Gamma-scintigraphy as a novel method to study the distribution and retention of a bioadhesive vaginal delivery system in sheep

Encapsulation and release of hydrocortisone from proliposomes govern vaginal delivery

Topical preparations of hydrocortisone can be used for the anti-inflammatory treatment of the female genital area. Although the drug is a low-strength corticosteroid, systemic absorption and distribution of the drug are the most common safety risks associated with this therapy. In the current investigation, we elucidate the physicochemical properties of lipid-based drug carrier systems that govern the local bioavailability of hydrocortisone for intravaginal administration. For this purpose, we compared various proliposome formulations with a commercial cream. Depending on the availability of physiological acceptors, encapsulation and drug release from the lipid phase were found to be the most important drivers of drug bioavailability. The high permeability of hydrocortisone leads to rapid transport of the drug across the mucosal cell layer as indicated by experiments using HEC-1-A and CaSki cell monolayer models. Under sink conditions, differences in the release from the liposomes as determined in the Dispersion Releaser were almost negligible. However, under non-sink conditions, the drug release plateaued at levels corresponding to the encapsulation efficiency. After redispersion, all liposomal formulations performed better than the commercial drug product indicating that the encapsulation into the lipid phase is the main driver sustaining the release.

Intravaginal Delivery of Polyphenon 60 and Curcumin Nanoemulsion Gel

Polyphenon 60 (P60) and curcumin (CUR) were loaded in a single nanoemulsion system and their combined antibacterial action was studied against uropathogenic Escherichia coli. To enhance availability at target organs and to inhibit enzymatic degradation in gastro intestinal tract, vaginal route of administration was explored. P60 + CUR nanoemulsion (NE) was formulated by ultra-sonication and optimized using Box-Behnken design. Optimized NE showed Z-average of 211.2 nm, polydispersity index of 0.343, and zeta potential of -32.7 mV. Optimized P60+ CUR NE was characterized by stability testing and transmission electron microscopy, and it was observed that NE was stable at 4°C for 30 days and monodisperse in nature with particle size of 195-205 nm. P60+ CUR NE was further formulated as gel and characterized by viscosity, growth curve analysis, and in vitro permeation studies. In vitro drug permeation studies in simulated vaginal media showed maximum permeation (84 ± 0.21%) of curcumin within 5 h and (91 ± 0.16%) of P60 within 8 h. Both the drugs maintained sustained permeation for 12 h. To investigate the transport via intravaginal route, gamma scintigraphy and biodistribution study of P60 + CUR NBG was performed on Sprague-Dawley rats using ^99mtechnetium pertechnetate for radiolabeling to P60 molecule. Following intravaginal administration, P60 + CUR NBG dispersed in the kidney and urinary bladder with (3.07 ± 0.15) and (3.35 ± 0.45) percentage per gram after 3 h for P60 and CUR, respectively, and remained active for 12 h. Scintigraphy images suggested that the P60 + CUR NBG given by intravaginal route led to effective distribution of actives in urinary tract, and this observation was in agreement with the biodistribution results.

A 32full factorial design for development and characterization of a nanosponge-based intravaginal in situ gelling system for vulvovaginal candidiasis

The rationale behind present research effort was to enhance CTZ solubility and efficacyviaforming complex with hydroxypropyl β-cyclodextrin (HP-β-CD) nanosponges.

Recent progresses in bioadhesive microspheres via transmucosal administration

Based on the advantages of adhesion preparations and the application status of microspheres (MSs) in mucous delivery, this paper primarily reviews the bioadhesive MSs via transmucosal administration routes, including the mucosa in alimentary tract and other lumens. Particularly, the detailed researches about of celladhesive MSs and some new-style bioadhesive MSs are mentioned. Furthermore, this review attempts to reveal the advances of bioadhesive MSs as cell-selective bioadhesion systems and the stimuli-responsive MSs as location-specific drug delivery systems. Although these MSs show powerful strength, some far-sighted ideas should be brought on agendas. In the future, mechanisms should be put under tight scrutiny and more attention should be focused on the excellent bioadhesive materials and the 'second generation mucoadhesives'. Meaningful clinical applications of these novel MSs are also of current concerns and need more detailed researches.

