Contraceptive efficacy and safety studies of a novel microemulsion-based lipophilic vaginal spermicide

A Comparative Study and Prediction of the Ex Vivo Permeation of Six Vaginally Administered Drugs across Five Artificial Membranes and Vaginal Tissue

The theoretical interpretation of the vaginal permeability phenomenon, the evaluation of the suitability of five artificial membranes, and the prediction of the behaviors of vaginal drugs were the main objectives of this study. Franz vertical diffusion cells and different validated HPLC methods were used to measure the permeability of six vaginally administered drugs (econazole, miconazole, metronidazole, clindamycin, lidocaine, and nonoxynol-9). This study was performed (in vitro) on different membranes of polyvinylidene fluoride (PVDF), plain cellulose or cellulose impregnated with isopropyl myristate (IPM), and cellulose combined with PVDF or IPM. The results were compared with those obtained from cow vaginal tissue (ex vivo), where cellulose was proven to be the best simulant. According to the permeability profiles (Papp), the water solubility of the drugs was considered a necessary criterion for their transport in the membranes or in the tissue, while the size was important for their penetration. Furthermore, it was found that polar compounds show clear superiority when penetrating cellulose or tissue, while non-polar ones show superiority when penetrating the lipophilic PVDF membrane. Finally, a successful attempt was made to predict the Papp values (|Papp-predPapp| < 0.005) of the six drugs under study based on a PLS (Partial Least Squares) in silico simulation model.

Non-oral routes, novel formulations and devices of contraceptives: An update

Family planning enables society to prevent unintended pregnancies and helps in attaining desired spacing between the pregnancies. It is done with the use of contraceptive methods and infertility treatments. The use of contraceptives serves to ease maternal ill-health and reduce pregnancy-related deaths and helps to decrease the number of unsafe abortions and HIV transmission from mothers to newborns. The most popular contraception method is a daily dose of combined oral contraceptives pills. However, poor compliance and various adverse effects are common problems of oral contraceptives that considerably reduce their long-term use. Thus, several non-oral contraceptive options have been developed for better compliance, reduced side effects and improved therapeutic efficacy. This review presented the non-oral contraceptive formulations given by different routes such as transdermal, nasal, subcutaneous, intramuscular, intrauterine and vaginal routes. These formulations delivering contraceptives, mainly through devices, include transdermal patches and microneedles, nasal sprays, intrauterine devices and intrauterine systems, vaginal rings, contraceptive implants and contraceptive injections, which are unique in their specific advantages and drawbacks.

Evaluation of the antifungal activity of an ebselen-loaded nanoemulsion in a mouse model of vulvovaginal candidiasis

Vulvovaginal candidiasis (VVC), caused by Candida albicans, is a common infection in women affecting their quality of life. Standard antifungal drugs (e.g., fluconazole, itraconazole) are typically fungistatic or rendered ineffective due to drug resistance indicating an urgent need to build an arsenal of novel antifungal agents. To surmount this issue, we tested the hypothesis that the organoselenium compound ebselen (EB) possesses antifungal efficacy in a mouse model of VVC. EB is a poorly water-soluble drug and DMSO as a vehicle has the potential to exhibit cytotoxic effects when administered in vivo. EB loaded self-nanoemulsifying preconcentrate (EB-SNEP) was developed, characterized in vitro, and tested in a mouse model of VVC. In vivo studies carried out with EB-SNEP (12.5 mg/kg) showed a remarkable decrease in infection by ~562-fold compared to control (infected, untreated animals). Taken together, EB nanoemulsion proved to be an effective and promising antifungal agent.

