A mucoadhesive, cyclodextrin-based vaginal cream formulation of itraconazole

Development of synergistic antifungal in situ gel of miconazole nitrate loaded microemulsion as a novel approach to treat vaginal candidiasis

Limited solubility is the main cause of the low local availability of anti-candidiasis drug, miconazole nitrate (MN). The study's objective was to develop and characterize microemulsion (ME) based temperature-triggered in situ gel of MN for intravaginal administration to enhance local availability and antifungal activity. The solubility of MN was initially studied in different oils, surfactants, and co-surfactants. Then, pseudo-ternary phase diagrams were constructed to select the best ratio of various components. The ME formulations were characterized by thermodynamic study, droplet size, polydispersity index (PDI), viscosity, and in-vitro antifungal mean inhibition zone (MIZ). Selected MEs were incorporated into different in situ gel bases using a combination of two thermosensitive polymers (poloxamer (PLX) 407 and 188), with 0.6% of hydroxypropyl methylcellulose (HPMC K4M) and gellan gum (GG) as mucoadhesive polymer. ME-based gels (MG) were investigated for gelation temperature, gelation time, viscosity, spreadability, mucoadhesive strength, in vitro release profile, and MIZ test. Furthermore, the optimum MG was assessed for in vivo animal irritation test and FESEM investigation. Tea tree oil, lavender oil, tween 80, and propylene glycol (PG) were chosen for ME preparation for the optimal formulation; formulation ME7 and ME10 were chosen. After incorporation of the selected formulation into a mixture of P407 and P188 (18:2% w/w) with 0.6% mucoadhesive polymer, the resultant MG formulation (MG1) revealed optimum gelation temperature (33 ± 0.01℃) and appropriate viscosity with enhanced sustained release (98%) and retention through sheep vaginal mucosa, MG1 exhibited a better MIZ compared to the 2% MN gel formulation and the marketed MN product, and no rabbit vagina irritation. In conclusion, the miconazole nitrate-loaded MG-based formula sustained the duration of action and better antifungal activity than the marketed miconazole nitrate formulation.

Intravaginal Gel for Sustained Delivery of Occidiofungin and Long-Lasting Antifungal Effects

Fungal infections are caused by opportunistic pathogens that can be life threatening or debilitating. Candida spp. are becoming increasingly resistant to current clinically approved antifungal therapeutics. Candida infections afflict not only immunosuppressed but also immunocompetent individuals. Recurrent vulvovaginal candidiasis (RVVC) is a disease that afflicts 5-9% of women. Occidiofungin is a novel cyclic peptide that has a broad spectrum of antifungal activity with a novel fungicidal mechanism of action. A gel formulation containing occidiofungin (OCF001) is being developed for use to treat vulvovaginal candidiasis. The formulated gel for intravaginal application used hydroxyethyl cellulose as the primary gelling agent and hydroxypropyl β-cyclodextrin as a solubilizing agent for occidiofungin. Franz cells and LC-MS/MS were used to determine the rate of drug substance diffusion in the gel formulation. The formulation was tested in an ex vivo mouse skin efficacy study, and the safety was tested following repeat intravaginal administration in rabbits. In this study, the gel formulation was shown to reduce the drug substance rate of diffusion across a skin memetic membrane. The study showed that the formulation extends exposure time to inhibitory concentrations of occidiofungin over a 24-h period and supports a single daily application for the treatment of RVVC.

In vitro assessment of the immobilized mannanase enzyme against infection-causing Candida

Background: Developing an effective treatment for fungal infections is among contemporary medicine's challenges. In this study we aimed to eradicate mannan in pathogenic Candidae's cell walls using a nontoxic method, mannanase. Materials & Methods: We investigated the in vitro antifungal activities of mannanase immobilized on zinc oxide nanoparticles (ZnONps) and reduced graphene oxide nanoparticles (RGONps), as well as therapeutics against Candidae. Mannanase was purified from Bacillus invictae (activity: 5.15 EU/ml; range: 60-80%) and then immobilized it to ZnO and RGO to enhance its effectiveness. Results: Mannanase immobilized on ZnONps had the highest activity, with a value of 4.97 EU/ml, more effective than amphotericin-B. However, it could not reach the inhibition rates of other antifungals. Conclusion: Mannanase immobilized on ZnONps could be an effective fungicide for Candida biocontrol.