Mucoadhesive and thermogelling systems for vaginal drug delivery

This review focuses on two formulation approaches, mucoadhesion and thermogelling, intended for prolonging residence time on vaginal mucosa of medical devices or drug delivery systems, thus improving their efficacy. The review, after a brief description of the vaginal environment and, in particular, of the vaginal secretions that strongly affect in vivo performance of vaginal formulations, deals with the above delivery systems. As for mucoadhesive systems, conventional formulations (gels, tablets, suppositories and emulsions) and novel drug delivery systems (micro-, nano-particles) intended for vaginal administration to achieve either local or systemic effect are reviewed. As for thermogelling systems, poly(ethylene oxide-propylene oxide-ethylene oxide) copolymer-based and chitosan-based formulations are discussed as thermogelling systems. The methods employed for functional characterization of both mucoadhesive and thermogelling drug delivery systems are also briefly described.

Toward mucoadhesive hydrogel formulations for the management of xerostomia: the physicochemical, biological, and pharmacological considerations

Although hydrogel formulations that may be applied to many mucosal surfaces are now readily accessible, little research effort has been concentrated on the development of systems that may be usefully employed for the prolonged hydration of the oral cavity. To this end, and set within the context of oral care in general, this review considers the requirements for the design of hydrogel formulations with an affinity for buccal cells and details methods for evaluating the performance of these formulations as treatments for the management of xerostomia.

Hydrogels in mucosal delivery

The concept of mucoadhesion and the molecular design requirements for the synthesis of mucoadhesive agents are both well understood and, as a result, hydrogel formulations that may be applied to mucosal surfaces are readily accessible. Nanosized hydrogel systems that make use of biological recognition or targeting motifs, by reacting to disease-specific environmental triggers and/or chemical signals to affect drug release, are now emerging as components of a new generation of therapeutics that promise improved residence time, faster response to stimuli and triggered release.

Vaginal distribution and retention of a multiparticulate drug delivery system, assessed by gamma scintigraphy and magnetic resonance imaging

BACKGROUND

For any new vaginal dosage form, the distribution and retention in the vagina has to be assessed by in vivo evaluation. We evaluated the vaginal distribution and retention of starch-based pellets in sheep as live animal model by gamma scintigraphy (using Indium-111 DTPA as radiolabel) and in women via magnetic resonance imaging (MRI, using a gadolinium chelate as contrast agent). A conventional cream formulation was used as reference in both studies.

METHOD

Cream and pellets were administered to sheep (n=6) in a two period-two treatment study and to healthy female volunteers (n=6) via a randomized crossover trial. Pellets (filled into hard gelatin capsule) and cetomacrogol cream, both labeled with Indium-111 DTPA (for gamma scintigraphy) or with gadolinium chelate (for MRI) were evaluated for their intravaginal distribution and retention over a 24h period. Spreading in the vagina was assessed based on the part of the vagina covered with formulation (expressed in relation to the total vaginal length). Vaginal retention of the formulation was quantified based on the radioactivity remaining in the vaginal area (sheep study), or qualitatively evaluated (women study).

RESULTS

Both trials indicated a rapid distribution of the cream within the vagina as complete coverage of the vaginal mucosa was seen 1h after dose administration. Clearance of the cream was rapid: about 10% activity remained in the vaginal area of the sheep 12h post-administration, while after 8h only a thin layer of cream was detected on the vaginal mucosa of women. After disintegration of the hard gelatin capsule, the pellet formulation gradually distributed over the entire vaginal mucosa. Residence time of the pellets in the vagina was longer compared to the semi-solid formulation: after 24h 23 ± 7% radioactivity was detected in the vaginal area of the sheep, while in women the pellet formulation was still detected throughout the vagina.

CONCLUSION

A multi-particulate system containing starch-based pellets was identified as a promising novel vaginal drug delivery system, resulting in complete coverage of the vaginal mucosa and long retention time.

