Improvement of Tenofovir vaginal release from hydrophilic matrices through drug granulation with hydrophobic polymers

Bigels based on polyelectrolyte complexes as vaginal drug delivery systems

Bigels in which the cationic polymer -chitosan- is combined with an anionic polymer -karaya gum, pectin or xanthan gum- were prepared. These polymers, thanks to the attraction of their charged surface groups, are liable to form a polyelectrolyte complex that would modify the characteristics of the bigel. The obtained bigels were subsequently freeze-dried and tested to study their behavior against different conditions occurring in the vaginal environment. Swelling and drug release profiles have been evaluated in a medium that simulates the ordinary vaginal conditions and simulating the conditions after ejaculation. Thanks to the formation of polyelectrolyte complexes, the bigel is able to provide a pH-independent sustained drug release. However, when one of the polymers predominates, the release of the active ingredient turns out to be pH-dependent -which can also be beneficial in some therapeutic applications-. It has been proved that the inclusion of a higher percentage of chitosan in the bigel improves its mechanical properties, while the mucoadhesivity of the system can be improved by increasing the anionic polymer. The versatility of these systems in modulating their physicochemical properties, provides a substantial advantage over the formulations currently available on the market for vaginal drug delivery.

Evaluation of polymer combinations in vaginal mucoadhesive tablets for the extended release of acyclovir

Genital herpes, caused by herpes simplex virus type 2 (HSV-2), affects nearly 500 million people, mostly women. Since the main route of transmission is sexual contact, the development of an acyclovir extended-release vaginal microbicide would be a suitable tool for the prevention of virus transmission. In this work, we evaluated the potential of three polymers with different characteristics (chitosan, xanthan gum and ethyl cellulose) for obtaining acyclovir extended-release vaginal tablets. By combining the polymers, certain useful synergies were observed to modify their mucoadhesive capacity and control drug release. In the swelling studies, it observed that a polyelectrolyte complex with more moderate swelling and sustained gelation was formed between chitosan and xanthan gum exclusively in acidic medium (simulated vaginal fluid). This complex allowed prolonging the mucoadhesion of the tablets in ex vivo studies performed with vaginal mucosa, which would translate into better retention in the vagina after administration. In addition, the combination of chitosan and xanthan gum allowed obtaining a controlled release of acyclovir for 5 days, regardless of the pH of the medium, which would guarantee that drug release continues even in the presence of seminal fluid.

Cell-Penetrating Drug Carrier by Molecular Recognition of Sphingomyelin on Plasma Membranes

Plasma membranes not only maintain the intracellular microenvironment through their phospholipid bilayer but also eliminate exogenous compounds outside the cell membranes. Most drugs especially with high polarity are prevented from entering into cells to exert their effects. Therefore, it is of great significance to design effective drug carriers with a penetrating ability toward plasma membranes. In this study, a dual-templated MIP (dt-MIPs) carrier with controllable microstructure and high drug loading capacity was prepared using highly expressed sphingomyelin on the plasma membrane and tenofovir (TFV), a first-line drug for HIV and chronic hepatitis B, as template molecules. The drug release experiments performed in vitro under simulated physiological conditions demonstrated that sustained and stable adsorption of TFV on dt-MIPs was more than 80% over 50 h. By a combination of flow cytometry and confocal microscopy, dt-MIPs were found to have efficient cell permeability. Furthermore, mass-spectrometry-based intracellular pharmacokinetic studies demonstrated that TFV was delivered completely into cells within 30 min with the delivery of dt-MIPs. The study presented above suggested that dt-MIPs are expected to be alternative nanoscale drug carriers for enhanced drug permeability and controlled release.

