An in vitro investigation into the effect of glycosaminoglycans on the skin partitioning and deposition of NSAIDs

Recently, Solaraze gel (Bioglan, Herts, UK) a topical hyaluronan (HA)/diclofenac formulation for the treatment of actinic keratosis has received regulatory approval in the US, Canada and Europe for the treatment of actinic keratosis. However, a mechanism of action to explain the topical delivery properties of HA remains to be elucidated. Thus, the aim of this study was to compare the effect of HA with other glycosaminoglycans (chondroitin sulphate (CS), heparin (HP)) and pharmaceutically relevant polysaccharides (sodium carboxymethyl cellulose and pectin) on the dermal partitioning and percutaneous penetration of diclofenac and ibuprofen. The studies demonstrated that HA significantly enhanced the partitioning of both diclofenac and ibuprofen into human skin when compared to an aqueous control, pectin and carboxymethylcellulose (P<0.01). Although the HA vehicle increased the partitioning of both drugs compared to the effects of the other glycosaminoglycans, CS and HP, this difference was not significant (P>0.05). However, the results from the Franz cell diffusion studies showed that HA (1% w/w) significantly enhanced the amount of drug localising within the skin when compared to all of the other polysaccharides (P<0.05). The results suggest that the use of HA as a vehicle excipient offers potential advantages in the dermal delivery and localisation of drugs.

Formulation of inhaled medicines: effect of delivery vehicle on immortalized epithelial cells

The small volume of airway lining fluid renders it susceptible to alteration by the deposition of inhaled formulations. The increasing popularity of the pulmonary route for drug delivery has led to an increasing number of pharmaceutical excipients being incorporated into inhaled dosage forms. The effects of drug delivery vehicle on airway epithelial cells can be studied with the aid of cell culture models of the respiratory epithelium. The effects of pH, osmolarity, and lactose on epithelial cell layers were studied using 16HBE14o- cells. Mannitol flux was used to assess epithelial permeability, enzymatic conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) was used as a measure of epithelial cell metabolism, and release of the cytosolic enzyme lactate dehydrogenase was used as a measure of cell integrity. The effect of buffer composition on epithelial cell mucus secretion was studied using HT29-clone H cells, with mucus secretion measured using an enzyme-linked lectin assay. The permeability of 16HBE14o- cell layers was increased by apical fluid of pH 5, 6, and 9 as well as osmolarities of 96 and 545 mOsm. MTT conversion was reduced by apical fluid of pH 5 and 6 and osmolarity of 96 mOsm. Lactate dehydrogenase release was only increased by apical fluid of pH 9. No effect of lactose solution (100 mM) on the epithelial cells was observed. Mucus secretion by HT29-clone H cells was lowest in Dulbecco's modified Eagle medium (2.92 +/- 0.23 ng per cell layer) and was increased in phosphate-buffered saline with magnesium and calcium (4.28 +/- 0.38 ng per cell layer) and phosphate-buffered saline without magnesium and calcium (6.56 +/- 0.72 ng per cell layer). These results suggest that the physicochemical properties of inhaled formulations should be carefully controlled. The effect of buffer composition on mucus secretion suggests that even the application of "physiological" solutions may affect the epithelium. These cell models represent an opportunity to investigate the interaction of drug delivery vehicles with the epithelium.

Effects of molecular weight of polyvinylpyrrolidone on the glass transition and crystallization of co-lyophilized sucrose

The purpose of the present study was to investigate the effects of molecular weight (MW) of polyvinylpyrrolidone (PVP) on glass transition and crystallization of sucrose. Thus, sucrose was co-lyophilized with 2.5 and 5.0% w/w PVP of different molecular weights, which were characterized using gel permeation chromatography. Freeze drying was carried out for 48 h at a shelf temperature of -40 degrees C and a pressure of about 36 Pa. The samples were then dried in a vacuum oven at 24 degrees C for 12 h before drying for a further 12 h at 40 degrees C. Differential scanning calorimetry (DSC) was employed to measure the glass transition temperature (Tg), dynamic crystallization temperature (Tc) and isothermal crystallization induction time (tc) at 85 degrees C of sucrose. Isothermal water vapour sorption of each sample was also measured at different relative humidities. Tg values of sucrose varied from 48.3+/-0.8 degrees C for freeze-dried (FD) sucrose alone to 58.8+/-0.8 degrees C for the mixture containing 5.0% PVP of nominal MW 300 K. PVP increased sucrose T(g) significantly (ANOVA P<0.05). Although there was no significant difference (P>0.05) in Tg of the mixtures containing 2.5% w/w PVP of different MW, samples with 5.0% PVP of MW 300 K produced a significantly higher (P<0.05) Tg than the other mixtures. All mixtures were shown to possess higher (P<0.01) Tc than FD sucrose alone, which exhibited a T(c) of approximately 85 degrees C. PVP of MW 300 K consistently induced a significantly (P<0.05) higher Tc of sucrose than PVP of smaller MW. Increasing PVP concentration from 2.5 to 5.0% also resulted in a substantial increase in sucrose Tc. Using isothermal water vapour absorption, sucrose tc was found to increase up to over 10 times when it was co-lyophilized with 2.5% PVP, the actual value of tc being dependent upon the MW of the PVP. For example, PVP of MW 300 K resulted in a sucrose tc at 85 degrees C (89.1-95.6 min), which was approximately seven times higher than that of 2.5% PVP of MW 24 or 40 K. A longer tc of sucrose was also observed for mixtures containing PVP of MW 300 K than when sucrose was mixed with PVP of smaller MW. Thus the effect of PVP on sucrose Tg, Tc and tc was found to be dependent upon MW. PVP of higher MW was more efficient in inhibiting sucrose crystallization and by stabilizing glassy structures of the sugar, these polymers may improve the stability of co-lyophilized proteins and peptides.