Topical hydrophilic gel with itraconazole-loaded polymeric nanomicelles improves wound healing in the treatment of feline sporotrichosis

Sporotrichosis is a superficial fungal disease that can affect animals and humans. The high number of infected cats has been associated with zoonotic transmission and contributed to sporotrichosis being considered by the World Health Organization as one of the main neglected tropical fungal diseases for 2021-2030. Oral administration of itraconazole (ITZ) is the first choice for treatment, but it is expensive, time-consuming, and often related to serious adverse effects. As a strategy to optimize the treatment, we proposed the development of a hydrophilic gel with nanomicelles loaded with ITZ (HGN-ITZ). The HGN-ITZ was developed using an I-optimal design and characterized for particle size, Zeta potential, drug content, microscopic aspects, viscosity, spreadability, in vitro drug release, in vitro antifungal activity, and clinical evaluation in cats. The HGN-ITZ showed a high content of ITZ (97.3 ± 2.1 mg/g); and characteristics suitable for topical application (viscosity, spreadability, globules size, Zeta potential, controlled drug release). In a pilot clinical study, cats with disseminated sporotrichosis were treated with oral ITZ or HGN-ITZ + oral ITZ. A mortality rate of 21.3% was observed for the oral ITZ group compared to 5.3% for the HGN-ITZ + oral ITZ group. In a cat with a single lesion, topical treatment alone (HGN-ITZ) provided complete healing of the lesion in 45 days. No signs of topical irritation were observed during the treatments, suggesting that HGN-ITZ can be a promising strategy in the treatment of sporotrichosis.

Technological evolution of cyclodextrins in the pharmaceutical field

We herein disclose how global cyclodextrin-based pharmaceutical technologies have evolved since the early 80s through a 1998 patents dataset retrieved from Derwent Innovation Index. We used text-mining techniques based on the patents semantic content to extract the knowledge contained therein, to analyze technologies related to the principal attributes of CDs: solubility, stability, and taste-masking enhancement. The majority of CDs pharmaceutical technologies are directed toward parenteral aqueous solutions. The development of oral and ocular formulations is rapidly growing, while technologies for nasal and pulmonary routes are emerging and seem to be promising. Formulations for topical, transdermal, vaginal, and rectal routes do not account for a high number of patents, but they may be hiding a great potential, representing opportunity research areas. Certainly, the progress in materials sciences, supramolecular chemistry, and nanotechnology, will influence the trend of that, apparently neglected, research. The bottom line, CDs pharmaceutical technologies are still increasing, and this trend is expected to continue in the coming years.

Patent monitoring allows the identification of relevant technologies and trends to prioritize research, development, and investment in both, academia and industry. We expect the scope of this approach to be applied in the pharmaceutical field beyond CDs technological applications.

Mechanical characterization and ex vivo evaluation of anticancer and antiviral drug printed bioadhesive film for the treatment of cervical cancer

