears against fixed objects or scratching by the toes, ear twitching and head shaking. In some severe cases violent head dashing against fixed objects was also noticed. Crackling sounds were detectable by gentle digital pressure on the ear base. In all cases, external auditory meatuses were found to be filled with yellowish-brown laminated scabs or waxy materials. Ten animals recovered after three to five applications of Lorexane cream 1% (ICI Ltd.) applied at an interval of 7 days. Two animals died after 2–3 days of treatment. Terramycin Otic Drop (Pfizer) was also applied to inhibit secondary bacterial infections and to promote the healing process. It is suggested that otoacariasis should be included in the list of differential diagnoses of brain diseases in goats.

Deposition of zeolite A on vegetal fibers

In situ deposition of zeolite A on various vegetal fibers is studied. It is found that the chemical composition and the structure of the fibers determine the degree of coverage. The effect of the content of cellulose, lignin, and waxy materials in the fibers on the process of the formation of zeolite coating is studied. The role of chemical and mechanical pretreatment of the support on the process of zeolite crystallization is discussed. It is shown that the amount of the deposited zeolite may be controlled by suitable fiber pretreatment.

Improvement of the quality of heavily weathered crude oils

Ways to improve the quality of highly weathered crude oils formed as a result of uncontrolled flow and seepage from damaged Kuwaiti oil wells were developed. Seven such oils collected from various lakes in different Kuwaiti oilfields had high contents of salts (up to 15 wt%) and water (up to 50 vol.%), high kinematic viscosity (815 mm 2 s −1 at 50°C) and low API gravity (8.2° API). Washing with fresh water removed the salt and water by up to 29 and 12 vol.%, respectively. Further washing increased the oil-water emulsion owing to the flocculant precipitation of waxy materials and high-molecular-weight compounds. The application of demulsifier, fresh water and heat broke the emulsion and allowed the water to settle out. The clean, water-free crude oil was similar in quality to a typical medium-API crude residue boiling > 300°C. This demonstrates that the oil had lost most of its light hydrocarbons.

Preparation of controlled release tablets of TA-5707F with wax matrix type and their in vivo evaluation in beagle dogs.

Studies on controlled release dosage forms were conducted by using waxy materials for a newly developed anti-allergy drug, 6-methyl-N-(1H-tetrazol-5-yl)-2-pyridinecarboxamide (TA-5707F), which is not maintained at an effective level in blood for a long duration. Four kinds of tablets were prepared by changing the amount of hydrogenated oil (K3 wax) and polyethyleneglycol-6000 in the tablets. Then, they were administered orally to beagle dogs, and the TA-5707F concentration in the plasma was determined by a HPLC method. The pharmacokinetic parameters were estimated and compared with the results of the in vitro dissolution test determined by the JP paddle method and by the disintegration method. The linearity between the in vivo mean dissolution time (MDT) and in vitro MDT was good in both in vitro dissolution methods. However, the MDTs obtained by the disintegration method were one-third of the in vivo MDT, while those obtained by the paddle methods were 3 times higher. This suggests that both the diffusion of TA-5707F through the waxy matrix and the erosion of the wax matrix caused by the gastrointestinal (GI) tract mobility contributed to the in vivo dissolution mechanism. The blood levels were very low when the tablet was administered after giving food. The prolongation of resident time in the stomach and the low solubility of TA-5707F in an acidic medium seemed to be related to the phenomena. By the depression of GI motility using propantheline bromide, the blood levels could be markedly prolonged and the area under the plasma concentration-time curve (AUC) increased 1.3 times.

Sustained Release Formulation of Salbutamol Sulphate

Sustained release tablets containing salbutamol sulphate has been prepared by wax matrix granulation method and were evaluated for in vitro release profile and in vivo availability studies in dogs. Out of the release retarding waxy materials used combinations of carnauba wax and stearyl alcohol in concentration range between 60 to 70% of the weight of the tablet were found to be optimum in fabricating sustained release tablets for twentyfour hours duration of action. The formulations were also compared with marketed products of salbutamol for in vitro release profile.

Thermal Treatment of Beads with Wax for Controlled Release

AbstractBeads prepared by extruder/marumerizer technology were formulated with water soluble drugs, microcrystalline cellulose and several waxy materials. The waxes (10 to 50% by weight) were included in an effort to slow drug release. Subsequent thermal treatment of these beads was applied. Beads were processed to determine the effect of varying wax level, excipient, active drug, and effect of heat treatment. In-vitro drug release profiles were evaluated for the untreated and thermal treated beads. In general, the simple incorporation of wax into the granulation did not provide the desired controlled release dissolution profile. Thermal treatment of the finished beads, however, resulted in products which behaved in a different manner during dissolution testing and in general provided slower release. Drug release was found to vary with the type and level of wax, drug, excipient, and the thermal treatment.