Activation of clindamycin phosphate by human skin

AIMS

To investigate the relative antimicrobial activity of clindamycin phosphate (CP) and clindamycin (Cly) and to examine the effect of skin homogenates on the activity of CP.

METHODS AND RESULTS

Minimum inhibitory concentrations (MIC) were determined against dermally relevant organisms and bactericidal activity was studied using time-kill methodology. The effect of skin homogenates on the antimicrobial activity of CP was studied by well-diffusion assay. The MIC of Cly was substantially lower than that of CP in all susceptible organisms. Clindamycin also showed greater bactericidal activity (rate of kill) than CP. Phosphatases in skin homogenates activated CP at pH 4-8 with a maximal activation at pH 4.

CONCLUSION

Phosphatases within the skin have been shown to convert CP to the more potent form Cly.

SIGNIFICANCE AND IMPACT OF THE STUDY

Conversion to Cly is a major determinant of antimicrobial activity in the skin layers following topical application of CP.

Turbidimetric and HPLC assays for the determination of formulated lysozyme activity

In several studies lysozyme has been employed as a model protein to investigate the effects of formulation factors upon biological activity. The aim of this work was to develop and validate an HPLC technique to assay lysozyme and to compare the results with biological activity determined from a validated turbidimetric assay. The turbidimetric assay was based upon the lytic action of lysozyme on Micrococcus lysodeikticus cells, whilst the reverse-phase HPLC assay employed an acetonitrile gradient in 0.1% trifluoroacetic acid. The limits of detection and quantification were 3.84 and 6.24 microg mL(-1) for HPLC assay, whilst the corresponding values for turbidimetric assay were 1.94 and 3.86 microg mL(-1). The methods were used to monitor the loss of enzyme activity after heating. Lysozyme concentrations determined from HPLC peak height were found to correlate (r2 = 0.9963) with those obtained from turbidimetric assay.

The use of lactose recrystallised from carbopol gels as a carrier for aerosolised salbutamol sulphate

Lactose was crystallised either from Carbopol gel without stirring or from a constantly-stirred aqueous solution, to obtain lactose crystals designated as Carbo and control lactose, respectively. The Carbo lactose was shown to have a more regular shape with smoother surface as compared with the control lactose. These lactoses were fractionated by sieving to produce batches with different sizes before blending separately with salbutamol sulphate (SS, VMD 5.8 microm) in a ratio of 67.5:1 w/w using the same mixing procedure. SS dispersion and deaggregation were investigated using a 4-stage liquid impinger after aerosolisation at 28.3, 60.0 and 96.0 l/min via a Rotahaler. At all flow rates, the Carbo lactose produced significantly higher (ANOVA, P<0.01) emission of SS from the Rotahaler as compared with the control lactose of a similar size. The Carbo lactose also resulted in a significantly (P<0.05) higher fine particle fraction of SS than the control lactose. Moreover, drug emission from formulations containing the Carbo lactose was consistently more reproducible than those of the control lactose blends. In conclusion, the efficiency and reproducibility of drug delivery by dry powder inhalers can be improved using carrier particles of precisely defined morphological features.

Periodontal pocket clearance by gamma scintigraphy in human volunteers

BACKGROUND

With the interest in the delivery of drugs to the periodontal pocket has come an increased need to determine the loss of formulations from the site of application. In this respect, gamma scintigraphy has been used to measure formulation clearance in mucosal sites such as the oesophagus, nose and eyes by assessing the persistence of an incorporated radiolabel. However, the technique has not been used to follow clearance from the periodontal pocket.

AIMS

The aim of this study was therefore to assess the potential of gamma scintigraphy to follow the loss of 2 contrasting formulations. 10% chitosan gel and normal saline.