As research progresses on personalized medicines, it is clear that personalized and flexible formulations can provide effective treatment with reduced side effects especially for diseases like cancer, characteristic of high patient variability. 2D and 3D printers are frequently reported in the literature for the preparation of pharmaceutical products with adjusted dose and selected drug combinations. However, in-depth characterization studies of these formulations are rather limited. In this paper, ex vivo and mechanical characterization studies of antiviral and anticancer drug printed film formulations designed for personalized application were performed. Effects of the printing process with pharmaceutical formulations such as paclitaxel (PCX):cyclodextrin (CD) complex or cidofovir (CDV) encapsulated into poly(ethylene glycol)-polycaprolactone (PEG-PCL) nanoparticles on the films were evaluated through a series of mechanical characterization studies. Inkjet printing process was found to cause no significant change in the thicknesses of the film formulations, while mechanical strength and surface free energy increased and nano-sized voids in the film structure decreased. According to the mechanical characterization data, the unprinted film had maximum force (F_max) value of 15.6 MPa whereas F_max increased to 43.8 MPa for PCX:CD complex printed film and to 37.7 MPa for the antiviral CDV-PEG-PCL nanoparticle printed film. In the light of ex vivo findings of sheep cervix-uterine tissue, bioadhesive properties of film formulations significantly improved after inkjet printing with different drug formulations. It has also been shown that the anticancer formulation printed on the film was maintained at the cervix tissue surface for >12 h. This study has shown for the first time that inkjet printing process does not adversely affect the mechanical properties of the bioadhesive film formulations. It has also been shown that durable bioadhesive film formulations for personalized dosing can be prepared by combining nanotechnology and inkjet printing.

Non-ionic thiolated cyclodextrins - the next generation

Introduction

The current study was aimed at developing a novel mucoadhesive thiolated cyclodextrin (CD) without ionizable groups and an intact ring backbone for drug delivery.

Materials and methods

Thiolated beta CD (β-CD) was prepared through bromine substitution of its hydroxyl groups followed by replacement to thiol groups using thiourea. The thiolated β-CD was characterized in vitro via dissolution studies, cytotoxicity studies, mucoadhesion studies on freshly excised porcine intestinal mucosa, and inclusion complex formation with miconazole nitrate.

Results

Thiolated β-CDs namely β-CD-SH₆₀₀ and β-CD-SH₁₂₀₀ displayed 558.66 ± 78 and 1,163.45 ± 96 µmol thiol groups per gram of polymer, respectively. Stability constant (Kc) of 190 M^-1 confirmed the inclusion complex formation of miconazole nitrate with β-CD-SH. Inclusion complexes of β-CD-SH₆₀₀ and β-CD-SH₁₂₀₀ resulted in 157- and 257-fold increased solubility of miconazole nitrate, respectively. In addition, more than 80% of thiol groups were stable even after 6 hours at pH 5. Both β-CD-SH compounds showed at least 1.3-fold improved solubility in water. In contrast to cationic thiolated CDs of the first generation, both thiomers showed no significant cytotoxicity. The mucoadhesive properties of the new thiolated CDs were 39.73- and 46.37-fold improved, respectively.

Conclusion

These results indicate that β-CD-SH might provide a new favorable tool for delivery of poorly soluble drugs providing a prolonged residence time on mucosal surfaces.

Development of Itraconazole Tablets Containing Viscous KinetiSol Solid Dispersions: In Vitro and In Vivo Analysis in Dogs

The formulation factors relevant to developing immediate and controlled release dosage forms containing poorly soluble drugs dispersed in amorphous systems are poorly understood. While the utility of amorphous solid dispersions is becoming apparent in the pharmaceutical marketplace, literature reports tend to concentrate on the development of solid dispersion particulates, which then must be formulated into a tablet. Amorphous solid dispersions of itraconazole in high molecular weight hydroxypropyl methylcellulose were prepared by KinetiSol® Dispersing and tablets were formulated to immediately disintegrate or control the release of itraconazole. Formulated tablets were evaluated by two non-sink dissolution methodologies and the dosage form properties that controlled the gelling tendency of the dispersion carrier, hydroxypropyl methylcellulose, were investigated. Selected formulations were evaluated in an exploratory beagle dog pharmacokinetic study; the results of which indicate potential for a prolonged absorption phase relative to the commercially extruded control.