Emulsion-Based Multicompartment Vaginal Drug Carriers: From Nanoemulsions to Nanoemulgels

In order to overcome the limitations associated with vaginal administration of drugs, e.g., the short contact time of the drug form with the mucosa or continuous carrier wash-out, the development of new carriers for gynecological use is necessary. Furthermore, high individual anatomical and physiological variability resulting in unsatisfactory therapeutic efficacy of lipophilic active substances requires application of multicompartment drug delivery systems. This manuscript provides an up-to-date comprehensive review of the literature on emulsion-based vaginal dosage forms (EVDF) including macroemulsions, microemulsions, nanoemulsions, multiple emulsions and self-emulsifying drug delivery systems. The first part of the paper discusses (i) the influence of anatomical-physiological conditions on therapeutic efficacy of drug forms after local and systemic administration, (ii) characterization of EVDF components and the manufacturing techniques of these dosage forms and (iii) methods used to evaluate the physicochemical and pharmaceutical properties of emulsion-based vaginal dosage forms. The second part of the paper presents (iv) the results of biological and in vivo studies as well as (v) clinical evaluation of EVDF safety and therapeutic efficacy across different indications.

Vaginal Administration of Contraceptives

While contraceptive drugs have enabled many people to decide when they want to have a baby, more than 100 million unintended pregnancies each year in the world may indicate the contraceptive requirement of many people has not been well addressed yet. The vagina is a well-established and practical route for the delivery of various pharmacological molecules, including contraceptives. This review aims to present an overview of different contraceptive methods focusing on the vaginal route of delivery for contraceptives, including current developments, discussing the potentials and limitations of the modern methods, designs, and how well each method performs for delivering the contraceptives and preventing pregnancy.

Nanosystems against candidiasis: a review of studies performed over the last two decades

The crescent number of cases of candidiasis and the increase in the number of infections developed by non-albicans species and by multi-resistant strains has taken the attention of the scientific community, which has been searching for new therapeutic alternatives. Among the alternatives found the use of nanosystems for delivery of drugs already commercialized and new biomolecules have grown, in order to increase stability, solubility, optimize efficiency and reduce adverse effects. In view of the growing number of studies involving technological alternatives for the treatment of candidiasis, the present review came with the intention of gathering studies from the last two decades that used nanotechnology for the treatment of candidiasis, as well as analysing them critically and pointing out the future perspectives for their application with this purpose. Different studies were considered for the development of this review, addressing nanosystems such as metallic nanoparticles, mesoporous silica nanoparticles, polymeric nanoparticles, liposomes, nanoemulsion, microemulsion, solid lipid nanoparticle, nanostructured lipid carrier, lipidic nanocapsules and liquid crystals; and different clinical presentations of candidiasis. As a general overview, nanotechnology has proven to be an important ally for the treatment against the diversity of candidiasis found in the clinic, whether in increasing the effectiveness of commercialized drugs and reducing their adverse effects, as well as allowing exploring more effectively properties therapeutics of new biomolecules.

Nanostructured lipid system as a strategy to improve the anti-Candida albicans activity of Astronium sp

The genus Astronium (Anacardiaceae) includes species, such as Astronium fraxinifolium, Astronium graveolens, and Astronium urundeuva, which possess anti-inflammatory, anti-ulcerogenic, healing, and antimicrobial properties. Nanostructured lipid systems are able to potentiate the action of plant extracts, reducing the required dose and side effects and improving antimicrobial activity. This work aims to evaluate a nanostructured lipid system that was developed as a strategy to improve the anti-Candida albicans activity of hydroethanolic extracts of stems and leaves from Astronium sp. The antifungal activity against C. albicans (ATCC 18804) was evaluated in vitro by a microdilution technique. In addition to the in vitro assays, the Astronium sp. that showed the best antifungal activity and selectivity index was submitted to an in vivo assay using a model of vulvovaginal candidiasis infection. In these assays, the extracts were either used alone or were incorporated into the nanostructured lipid system (comprising 10% oil phase, 10% surfactant, and 80% aqueous phase). The results indicated a minimal inhibitory concentration of 125.00 µg/mL before incorporation into the nanostructured system; this activity was even more enhanced when this extract presented a minimal inhibitory concentration of 15.62 µg/mL after its incorporation. In vivo assay dates showed that the nanostructure-incorporated extract of A. urundeuva leaves was more effective than both the unincorporated extract and the antifungal positive control (amphotericin B). These results suggest that this nanostructured lipid system can be used in a strategy to improve the in vitro and in vivo anti-C. albicans activity of hydroethanolic extracts of Astronium sp.