METHOD

Technitium-99m was used as the radionuclide and was incorporated into the formulations on the day of use. 9 subjects contributed up to 2 pockets for each formulation with probing depths > or = 5 mm.

RESULTS

The results demonstrated that gamma scintigraphy was able to follow the loss of the radiolabel despite the small volumes of formulation placed in situ. The mean (SD) times (min) for the original counts to decline to 10%, 50% and 90% of the original values were: T10: chitosan 74.5 (59.0), saline 40.3 (21.1), T50: chitosan 41.5 (34.1) saline 20.8 (11.7) and T90: chitosan 8.5 (10.8), saline 1.4 (3.7) respectively. Clearance times of the 2 formulations were significantly different from each other (p<0.05).

CONCLUSION

In conclusion, gamma scintigraphy is a sensitive method for assessing clearance from the periodontal pocket, and further studies are merited to optimise the use of the technique.

The use of different sugars as fine and coarse carriers for aerosolised salbutamol sulphate

The aim of this study was to investigate the dispersion and deaggregation of a model drug, salbutamol sulphate (SS), using lactose, mannitol or sorbitol as coarse and fine carriers. Binary and tertiary formulations containing micronised salbutamol sulphate (SS) and sieved (63-90 microm) coarse sugar crystals or salbutamol sulphate (SS) with a mixture of coarse and fine sugar particles were prepared. Factorial design was employed to investigate the effects of three variables, i.e. the chemical entity of the coarse sugar carrier, the chemical entity of the fine sugar and the concentration of fine sugar, on the dispersion and deaggregation of salbutamol sulphate after aerosolisation at 60 l/min via a Rotahaler(R) into a twin stage liquid impinger (TSI). The binary formulations containing the different sugar entities produced differences in the fine (<6.4 microm) particle fraction (FPF) of SS in a decreasing order of mannitol >sorbitol >lactose, but failed to produce efficient dispersion of SS since the FPF was <10%. Adding fine sugar particles and increasing their concentration to the binary mixtures generally resulted in an increase in the FPF of salbutamol sulphate. The chemical nature of the fine carriers was found to play a less important role in determining respirable fraction of the drug than the coarse carriers. In conclusion, other sugars such as mannitol or sorbitol, besides lactose, may be employed as coarse and/or fine carriers for incorporation into dry powder aerosol formulations to increase FPF.

The effects of carrier size and morphology on the dispersion of salbutamol sulphate after aerosolization at different flow rates

We have investigated the interdependence of various factors (particle size, surface smoothness, carrier particle shape, inhalation flow rate) on the deposition of a model drug (salbutamol sulphate) after aerosolization from a model inhaler device (Rotahaler). Different batches of alpha-lactose monohydrate were prepared to have different particle size, particle shape and surface smoothness. Each batch of lactose was then mixed separately with salbutamol sulphate in a ratio of 67.5 : 1 (w/w), under similar conditions. Drug deposition from each formulation was investigated using a 4-stage liquid impinger after aerosolization at 28.3, 60.0 and 96.0 L min(-1) via a Rotahaler. At a flow rate of 28.3 L min(-1), a large portion of drug particles was not emitted from the inhaler, the % emission varying from 29.6% to 66.6% for all formulations investigated. Drug emission tended to increase with particle size of the carrier whilst fine particle fraction, fine particle dose and dispersibility appeared to increase with decreasing particle size but increasing elongation ratio of the carrier particles. Increasing the flow rate to 60.0 L min(-1) was shown to increase drug emission since > 75% total dose was found to be emitted from the inhaler. Again, smaller or more elongated lactose particles resulted in a higher fine particle dose or fine particle fraction of salbutamol sulphate than the coarser carrier, although they produced a similar (analysis of variance P > 0.05) drug emission. Increasing the flow rate to 96.0 L min(-1) did not increase drug emission. Increasing the flow rate resulted in an increase in the fine particle fraction and fine particle dose of salbutamol sulphate from all formulations. The flow rate of the airstream appeared to play the most important role, followed by particle size and elongation ratio of the carrier particles, with the surface smoothness relatively less significant in determining the deposition of salbutamol sulphate from the Rotahaler.