A vaginal drug delivery model

Efficient drug delivery at vaginal cavity is often a challenge owing to its peculiar physiological variations including vast differences in pH. Keeping in view this attribute of the target site, the current work was aimed at developing formulation strategies which could overcome this and successfully deliver molecules like itraconazole through SLNs. Optimized SLNs with the given composition was selected for further development into mucoadhesive and thermosensitive gel. Stearic acid and Compritol 888 (1:1, w/w ratio) as lipid, a mixture of 3% Poloxomer 188 and 0.5% sodium taurocholate as surfactant and organic to aqueous ratio of 10:50 was taken. Carbopol 934 and Pluronic F 127 were taken for the development of gel. Optimized gel exhibited a desired gelling temperature (35 °C); viscosity (0.920 PaS) and appreciable in vitro drug release (62.2% in 20 h). MTT assay did not show any cytotoxic effect of the gel. When evaluated in vivo, it did not exhibit any irritation potential despite appreciable bioadhesion. A remarkable decrease in CFUs was also observed in comparison with control and marketed formulation when evaluated in rat infection model. Thus, the proposed study defines the challenges for developing a suitable formulation system overcoming the delivery barriers of the vaginal site.

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.

New strategies for local treatment of vaginal infections

Vaginal infections are extremely prevalent, particularly among women of reproductive age. Although they do not result in high mortality rates, these infections are associated with high levels of anxiety and reduction of quality of life. In most cases, topical treatment of vaginal infections has been shown to be at least as effective as oral treatment, resulting in higher local drug concentrations, with fewer drug interactions and adverse effects. Furthermore, the emergence of microbial resistance to chemotherapeutics and the difficulties in managing infection recurrences sustain the need for more effective local treatments. However, conventional dosage forms have been associated with low retention in the vagina and discomfort. Formulation strategies such as the development of bioadhesive, thermogelling systems and microtechnological or nanotechnological approaches have been proposed to improve delivery of traditional drugs, and other treatment modalities such as new drugs, plant extracts, and probiotics are being studied. This article reviews the recent strategies studied to improve the treatment and prevention of the commonest vaginal infections-namely, vaginal bacteriosis, aerobic vaginitis, vulvovaginal candidosis, and trichomoniasis-through the intravaginal route.

Formulation optimization of itraconazole loaded PEGylated liposomes for parenteral administration by using design of experiments

The aim of this study was to systematically characterize and optimize the encapsulation process of itraconazole (ITZ) into the PEGylated liposomes. ITZ was used as a model compound for poorly soluble drugs. PEGylated liposomes were prepared using the film hydration method combined with sonication in order to produce small unilamellar vesicles (SUV). The concentration of encapsulated ITZ was measured by a reversed phase-high-performance liquid chromatography (RP-HPLC) method. Systematic characterization of encapsulation process was performed using the design of experiments (DoE) approach. The systematic screening of process parameters and well designed settings of parameter levels in optimization phase improved the ITZ encapsulation process. Optimization demonstrated that only minimal range of design space could be used to achieve the highest encapsulation efficiency (EE (%)), more precisely the EE of 90% was gained using 25mg/ml of lipid and drug loading of 0.3% (w/w). However, the desirable drug loading could be predicted and adjusted by using mathematical modeling behind the DoE approach. The entire encapsulation process was shown to be repeatable with high significance (p<0.05). It could be demonstrated that DoE plays an important role in optimization experiments leading to robust results supporting high quality.

In vitro/in vivo performance of different complexes of itraconazole used in the treatment of vaginal candidiasis

A large majority of new chemical entities and many existing drug molecules exhibit poor aqueous solubility, which may limit their potential use in developing drug formulations, with optimum bioavailability. One of the approaches to improve the solubility of a poorly water soluble drug and eventually its bioavailability is complexation with agents like humic acid (HA), fulvic acid (FA), β-cyclodextrin (β-CD), 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and caffeine (Caff). The current work emphasized at employing these agents to prepare different complexes and their in vitro/in vivo assessment. All the complexes evaluated for their complexation efficiency and authenticated by molecular modeling; conformational analysis, differential scanning calorimetry (DSC), X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and mass spectroscopy. Furthermore, the complexes were assessed in an in vivo, rat vaginal model for their efficacy in treatment of vaginal candidiasis. Amongst the five tested complexes, fulvic acid-itraconazole complex yielded better solubility as well as in vivo efficacy and therefore may further be explored for developing a commercial formulation for treating vaginal candidiasis.