Injectable PAMAM dendrimer-PEG hydrogels for the treatment of genital infections: formulation and in vitro and in vivo evaluation

Local intravaginal drug therapy is preferred for treatment of ascending genital infections during pregnancy. In the present study, an in situ forming biodegradable hydrogel for sustained release of amoxicillin in the cervicovaginal region is described. A generation 4 poly(amidoamine) [G4-(NH(2))(64)] dendrimer with peripheral thiopyridyl terminations is cross-linked with 8-arm polyethylene glycol (PEG) bearing thiol terminations. The hydrogels were formulated and tested in vivo in a pregnant guinea pig model for volume, retention times, biodegradation, tolerability and transport across fetal membrane. The physicochemical characterization of the hydrogels was carried out using differential calorimetry, SEM, and confocal imaging. The hydrogels offer antibacterial activity arising from sustained release of amoxicillin from gels. The in vivo studies in guinea pig showed that 100-200 μL of gel sufficiently covered the cervicovaginal region with a residence time of at least 72 h and gel was primarily retained in the maternal tissues without crossing the fetal membranes into the fetus. The dendrimer gels were stable up to 72 h, and the in vivo biodegradation of gel occurred after 72 h; this correlated well with the in vitro degradation pattern. The pH of the vagina was not altered upon application of the gel, and none of the animals aborted up to 72 h after application of gel. The histological evaluation of the cervical tissues showed absence of edema in the epithelial cell layer, no sloughing of the epithelial or superficial mucous layer, and absence of necrosis and infiltration of inflammatory cells in the submucosal layers, confirming that tissues were tolerant to the gel. The immunohistofluorescence images showed the localization of the gel components on the superficial mucified epithelial layer. The cross-linking density and swelling of hydrogels was impacted by the polymer content, and the 10% hydrogels exhibited the highest cross-link density. The in vitro drug release studies carried out using Franz diffusion cells showed that amoxicillin release from 6 and 10% gels was sustained for 240 h as compared to 3% gels. As the polymer concentration increased to 10%, the release pattern from gels approached diffusion controlled mechanism with diffusional exponent n = 0.49. In conclusion, the biodegradable in situ forming hydrogels of the present study offer a therapeutic option to provide sustained localized delivery of amoxicillin intracervically to the pregnant woman for the treatment of ascending genital infections.

Nano-microbicides: challenges in drug delivery, patient ethics and intellectual property in the war against HIV/AIDS

As we continue to be embroiled in the global battle against the human immunodeficiency virus (HIV), there has been an ongoing evolution in the understanding of the molecular mode of sexual transmission of HIV. This has gone hand-in-hand with a paradigm shift and research focus on the development of microbicides - compounds designed for vaginal (and possibly rectal) administration that are envisaged to put safe, affordable and accessible protection into the hands of women. However, an effective microbicide is not yet available; innovative approaches for the design of topical vaginal microbicides are urgently needed. The potential of the advancing field of nanomedicine has been earmarked in the increasing efforts to address the major health problems of the developing world. In this review, advances in the design of innovative microbicide nanocarriers and nano-enabled microbicides, henceforth referred to as 'nano-microbicides', are presented; elaborating on nanotechnology's role in the antiviral arena. The role of nanotechnology in the antiviral arena and the unique issues facing the generation of intellectual property relating to nano-microbicides in the ongoing global 'tug-of-war' of 'patients versus patents' are also explicated.

Microemulsion-based vaginal gel of clotrimazole: formulation, in vitro evaluation, and stability studies

The objective of the present investigation was to develop and evaluate microemulsion-based gel for the vaginal delivery of clotrimazole (CMZ). The solubility of CMZ in oils and surfactants was evaluated to identify components of the microemulsion. The ternary diagram was plotted to identify the area of microemulsion existence. Various gelling agents were evaluated for their potential to gel the CMZ microemulsion without affecting its structure. The bioadhesive potential and antifungal activity of the CMZ microemulsion-based gel (CMZ-MBG) was determined in comparison to the marketed clotrimazole gel (Candid-V gel) by in vitro methods. The chemical stability of CMZ in CMZ-MBG was determined as per the International Conference on Harmonization guidelines. The CMZ microemulsion exhibited globule size of 48.4 nm and polydispersity index of 0.75. Carbopol ETD 2020 could successfully gel the CMZ microemulsion without disturbing the structure. The CMZ-MBG showed significantly higher (P < 0.05) in vitro bioadhesion and antifungal activity as compared to that of Candid-V gel. The stability studies indicated that CMZ undergoes acidic pH-catalyzed degradation at all the storage conditions at the end of 3 months.