Vaginal irritation models: the current status of available alternative and in vitro tests

Mucosal surfaces, such as the vaginal epithelium, are natural barriers to infection that are constantly exposed to bacteria and viruses, and are therefore potential sites of entry for numerous pathogens. The vaginal epithelium can be damaged mechanically, e.g. by the incorrect use of objects such as tampons, and by chemicals that are irritating or corrosive. Consequently, this can lead to an increase in susceptibility to further damage or infection. Pharmaceutical, cosmetic and personal care products that are specifically formulated for application onto human external mucosae can occasionally induce undesirable local or systemic side-effects. Therefore, the compatibility of applied materials with this mucosal surface represents a key issue to be addressed by manufacturers. The most frequently used method for assessing vaginal mucosal irritation is the in vivo rabbit vaginal irritation test. However, the current emphasis in the field of toxicology is to use alternative in vitro methods that reduce, refine, and replace the use of animals, and which model and predict human, not animal, responses. Such an approach is of particular interest to the personal care and cosmetic industries in their effort to comply with European legislative measures, such as the 7th Amendment to the EU Cosmetics Directive that does not permit the marketing of cosmetic products if they, or their ingredients, have been tested for irritation responses in animals. The focus of this review is to provide an overview of the alternative and in vitro tests that are currently available for vaginal mucosal irritation assessment, and which are already used, or may become useful, to establish the safety of newly-designed products for human use.

Safety studies of sperm agglutinating factor produced by Staphylococcus aureus as a vaginal contraceptive: in vivo studies

Sperm agglutinating factor (SAF) isolated from Staphylococcus aureus when applied at concentration 10 μg before mating completely prevented conception in the mouse. The objective of the present study was to evaluate its safety, as safety is an important concern to be addressed before a compound is selected for contraceptive use. Our results showed that SAF has a very high safety profile. Vaginal application of SAF at 10 μg to the mouse for 14 consecutive days caused no systemic toxicity and vaginal irritation as indicated by lack of effect on organ weights and histology. Moreover, no adverse effect was observed on the subsequent reproductive capability, perinatal outcome and growth and development of the offspring. SAF (10 μg) did not irritate the skin or penile mucosa. Oral administration of 2 mg/kg body weight of SAF did not show any toxicity to reproductive and non-reproductive organs. Therefore, SAF with spermicidal activity and lack of toxicity may have the potential to become the active ingredient of a vaginal contraceptive.