Phase behavior of itraconazole-phenol mixtures and its pharmaceutical applications

The aims of this study were to examine the phase behavior of itraconazole-phenol mixtures and assess the feasibility of topical formulations of itraconazole using eutectic mixture systems. Itraconazole-phenol eutectic mixtures were characterized using differential scanning calorimetry, Fourier transform infrared spectroscopy, (1)H-nuclear magnetic resonance, and powder X-ray diffractometry. The skin permeation rates of itraconazole-phenol eutectic formulations were determined using Franz diffusion cells fitted with excised hairless mouse skins. Itraconazole can form eutectic compounds with phenol, and the hydrogen-bonding interactions between the carbonyl group in the itraconazole and hydroxyl group in phenol play a major role in itraconazole-phenol eutectic formation. Despite its high molecular weight and hydrophobicity, the drug (i.e., itraconazole) can be permeated through excised hairless mouse skins from itraconazole-phenol eutectic formulations. The findings of this study emphasize the capabilities of the topical application of itraconazole via external preparations.

Mucoadhesive drug delivery systems

Mucoadhesion is commonly defined as the adhesion between two materials, at least one of which is a mucosal surface. Over the past few decades, mucosal drug delivery has received a great deal of attention. Mucoadhesive dosage forms may be designed to enable prolonged retention at the site of application, providing a controlled rate of drug release for improved therapeutic outcome. Application of dosage forms to mucosal surfaces may be of benefit to drug molecules not amenable to the oral route, such as those that undergo acid degradation or extensive first-pass metabolism. The mucoadhesive ability of a dosage form is dependent upon a variety of factors, including the nature of the mucosal tissue and the physicochemical properties of the polymeric formulation. This review article aims to provide an overview of the various aspects of mucoadhesion, mucoadhesive materials, factors affecting mucoadhesion, evaluating methods, and finally various mucoadhesive drug delivery systems (buccal, nasal, ocular, gastro, vaginal, and rectal).

Early identification of availability issues for poorly water-soluble microbicide candidates in biorelevant media: a case study with saquinavir

In the search for a successful HIV microbicide, many poorly water-soluble antiviral agents are currently being investigated. Unfortunately, solubility and precipitation issues may limit intravaginal concentrations and thus availability of these agents upon application of an aqueous gel formulation. In the present study, we evaluated the in vitro precipitation behavior of the HIV protease inhibitor saquinavir in vaginal and seminal fluid simulants (VFS and SFS). Despite its limited solubility, the mesylate salt of saquinavir enables formulation of sufficiently high concentrations (2.5 mM, i.e. ca. 10(5)-fold in vitro IC(50) values) in a standard aqueous vehicle. While saquinavir stays in solution upon dilution with VFS, SFS induces precipitation of saquinavir, resulting in a 5-fold reduced availability and antiviral potency. Inclusion of the solubilizing excipients polyethylene glycol 1000 (12%) and hydroxypropyl-β-cyclodextrin (2.5%) was required to avoid saquinavir precipitation in SFS and to restore the antiviral potency of the formulation. This study illustrates the importance of identifying solubility and precipitation issues of microbicide candidates in biorelevant media and provides a simple in vitro procedure to implement this evaluation in early microbicide development.

Pharmaceutical applications of cyclodextrins: effects on drug permeation through biological membranes

Objectives

Cyclodextrins are useful solubilizing excipients that have gained currency in the formulator's armamentarium based on their ability to temporarily camouflage undesirable physicochemical properties. In this context cyclodextrins can increase oral bioavailability, stabilize compounds to chemical and enzymatic degradation and can affect permeability through biological membranes under certain circumstances. This latter property is examined herein as a function of the published literature as well as work completed in our laboratories.