Antimicrobial activity of clove oil and its potential in the treatment of vaginal candidiasis

In the present study, we evaluated antimicrobial activity of clove oil against a range of fungal pathogens including that responsible for urogenital infection. Clove oil was found to possess strong antifungal activity against opportunistic fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, etc. The oil was found to be extremely successful in the treatment of experimental murine vaginitis in model animals. On evaluating various formulations, topical administration of the liposomized clove oil was found to be most effective against treatment of vaginal candidiasis.

MIP3 alpha stimulates the migration of Langerhans cells in models of human papillomavirus (HPV)-associated (pre)neoplastic epithelium

Although human papillomavirus (HPV) DNA is detected in the majority of cervical cancers and their precursors (squamous intraepithelial lesions; SIL), the persistence or progression of cervical lesions could be associated with quantitative and functional alterations of dendritic/Langerhans cells (DC/LC). As LC abnormalities have been associated with a decreased expression of macrophage inflammatory protein 3alpha (MIP3alpha) in cervical SIL, we tested the effect of exogenous MIP3alpha on the migration of LC in a (pre)neoplastic epithelium formed in vitro. By using a Boyden chamber assay, we first showed that the migratory capacity of LC generated in vitro is significantly increased in the presence of MIP3alpha compared to control medium. We next demonstrated that MIP3alpha is able to increase the 3D infiltration of LC in organotypic cultures of HPV-transformed keratinocytes. This property to stimulate LC migration was not altered after inclusion of MIP3alpha in a bioadhesive polycarbophil gel. Moreover, the function of DC to exert cytostatic effects and to present alloantigens was not altered in the presence of MIP3alpha.

Characterisation and in vitro evaluation of bioadhesive liposome gels for local therapy of vaginitis

The purpose of this study was to design and evaluate a new vaginal delivery system for the local treatment of vaginitis. Liposomes containing two commonly applied drugs in the treatment of vaginal infections, namely clotrimazole and metronidazole, were prepared by the proliposome and the polyol dilution methods. Both types of liposomes were characterised and compared for particle size, polydispersity, entrapment efficiency, and tested for in vitro stability in media that mimic human vaginal conditions (buffer, pH 4.5, and vaginal fluid simulant). To achieve application viscosity and to further improve their stability, liposomes containing drugs were incorporated in a bioadhesive gel made of Carbopol 974P NF resin. In vitro release studies have demonstrated that even after 24 h of incubation in vaginal fluid simulant (at 37 degrees C) more than 30% of the originally entrapped clotrimazole (or 50% of metronidazole) was still retained in the gel. Storage stability studies have proved the ability of Carbopol 974P NF gel to preserve original size distributions of incorporated liposomes. All the performed experiments confirm the applicability of bioadhesive liposome gels as a novel delivery system for local therapy of vaginal infections.

In vitro and in vivo studies on mucoadhesive microspheres of amoxicillin

Amoxicillin mucoadhesive microspheres (Amo-ad-ms) were prepared using ethylcellulose (Ec) as matrix and carbopol 934P as mucoadhesive polymer for the potential use of treating gastric and duodenal ulcers, which were associated with Helicobacter pylori. The morphological characteristics of the mucoadhesive microspheres were studied under scanning electron microscope. In vitro release test showed that amoxicillin released faster in pH 1.0 hydrochloric acid (HCl) than in pH 7.8 phosphate buffer. Yet, it would be degraded to some extent in a pH 1.0 HCl medium at 37 degrees C, which indicated that amoxicillin was not stable in an acidic surrounding. It was also found that amoxicillin entrapped within the microspheres could keep stable. In vitro and in vivo mucoadhesive tests showed that Amo-ad-ms adhered more strongly to gastric mucous layer than nonadhesive amoxicillin microspheres (Amo-Ec-ms) did and could retain in gastrointestinal tract for an extended period of time. Amo-ad-ms and amoxicillin powder were orally administered to rats. The amoxicillin concentration in gastric tissue was higher in the Amo-ad-ms group. In vivo H. pylori clearance tests were also carried out by administering, respectively, Amo-ad-ms or amoxicillin powder, to H. pylori infectious BALB/c mice under fed conditions at single or multiple dose(s) in oral administration. The results showed that Amo-ad-ms had a better clearance effect than amoxicillin powder did. In conclusion, the prolonged gastrointestinal residence time and enhanced amoxicillin stability resulting from the mucoadhesive microspheres of amoxicillin might make contribution to H. pylori clearance.

