Indomethacin-omeprazole as therapeutic hybrids? Salt and co-amorphous systems enhancing physicochemical and pharmacological properties.

Multidrug therapeutic hybrids constitute a promising proposal to overcome problems associated with traditional formulations containing physical mixtures of drugs, potentially improving pharmacological and pharmaceutical performance. Indomethacin (IND) is a non-selective non-steroidal anti-inflammatory drug (NSAIDs) that acts by inhibiting normal processes of homeostasis, causing a series of side effects, such as gastrointestinal symptoms. Proton pump inhibitors, such as omeprazole (OME), have been used to treat such gastrointestinal tract symptoms. In this work, two new multidrug therapeutic hybrids were prepared (an IND:OME salt and an IND:OME co-amorphous system) by ball mill grinding crystalline IND and OME under different conditions, i.e., liquid assisted grinding (LAG) with ethanol and dry grinding, respectively. The crystalline salt returned to a neutral state co-amorphous system when submitted to ball mill grinding in the absence of solvent (dry grinding), but the reverse process (LAG of the IND:OME co-amorphous system) showed partial decomposition of OME. The IND:OME co-amorphous system showed a higher physical stability than the neat IND and OME amorphous materials (with an amorphous stability longer than 100 days, compared to 4 and 16 h for the neat amorphous drugs, respectively, when stored at dry conditions at room temperature). Furthermore, OME presented a higher chemical stability in solution when dissolved from a salt form than from the pure crystalline form. The dissolution studies showed a dissolution enhancement for IND in both salt (1.8-fold after 8 h of dissolution) and co-amorphous (2.5-fold after 8 h of dissolution) forms. Anti-inflammatory activity using a mice paw oedema model showed an increase of the pharmacological response to IND at a lower dose (∼5mg/kg) for both IND:OME salt (2.8-fold) and IND:OME co-amorphous system (3.2-fold) after 6 h, when compared to the positive control group (IND, administered at 10 mg/kg). Additionally, the anti-inflammatory activity of both salt and co-amorphous form was faster than for the crystalline IND. Finally, an indomethacin-induced gastric ulceration assay in mice resulted in a higher mucosal protection at the same dose (40 mg/kg) for both IND:OME salt and IND:OME co-amorphous system when compared with crystalline OME.

Improving the drug load and in vitro performance of supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) using polymeric precipitation inhibitors.

In this study, the influence of the polymeric precipitation inhibitor (PPI) PVP/VA 64 (polyvinylpyrrolidone-co-vinyl acetate) on the physical stability and in vitro performance of supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) containing the model drug simvastatin (SIM) was investigated. A heating-cooling cycle was employed to dissolve (i) the drug in the SNEDDS preconcentrate, generating super-SNEDDS, or (ii) the drug and PPI generating PPI super-SNEDDS, both containing drug loads of 200% and 250% (with regard to the equilibrium solubility of SIM in the blank SNEDDS). PPI super-SNEDDS were prepared at PPI concentrations of 1%, 10% and 20% (w/w), respectively. The formulations were characterized using polarized light microscopy, dynamic light scattering, rheological profiling and dynamic in vitro lipolysis. The physical stability of PPI super-SNEDDS correlated with an increase in viscosity due to the additionally dissolved PVP/VA 64. PPI super-SNEDDS with drug loads of 200% and 250% containing 20% (w/w) PPI showed no drug recrystallization after more than 6 months of storage at room temperature, whereas PPI-free super-SNEDDS (250% drug load) recrystallized within two hours after equilibration to room temperature. All formulations formed nanosized droplets after emulsification in Milli-Q water. The droplet size was not affected by the PPI, but increased slightly with increasing drug load (z-average of 47.3 ± 0.4 nm for SNEDDS with 200% drug load and 55.6 ± 1.3 nm for SNEDDS with 250% drug load). PPI super-SNEDDS with a drug load of 200% containing 20% (w/w) PVP/VA 64 showed an improved performance during dynamic in vitro lipolysis, maintaining a 2.5-fold higher degree of supersaturation after 15 min of digestion compared to PPI-free super-SNEDDS of the same drug load. In conclusion, the study demonstrated the feasibility of stabilizing higher drug loads and improving the in vitro performance of super-SNEDDS by incorporating PVP/VA 64 into the preconcentrate.

