Vaginal deployment and tenofovir delivery by microbicide gels.

Gels are one of the soft material platforms being evaluated to deliver topically acting anti-HIV drugs (microbicides) to the vaginal environment. For each drug, its loaded concentration, gel properties and applied volume, and frequency of dosing can be designed to optimize PK and, thence, PD. These factors also impact user sensory perceptions and acceptability. Deterministic compartmental modeling of vaginal deployment and drug delivery achieved by test gels can help delineate how multiple parameters characterizing drug, vehicle, vaginal environment, and dosing govern details of PK and PD and also gel leakage from the canal. Such microbicide delivery is a transport process combining convection, e.g., from gel spreading along the vaginal canal, with drug diffusion in multiple compartments, including gel, mucosal epithelium, and stroma. The present work builds upon prior models of gel coating flows and drug diffusion (without convection) in the vaginal environment. It combines and extends these initial approaches in several key ways, including: (1) linking convective drug transport due to gel spreading with drug diffusion and (2) accounting for natural variations in dimensions of the canal and the site of gel placement therein. Results are obtained for a leading microbicide drug, tenofovir, delivered by three prototype microbicide gels, with a range of rheological properties. The model includes phosphorylation of tenofovir to tenofovir diphosphate (which manifests reverse transcriptase activity in host cells), the stromal concentration distributions of which are related to reference prophylactic values against HIV. This yields a computed summary measure related to gel protection ("percent protected"). Analyses illustrate tradeoffs amongst gel properties, drug loading, volume and site of placement, and vaginal dimensions, in the time and space history of gel distribution and tenofovir transport to sites of its anti-HIV action and concentrations and potential prophylactic actions of tenofovir diphosphate therein.

Screening of mucoadhesive vaginal gel formulations

Rational design of vaginal drug delivery formulations requires special attention to vehicle properties that optimize vaginal coating and retention. The aim of the present work was to perform a screening of mucoadhesive vaginal gels formulated with carbomer or carrageenan in binary combination with a second polymer (carbomer, guar or xanthan gum). The gels were characterised using in vitro adhesion, spreadability and leakage potential studies, as well as rheological measurements (stress and frequency sweep tests) and the effect of dilution with simulated vaginal fluid (SVF) on spreadability. Results were analysed using analysis of variance and multiple factor analysis. The combination of polymers enhanced adhesion of both primary gelling agents, carbomer and carrageenan. From the rheological point of view all formulations presented a similar behaviour, prevalently elastic and characterised by loss tangent values well below 1. No correlation between rheological and adhesion behaviour was found. Carbomer and carrageenan gels containing the highest percentage of xanthan gum displayed good in vitro mucoadhesion and spreadability, minimal leakage potential and high resistance to dilution. The positive results obtained with carrageenan-xanthan gum-based gels can encourage the use of natural biocompatible adjuvants in the composition of vaginal products, a formulation field that is currently under the synthetic domain.

O planejamento racional de formulações para a liberação vaginal de fármacos requer atenção especial às propriedades do veículo, que otimizem o revestimento e a retenção vaginal. O objetivo do presente trabalho foi realizar uma triagem de géis vaginais mucoadesivos formulados com carbomero ou carragenina em combinação binária com um segundo polímero (carbomero, goma guár ou xantana). Os géis foram caracterizados usando estudos in vitro de aderência, espalhabilidade e potencial de vazamento, bem como medições reológicas (testes de varredura de tensão e frequência) e o efeito de diluição com fluido vaginal simulado (SVF) na espalhabilidade. Os resultados foram analisados utilizando a análise de variância e de fator múltiplo. A combinação de polímeros reforçou a adesão de ambos os agentes gelificantes primários, carbomero e carragenina. Do ponto de vista reológico todas as formulações apresentaram comportamento semelhante, predominantemente elástico e caracterizado por valores de tangente de perda bem abaixo de 1. Não se encontrou correlação entre as medições reológicas e o comportamento de adesão. Os géis de carbomero e carragenina contendo o maior porcentual de goma xantana apresentaram melhor mucoadesão e espalhabilidade, menor potencial de vazamento e maior resistência à diluição in vitro. Os resultados positivos obtidos com géis de carragenina-goma xantana podem incentivar o uso de adjuvantes biocompatíveis naturais na composição dos produtos vaginais, um campo de formulação atualmente sob o domínio de produtos sintéticos.