Hyaluronan-based microspheres as tools for drug delivery: a comparative study

The present paper describes the production of biodegradable microparticles using different hyaluronan polymers, such as native hyaluronan, the esterified derivative of hyaluronan Hyaff 11p50 (where 50% of the carboxy groups of hyaluronic acid are esterified with benzyl alcohol) and the autocross-linked polymer (ACP) internally esterified derivative of hyaluronan, by solvent evaporation and spray-drying methods. As model drugs cromolyn sodium salt, metronidazole and prednisolone hemisuccinate sodium salt were employed. The influence of polymer and preparation procedure has been evaluated on microparticle characteristics (i.e. morphology and encapsulation yield) and on the drug release profiles. The use of solvent evaporation method, a polymeric matrix constituted of Hyaff 11p50 3% (w/v), a dispersing phase constituted of 80 g of mineral oil (w/o ratio: 0.1), Span 85 0.1% (w/w) as stabilizer, and a stirring speed of 700 rpm resulted in the production of microspheres characterized by spherical shape, absence of aggregates, a mean diameter of 6.4 microm and a recovery of 90% (w/w). The production of drug containing microspheres led to an increase of mean diameter of microspheres and to high encapsulation yields. Moreover in vitro models have demonstrated that in all cases drugs were released from Hyaff 11p50 microspheres in a controlled fashion. Finally mathematical analysis of the drug release modalities has evidenced that drug release from Hyaff 11p50 microspheres is more consistent with kinetics of the diffusion rather than of the dissolution type.

Mucoadhesive microspheres for controlled drug delivery

Mucoadhesion is a topic of current interest in the design of drug delivery systems. Mucoadhesive micro-spheres exhibit a prolonged residence time at the site of application or absorption and facilitate an intimate contact with the underlying absorption surface and thus contribute to improved and/or better therapeutic performance of drugs. In recent years such mucoadhesive microspheres have been developed for oral, buccal, nasal, ocular, rectal and vaginal routes for either systemic or local effects. The objective of this article is review the principles underlying the development and evaluation of mucoadhesive microspheres and the research work carried out on these systems.

Pharmaceutical applications of mucoadhesion for the non-oral routes

The adhesion of pharmaceutical formulations to the mucosal tissue offers the possibility of creating an intimate and prolonged contact at the site of administration. This prolonged residence time can result in enhanced absorption and, in combination with a controlled release of the drug, also improved patient compliance by reducing the frequency of administration. During the almost 30 years over which mucoadhesion has been studied, a considerable amount of knowledge has been gained, and much has been learned about the different mechanisms occurring at the formulation-mucus interface and the properties that affect these mechanisms. The in-vivo performance of a dosage form not only depends on the mechanisms occurring at the interface, but also on the properties of the total mucoadhesive complex: the dosage form, the mucosa and the interface between them. A wide variety of methods are used for studying mucoadhesion; some rather similar to the in-vivo situation and some mimicking the interface alone. In this review, the mucus surface, the methods used for the study of mucoadhesion, the different mechanisms involved in mucoadhesion and theories underpinning them have been described. The complexity of mucoadhesion when trying to systemize the subject will also be discussed. The last part of the review describes the buccal, nasal, ocular, vaginal and rectal routes and provides examples of what can be achieved in-vivo when using mucoadhesive formulations.

Evaluation of the clearance characteristics of various microspheres in the human nose by gamma-scintigraphy