Key findings

Cyclodextrins can increase the uptake of drugs through biological barriers if the limiting barrier component is the unstirred water layer (UWL) that exists between the membrane and bulk water. This means that cyclodextrins are most useful when they interact with lipophiles in systems where such an UWL is present and contributes significantly to the barrier properties of the membrane. Furthermore, these principles are used to direct the optimal formulation of drugs in cyclodextrins. A second related critical success factor in the formulation of cyclodextrin-based drug product is an understanding of the kinetics and thermodynamics of complexation and the need to optimize the cyclodextrin amount and drug-to-cyclodextrin ratios. Drug formulations, especially those targeting compartments associated with limited dissolution (i.e. the eye, subcutaneous space, etc.), should be carefully designed such that the thermodynamic activity of the drug in the formulation is optimal meaning that there is sufficient cyclodextrin to solubilize the drug but not more than that. Increasing the cyclodextrin concentration decreases the formulation ‘push’ and may reduce the bioavailability of the system.

Conclusions

A mechanism-based understanding of cyclodextrin complexation is essential for the appropriate formulation of contemporary drug candidates.

A novel itraconazole bioadhesive film for vaginal delivery: design, optimization, and physicodynamic characterization

The purpose of this work was to design and optimize a novel vaginal drug delivery system for more effective treatment against vaginal candidiasis. Itraconazole was formulated in bioadhesive film formulations that could be retained in the vagina for prolonged intervals. The polymeric films were prepared by solvent evaporation and optimized for various physicodynamic and aesthetic properties. In addition, percentage drug retained on vaginal mucosa was evaluated using a simulated dynamic vaginal system as function of time. A polymeric film containing 100 mg itraconazole per unit (2.5 cm x 2.5 cm) have been developed using generally regarded as safe listed excipients. The pH of vaginal film was found to be slightly acidic (4.90 +/- 0.04) in simulated vaginal fluid and alkaline (7.04 +/- 0.07) in water. The little moisture content (7.66 +/- 0.51% w/w) was present in the film, which helps them to remain stable and kept them from being completely dry and brittle. The mechanical properties, tensile strength, and percentage elongation at break (9.64 N/mm(2) and 67.56% for ITRF(65)) reveal that the formulations were found to be soft and tough. The films (ITRF(65)) contained solid dispersion of itraconazole (2.5)/hydroxypropyl cellulose (1)/polyethylene glycol 400 (0.5), which was found to be the optimal composition for a novel bioadhesive vaginal formulation, as they showed good peelability, relatively good swelling index, and moderate tensile strength and retained vaginal mucosa up to 8 h. Also, the film did not markedly affect normal vaginal flora (lactobacillus) and was noncytotoxic as indicated by the negligible decrease in cell viability.

Suspensions for intravenous (IV) injection: a review of development, preclinical and clinical aspects

There has been growing interest in nanoparticles as an approach to formulate poorly soluble drugs. Besides enhanced dissolution rates, and thereby, improved bioavailability, nanoparticles can also provide targeting capabilities when injected intravenously. The latter property has led to increased research and development activities for intravenous suspensions. The first intravenously administered nanoparticulate product, Abraxane (a reformulation of paclitaxel), was approved by the FDA in 2006. Additional clinical trials have been conducted or are ongoing for multiple other indications such as oncology, infective diseases, and restenosis. This article reviews various challenges associated with developing intravenous nanosuspension dosage forms. In addition, various formulation considerations specific to intravenous nanosuspensions as well as reported findings from various clinical studies have been discussed.