Mitigation of surfactant erythrocyte toxicity by egg phosphatidylcholine

Polyoxyethylene alkyl ether surfactants have been shown to have excellent penetration enhancing abilities although they are associated with a high level of local toxicity. We have compared the toxicity of a range of polyoxyethylene alkyl ethers (Brij 96, Brij 76, Brij 56, 10 lauryl ether and 9 lauryl ether) to an anionic surfactant (sodium dodecyl sulphate (SDS)), an ampholytic surfactant (lysophosphatidylcholine) and a cationic surfactant (tetradecyltrimethylammonium bromide (TTAB)), in the presence and absence of egg phosphatidylcholine. The toxicity of the surfactants or phospholipid/surfactant mixtures was assessed by measuring haemolytic activity. The test samples were incubated with a suspension of red blood cells for 30 min and Drabkin's reagent was used to indicate the amount of haemoglobin released. All of the polyoxyethylene alkyl ethers, SDS, TTAB and lysophosphatidylcholine exhibited haemolytic activity at concentrations between 0.10 and 0.25 mM. The addition of egg phosphatidylcholine reduced the toxicity for all of the surfactants, with the toxicity of Brij 96 being mitigated to a greater extent than the toxicity of the other polyoxyethylene surfactants examined. The rate of haemolysis induced by Brij 96 or 10 lauryl ether was also reduced by increasing concentrations of phosphatidylcholine. As the phosphatidylcholine content of a mixed surfactant system comprising egg phosphatidylcholine: Brij 96 was replaced by lysophosphatidylcholine and fatty acid, the haemolytic action of the mixture increased markedly. The results from this study show that the toxicity of surfactants to erythrocytes can be mitigated by the addition of egg phosphatidylcholine. Synthetic surfactants combined with phosphatidylcholine may generate drug delivery systems worthy of more extensive investigation.

Crystallization of lactose from carbopol gels

PURPOSE

To crystallize lactose under static conditions with a view to preparing crystals of well-defined morphology.

METHODS

et-Lactose monohydrate was crystallized from neutralized Carbopol 934 gels. When the majority of crystals had grown to maturity, the gels were acidified using diluted hydrochloric acid and the crystals were harvested by filtration or centrifugation and washed with ethanol-water mixtures.

RESULTS

Crystals prepared from the gel had a consistently narrower size distribution than control crystals, prepared from solution under constant stirring. If crystallization was effected in the gel without sedimentation of the crystals, then the resultant crystals had smooth surfaces without visually detectable surface roughness or asperities viewed by optical microscopy. The crystals from Carbopol gels also exhibited the uniform shape of an elongated tomahawk regardless of the crystallization conditions, in contrast to crystallization under constant stirring, where the crystal shape of lactose changed with crystallization conditions especially as a function of the initial concentration of lactose. All batches of lactose crystals prepared from Carbopol gels existed as alpha-lactose monohydrate, which showed better flowability than the controls of a similar particle size.

CONCLUSIONS

Crystallization from Carbopol gel produces lactose crystals of uniform size, regular shape, smooth surface, and improved flowability.

A human oral-throat cast integrated with a twin-stage impinger for evaluation of dry powder inhalers

The aim of this study was to investigate the applicability of replacing the glass throat from a twin-stage impinger (TSI) with a human oral-throat cast. Monodisperse aerosols were used to calibrate the human oral cast-TSI at 60 L min(-1) and cut-off in particle size was compared with that of the TSI described in the British Pharmacopoeia which employs a glass throat. The amount of salbutamol sulphate (and lactose) delivered by the Cyclohaler depositing on various elements of the in-vitro model were determined. The calibration of the model containing a human oral-throat cast at 60 L min(-1) gave a particle size cut-off of 5.2 microm which was less than that of the TSI (6.3 microm). The oral-throat cast trapped more drug than the glass throat model with a formulation that employed the larger carrier (63-90 microm; P<0.05) while it trapped a lesser amount of drug with those filled with the lower size carrier (Lactochem, micronised lactose). The greater amount of lactose in the formulation that employed the larger-sized carrier (63-90 microm) was deposited closer to the inlet of the oral-throat cast than to the inlet of the glass throat model. Replacement of the glass throat in the TSI by the human oral-throat cast, leads to a change in deposition efficiency, with the cast having a higher filter efficiency and hence more aerosol particles being captured before their entry into the TSI. This should be investigated further to determine whether such a model might provide a more realistic assessment of the in-vivo characteristics of an aerosol in comparison with the TSI currently being employed, which utilises the glass throat as the portal of entry.

The influence of crystallization conditions on the morphology of lactose intended for use as a carrier for dry powder aerosols

Lactose has been widely used as a carrier for inhalation aerosols. The carrier morphology is believed to affect the delivery of the drug. The aim of this study was to investigate the effects of crystallization conditions on the morphology of alpha-lactose monohydrate intended for use as the carrier for dry powder aerosols. The crystallization of lactose was carried out from aqueous solutions at different supersaturations, temperatures, different stages of crystallization and in the presence of different water-miscible organic solvents. The majority of lactose crystals were found to be either tomahawk-shaped or pyramidal after crystallization at an initial lactose concentration between 33-43% w/w, but these became prismatic if the lactose concentration was increased to 50% w/w. A further increase in the lactose concentration to 60% w/w led to the preparation of elongated cuboidal crystals. Higher initial lactose concentrations tended to result in the crystallization of more elongated particles. Crystallization at 40 degrees C was shown to prepare lactose crystals with a more regular shape and a smoother surface than those crystallized at 0 degrees C. Lactose particles generated during the later stage of crystallization were found to be more regular in shape with a smoother surface than those prepared in the earlier stage. The addition of 10% (v/v) methanol or ethanol or acetone to the mother liquor increased the growth rate of lactose particles whereas addition of propanol or glycerine inhibited the rate of crystal growth. Lactose crystals prepared in the presence of glycerine were more regularly shaped with a smoother surface than those prepared in the presence of ethanol or acetone. All the resultant crystals were shown to comprise alpha-lactose monohydrate. Lactose crystals could be prepared with a precisely defined morphology by means of carefully controlling the crystallization conditions.