Microemulsions as transdermal drug delivery vehicles

Microemulsions are clear, stable, isotropic mixtures of oil, water, and surfactant, frequently in combination with a cosurfactant. Microemulsions have been intensively studied during the last decades by many scientists and technologists because of their great potential in many food and pharmaceutical applications. The use of microemulsions is advantageous not only due to the facile and low cost preparation, but also because of the improved bioavailability. The increased absorption of drugs in topical applications is attributed to enhancement of penetration through the skin by the carrier. Saturated and unsaturated fatty acids serving as an oil phase are frequently used as penetration enhancers. The most popular enhancer is oleic acid. Other permeation enhancers commonly used in transdermal formulations are isopropyl myristate, isopropyl palmitate, triacetin, isostearylic isostearate, R(+)-limonene and medium chain triglycerides. The most popular among the enhancing permeability surfactants are phospholipids that have been shown to enhance drug permeation in a different mode. l-alpha-phosphatidylcholine from egg yolk, l-alpha-phosphatidylcholine 60%, from soybean and dioleylphosphatidyl ethanolamine which are in a fluid state may diffuse into the stratum corneum and enhance dermal and transdermal drug penetration, while distearoylphosphatidyl choline which is in a gel-state has no such capability. Other very commonly used surfactants are Tween 20, Tween 80, Span 20, Azone, Plurol Isostearique and Plurol Oleique. As cosurfactants commonly serve short-chain alkanols such as ethanol and propylene glycol. Long-chain alcohols, especially 1-butanol, are known for their enhancing activity as well. Decanol was found to be an optimum enhancer among other saturated fatty alcohols that were examined (from octanol to myristyl alcohol). Many enhancers are concentration-dependent; therefore, optimal concentration for effective promotion should be determined. The delivery rate is dependent on the type of the drug, the structure and ingredients of the carrier, and on the character of the membrane in use. Each formulation should be examined very carefully, because every membrane alters the mechanism of penetration and can turn an enhancer to a retarder. Various potential mechanisms to enhance drug penetration through the skin include directly affecting the skin and modifying the formulation so the partition, diffusion, or solubility is altered. The combination of several enhancement techniques such as the use of iontophoresis with fatty acids leads to synergetic drug penetration and to decrease in skin toxicity. Selected studies of various microemulsions containing certain drugs including retinoic acid, 5-fluorouracil, triptolide, ascorbic acid, diclofenac, lidocaine, and prilocaine hydrochloride in transdermal formulations are presented in this review. In conclusion, microemulsions were found as an effective vehicle of the solubilization of certain drugs and as protecting medium for the entrapped of drugs from degradation, hydrolysis, and oxidation. It can also provide prolonged release of the drug and prevent irritation despite the toxicity of the drug. Yet, in spite of all the advantages the present formulations lack several key important characteristics such as cosmetic-permitted surfactants, free dilution in water capabilities, stability in the digestive tracts and sufficient solubilization capacity.

Dawn of non-nucleoside inhibitor-based anti-HIV microbicides

The emergence of HIV/AIDS as a disease spread through sexual intercourse has prompted the search for safe and effective vaginal and rectal microbicides for curbing mucosal viral transmission via semen. Since endogenous reverse transcription is implicated in augmenting the sexual transmission of HIV-1 infection, potential microbicides should have the inherent ability to optimally inhibit both wild-type and drug-escape mutants. The non-nucleoside reverse transcriptase inhibitors (NNRTIs), which bind to an allosteric site on RT, are an important arsenal of drugs against HIV-1. The clinical success of NNRTI-based HIV/AIDS therapies has led to extensive structural and molecular modelling studies of enzyme complexes and chemical synthesis of second- and third-generation NNRTIs. Rationally designed NNRTIs deduced from changes in binding pocket size, shape and residue character that result from clinically observed NNRTI resistance-associated mutations exhibit high binding affinity for HIV-1 RT and robust anti-HIV activity against the wild-type and drug-escape mutants without cytotoxicity. Notably, membrane permeable tight binding NNRTIs have the ability to inactivate cell-free as well as cell-associated HIV-1 in semen without metabolic activation. Consequently, NNRTIs currently under development as experimental microbicides include thiourea-PETT (where PETT stands for phenethylthiazolylthiourea) derivatives (PHI-236, PHI-346 and PHI-443), urea-PETT derivatives (MIV-150), oxypyrimidines (S-DABOs), thiocarboxanilides (UC-781) and diarylpyrimidines (TMC-120). Mucoadhesive formulations of these NNRTIs have been studied for safety and efficacy in animal models and some have entered Phase I safety testing in humans. This review focuses on the structural, biological and preclinical studies relevant to the clinical development of these NNRTIs as molecular virucides intended to prevent the sexual transmission of HIV-1.