Silicon Oxycarbide Porous Particles and Film Coating as Strategies for Tenofovir Controlled Release in Vaginal Tablets for HIV Prevention

Sustained release of antiretroviral drugs is currently the most encouraging strategy for the prevention of the sexual transmission of HIV. Vaginal tablets based on hydrophilic gelling polymers are an interesting dosage form for this purpose, since they can be developed to modify the release of the drug depending on the tablet swelling. Tenofovir is a drug with proven activity in the prevention of HIV-1 infection, and it is possible to have it loaded in the surface of γ-aminopropyl trimethoxy silane-functionalized oxycarbide particles. These particles can be incorporated into the tablets, thus providing a sustained release of the drug. Moreover, the presence of the particles modifies the microstructure of the gel formed, as observed in scanning electron microscopy and Hg porosimetry studies, resulting into a gel with a narrow pore size distribution between 10 and 100 µm. This implies a lower volume of fluid incorporated into the gel during swelling studies, and therefore improved mucoadhesion times in ex vivo test. The coating of the formulations with Eudragit® RS modifies the swelling behavior of the tablets, which not only is decreased in magnitude but also extended in time, and as consequence the drug release is also prolonged for up to 7 days.

Women-specific routes of administration for drugs: A critical overview

The woman's body presents a number of unique anatomical features that can constitute valuable routes for the administration of drugs, either for local or systemic action. These are associated with genitalia (vaginal, endocervical, intrauterine, intrafallopian and intraovarian routes), changes occurring during pregnancy (extra-amniotic, intra-amniotic and intraplacental routes) and the female breast (breast intraductal route). While the vaginal administration of drug products is common, other routes have limited clinical application and are fairly unknown even for scientists involved in drug delivery science. Understanding the possibilities and limitations of women-specific routes is of key importance for the development of new preventative, diagnostic and therapeutic strategies that will ultimately contribute to the advancement of women's health. This article provides an overview on women-specific routes for the administration of drugs, focusing on aspects such as biological features pertaining to drug delivery, relevance in current clinical practice, available drug dosage forms/delivery systems and administration techniques, as well as recent trends in the field.

Influence of Plasticizers on the pH-Dependent Drug Release and Cellular Interactions of Hydroxypropyl Methylcellulose/Zein Vaginal Anti-HIV Films Containing Tenofovir

Vaginal films featuring the pH-dependent release of tenofovir (TFV) were developed for the prevention of sexual transmission of human immunodeficiency syndrome (HIV). Films based on hydroxypropyl methylcellulose and zein were prepared incorporating different plasticizers [oleic acid, lactic acid, glycerol, and polyethylene glycol 400 (PEG)] and evaluated for in vitro drug release in an acidic simulated vaginal fluid (pH 4.2) and a slightly alkaline mixture of simulated seminal and vaginal fluids (pH 7.5). Results revealed that optimal biphasic TFV release was possible with proper combination of plasticizers (PEG and oleic acid, 1:7 w/w) and by adjusting the plasticizer/matrix-forming material ratio. The films had similar or higher levels of TFV associated with genital epithelial cells (Ca Ski or HEC-1-A cells) but lower drug permeability compared to the free drug. These data confirm that films have the potential to achieve suitable mucosal levels of TFV with low systemic exposure. The films developed could protect women from HIV sexual transmission.

Vaginal Polyelectrolyte Layer-by-Layer Films Based on Chitosan Derivatives and Eudragit® S100 for pH Responsive Release of Tenofovir

Women are still at high risk of contracting the human immunodeficiency virus (HIV) virus due to the lack of protection methods under their control, especially in sub-Saharan countries. Polyelectrolyte multilayer smart vaginal films based on chitosan derivatives (chitosan lactate, chitosan tartate, and chitosan citrate) and Eudragit^® S100 were developed for the pH-sensitive release of Tenofovir. Films were characterized through texture analysis and scanning electron microscopy (SEM). Swelling and drug release studies were carried out in simulated vaginal fluid and a mixture of simulated vaginal and seminal fluids. Ex vivo mucoadhesion was evaluated in bovine vaginal mucosa. SEM micrographs revealed the formation of multilayer films. According to texture analysis, chitosan citrate was the most flexible compared to chitosan tartrate and lactate. The swelling studies showed a moderate water uptake (<300% in all cases), leading to the sustained release of Tenofovir in simulated vaginal fluid (up to 120 h), which was accelerated in the simulated fluid mixture (4–6 h). The films had high mucoadhesion in bovine vaginal mucosa. The multilayer films formed by a mixture of chitosan citrate and Eudragit^® S100 proved to be the most promising, with zero toxicity, excellent mechanical properties, moderate swelling (<100%), high mucoadhesion capacity, and Tenofovir release of 120 h and 4 h in vaginal fluid and the simulated fluid mixture respectively.