Preparation and evaluation of the in vitro drug release properties and mucoadhesion of novel microspheres of hyaluronic acid and chitosan

Rapid mucociliary clearance of intranasally administered drugs is often a key factor in determining the bioavailability of such therapeutic agents. The use of mucoadhesive microparticles provide a potential strategy for improving retention of drugs within the nasal cavity, and thereby improve the resultant pharmacokinetic profile. This study describes the comparison of a number of novel, potentially mucoadhesive microspheres, prepared by solvent evaporation, composed of hyaluronic acid (HA), chitosan glutamate (CH) and a combination of the two with microcapsules of HA and gelatin prepared by complex coacervation. The microspheres had a mean particle size of 19.91+/-1.57 microm (HA), 28.60+/-1.34 microm (HA/CH), 29.47+/-3.58 microm (CH). The incorporation of a model drug, gentamicin sulphate (%) was 46.90+/-0.53 (HA), 28.04+/-1.21 (HA/CH) and 13.32+/-1.04 (CH). The in vitro release profiles of microsphere formulations prepared by solvent evaporation were determined. The release of gentamicin from HA and HA/CH was 50% longer than CH and was best modelled as a release from a matrix. The degree of mucoadhesion of each formulation was investigated by determining the mucociliary transport rate (MTR) of the microparticles across an isolated frog palate. Acacia/gelatin microcapsules were used as a positive control. The rank order of mucoadhesion for the microspheres and the microparticles was HA=HA/CH>CH>HA/gelatin>CHins. The entrapment of gentamicin did not affect the mucoadhesive properties (P>0.05, Mann--Whitney U-test). The combination of HA with chitosan may afford additional advantages in combining the mucoadhesive potential of HA with the penetration enhancing effect of chitosan.

Transition to CFC-free metered dose inhalers--into the new millennium

Metered dose inhalers (MDIs) are the most popular vehicle for drug delivery into the lungs and some 500 million are manufactured each year. All MDIs marketed prior to 1995 contained chlorofluorocarbons (CFC) as a propellant. These are implicated in the depletion of stratospheric ozone and, except for specific exemptions, their production has been banned since 1996 under the terms of the Montreal Protocol. Hydrofluoroalkanes have been identified as suitable alternatives for MDI propellants but their physico-chemical properties differ significantly from CFCs and an extensive redevelopment and testing programme has been required to demonstrate the safety, quality and efficacy of HFA containing MDIs. Hydrofluoroalkanes contribute to global warming but the benefit to human health through continued MDI availability currently outweighs the environmental concern. Several HFA-MDIs have reached the market and the transition to replace existing CFC-MDIs is now underway.

Evaluation of matrices containing molecularly imprinted polymers in the enantioselective-controlled delivery of beta-blockers

Granules and beads of methacrylic acid (MAA) and granules of N-acryloyl-alanine polymer (NAA) were produced using ethylene glycol dimethacrylate as cross-linking monomer either by bulk (in the case of granules) or suspension (in the case of beads) polymerization. Either R- or S-propranolol, were used as an imprint molecule, acting as a template, with a view to conferring enantioselectivity of release upon the polymer. The molecularly imprinted polymers (MIPs) or nonMIPs (control) were formulated with racemic propranolol and other excipients and compressed to form matrix tablets. Enantioselective release of propranolol in vitro was monitored using a stereoselective HPLC assay. The influence of the method of polymer synthesis, drug: polymer ratio, pH and temperature on the release of the two enantiomers was determined. Stereoselectivity of release was identified in tablets containing either MAA or NAA granules or MAA beads, with the latter showing the greatest differences between enantiomers. Release of the enantiomer used as the print was always faster than the release of the nonprint enantiomer. In the case of S-propranolol-MIP bead matrices composed of MAA, greater differences in the release of enantiomers could be promoted by increasing the polymer: drug ratio of the tablet. Differences in the release rate of the two propranolol enantiomers was still apparent as the pH was varied between 3 and 7.4 and when the temperature was decreased from 37 to 25 degrees C. S-Propranolol-MIP bead matrices demonstrated cross-reactivities of stereoselective dissolution for enantiomers of pindolol and oxprenolol, both of which have structural similarities to the imprint molecule. It is concluded that polymers of this type may have great potential in controlling, via means of formulation, the release of drug eutomer whilst enhancing retention of distomer in the dosage form.