Comparison of lipases for in vitro models of gastric digestion: lipolysis using two infant formulas as model substrates.

The aim of this study was to find a lipase suitable as a surrogate for Human Gastric Lipase (HGL), since the development of predictive gastrointestinal lipolysis models are hampered by the lack of a lipase with similar digestive properties as HGL. Three potential surrogates for HGL; Rhizopus Oryzae Lipase (ROL), Rabbit Gastric Lipase (RGL) and recombinant HGL (rHGL), were used to catalyze the in vitro digestion of two infant formulas (a medium-chain triacylglyceride enriched formula (MC-IF) and a predominantly long-chain triacylglyceride formula (LC-IF)). Digesta were withdrawn after 0, 5, 15, 30, 60 min of gastric digestion and after 90 or 180 min of intestinal digestion with or without the presence of pancreatic enzymes, respectively. The digesta were analyzed by scanning electron microscopy and gas chromatography to quantify the release of fatty acids (FAs). Digestions of both formulas, catalyzed by ROL, showed that the extent of gastric digestion was higher than expected from previously published in vivo data. ROL was furthermore insensitive to FA chain length and all FAs were released at the same pace. RGL and rHGL favoured the release of MC-FAs in both formulas, but rHGL did also release some LC-FAs during digestion of MC-IF, whereas RGL only released MC-FAs. Digestion of a MC-IF by HGL in vivo showed that MC-FAs are preferentially released, but some LC-FAs are also released. Thus of the tested lipase rHGL replicated the digestive properties of HGL the best and is a suitable surrogate for HGL for use in in vitro gastrointestinal lipolysis models.

In Vivo Precipitation of Poorly Soluble Drugs from Lipid-Based Drug Delivery Systems.

Precipitation of poorly water-soluble drugs from lipid-based drug delivery systems (LbDDS) has been studied extensively during in vitro lipolysis but has never been shown in vivo. The aim of this study was therefore to investigate if drug precipitation can occur from LbDDS during transit of the gastrointestinal tract in vivo. Rats were administered 300 µL of either of two LbDDS (LbDDS I and LbDDS II) loaded with danazol or fenofibrate (or paracetamol to assess gastric emptying). The rats were euthanized at various time points after administration of both LbDDS containing either drug, and the contents of the stomach and proximal part of the small intestine were harvested. The contents were analyzed for crystalline drug by X-ray powder diffraction and polarized light microscopy. No drug precipitation was evident in the stomach or the intestine after administration of LbDDS I containing danazol at the tested time points. Fenofibrate precipitation was absent in the stomach initially after administration of LbDDS I, but was evident in the stomach 90 min after dosing. No crystalline fenofibrate was observed in the intestine. Danazol and fenofibrate precipitation was evident in the stomach following administration of LbDDS II containing either drug, but not in the intestine at the tested time point. Drug precipitation from LbDDS was observed in the stomach, but not in the intestine, which is contrary to what in vitro lipolysis data (obtained under human GI conditions) suggests. Thus, precipitation of drugs from LbDDS in vivo in rats is much lower than might be anticipated from in vitro lipolysis data.

Unintended and in situ amorphisation of pharmaceuticals.

Amorphisation of poorly water-soluble drugs is one approach that can be applied to improve their solubility and thus their bioavailability. Amorphisation is a process that usually requires deliberate external energy input. However, amorphisation can happen both unintentionally, as in process-induced amorphisation during manufacturing, or in situ during dissolution, vaporisation, or lipolysis. The systems in which unintended and in situ amorphisation has been observed normally contain a drug and a carrier. Common carriers include polymers and mesoporous silica particles. However, the precise mechanisms by which in situ amorphisation occurs are often not fully understood. In situ amorphisation can be exploited and performed before administration of the drug or possibly even within the gastrointestinal tract, as can be inferred from in situ amorphisation observed during in vitro lipolysis. The use of in situ amorphisation can thus confer the advantages of the amorphous form, such as higher apparent solubility and faster dissolution rate, without the disadvantage of its physical instability.

Dissolution properties of co-amorphous drug-amino acid formulations in buffer and biorelevant media.