Development of mucoadhesive vaginal films based on HPMC and zein as novel formulations to prevent sexual transmission of HIV

Although vaginal films were initially developed for a fast release of the drug, with the adequate formulation they can also be useful for sustained release. The latest strategies for the prevention of the sexual transmission of HIV have moved towards sustained-release dosage forms, so films may be an effective strategy that could also improve the patient's comfort. A hydrophilic polymer (hydroxypropylmethyl cellulose) and an amphiphilic polymer (zein) have been evaluated for the development of Tenofovir sustained-release vaginal films. The modification of the film's properties by the inclusion of polar (glycerol and polyethylene glycol 400 (PEG)) and amphiphilic (tributyl citrate and oleic acid) plasticisers was also evaluated. The films' physicochemical and mechanical properties were determined. The in vitro release of Tenofovir from the films and their bioadhesive capacity and behaviour in simulated vaginal fluid were also assessed. The combination of hydroxypropylmethyl cellulose and zein in films (ratio 1:5), with the inclusion of PEG (40% w/w) proved not only to have excellent mechanical properties, but was also able to release TFV in a sustained manner for 120 h and remain attached to biological tissues throughout this time. This film could be an interesting option for the prevention of sexual transmission of HIV.

Topical Inserts: A Versatile Delivery Form for HIV Prevention

The development of topical inserts for the prevention of sexually transmitted infections (STIs), particularly human immunodeficiency virus (HIV), represents a promising alternative to oral and parenteral pre-exposure prophylaxis (PrEP) dosage forms. They may be used for vaginal and/or rectal administration of a variety of agents with antiviral activity. Topical inserts deliver drugs to the portal of viral entry, i.e., the genital or rectal mucosa, with low systemic exposure, and therefore are safer and have fewer side effects than systemic PrEP agents. They may dissolve fast, releasing the active drugs within minutes of insertion, or slowly for long-acting drug delivery. Furthermore, they are user-friendly being easy to administer, discreet and highly portable. They are also economical and easy to manufacture at scale and to distribute, with excellent stability and shelf-life. Altogether, topical inserts represent a particularly promising form of drug delivery for HIV and STI prevention. Highlighted within this review are end-user acceptability research dedicated to understanding preferred attributes for this form of drug delivery, advantages and disadvantages of the formulation platform options, considerations for their development, clinical assessment of select placebo prototypes, future directions, and the potential impact of this dosage form on the HIV prevention landscape.

Smart Freeze-Dried Bigels for the Prevention of the Sexual Transmission of HIV by Accelerating the Vaginal Release of Tenofovir during Intercourse

Sub-Saharan African women are still at risk from the human immunodeficiency virus (HIV), and sex with men is the main route of transmission. Vaginal formulations containing antiretroviral drugs are promising tools to give women the power to protect themselves. The aim of this work was to obtain freeze-dried bigels containing pectin, chitosan, or hypromellose for the vaginal controlled release of Tenofovir, which is accelerated in the presence of semen. Nine batches of bigels were formulated using different proportions of these polymers in the hydrogel (1, 2, and 3% w/w). The bigels obtained were freeze-dried and then underwent hardness and deformability, mucoadhesion, swelling, and drug release tests, the last two in simulated vaginal fluid (SVF) and SVF/simulated seminal fluid (SSF) mixture. The formulation containing 3% pectin (fd3P) has the highest values for hardness, resistance to deformation, and good mucoadhesivity. Its swelling is conditioned by the pH of the medium, which is responsive to the controlled release of Tenofovir in SVF, with the fastest release in the SVF/SSF mixture. fd3P would be an interesting smart microbicidal system to allow faster release of Tenofovir in the presence of semen, and thus increase women’s ability to protect themselves from the sexual transmission of HIV.