Conceival, a novel noncontraceptive vaginal vehicle for lipophilic microbicides

The objective of this study was to develop a nontoxic and noncontraceptive vaginal drug delivery vehicle for lipophilic anti-human immunodeficiency virus (HIV) microbicides. Three representative poorly water-soluble novel broad-spectrum anti-HIV microbicides, PHI-113, PHI-346, and PHI-443, were evaluated in 11 different solvent systems. Based on their solubility profiles, a novel nonspermicidal self-emulsifying gel (viz Conceival) composed of pharmaceutical excipients, sorbitol, polyethylene glycol 400, polysorbate 80, microcrystalline cellulose, xanthan gum, and water was optimized. Conceival enhanced the solubility of these poorly water-soluble (<0.001 mg/mL) anti-HIV drugs by at least 150- to 270-fold. Conceival was evaluated in vivo in the New Zealand white rabbit model for the preservation of sperm function based on pregnancy outcome and the potential for vaginal irritation following single and multiple intravaginal applications, respectively. Conceival administered intravaginally immediately prior to artificial insemination with semen had no adverse effects on subsequent reproductive performance, neonatal survival, or pup development when compared with untreated control group. Histologic evaluation of vaginal tissues of rabbits exposed intravaginally to Conceival for 14 consecutive days revealed lack of epithelial, submucosal, and vascular changes at the gel application site (total irritation score <3 out of a possible 16). These findings indicate that Conceival has potential to become a clinically useful, safe noncontraceptive vaginal vehicle for lipophilic microbicides.

Contraceptive activity of a spermicidal aryl phosphate derivative of bromo-methoxy-zidovudine (compound WHI-07) in rabbits

OBJECTIVE

To determine the vaginal contraceptive activity of WHI-07 in the rabbit model.

DESIGN

Prospective, controlled study.

SETTING

Center for advanced preclinical sciences.

ANIMAL(S)

Subgroups of 15, 16, or 24 New Zealand White does and 24 bucks per experiment.

INTERVENTION(S)

Ex vivo (Experiment 1) and in vivo (Experiments 2 and 3) treatment of semen with WHI-07 or Nonoxynol-9 (N-9). In Experiment I, ovulated does in subgroups of 15 were artificially inseminated with semen mixed with WHI-07 or vehicle. In Experiment 2, ovulated does in subgroups of 24 were artificially inseminated within 2 min after intravaginal administration of 2% WHI-07 gel-microemulsion or 2% N-9 gel and allowed to complete term pregnancy. In Experiment 3, ovulated does in subgroups of 16 were artificially inseminated at 15, 30, or 60 minutes.

MAIN OUTCOME MEASURE(S)

The numbers of implanted embryos on postinsemination day 8 or the proportion of does that became pregnant and delivered newborn rabbits; the litter size, weight, growth, and viability of pups until lactation day 5.

RESULT(S)

Exposure of semen to WHI-07 at the time of artificial insemination completely inhibited pregnancy rates (WHI-07-pretreated, 0%, vs. control, 60%) and embryo implantation (WHI-07-pretreated, 0/175 vs. control, 68/170). Intravaginal administration of a 2% WHI-07 gel-microemulsion or 2% N-9 gel before artificial insemination significantly inhibited pregnancy rates (81% and 85% inhibition, respectively) when compared with control. Furthermore, the 2% WHI-07 gel-microemulsion provided >90% inhibition of fertility even when insemination was delayed until 60 minutes after intravaginal application. Rabbits that delivered litters despite intravaginal application of 2% WHI-07 gel-microemulsion had healthy offsprings with no perinatal or postnatal repercussions.

CONCLUSION(S)

WHI-07 is a potent contraceptive agent in vivo. Intravaginal use of WHI-07 gel-microemulsion has clinical potential as a safe prophylactic contraceptive, in addition to its microbicide activity to curb the sexual transmission of HIV.