Co-amorphous formulations, particularly binary drug-amino acid mixtures, have been shown to provide enhanced dissolution for poorly-soluble drugs and improved physical stability of the amorphous state. However, to date the dissolution properties (mainly intrinsic dissolution rate) of the co-amorphous formulations have been tested only in buffers and their supersaturation ability remain unexplored. Consequently, dissolution studies in simulated intestinal fluids need to be conducted in order to better evaluate the potential of these systems in increasing the oral bioavailability of biopharmaceutics classification system class II drugs. In this study, solubility and dissolution properties of the co-amorphous simvastatin-lysine, gibenclamide-serine, glibenclamide-threonine and glibenclamide-serine-threonine were studied in phosphate buffer pH 7.2 and biorelevant media (fasted and fed state simulated intestinal fluids (FaSSIF and FeSSIF, respectively)). The co-amorphous formulations were found to provide a long-lasting supersaturation and improve the dissolution of the drugs compared to the crystalline and amorphous drugs alone in buffer. Similar improvement, but in lesser extent, was observed in biorelevant media suggesting that a dissolution advantage observed in aqueous buffers may overestimate the advantage in vivo. However, the results show that, in addition to stability advantage shown earlier, co-amorphous drug-amino acid formulations provide dissolution advantage over crystalline drugs in both aqueous and biorelevant conditions.

Polymer incorporation method affects the physical stability of amorphous indomethacin in aqueous suspension.

This study reports the potential of different polymers and polymer incorporation methods to inhibit crystallisation and maintain supersaturation of amorphous indomethacin (IND) in aqueous suspensions during storage. Three different polymers (poly(vinyl pyrrolidone) (PVP), hydroxypropyl methylcellulose (HPMC) and Soluplus® (SP)) were used and included in the suspensions either as a solid dispersion (SD) with IND or dissolved in the suspension medium prior to the addition of amorphous IND. The total concentrations of both IND and the polymer in the suspensions were kept the same for both methods of polymer incorporation. All the polymers (with both incorporation methods) inhibited crystallisation of the amorphous IND. The SDs were better than the predissolved polymer solutions at inhibiting crystallisation. The SDs were also better at maintaining drug supersaturation. SP showed a higher IND crystallisation inhibition and supersaturation potential than the other polymers. However, this depended on the method of addition. IND in SD with SP did not crystallise, nor did the SD generate any drug supersaturation, whereas IND in the corresponding predissolved SP solution crystallised (into the recently characterised η polymorphic form of the drug) but also led to a more than 20-fold higher IND solution concentration than that observed for crystalline IND. The ranking of the polymers with respect to crystallisation inhibition potential in SDs was SP≫PVP>HPMC. Overall, this study showed that both polymer type and polymer incorporation method strongly impact amorphous form stability and drug supersaturation in aqueous suspensions.

Application of terahertz pulsed imaging to analyse film coating characteristics of sustained-release coated pellets.

Terahertz pulsed imaging (TPI) was employed to explore its suitability for detecting differences in the film coating thickness and drug layer uniformity of multilayered, sustained-release coated, standard size pellets (approximately 1mm in diameter). Pellets consisting of a sugar starter core and a metoprolol succinate layer were coated with a Kollicoat(®) SR:Kollicoat(®) IR polymer blend for different times giving three groups of pellets (batches I, II and III), each with a different coating thickness according to weight gain. Ten pellets from each batch were mapped individually to evaluate the coating thickness and drug layer thickness between batches, between pellets within each batch, and across individual pellets (uniformity). From the terahertz waveform the terahertz electric field peak strength (TEFPS) was used to define a circular area (approximately 0.13 mm(2)) in the TPI maps, where no signal distortion was found due to pellet curvature in the measurement set-up used. The average coating thicknesses were 46 µm, 71 µm and 114 µm, for batches I, II and III respectively, whilst no drug layer thickness difference between batches was observed. No statistically significant differences in the average coating thickness and drug layer thickness within batches (between pellets) but high thickness variability across individual pellets was observed. These results were confirmed by scanning electron microscopy (SEM). The coating thickness results correlated with the subsequent drug release behaviour. The fastest drug release was obtained from batch I with the lowest coating thickness and the slowest from batch III with the highest coating thickness. In conclusion, TPI is suitable for detailed, non-destructive evaluation of film coating and drug layer thicknesses in multilayered standard size pellets.