Assessment of demand for a job placement service for the Poultry Science Association

A placement service for the membership of the Poultry Science Association (PSA) is a possible future consideration. This service should provide a formal national platform that could aid membership and their employers in position services. A survey was conducted with the objective of determining the interest of the membership in such a placement service and the maximum expense that members would be willing to pay for the service. Ten questions in an undisguised questionnaire format, covering demographic, historical, and interest points was devised with survey questions designed for a forced response on most of the questions. A total of 2,050 surveys was mailed to PSA members in the US, including 1,850 regular members and 200 student members; 518 responded to the survey. A majority of all age groups favored the construction of a placement service, but the respondents' willingness to use the service depended upon age, education, and work experience and whether or not they believed a placement service was needed. Sources of information used in finding a position varied with age; trade journals and publications were the most frequent sources for the responses. It appears that the membership likes the idea of a placement service, is willing to pay something for it, and would use it if it were available.

The influence of carrier morphology on drug delivery by dry powder inhalers

Alpha-lactose monohydrate was prepared to have different morphological features but with similar particle size. The crystal shape and surface smoothness of lactose were quantified by a number of shape descriptors and these were supported qualitatively by the visual examination of scanning electron (SE) micrographs of the crystals. All batches of lactose were subjected to a similar history of processing before blending separately with micronised salbutamol sulphate (SS) in a ratio of 67.5:1, w/w, using similar procedures. In vitro deposition of SS from these formulations was investigated after aerosolisation of the formulations at 60 l min(-1) via the Rotahaler and the Cyclohaler into a twin stage liquid impinger. The formulations prepared using the different batches of lactose produced different deposition profiles of SS. The fine particle (< 6.4 microm) fraction (FPF) of aerosolised SS varied from 12.6 +/- 2.4 to 25.6 +/- 1.5% after aerosolisation from the Cyclohaler whilst it changed from 15.0 +/- 2.2 to 24.4 +/- 0.8% after aerosolisation from the Rotahaler. The fine particle dose (FPD) and dispersibility of SS followed a similar trend to the change in the FPF of the drug. No significant difference (ANOVA P > 0.05) was observed for the deposition profiles of SS after aerosolisation from the Rotahaler and the Cyclohaler. The FPF and dispersibility of SS increased with either the surface smoothness (P < 0.01) or elongation ratio (P < 0.01) of lactose crystals. The t-ratio values of FPF and dispersibility of SS generated by changes in the surface smoothness were similar to those resulting from changes in elongation ratio. Increasing either the surface smoothness or the elongation ratio of lactose crystals will increase the potentially respirable fraction of SS from dry powder formulations for inhalation.

Synthesis and bacterial degradation of an azopolymer

Azopolymers were synthesised with differing degrees of hydrophobicity, from 2-hydroxyethylmethacrylate (HEMA), styrene and 2,2'-dimethylacryloyloxyazobenzene as azo crosslinker. Bacterial degradation of the series of polymers was assessed using a pure culture of the colonic organism Enterococcus faecalis and rat caecal contents. Polymer degradation was determined in terms of weight loss on polymer coated glass beads and using scanning electron microscopy after incubation. Similar weight loss occurred on incubation of polymers in both bacterial cultures and non-bacterial control. The presence of styrene was found to decrease the amount of weight loss. The polymer surfaces showed microscopic cracks and holes after incubation, again, this phenomenon was less pronounced with increasing styrene content. As there was no increase in polymer degradation in the presence of azo reducing microorganisms, the results of this study suggest that these polymers are degraded by mechanisms other than azo reduction.

The influence of lactose carrier on the content homogeneity and dispersibility of beclomethasone dipropionate from dry powder aerosols