A novel breath test to directly measure use of vaginal gel and condoms.

We assessed the feasibility of a breath test to detect women's single or concurrent use of vaginal products by adding ester taggants to vaginal gel and condom lubricant. Healthy non-pregnant women were enrolled into a two-day cohort (N = 13) and a single-day cohort (N = 12) in San Francisco. Within each cohort, women were randomized (5:1) to tagged or untagged products, and inserted in a clinical setting: 4 mL of tenofovir placebo gel (ten tagged with 15 mg 2-pentyl acetate; three untagged), and an artificial phallus with a lubricated condom (11 tagged with 15 mg 2-butyl acetate; two untagged), on two separate days (two-day cohort) or concurrently (single-day cohort). Using a portable mini-gas chromatograph, the presence/absence of taggants was determined in breath specimens collected prior to, and at timed intervals following product exposure. Demographic, clinical and product use experience data were collected by structured interview. All participants completed all visits and inserted their assigned products. At 5 min post-insertion, the breath test was 100% accurate in identifying insertion of the tagged (or untagged) gel and/or condom. The half-life in breath of the two esters tested was <1 h with large variability between individuals, taggants and cohorts. Overall, among those receiving tagged product, six mild and two moderate product-related AEs were reported. All were transient and resolved spontaneously. Additional sensations included taste in mouth (N = 4) and scent (N = 5). The tagged products were well tolerated. This breath test has the potential to accurately and objectively monitor adherence to vaginal gel and condom used separately or concurrently.

In vivo optical imaging of human vaginal gel thickness distributions with a probe-based, dual-modality instrument.

ABSTRACT. We used a probe-based dual-modality optical imaging instrument to measure in vivo coating thickness distributions of a gel distributed along the vaginal lumen, in a clinical study. The gel was a surrogate for one delivering an anti-HIV topical microbicide. Imaging data from Fourier-domain multiplexed low-coherence interferometry (mLCI) and fluorimetric measurements were compared to assess the feasibility and accuracy of mLCI in measuring in vivo gel coating thickness distributions. In each study session, 3.5 mL of Replens gel was inserted to the vaginal fornix while the participant was supine. The participant either: 1. remained supine (10 or 60 min); or 2. sat up (1 min), stood up (1 min), sat down (1 min) and returned to the supine position; net elapsed time was 10 or 60 min after which the gel distribution was imaged. Local coating thickness distributions were qualitatively and quantitatively similar. Here mLCI did not accurately measure thicker gel coatings (>0.8 mm), a limitation not seen with fluorimetry. However, mLCI is capable of measuring in vivo microbicide gel distributions with resolution on the order of 10 µm, without the need for exogenous contrast agents, and can accurately capture relevant summary coating measures in good agreement with fluorimetry.

Advances in development, scale-up and manufacturing of microbicide gels, films, and tablets.

Vaginal HIV microbicides are topical, self administered products designed to prevent or significantly reduce transmission of HIV infection in women. The earliest microbicide candidates developed have been formulated as coitally dependent (used around the time of sex) gels and creams. All microbicide candidates tested in Phase III clinical trials, so far, have been gel products with non-specific mechanisms of action. However, recently, research is focusing on compounds containing highly potent and specific anti-retrovirals. These specific anti-retrovirals are being formulated as primary dosage forms such as vaginal gels or in alternative dosage forms such as fast dissolve films and tablets. Recent innovations also include development of combination products of highly active antiviral drugs such as reverse transcriptase inhibitors and entry inhibitors, which would theoretically be more effective and would reduce the possibility of drug resistance. In this article, an overview of recent advances in the microbicide gel, film, and tablet formulations and issues pertaining to scale-up, formulation, and evaluation challenges and regulatory guidelines have been presented. This article forms part of a special supplement covering presentations on gels, tablets, and films from the symposium on "Recent Trends in Microbicide Formulations" held on 25 and 26 January 2010, Arlington, VA.