Cubosomes containing the adjuvants imiquimod and monophosphoryl lipid A stimulate robust cellular and humoral immune responses.

New generation vaccines increasingly utilize highly purified peptides and proteins as the target antigen, however these are often poorly immunogenic. One of the most promising strategies for improving immunogenicity of such subunit vaccines is through incorporation into particulate carriers. Here we report the preparation, physicochemical characterization and in vivo immunological activity of cubosomes, a novel lipid-based nanostructured particulate carrier, modified to include the Toll-like receptor agonists monophosphoryl lipid A and imiquimod. The immunological activity of cubosome formulations was compared to that of liposome and alum formulations. Sustained release of the model antigen ovalbumin (Ova) was observed in vitro and in vivo from cubosomes. Cubosomes+adjuvants induced robust CD8⁺ and CD4⁺ T cell proliferation and interferon-γ production, as well as the production of Ova-specific antibodies. Cubosomes+adjuvants were more efficient at generating Ova-specific cellular responses and were equally as effective in generating humoral responses when compared to liposomes+adjuvants and alum. Overall, the results show that cubosomes have the potential to act as effective sustained release vaccine delivery systems.

The impact of surface- and nano-crystallisation on the detected amorphous content and the dissolution behaviour of amorphous indomethacin.

The crystallinity and physical stability of amorphous drugs has previously been studied using different analytical techniques. However, the effect of the measurement method on observed crystallinity and its importance for critical quality attributes, such as dissolution, has not yet been widely investigated. The aim of this study was to (i) qualitatively analyse and understand the recrystallisation behaviour of amorphous indomethacin during storage, (ii) quantify the amorphous content during storage with complementary analytical techniques and (iii) investigate the relationship between observed recrystallisation behaviour and dissolution behaviour. Quench cooled indomethacin was stored and the samples were visualised by scanning electron microscopy to gain spatially resolved information about the recrystallisation behaviour. Crystallisation was quantified by Fourier transform attenuated total reflectance infrared (FT-ATR-IR) spectroscopy, differential scanning calorimetry and X-ray powder diffraction. These techniques resulted in different observed recrystallisation profiles. The physicochemical phenomena detected and sampling geometry for each technique together with the sample recrystallising from the surface and appearance of nano-crystals were used to explain the differences. The dissolution behaviour at the observed recrystallisation endpoints for the different analytical techniques revealed that FT-ATR-IR spectroscopy predicted the changes in dissolution behaviour due to crystallisation best.

In vitro and in vivo performance of novel supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS).

Novel supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) containing the poorly water-soluble drug halofantrine above equilibrium solubility (150% S(eq)) were compared in vitro and in vivo with conventional SNEDDS containing the drug below equilibrium solubility (75% S(eq)). Pre-concentrates comprising of either medium chain lipids (Captex 300/Capmul MCM) or long chain lipids (soybean oil/Maisine), Cremophor RH40 and ethanol were formulated maintaining the lipid-to-surfactant-to-cosolvent ratio constant (55:35:10, w/w %). The ability of super-SNEDDS to increase the absorption of halofantrine in dogs, as well as the predictivity of the dynamic in vitro lipolysis model was studied. In vitro lipolysis of SNEDDS and super-SNEDDS showed rapid drug precipitation from all formulations while the same drug concentrations in the digestion medium were found during digestion of equal amounts of SNEDDS and super-SNEDDS. Elevated halofantrine solubilisation during in vitro lipolysis was observed only when multiple capsules of conventional SNEDDS were subjected to in vitro digestion. After lipolysis the isolated super-SNEDDS pellets were characterised by XRPD revealing no crystalline halofantrine from any of the investigated formulations. Subsequent dissolution studies of the super-SNEDDS pellet in the lipolysis medium demonstrated enhanced dissolution of halofantrine suggesting that halofantrine in the pellet was amorphous. The enhanced dissolution of the amorphous halofantrine was also reflected in vivo since two capsules of conventional SNEDDS were needed to achieve similar AUC and C(max) as obtained after dosing of a single capsule of super-SNEDDS. The study demonstrated that the absorption of halofantrine was not hampered by drug precipitation. Super-SNEDDS lead to precipitation of halofantrine in an amorphous form, which can be the driving force for enhanced absorption. Since super-SNEDDS were also physically stable for at least 6 months they represent a potential novel oral lipid-based drug delivery system for low aqueous soluble compounds.