Dry powder formulations for inhalation usually comprise a mixture of coarse lactose (CL), employed as a carrier, and micronized drug. It was the aim of this study to determine the effects of fine lactose (FL), blended as a tertiary component on the mixing homogeneity and dispersibility of a model hydrophobic drug, beclomethasone dipropionate (BDP). BDP particles (volume median diameter (VMD) 4.6 microm) existed mainly as agglomerates, the majority of which were not dispersed into primary particles after aerosolization at a high shear force (4.7 psi). The resultant particle size distribution of BDP was multi-modal with VMD varying between 4.7 and 30.2 microm. Ternary interactive mixtures were prepared to consist of CL, FL and BDP with a fixed ratio of lactose to BDP of 67.5:1 w/w, but two concentrations of FL, i.e. 2.5 and 5%, w/w. The mixing was carried out using different sequences of adding the three components for two mixing times (15 and 60 min). Binary mixtures composed of CL and BDP were prepared for both mixing times as the controls, and these exhibited a coefficient of variation (COV) in BDP content <= 5%. Addition of FL to the binary formulations greatly reduced the content uniformity of BDP if the final powder were prepared by first mixing CL with FL before mixing with the drug (COV>20%, after mixing for 15 min). However, the mixtures, prepared using other mixing sequences, had a similar uniformity of BDP content to the binary mixtures. All ternary mixtures containing 2.5% FL consistently produced a significantly higher (ANOVA P<0.01) fine particle fraction (FPF, 3.1--6.1%) and fine particle dose (FPD, 13.6--30.1 microg) of BDP than the binary mixtures (FPF, 0.3-0.4%; FPD, 1.6-2.1 microg) after aerosolization at 60 l min(-1) via a Rotahaler into a twin stage liquid impinger. The mixing sequences exerted a significant (P<0.05) effect on the dispersion and deaggregation of BDP from the formulations prepared using a mixing time of 15 min but such an effect disappeared when the mixing time was lengthened to 60 min. The dispersibility of BDP was always higher from the ternary mixtures than from the binary mixtures. BDP delivery from dry powder inhalers was improved markedly by adding FL to the formulation, without substantial reduction in the content uniformity of the drug.

Anti-mucus polyclonal antibody production, purification and linkage to the surface of albumin microspheres

This aim of this study was to develop a microparticulate based oral drug delivery system, which could prolong gut transit time by binding via specific interactions to the gut mucus layer. Porcine gastric mucus was semi-purified and used as an antigen to raise a polyclonal antiserum in rabbits. The immunoglobulin fraction of this serum was isolated, purified and tested for homogeneity and cross reactivity. High cross-reactivity was displayed when the antiserum was challenged against types of mucus other than that used as an antigen, but no significant cross-reactivity occurred when challenged against some other common macromolecules. The antibody fraction of this serum was covalently linked to three types of albumin microspheres (MS) using 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide. The MS employed had either a hydrophobic, a hydrophilic or a carboxymethylated surface, and were prepared and characterised as described earlier (MacAdam, A.B., Shafi, Z.B., Martin, G.P. and James, S.L. 1997. Preparation of hydrophobic and hydrophilic MS and determination of surface carboxylic acid and amino residues. Int. J. Pharm. 151, 47-55). Binding of these MS to both radioiodinated mucin in suspension and to isolated gut segments was measured. Hydrophilic and carboxymethylated MS with surface-associated antibody bound significantly more mucin from a suspension than did uncoated controls. Similarly, anti-mucus antibody-coated hydrophilic and carboxymethylated MS bound more strongly to an isolated gut segment than did uncoated controls or controls coated in an antibody specific for albumin. These results suggest anti-mucus antibody coated albumin MS may be a useful model to act as comparators in studies aimed at developing drug delivery systems with delayed gastrointestinal transit.

A study of drug-carrier interactions in dry powder inhaler formulations using the Andersen cascade impactor, X-ray microanalysis and time of flight aerosol beam spectrometry (TOFABS)

The purpose of this study was to determine the in vitro deposition of both drug (albuterol sulfate) and carrier (lactose) particles in relation to each other from a dry powder inhaler formulation using an Andersen cascade impactor (ACI) and time of flight aerosol beam spectrometry (TOFABS). In addition, scanning electron microscopy (SEM) combined with X-ray microanalysis was employed to distinguish albuterol sulfate from lactose. Drug particles apparently penetrated deeper into the impactor than lactose particles contained in the formulation. In some certain stages of impactor, drug particles were separated from lactose particles. Although the TOFABS cannot distinguish between albuterol sulfate and lactose, the TOF spectra obtained from the Aerosizer would appear to be partly indicative of the interactions which exist between drug and carrier. One symmetrical TOF peak was obtained from drug or lactose alone. The TOF peak of the drug was always lower than the TOF of lactose. The times obtained for each powder between experiments were highly reproducible and typical of material and particle size. The use of SEM-X-ray microanalysis also allowed some qualitative characterization of shape and state of association of the two components.