The nasal cavity possesses many advantages as a site for drug delivery, such as; ease of administration, applicability for long-term treatments and a large surface area for absorption. One important limiting factor for nasal drug delivery is the limited time available for absorption within the nasal cavity due to mucociliary clearance. Several drug delivery systems including different kinds of microspheres have been tried for encapsulation of drugs and increasing the residence time in nasal cavity. In this study the clearance rate of three kinds of microspheres (Alginate, PLGA, and Sephadex) was determined by gamma-scintigraphy with lactose powder being used as negative control. (99m)Tc labeled microspheres were prepared using technetium pertechnetate in the presence of a potent reducing agent, stannus chloride. The labeling procedure was set in a manner that each 3-5 mg of microspheres contained 2 MBq of radioactivity. Labeling efficiency was calculated by paper chromatography using acetone as a mobile phase. Each delivery system containing 2 MBq of activity was administered into right nostril of four healthy volunteers and 1 min static views were repeated each half an hour until 4 h. Clearance rates were compared using two regions of interest (ROIs); the initial site of deposition of particles, and all of the nasopharynx region. The clearance rate of each one of microspheres was calculated after applying the physical decay corrections. The mean labeling efficiencies for Alginate, PLGA, and Sephadex microspheres were calculated as 60%, 59%, and 74%, respectively. The cleared percent of formulations from nasopharynx region after 4 h was determined as follows: PLGA microspheres 48.5 +/- 8.2%; Alginate microspheres 45.0 +/- 0.8%; Sephadex microspheres 63.1 +/- 3.4%; lactose powder 74.5 +/- 4.9%. Alginate and PLGA microspheres showed the lowest clearance rate compared to lactose powder (P < 0.0001 and P < 0.001, respectively), followed by Sephadex microspheres (P < 0.01). The clearance profiles of formulations from deposition ROI and nasopharynx ROI were identical. This study shows that Alginate and PLGA microspheres have the highest mucoadhesion properties and are suitable nasal delivery systems. Futhermore, this study proves that limiting step for the nasal clearance of nasally administered particulate systems is their dislocation from the initial site of deposition, and their following interactions with mucus layer in the rest of the nasal passage does not significantly affect the clearance time.

Delivery of granulocyte-macrophage colony-stimulating factor in bioadhesive hydrogel stimulates migration of dendritic cells in models of human papillomavirus-associated (pre)neoplastic epithelial lesions

Because of the central role of dendritic cells and/or Langerhans cells(DC/LC) in the induction of cellular immune responses, pharmacological agents that modulate the recruitment of these cells might have a clinical interest. The present study was designed to evaluate the capacity of several pharmaceutical formulations to topically deliver granulocyte-macrophage colony-stimulating factor (GM-CSF) on human papillomavirus (HPV)-associated genital (pre)neoplastic lesions. The formulations were evaluated for their bioactivity and for their potential to recruit DC in organotypic cultures of HPV-transformed keratinocytes. We found that a bioadhesive polycarbophil gel (Noveon) at pH 5.5 is able to maintain the bioactivity of GM-CSF at 4 or 37 degrees C for at least 7 days, whereas a decreased activity of GM-CSF was observed when the molecule is included in other polymer gels. GM-CSF incorporated in the polycarbophil gel was also a potent factor in enhancing the colonization of DC into organotypic cultures of HPV-transformed keratinocytes since the infiltration of DC in the in vitro-formed (pre)neoplastic epithelium was very low under basal conditions and dramatically increased in the presence of GM-CSF gel. We next demonstrated that GM-CSF incorporated in polycarbophil gel induces the recruitment of human DC in a human (pre)neoplastic epithelium grafted into NOD/SCID mice. The efficacy of GM-CSF in this formulation was equivalent to that observed with liquid GM-CSF. These results suggest that GM-CSF incorporated in polycarbophil gel could play an important role in the recruitment of DC/LC in mucosal surfaces and be useful as a new immunotherapeutic approach for genital HPV-associated (pre)neoplastic lesions.

In vitro test to evaluate the interaction between synthetic cervical mucus and vaginal formulations

The interaction and mixing between a bilayer sample of mucus and vaginal formulation was evaluated through viscosity measurements with respect to time and shear. Physical mixtures of mucus and vaginal formulation were used as controls. Three test protocols were designed: (1) constant shear, (2) intermittent shear, and (3) delayed shear. Several marketed vaginal products (Gynol II, KY Plus, KY, and Advantage-S) and experimental formulations (C31G with hydroxyethylcellulose [HEC]) were evaluated and compared by these tests. The results of the constant shear test showed that the shear stress profile of the bilayer approached that of the corresponding physical mixture, consistent with complete mixing of the bilayer under shear. The time taken for the bilayer to mix completely was in the following order: KY Plus > Gynol II and C31G > KY > Advantage-S. Under the intermittent shear protocol, the following order for complete mixing was observed: KY Plus > C31G > Gynol II > KY > Advantage-S. The 2 products evaluated by the delayed shear test, C31G and Gynol II, were both completely mixed at 180 minutes. The development of an in vitro test, when coupled with in vivo data, should serve in the screening and evaluation of future vaginal formulations.