Investigations on the effect of different cooling rates on the stability of amorphous indomethacin.

Amorphous forms of indomethacin have previously been prepared using various preparation techniques and it could be demonstrated that the way the material was prepared influenced the physicochemical properties of the amorphous form of the drug. The aim of this study was to use one preparation technique (transformation via the melt) to prepare amorphous indomethacin and to investigate the influence of the cooling rate (as a processing parameter) on the physical stability of the resulting amorphous form. The amorphous materials obtained were analysed for their structural characteristics using Raman spectroscopy in combination with multivariate data analysis. The onset of crystallisation was determined as an indicator of the physical stability of the materials using differential scanning calorimetry (DSC) and polarising light microscopy. The Johnson-Mehl-Avrami (JMA) model and Sestak-Berggren (SB) model were used in this study to describe the non-isothermal crystallisation behaviour. All differently cooled samples were completely X-ray amorphous. Principal component analysis of the Raman spectra of the various amorphous forms revealed that the samples clustered in the scores plot according to the cooling rate, suggesting structural differences between the differently cooled samples. The minimum cooling rate required to obtain amorphous indomethacin was 1.2 K min(-1), as assessed from the time-temperature-transformation (TTT) diagram. The physical stability of the samples was found to increase as a function of cooling rate in the order of 30 K min(-1) > 20 K min(-1) > 10 K min(-1) > 5 K min(-1) > 3 K min(-1) ≈ 1.2 K min(-1) and was in agreement with calculated descriptors for the glass forming ability (GFA), including the reduced glass transition temperature (T(rg)) and the reduced temperature (T(red)). The JMA model could not be applied to describe the crystallisation process for the differently cooled melts of indomethacin in this study. The kinetic exponent M from the autocatalytic SB model however, showed a positive correlation with glass stability.

Preparation of phytantriol cubosomes by solvent precursor dilution for the delivery of protein vaccines.

Different delivery strategies to improve the immunogenicity of peptide/protein-based vaccines are currently under investigation. In this study, the preparation and physicochemical characterisation of cubosomes, a novel lipid-based particulate system currently being explored for vaccine delivery, was investigated. Cubosomes were prepared from a liquid precursor mixture containing phytantriol or glycerylmonooleate (GMO), F127 for particle stabilisation, and a hydrotrope (ethanol or polyethylene glycol (PEG(200)) or propylene glycol (PG)). Several liquid precursors were prepared, and the effect of varying the concentrations of F127 and the hydrotrope on cubosome formation was investigated. Formulations were prepared by fragmentation for comparison. The model protein ovalbumin (Ova) was also entrapped within selected formulations. Submicron-sized particles (180-300 nm) were formed spontaneously upon dilution of the liquid precursors, circumventing the need for the preformed cubic phase used in traditional fragmentation-based methods. The nanostructure of the phytantriol dispersions was determined to be cubic phase using SAXS whilst GMO dispersions had a reverse hexagonal nanostructure coexisting with cubic phase. The greatest entrapment of Ova was within phytantriol cubosomes prepared from liquid precursors. Release of Ova from the various formulations was sustained; however, release was significantly faster and the extent of release was greater from fragmented dispersions compared to liquid precursor formulations. Taken together, these results suggest that phytantriol cubosomes can be prepared using liquid precursors and that it is a suitable alternative to GMO. Furthermore, the high entrapment and the slow release of Ova in vitro highlight the potential of phytantriol cubosomes prepared using liquid precursors as a novel vaccine delivery system.

Deeper insight into the drug release mechanisms in Eudragit RL-based delivery systems.