The influence of hydrocolloid patch composition on the bioavailability of triamcinolone acetonide in humans

Triamcinolone acetonide (TACA) is a corticosteroid; it is used in the systemic and topical treatment of a variety of inflammatory conditions, including eczema and psoriasis. Conventionally, for topical use, the drug is formulated in a cream or ointment. However, it has been observed in vitro that percutaneous penetration of corticosteroids can be influenced by hydrocolloid patches. Corticosteroids produce a pallor or blanching when applied to the skin that correlates with anti-inflammatory activity; this property has been used extensively as a bioassay. The aim of this study therefore was to evaluate the occlusive properties of a range of hydrocolloid patches containing TACA on the drug's penetration in vivo using visual assessment and a graded multiple measurement. The in vivo hydration of these dermatological patches was also investigated. Statistical analysis of the weight gains of patches containing either NaCMC 39% or pectin 39% showed that there was a significant difference in the rates of hydration of the two types of patch (p < .005). An increase in application time of the hydrocolloid patches allowed more TACA to be released, which was illustrated by an increase in both the maximum percentage total possible score (%TPS) values and AUC, although changes in the hydrocolloid composition did not significantly alter the blanching response. All of the patches adhered well, were unobtrusive to the normal activity of the wearers, and showed great potential for the convenient, localized, prolonged delivery of drugs to the skin.

The use of different grades of lactose as a carrier for aerosolised salbutamol sulphate

Five different grades of lactose namely, anhydrous lactose, medium lactose, regular lactose, lactose crystals and foremost lactose were fractionated under similar conditions to obtain a size range of 63-90 microm and were characterised using laser diffraction and time-of-flight particle sizing techniques, scanning electron microscopy, optical microscopy image analysis, thermal gravimetric analysis and differential scanning calorimetry. Each of these lactose fractions were then blended separately with micronised salbutamol sulphate in a ratio of 67.5:1 (w/w). The mixing uniformity and percentage recovery of salbutamol sulphate in the powder blends were analysed using a validated HPLC method. The deposition profiles of the drug were determined using a 5-stage liquid impinger after aerosolisation at 60 l min(-1) via a Rotahaler. Despite the identical processing conditions, the lactose fractions were shown to differ in particle size, size distribution and concentrations of fine particles. The particles from each fraction also exhibited different surface textures and dissimilar DSC thermograms. However, all the blends of the lactose with salbutamol sulphate were found to have a relatively high uniformity of salbutamol sulphate content, as suggested by a coefficient of variation of less than 3.2%. Anhydrous and medium lactose produced a more efficient delivery of salbutamol sulphate when aerosolised from the Rotahaler in comparison to other grades of lactose. For example, the fine particle fraction (FPF) and fine particle dose (FPD) of drug from formulations containing anhydrous lactose were 13.4+/-4.2% and 57.3+/-17.6 microg, respectively, which were approximately two times higher than the respective values of the formulation containing regular lactose. Medium lactose resulted in drug FPF (7. 9+/-2.7%) and FPD (32.4+/-11.8 microg), which were significantly (ANOVA P<0.05) higher than the same parameters obtained using lactose crystals, foremost lactose and regular lactose. More efficient drug delivery from anhydrous lactose may be partly attributed to the relatively higher concentration of fine lactose in this grade of carrier, although it showed a rougher surface than the other grades of lactose. However, the relatively high FPF of the drug from medium lactose may have been due to the relatively small mean particle size and smooth surface of the particles. Therefore, the source and grade of lactose may have a substantial effect on drug delivery from dry powder inhaler formulations and care should be taken in establishing appropriate quality control parameters when selecting an appropriate grade of carrier.

Effects of particle size and adding sequence of fine lactose on the deposition of salbutamol sulphate from a dry powder formulation

Ternary mixtures composed of coarse lactose (CL) (90.8 microm), salbutamol sulphate (SS) (5.8 microm) and either micronised lactose (ML) (5 microm) or intermediate sized lactose (IML) (15.9 microm) in a ratio of 66.5:1:1 w/w were prepared using different mixing sequences of the various components. In addition, a binary mixture composed of CL and SS (67.5:1 w/w) was also prepared as the control. The in vitro deposition of SS was measured using a twin stage impinger after aerosolisation at 60 and 90 l min-1 via a Rotahaler. The aerodynamic particle size distribution of both the aerosolised SS and lactose was further analysed using an Andersen cascade impactor at 60 l min-1. All ternary mixtures produced a significantly higher (analysis of variance, P<0.01) fine particle fraction (FPF) and fine particle dose (FPD) of SS than the control after aerosolisation at either 60 or 90 l min-1. Formulations containing the ML produced significantly (P<0.05) higher FPF and FPD of SS than those containing the IML at both aerosolisation flow rates. Different mixing sequences were also shown to result in different deposition profiles of both SS and lactose after aerosolisation of the ternary mixtures containing ML at 60 l min-1. The formulation prepared by first blending ML with CL before mixing with SS produced a higher FPF and FPD of SS but a lower FPF of lactose than the same formulation in terms of composition but prepared using different mixing orders of the three components. In contrast, the formulations containing IML produced a similar deposition profile to SS, regardless of the mixing sequences, and so did the formulations containing ML aerosolised at 90 l min-1. These results suggest that the effect of mixing sequences on drug deposition may become more prominent at lower aerosolisation flow rates and by reducing the size of any added fine lactose.