Potent dual anti-HIV and spermicidal activities of novel oxovanadium(V) complexes with thiourea non-nucleoside inhibitors of HIV-1 reverse transcriptase

We have previously demonstrated that tetrahedral bis(cyclopentadienyl)vanadium(IV) complexes and square pyramidal oxovanadium(IV) complexes of vanadium are rapid and selective spermicidal agents at low micromolar concentrations. This study investigated the potential utility of oxovanadium in combination with thiourea non-nucleoside inhibitors (NNIs) of HIV-1 reverse transcriptase (RT) for the development of an effective dual-function anti-HIV spermicide. Two rationally designed substituted phenyl-ring containing pyridyl thiourea NNIs, N-[2-(2-chlorophenethyl)]-N(')-[2-(5-bromopyridyl)-thiourea) [1] and N-[2-(2-methoxyphenethyl)]-N(')-[2-(pyridyl)-thiourea [2] that exhibited subnanomolar IC(50) values against the drug-sensitive, drug-resistant, and multidrug-resistant strains of HIV-1, were complexed with oxovanadium. The oxovanadium-thiourea [OVT] NNIs, C(29)H(27)Br(2)Cl(2)N(6)O(2)S(2)V [3], and C(31)H(35)N(6)O(4)S(2)V [4], were synthesized by reacting VOSO(4), a V(IV) compound, with the corresponding deprotonated thiourea NNI compounds as ligands. Elemental analysis showed that each OVT-NNI used two thiourea molecules as ligands. The existence of the Vz.dbnd6;O bond (968cm(-1)) was confirmed by IR spectroscopy. No d-d bands were observed in the visible spectra of OVT-NNIs and their EPR spectra were featureless, indicating that the vanadium centers were oxidized to V(V). The new OVT-NNIs as well as their thiourea NNI ligands were evaluated for (i) anti-HIV activity using the cell-free recombinant RT inhibition assays, (ii) cellular HIV replication assays, (iii) spermicidal activity against human sperm by computer-assisted sperm analysis (CASA), and (iv) cytotoxicity against normal human female genital tract epithelial cell using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) dye-reduction assays. Similar to thiourea NNIs 1 and 2, the OVT-NNIs 3 and 4, exhibited potent anti-HIV activity with submicromolar IC(50[p24]) values (0.08 and 0.128 microM, respectively) and submicromolar IC(50[RT]) values (2.1 and 0.87 microM, respectively). Notably, OVT-NNIs were spermicidal against human sperm at low micromolar concentrations (IC(50)=34 and 55 microM, respectively) and induced rapid sperm immobilization (T(1/2)=12 and 240s) when compared with their respective thiourea NNI ligands (EC(50)=>400 microM and T(1/2)=>180min). Moreover, OVT-NNIs displayed high selectivity indices against normal female genital tract epithelial cells (IC(50) values >250 microM) when compared to the detergent-type spermicide, nonoxynol-9, which was cytotoxic at spermicidal concentrations (IC(50) values 32-64 microM). This is the first report on the dual anti-HIV and spermicidal activities of a vanadium/oxovanadium complex. Our discovery of potent anti-HIV and rapid spermicidal activities of OVT-NNIs may be useful for the development of an effective and safe vaginal anti-HIV spermicide for women who are at high risk for acquiring HIV/AIDS by heterosexual transmission.

Structural requirements for potent anti-human immunodeficiency virus (HIV) and sperm-immobilizing activities of cyclohexenyl thiourea and urea non-nucleoside inhibitors of HIV-1 reverse transcriptase