Tartaric acid, metoprolol free base and metoprolol tartrate act as plasticisers for Eudragit RL, in the dry but also in the wet state. Fitting analytical solutions of Fick's second law of diffusion allowed for the determination of the apparent diffusivities of water and of tartaric acid, metoprolol free base and metoprolol tartrate upon exposure of thin films to 0.1M HCl, phosphate buffer pH 7.4 and distilled water. Based on these calculations, it could be shown that water penetration into the systems is predominantly controlled by pure diffusion, irrespective of the type of bulk fluid. Interestingly, the plasticising effect of metoprolol tartrate was much more pronounced than that of tartaric acid, resulting in monotonically increasing diffusion coefficients with increasing initial drug content. In contrast, the plasticising activity of metoprolol free base was very limited in the wet state, due to drug precipitation in aqueous environments. Partially observed film shrinking (after an initial system swelling) could be attributed to the leaching of the plasticising compound into the release medium, resulting in less flexible polymeric networks and squeezing out of water. Also the release of tartaric acid, metoprolol free base and metoprolol tartrate into the investigated bulk fluids was predominantly diffusion controlled. However, the precipitation of the free base in wet films rendered the mass transport mechanisms more complex, at moderate and high initial drug loadings. The obtained new insight into the underlying drug release mechanisms in Eudragit RL networks can help to facilitate the optimisation of this type of dosage forms.

Polymeric nanoparticles as an oral delivery system for biocontrol agents for the brushtail possum (Trichosurus vulpecula).

AIM: To investigate polymeric nanoparticles as an oral delivery system for protein biocontrol agents for control of the brushtail possum, Trichosurus vulpecula. METHODS: Insulin-loaded poly(ethyl 2-cyanoacrylate) (PECA) nanoparticles were prepared using interfacial polymerisation, and characterised for size, zeta potential, and efficiency of encapsulation of insulin. In-vitro release of insulin-loaded PECA nanoparticles was quantified using reverse-phase high-pressure liquid chromatography (HPLC). The in-vivo pharmacokinetics of insulin in PECA nanoparticles was investigated following I/V administration, and when injected directly into the caecum alone or in conjunction with the permeation enhancer EDTA. Blood samples were collected at intervals from -5 to 180 minutes, and the concentration of insulin in plasma was quantified using a radioimmunoassay (RIA) validated for possum plasma. RESULTS: Poly(ethyl 2-cyanoacrylate) nanoparticles were produced with a uniform particle size of 200-300 nm, and the mean entrapment of insulin was 78%. In-vitro release of insulin from the PECA nanoparticles was controlled, although incomplete, and approximately 30% of the insulin remained entrapped. The bioavailability of insulin when administered in a PECA nanoparticulate formulation injected directly into the caecum was <1%, and was not increased by addition of the permeation enhancer. CONCLUSIONS: The nanoparticulate formulations investigated as part of this study resulted in low bioavailability of the peptide insulin in the brushtail possum.

Characterisation of quaternary polymethacrylate films containing tartaric acid, metoprolol free base or metoprolol tartrate.

The aim of this study was to better understand the interactions between metoprolol tartrate and quaternary polymethacrylate (Eudragit RL and Eudragit RS) films. For reasons of comparison, polymeric films containing the free base metoprolol or free tartaric acid were also prepared. Systems containing various amounts of the free base, free acid and the salt were characterised using polarising light microscopy, X-ray powder diffraction, differential scanning calorimetry and mechanical analysis (puncture test). The free base is the most efficient plasticiser of the three species for Eudragit RL and Eudragit RS, but with limited solubility in the polymers. Due to its hydrophobicity, it can interact with the hydrophobic polymer backbones. In contrast, in salt containing films, ionic interactions between the positively charged quaternary ammonium groups and the negatively charged tartrate anions apparently occur, this being suggested by the different effects on Eudragit RL versus RS, which have different contents of quaternary ammonium groups. Importantly, the combination of acid and base as a salt avoids drug precipitation at higher metoprolol contents. The obtained new insight into the occurring drug-polymer interactions can help to facilitate the development/optimisation of this type of dosage forms.

Liquid crystalline systems of phytantriol and glyceryl monooleate containing a hydrophilic protein: Characterisation, swelling and release kinetics.