Hot-melt extrusion for enhanced delivery of drug particles

With the recent advent of nanotechnology for pharmaceutical applications, drug particle engineering is the focus of increasing interest as a viable approach for overcoming solubility limitations of poorly water-soluble drugs. Although these particle engineering techniques have been proven successful for enhancing the dissolution properties of many poorly water-soluble drugs, there are limitations associated with them such as particle aggregation, morphological instability, and poor wettability. The aim of this study was to demonstrate a processing technique in which hot-melt extrusion (HME) is utilized to overcome these limitations. Micronized particles of amorphous itraconazole (ITZ) stabilized with PVP or HPMC were produced and subsequently melt extruded with poloxamer 407 and PEO 200 M to deaggregate and disperse the particles into the hydrophilic polymer matrix. Differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy were used to demonstrate that the HME process did not alter the properties of the micronized particles. Dissolution testing conducted at sink conditions revealed that the dissolution rate of the micronized particles was improved by HME due to particle deaggregation and enhanced wetting. Supersaturation dissolution testing demonstrated that the ITZ-HPMC micronized particle extrudates provided superior supersaturation of ITZ compared to the ITZ-PVP micronized particle extrudates. Supersaturation dissolution testing incorporating a pH change (from pH 1.2 to 6.8 at 2 h) revealed that neither micronized particle extrudate formulation significantly reduced the rate of ITZ precipitation from supersaturated solution once pH was increased. Moreover, the two extrudate formulations performed very similarly when only considering dissolution testing from just before pH adjustment through the duration of testing at neutral pH. From oral dosing of rats, it was determined that the two extrudate formulations performed similarly in vivo as confirmed by their statistically equivalent AUC values. By correlating the results of supersaturation dissolution testing with pH change to the in vivo AUC, it appears that rapid precipitation of ITZ occurs upon entrance into the more neutral pH environment of the small intestine resulting in a brief opportunity for absorption. This suggests that perhaps the optimum formulation approach for ITZ is to control drug release so as to retard precipitation as pH is increased and extend the absorption window in the small intestine.

Advances in the use of tocols as drug delivery vehicles

There has been increasing interest in recent years in the drug delivery applications of tocols and their derivatives. Their biocompatibility and potential to deliver both poorly soluble and water-soluble drugs make tocols attractive as drug delivery vehicles. This review article will focus primarily on topical, oral, and parenteral drug administration using tocols, although other routes of delivery such as pulmonary and nasal will also be discussed. After an overview of the tocol structures, physicochemical properties with emphasis on their solvent properties, functions, and metabolism, specific case studies will be discussed where tocols have been successfully used in topical, oral, and parenteral drug formulations and marketed drug products. Case studies will be extended to those where tocol-based formulations were administered pulmonarily and nasally. As more clinical data and marketed drug products emerge, the utility and therapeutic value of tocols will certainly increase.

The transport of chemicals in semen

Three mechanisms have been proposed for exposure of the conceptus to chemicals in semen: access of chemicals to the maternal circulation after absorption from the vagina, direct chemical exposure of the conceptus following transport from the vagina to the uterine cavity, and delivery to the egg and subsequent conceptus of chemical bound to the sperm cell. We review published data for each of these three mechanisms. Human seminal fluid chemical concentrations are typically similar to or lower than blood concentrations, although some antimicrobial agents achieve higher concentrations in semen than in blood. Vaginal absorption of medications has been shown to occur, although the vehicles in which these medications are delivered to the vagina may maintain contact with the vaginal epithelium to a greater extent than does semen. Assuming total absorption of a seminal dose of a chemical with a high semen:blood concentration ratio, distribution within the recipient woman would result in a blood concentration at least three orders of magnitude lower than that in the man. Direct delivery of seminal chemicals into the uterine cavity of humans has not been shown to occur, although it may occur in species such as the rat in which seminal fluid has access to the uterine cavity. Chemicals in or on human sperm cells have been demonstrated with respect to tetracycline and cocaine in vitro and aluminum, lead, and cadmium in vivo. The in vitro cocaine study offers sufficiently quantitative data with which to predict that oocyte concentrations would be five orders of magnitude lower than blood concentrations associated with cocaine abuse, assuming a maximally cocaine-bound sperm were capable of fertilizing. Thus, even using liberal assumptions about transmission of chemicals in semen or sperm, predicted exposure levels of a pregnant woman or of the conceptus are three or more orders of magnitude lower than blood concentrations in the man whose semen is the putative vehicle for chemical transport.