Development pharmaceutics of microbicide formulations. Part II: formulation, evaluation, and challenges

In recent years, AIDS and sexually transmitted diseases (STDs) have become a burgeoning problem and are spreading at an alarming rate. Microbicides are being developed as a new therapeutic category for prevention of transmission of sexually transmitted infections (STIs) and HIV. Many of the microbicide formulations (MF) may fail to elicit a protective response either because of a lack of efficacy or inadequate formulation. Manufacturing a stable, efficacious, safe, and optimal product is the main objective of formulation development programs. Preformulation parameters (PP), as discussed in Part I of this series, influence formulation development significantly and should be considered carefully before designing a formulation strategy. Initially, based on PP and market research, a target product profile (TPP) is generated, which defines product attributes that can be normally classified as "essential" and "desirable." A complex and dynamic process begins thereafter that takes into consideration myriad factors starting from selection of delivery system, selection of excipients, compatibility study, prototype composition, selection of process and optimization, stability testing, scale up, manufacturing under good manufacturing practices (GMP), and packaging development. Prototype formulations are evaluated for several performance characteristics (e.g., dispersion behavior, bioadhesion, retention, spreading, rheology). These compositions are also subjected to biologic evaluation by various in vitro and in vivo models. Such a well-planned, well-coordinated, and well-implemented formulation development program not only accelerates overall development but also minimizes failures in subsequent clinical development studies. The objective of this review is to highlight the importance of formulation science, outline the steps involved in this process, and explore how these can be exploited for achieving optimal MF.

Bioadhesive microspheres as a controlled drug delivery system

The concept of controlled drug delivery has been traditionally used to obtain specific release rates or spatial targeting of active ingredients. The phenomenon of bioadhesion, introduced by Park and Robinson [Park, K., Robinson, J.R., 1984. Bioadhesive polymers as platforms for oral controlled drug delivery: method to study bioadhesion. Int. J. Pharm. 198, 107-127], has been studied extensively in the last decade and applied to improve the performance of these drug delivery systems. Recent advances in polymer science and drug carrier technologies have promulgated the development of novel drug carriers such as bioadhesive microspheres that have boosted the use of "bioadhesion" in drug delivery. This article presents the spectrum of potential applications of bioadhesive microspheres in controlled drug delivery ranging from the small molecules, to peptides, and to the macromolecular drugs such as proteins, oligonucleotides and even DNA. The development of mucus or cell-specific bioadhesive polymers and the concepts of cytoadhesion and bioinvasion provide unprecedented opportunities for targeting drugs to specific cells or intracellular compartments. Developments in the techniques for in vitro and in vivo evaluation of bioadhesive microspheres have also been discussed.

Liposomal gels for vaginal drug delivery

The aim of our study was to develop a liposomal drug carrier system, able to provide sustained and controlled release of appropriate drug for local vaginal therapy. To optimise the preparation of liposomes with regards to size and entrapment efficiency, liposomes containing calcein were prepared by five different methods. Two optimal liposomal preparations (proliposomes and polyol dilution liposomes) were tested for their in vitro stability in media that simulate human vaginal conditions (buffer, pH 4.5). To be closer to in vivo application of liposomes and to achieve further improvement of their stability, liposomes were incorporated in vehicles suitable for vaginal self-administration. Gels of polyacrylate were chosen as vehicles for liposomal preparations. Due to their hydrophilic nature and bioadhesive properties, it was possible to achieve an adequate pH value corresponding to physiological conditions as well as desirable viscosity. In vitro release studies of liposomes incorporated in these gels (Carbopol 974P NF or Carbopol 980 NF) confirmed their applicability as a novel drug carrier system in vaginal delivery. Regardless of the gel used, even 24 h after the incubation of liposomal gel in the buffer pH 4.5 more than 80% of the originally entrapped substance was still retained.

The scope and potential of vaginal drug delivery

The vagina, in addition to being a genital organ with functions related to conception, serves as a potential route for drug administration. Mainly used for local action in the cervico-vaginal region, it has the potential of delivering drugs for systemic effects and uterine targeting. Currently available vaginal dosage forms have several limitations, necessitating the need to develop novel drug delivery systems. In addition, consideration of the regulatory aspects and consumer preferences for vaginal formulations is also required in the early stages of development.