Vaginal gel adsorption and retention by human vaginal cells: visual analysis by means of inorganic and organic markers.

To improve efficiency and prolong protection, modern gynecological preparations frequently incorporate polymeric molecules that add a certain degree of viscosity in order to increase adhesion with vaginal cells and prolong local delivery of active molecules. The aim of this study was to investigate the possibility of visualising the ability of a commercial medicated gynecological gel to bind to and be retained by human vaginal cells. The gel formulation included the essential oils of Thymus vulgaris and Eugenia cariophylla, which contain active molecules such as thymol and eugenol that are known to have useful antibacterial and antimycotic activities. The adherence of different dilutions of the gel to human vaginal cells was visualised by means of Nomarski interference contrast microscopy and scanning electron microscopy using ferric oxide particles and Escherichia coli as inorganic and organic markers, both of which made it possible to visualise the binding of the thin transparent layer of gel and the retaining effect, which was proportional to the degree of dilution.

Spectrofluorimetric determination of ciclopirox olamine via ternary complex with Tb(III) and EDTA.

A highly sensitive and selective spectrofluorimetric method was developed for the determination of ciclopirox olamine in raw material and in dosage forms. The proposed method is based on the formation of a ternary complex with Tb(III) in the presence of ethylenediaminetetraacetic acid. It was found that this complex manifests intense fluorescence at lambda(em) 489 and 545 nm with excitation at 295 nm. Different experimental parameters affecting the fluorescence intensity of the complex were carefully studied and incorporated into the procedure. Under the described conditions, the method is applicable over the concentration range 30-150 and 10-70 ng mL(-1) with minimum detectability of 6.7 and 0.9 ng mL(-1) at lambda(em) 489 and 545 nm, respectively. The mean percentage recovery at lambda(em) 489 and lambda(em) 545 nm ranged between 98.7 and 100.2 for the pure substance, solution, and cream. Relative error of 0.1-0.4% and RDS of up to 0.9% were estimated at lambda(em) 489 and 545 nm. A proposal of the reaction pathway is given.

Magnetic resonance imaging to determine the distribution of a vaginal gel: before, during, and after both simulated and real intercourse.

To provide effective contraception and protection against sexually transmitted disease, vaginal gels should maximally cover the cervical os and the vaginal epithelium before, during and after intercourse. To non-invasively monitor the intravaginal distribution of an applied intravaginal gel, we performed high-resolution magnetic resonance imaging (MRI) of the female pelvis before, during and after both real and simulated sexual intercourse. We sought to determine whether simulated intercourse with a plastic phallus could be used as a surrogate for real intercourse for such experiments. Dilute gadolinium chelate solution was mixed with Gynol-II gel and introduced intravaginally to volunteer female human subjects using a conventional applicator. MRI was performed at 1.5 Tesla with a surface coil. Imaging of the female pelvis was performed: (1) immediately after insertion of the gel; (2) during real intercourse with a male partner (2 subjects) or simulated intercourse with a plastic phallus (4 subjects); and (3) after completion of real or simulated intercourse. Subjects were studied after application of both 3 mL and 5 mL of vaginal gel. Measurements of gel thickness covering the vaginal mucosa were made digitally using electronic calipers. The bolus of gel is initially located in the upper vaginal canal, superior to the urogenital diaphragm. Both real and simulated intercourse dramatically increases the spread of gel to the lower vagina. The cervix appears to be adequately covered with gel both before and after intercourse. Increasing the volume of the gel increases initial vaginal mucosal coverage but also increases leakage from the introitus. No statistically significant differences in vaginal mucosal coverage were found between patients having undergone real vs. simulated intercourse, or on post-intercourse scans of 3 mL versus 5 mL. MRI is a sensitive, reproducible means of tracking the spread of intravaginal medications.