Chitosan-Based Mucoadhesive Vaginal Tablets for Controlled Release of the Anti-HIV Drug Tenofovir

Vaginal microbicides have the potential to give women at high risk of contracting HIV the option of self-protection by preventing the sexual transmission of the virus. In this paper, mucoadhesive vaginal tablets based on chitosan, alone and in combination with pectin and locust bean gum, were developed for the sustained release of tenofovir (an antiretroviral drug). The formulations were placed in simulant vaginal fluid (SVF) to swell, and Hg porosity and SEM microscopy were used for the microstructural characterization of the swelling witnesses. The results show that the association of pectin and chitosan generated polyelectrolyte complexes and produced a robust system able to maintain its structure during the swelling process, when small pores are formed. Drug release and bovine vaginal mucoadhesion studies were performed in SVF showing that tenofovir-controlled dissolution profiles and adhesion to the mucosa were conditioned by the swelling processes of the polymer/s in each formulation. Tablets based on chitosan/pectin have the most homogeneous tenofovir dissolution profiles and last up to 96 h, remaining attached to the vaginal mucosa for the same period. These formulations can therefore be considered a good option for the self-protection of women from the sexual transmission of HIV.

The applicability of pharmaceutical polymeric blends for the fused deposition modelling (FDM) 3D technique: Material considerations-printability-process modulation, with consecutive effects on in vitro release, stability and degradation

The three dimensional printing (3DP) in the pharmaceutical domain constitutes an alternative, innovative approach compared to the conventional production methods. Fused deposition modelling (FDM), is a simple, cost-effective 3DP technique, however the range of pharmaceutical excipients that can be applied for this methodology is restricted. The study set to define the requirements of the FDM printability, using as technical support custom made, pharmaceutical polymer based filaments and to evaluate if these new dosage forms can live up to the current GMP/GCP quality standards. Formulation rationale was assessed in accordance to the apparatus functionality. Blends were pre-screened based on the processability under the API (carvedilol) thermogravimetric analysis determined critical limit. The technological process implied the use of FDM coupled with hot melt extrusion (HME), while printability was defined by means of thermal, rheological and mechanical measurements. From the pharmaceutical standpoint, the consistency of the in vitro dissolution kinetics was monitored 'at release' and 'in stability', while the print process impact was evaluated based on the previously determined processability potential. Results showed that FDM printability is multifactorial, with brittleness and melt viscosity as primary limitation factors. The increase in shear-thinning and flexural modulus can enable broader processability intervals, which in turn proved to be essential in limiting degradation product formation. The 3DP tablets released the API in an extended rate, however the temperature and humidity along production and storage should be carefully considered as it may affect the final product quality in time. In conclusion, HME + FDM can be considered as an alternative production methodology, with prospects of applicability in the clinical sector, however for some formulations extensive packaging development will be necessary before confirming their suitability.

Lyophilized tablets for focal delivery of fluconazole and itraconazole through vaginal mucosa, rational design and in vitro evaluation

The present work deals with the rational design and in vitro evaluation of vaginal tablets for focal delivery of fluconazole (FLZ) and itraconazol (ITZ). Drug loaded liposomes with and without d-alpha-tocopheryl polyethylene glycol 1000 succinate (vit E TPGS) were prepared by direct sonication of the components and mixed with albumin to obtain albusomes. Tablets were obtained by direct compression of the lyophilized cake. The influence of vit E TPGS on size, zeta potential and entrapment efficiency (EE%) of liposomes and albusomes was evaluated. Tablet swelling and drug release were studied by in vitro assays. Vit E TPGS neither affected the zeta potential nor the EE% of liposomes and albusomes, but affected the liposomes size and the tablet disintegration time. A rapid erosion was observed for the tablets with the highest content of vitamin, while a slow swelling for those lacking the vitamin (swelling index = 57.76 ± 13.51%). A faster drug release profile was obtained for the former compared to the latter. The in vitro assay showed that FLZ diffused and solved in the vaginal fluid simulant while ITZ remained into the albusomes, which slowly released ITZ-albumin complex and ITZ-loaded liposomes, both suitable carriers for drug transport to deeper vaginal endothelium.