Effects of Some Environmental Factors on Growth Characteristics of Candida utilis on Peat Hydrolysates

Samples of peat from Pine Island and Brookston bogs in Minnesota were hydrolyzed with various concentrations of HCl or H(2)SO(4) solutions, before or after debituminization (an extraction process used to remove waxy materials, bitumens, from peat), to produce peak hydrolysates as growth substrates for Candida utilis. Hydrolysates were neutralized with concentrated NaOH solution to pH 3.5, 4.5, 5.0, 5.5, 6.0, and 7.0. The precipitated humates were removed by filtration. The resulting peat hydrolysates were amended with reagent-grade K(2)HPO(4), K(2)SO(4), and MgSO(4), 200, 100, and 50 mg per liter of peat hydrolysate, respectively. The debituminized peat produced more total nitrogen (TN) and reducing substances (RS) than the nondebituminized peat. Peat hydrolysates produced by HCl solutions contained slightly higher RS and TN than those produced by H(2)SO(4) solutions; however, the latter were better growth substrates than the former. The yield coefficients in both H(2)SO(4) and HCl hydrolysates initially decreased at 12 to 24 h and then increased gradually over the remaining incubation period (24 to 96 h). As TN and RS were increased, an increase in cell density, biomass, and productivity was observed. In contrast, a decrease in specific growth rate occurred as the RS and TN were increased. The generation time of C. utilis was affected by the concentrations of RS and TN. A peak substrate yield coefficient was found at pH 5.0 in HCl hydrolysates and at pH 6.0 to 6.5 in H(2)SO(4) hydrolysates. Good linear correlation coefficients were found between RS and biomass of C. utilis. The coefficients of correlation increased as the TN level in hydrolysates was increased.

Cationic polymerization of 5-methyl-2-oxazoline and alkaline hydrolysis of product polymer to linear poly(propylenimine)

A new monomer of 5-methyl-2-oxazoline(5-MeOZO) was prepared. It was found that 5-MeOZO underwent the cationic ring-opening isomerization polymerization to produce poly(N-formylpropylenimine) 1 of waxy or powdery materials. Alkaline hydrolysis of 1 gave linear poly(propylenimine) 2. Polymers 1 and 2 are the same as the respective polymers derived from 4-methyl-2-oxazoline.

Flowability techniques in the processing of powdered explosives, propellants, and pyrotechnics

A very effective flowability additive developed by Dow Corning Corporation is obtained by converting a hydrophilic silica aerogel to a hydrophobic colloidal silica by reacting with hexamethyldisilazane. This additive has been used to prepare homogeneous powder mixtures with a minimum of mixing, to mil difficult materials, and to obtain amazing flow properties in troublesome powders. This hydrophobic silica has an exceedingly light bulk density of about 0.05 g/cc, and a particle size of about one millimicron. It can be premixed before milling and will allow milling of waxy materials. After treatment the powder becomes water repellant and the bulk density increases. Hydrophobic silica additive in amounts less than one percent by weight has often proven effective.

Rate Controlled Release of Naproxen from HPMC Based Sustained Release Dosage Form: I. Microcapsule Compressed Tablet and Matrices

The aim of the present study was to investigate the release kinetic profiles of Naproxen (NP) from microcapsule compressed as well as matrix tablets using a combination of water insoluble materials with hydrophilic polymers. The ethyl cellulose (EC)/ hydroxy propyl methyl cellulose (HPMC) combination controlled the release rate of NP by their concentration ratios from the microcapsule compressed tablets. When the hydrophilic part of the combination was increased, the release rate of NP was rationally increased. Accordingly their kinetic constants as well as diffusion coefficients also increased. It can be concluded that the hydrophilic part HPMC could contribute a developed-macromolecular network structure along with EC, through which the NP release can be controlled like twining-release system. On the other hand introduction of waxy materials like bees wax (BW), cetyl alcohol (CA) and stearic acid (SA) into the HPMC based matrices showed a different release pattern. In this case increased hydrophobic part of the combinations decreased the release profiles including kinetic constant as well as diffusion coefficient. The first 60% kinetic profiles showed that tablets using all the additives released the drug by a non-Fickian diffusion (approx. zero order Model). 
 
 Key words: Sustained release, Microcapsule, Naproxen, Diffusion exponent, Kinetic constant, Diffusion coefficient
 
 Dhaka Univ. J. Pharm. Sci. Vol.4(1) 2005
 
 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

Alkane Distribution as Biological Markers: Presence and Possible Origin of n-Alkanes in Guttiferae Heartwoods

THE thin waxy materials coating the stem, leaf, flower and fruit of most plants usually consist of homologous series of long chain alcohols, aldehydes, esters and hydrocarbons. The hydrocarbons contain a homologous series of n-alkanes ranging from about C20 to C35 with the alkanes having an odd number of carbon atoms sometimes occurring ten times more abundantly than those with an even number. The centre of the distribution of the series is frequently around the n-alkanes C29 and C31 (ref. 1). These features are also obvious in some hydrocarbons from fossils and it has been suggested that this predominance of n-alkanes with an odd number of carbon atoms can be used to indicate that the hydrocarbons are of biological origin1. For petroleum, which does not have this distribution of n-alkanes, Robinson has proposed that the hydrocarbons arise from partly biological and partly non-biological sources1,2. More recent work has shown that lower organisms such as mosses, algae and lichens contain n-alkanes where the ratio of odd-numbered homologues to the even-numbered ones is about equal and it was suggested that crude oils may originate from lower organisms3.