Swelling and phase behaviour of phytantriol and glyceryl monooleate (GMO) matrices with varying water loadings were investigated. Release of a model protein, FITC-Ova was subsequently examined. Polarised light microscopy and small angle X-ray scattering analysis showed that the addition of FITC-Ova only altered the liquid crystalline structure of phytantriol matrices at low water loadings, and that postrelease study, the phase structure of matrices at both low and high loading reflected that of the binary system. Addition of FITC-Ova to GMO matrices also altered the liquid crystalline structure when compared to the respective binary system at low but not at high loading. All samples analysed after the release study had transformed to the reverse hexagonal phase (H(II)). Swelling studies revealed a faster and more extensive swelling of GMO when compared to phytantriol. Release of FITC-Ova from phytantriol matrices was faster and occurred to a greater extent most likely due to the conversion of GMO matrices into the H(II) phase. No effect on release as a function of initial water content was observed for either lipid. We have confirmed that phytantriol based liquid crystalline matrices can sustain the release of a hydrophilic protein, suggesting its suitability as a potential sustained antigen-delivery system.

Effects of some terpenes on the in vitro permeation of LHRH through newborn pig skin.

The objective of this work was to investigate the effect of oxygen containing terpenes (carvacrol, menthol and carvone) at 5%w/v in hydroalcoholic mixtures (40% ethanol) on the permeation of LHRH across newborn pig skin in vitro. In addition, the amount of LHRH retained in the skin after 24 h of diffusion was determined. It was found that the passive permeation of LHRH was very limited. Although percutaneous absorption of LHRH improved in the presence of the enhancers, a significant enhancement was observed only with carvacrol, an aromatic terpene. The rank order of enhancement ratio for skin permeation was found to be carvacrol > carvone > menthol. The enhancers also affected the retention of LHRH in the skin. The rank order of enhancement ratio for skin retention was carvone > carvacrol > menthol. The results of the in vitro skin metabolism study of LHRH using fresh newborn pig skin showed that the degradation products were detected and the amount of the degraded LHRH increased with increasing duration of incubation time.

Immunogenicity of lipid sustained release implants containing imiquimod, alpha-galactosylceramide, or Quil-A.

The aim of this study was to investigate and compare the immunogenicity of liposome-forming, sustained release lipid implants containing either an alpha-galactosylceramide (alpha-GalCer) analogue, imiquimod or Quil-A (QA) as adjuvants. Ovalbumin (OVA) was used as a model antigen. Groups of C57Bl/6 mice were subcutaneously immunised with lipid implants containing one of the adjuvants, or inoculated with OVA in alum. The expansion of CD8+ and CD4+ transgenic T cells was analysed to assess the ability of these implants to stimulate cell-mediated immunity. In addition, the production of OVA-specific IgG antibodies was determined. QA-containing lipid implants were more efficient in the stimulation of CD8+ T cells and IgG antibodies than the two immunomodulators alpha-GalCer and imiquimod. These results suggest that, using this immunisationprotocol and dose of immunomodulators, QA was superior to imiquimod and alpha-GalCer.

Analysis of sustained-release tablet film coats using terahertz pulsed imaging.

The coating quality of a batch of lab-scale, sustained-release coated tablets was analysed by terahertz pulsed imaging (TPI). Terahertz radiation (2 to 120 cm(-1)) is particularly interesting for coating analysis as it has the capability to penetrate through most pharmaceutical excipients, and hence allows non-destructive coating analysis. Terahertz pulsed spectroscopy (TPS) was employed for the determination of the terahertz refractive indices (RI) on the respective sustained-release excipients used in this study. The whole surface of ten tablets with 10 mg/cm(2) coating was imaged using the fully-automated TPI imaga2000 system. Multidimensional coating thickness or signal intensity maps were reconstructed for the analysis of coating layer thickness, reproducibility, and uniformity. The results from the TPI measurements were validated with optical microscopy imaging and were found to be in good agreement with this destructive analytical technique. The coating thickness around the central band was generally 33% thinner than that on the tablet surfaces. Bimodal coating thickness distribution was detected in some tablets, with thicker coatings around the edges relative to the centre. Aspects of coating defects along with their site, depth and size were identified with virtual terahertz cross-sections. The inter-day precision of the TPI measurement was found to be within 0.5%.