The current pandemic of sexually transmitted human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) has created an urgent need for a new type of microbicide, one that is both a spermicide and a virucide. In a systematic effort to identify a non-detergent-type antiviral spermicide, we have rationally designed and synthesized a series of cyclohexenyl thiourea (CHET) nonnucleoside inhibitors (NNIs) of HIV-1 reverse transcriptase (RT) with sperm-immobilizing activity (SIA). To gain further insight into the structural requirements for the optimal activity of these dual-function NNIs, we compared the effects of thiazolyl, benzothiazolyl, and pyridyl ring substitutions and functionalization with electron-donating and electron-withdrawing groups as well as the importance of thiourea and urea moieties of 15 heterocyclic ring-substituted NNIs. RT activity and p24 antigen production in HIV-infected peripheral blood mononuclear cells were used as markers of viral replication. Computer-assisted sperm analysis was used for evaluating SIA of CHET compounds. The rabbit model was used for evaluation of in vivo mucosal toxicity and contraceptive activity of the lead NNIs. Three CHET-NNIs with a bromo, chloro, or methyl substitution at the 5 position of the pyridyl ring exhibited potent anti-HIV activity at nanomolar concentrations (IC(50) = 3-5 nM) and SIA at micromolar concentrations (EC(50) = 45-96 micro M). The dual-function CHET-NNIs were potent inhibitors of drug-resistant HIV-1 strains with genotypic and phenotypic NNI resistance. Upon substitution of the sulfur atom of the thiourea moiety with an oxygen atom, the most striking difference noted was a 38-fold reduction in time required for 50% sperm immobilization (T(1/2)). A quantitative structure-activity relationship (QSAR) analysis was used in deriving regression equations between 20 physicochemical properties and SIA of NNIs. QSAR analysis showed that the T(1/2) values positively correlated with values for molecular refractivity (r = 0.88), hydrophobicity (r = 0.72), atomic polarizability (r = 0.70), and principal moment of inertia (r = 0.63) of spermicidal NNIs. A stepwise multiple regression model to describe the relationship of T(1/2) values with these four regressors provided excellent predictability (r = 0.93). Exposure of semen to thiourea/urea NNIs either alone or in combination at the time of artificial insemination led to marked or complete inhibition of pregnancy in rabbits as assessed by the number of embryo implants versus corpora lutea on Day 8 of pregnancy. Repeated intravaginal application of a gel-microemulsion with and without 0.5%, 1%, and 2% CHET-NNI or its urea analog either alone or in combination did not induce mucosal toxicity. We hypothesize that the gain of spermicidal function by CHET-NNIs is due to their metabolic oxidation to urea analogs by sperm. Three reaction pathways are discussed. The extremely rapid SIA of the urea analog as well as the broad-spectrum anti-HIV activity of spermicidal CHET-NNIs together with their lack of mucosal toxicity and the marked ability to reduce in vivo fertility is particularly useful for the clinical development of a dual-function spermicidal microbicide. The cyclohexenyl pyridyl NNIs, especially N-[2-(1-cyclohexenyl)ethyl] N'-[2-(5-bromopyridyl)]-thiourea in combination with the urea analog, show unique clinical potential as anti-HIV spermicides aimed at curbing the sexual transmission of multidrug-resistant HIV-1 while providing effective fertility control for women.

Gel-microemulsions as vaginal spermicides and intravaginal drug delivery vehicles

There is a need for novel formulations to improve the bioavailability through the vaginal/rectal mucosa of microbicidal drug substances against sexually transmitted diseases. In addition, there is a need for more effective and less toxic vaginal spermicides. Here we review our recent discovery of novel gel-microemulsions (GM) as nontoxic, dual-function intravaginal spermicides, which can be used as delivery vehicles for lipophilic drug substances targeting sexually transmitted pathogens. We describe the formulation and biologic properties of 2 novel, submicron-particle-size GMs, GM-4 and GM-144, which were prepared from commonly available pharmaceutical excipients. These GMs comprising oil-in-water microemulsion and polymeric hydrogels were designed to solubilize lipophilic antiviral/antimicrobial agents and exhibited rapid spermicidal activity in human semen. Preclinical studies comparing the in vivo contraceptive efficacy of GM-4 and GM-144 versus nonoxynol-9-based detergent spermicide (Gynol II) in the rigorous rabbit model confirmed the potent contraceptive activity of these GMs. Unlike nonoxynol-9, repeated intravaginal applications of GM-4 and GM-144 in the rabbit vaginal irritation test were not associated with local inflammation or damage of the vaginal mucosa or epithelium. Furthermore, in short-term toxicity studies performed in mice, repetitive intravaginal application of spermicidal GM-4 and GM-144 for up to 13 weeks was not associated with any local, systemic, or reproductive toxicity. Spermicidal GMs have unprecedented potential as dual function microbicidal contraceptives to improve vaginal bioavailability of poorly soluble antimicrobial agents without causing significant vaginal damage.