Analise do terconazol em formulacoes farmaceuticas por cromatografia liquida de alta eficiencia (CLAE) / Analysis terconazole in pharmaceutical formulations by liquid chromatography (HPLC)

Cromatografia liquida de alta eficiencia e utilizada para identificacao do terconazol na materia prima e determibacao quantitativa deste farmaco nas especialidades farmaceuticas de creme e ovulo. A analise do terconazol por CLAE apresenta resultados que comprovam a exatidao e precisao do metodo proposto. os resultados de recuperacao analisados, com valor medio de 99,33 por cento e 99,89 por cento para as especialidades farmaceuticas ovulos e creme, respectivamente, nos permitem indicar a cromatografia liquida de alta eficiencia como metodo ideal para determinacao do terconazol nas formas farmaceuticas comercializadas no Brasil

Evaluation of fluorometric determination-thin layer chromatographic identification of aminacrine hydrochloride in drug preparations.

Utilizing the fluorescent property of aminacrine hydrochloride and a filter fluorometer, a fluorometric method for aminacrine hydrochloride in drug combinations was developed, collaboratively studied, and adopted as official first action in the 11th edition of Official Methods of Analysis. Identity was confirmed by thin layer chromatography (TLC). Additional analytical work was undertaken with a grating fluorometer to support a change in the method status to official final action. The grating instrument recorded the aminacrine hydrochloride spectrum as opposed to the total fluorescence emission measured by the filter instrument. The spectrum of aminacrine hydrochloride showed that the molecule was exhibiting self-absorption of the emitted radiation even at concentrations of 10(-6)M and that the ratio of the 2 peaks in the emission spectrum varied with concentration. Additional analyses of an authentic cream preparation that also contained sulfanilamide gave an average recovery of 86.0% for aminacrine hydrochloride in 10 replicate portions. Because of these observations, the current Associate Referee's recommendation to delete the fluorometric procedure from the 13th edition of Official Methods of Analysis was adopted. A recommended deletion of the TLC identification test was also adopted.

Spectrophotometric determination of aminacrine hydrochloride in creams, jellies, and suppositories.

A visible spectrophotometric method has been developed for the quantitation of aminacrine hydrochloride in creams, jellies, and suppositories. Aminacrine hydrochloride was extracted into acidic ethanol and its visible spectrum was recorded. The amount present was calculated by determining the net absorbance between the absorbance maximum at about 402 nm and one-half the sum of the absorbances of the minima at about 389 and 412 nm. Aminacrine and a trace contaminant, 9(10H)-acridone, were independently identified by different thin layer chromatographic systems.

Analysis of conjugated estrogens in a vaginal cream formulation by capillary gas chromatography.

A capillary gas-chromatographic method is described for the quantitative analysis of nine equine estrogens in a vaginal cream formulation. The sodium sulfate ethers of the estrogens were selectively extracted from the formulation, subjected to enzyme hydrolysis, and derivatized to their oxime-trimethylsilyl esters. Resolution of the resulting derivatives was achieved on short (15 m) capillary column, wall-coated with cyanopropylmethyl silicon stationary phase.

Analysis of dienestrol and its dosage forms by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) analysis is described for dienestrol as a drug substance and in cream, foam, and tablet dosage forms. After incorporation of the drug or dosage form into a solvent mixture containing an internal standard, biphenyl, an aliquot was chromatographed using a reversed-phase medium, followed by UV spectrophotometric detection at 254 nm. The response of the chromatographic system was linear over a concentration range corresponding to 50-200% of the labeled amount of dienestrol. Satisfactory accuracy and precision were confirmed by analyzing cream by the standard addition method. The advantages of the HPLC method are its simplicity, speed, and sensitivity, which permit direct analysis of single-dose quantities of dienestrol.